Table of Contents
- 1 Synopsis
- 2 Description
- 3 Options
- 4 Writers
- 5 Timecode
- 6 Syntax
- 7 Expression Evaluation
- 8 Codec Options
- 9 Decoders
- 10 Video Decoders
- 11 Audio Decoders
- 12 Subtitles Decoders
- 13 Bitstream Filters
- 13.1 aac_adtstoasc
- 13.2 av1_metadata
- 13.3 chomp
- 13.4 dca_core
- 13.5 dovi_rpu
- 13.6 dump_extra
- 13.7 dv_error_marker
- 13.8 eac3_core
- 13.9 extract_extradata
- 13.10 filter_units
- 13.11 hapqa_extract
- 13.12 h264_metadata
- 13.13 h264_mp4toannexb
- 13.14 h264_redundant_pps
- 13.15 hevc_metadata
- 13.16 hevc_mp4toannexb
- 13.17 imxdump
- 13.18 mjpeg2jpeg
- 13.19 mjpegadump
- 13.20 mov2textsub
- 13.21 mpeg2_metadata
- 13.22 mpeg4_unpack_bframes
- 13.23 noise
- 13.24 null
- 13.25 pcm_rechunk
- 13.26 pgs_frame_merge
- 13.27 prores_metadata
- 13.28 remove_extra
- 13.29 setts
- 13.30 showinfo
- 13.31 text2movsub
- 13.32 trace_headers
- 13.33 truehd_core
- 13.34 vp9_metadata
- 13.35 vp9_superframe
- 13.36 vp9_superframe_split
- 13.37 vp9_raw_reorder
- 14 Format Options
- 15 Demuxers
- 15.1 aa
- 15.2 aac
- 15.3 apng
- 15.4 asf
- 15.5 concat
- 15.6 dash
- 15.7 dvdvideo
- 15.8 ea
- 15.9 imf
- 15.10 flv, live_flv, kux
- 15.11 gif
- 15.12 hls
- 15.13 image2
- 15.14 libgme
- 15.15 libmodplug
- 15.16 libopenmpt
- 15.17 mov/mp4/3gp
- 15.18 mpegts
- 15.19 mpjpeg
- 15.20 rawvideo
- 15.21 rcwt
- 15.22 sbg
- 15.23 tedcaptions
- 15.24 vapoursynth
- 15.25 w64
- 15.26 wav
- 16 Metadata
- 17 Protocol Options
- 18 Protocols
- 18.1 amqp
- 18.2 async
- 18.3 bluray
- 18.4 cache
- 18.5 concat
- 18.6 concatf
- 18.7 crypto
- 18.8 data
- 18.9 fd
- 18.10 file
- 18.11 ftp
- 18.12 gopher
- 18.13 gophers
- 18.14 hls
- 18.15 http
- 18.16 Icecast
- 18.17 ipfs
- 18.18 mmst
- 18.19 mmsh
- 18.20 md5
- 18.21 pipe
- 18.22 prompeg
- 18.23 rist
- 18.24 rtmp
- 18.25 rtmpe
- 18.26 rtmps
- 18.27 rtmpt
- 18.28 rtmpte
- 18.29 rtmpts
- 18.30 libsmbclient
- 18.31 libssh
- 18.32 librtmp rtmp, rtmpe, rtmps, rtmpt, rtmpte
- 18.33 rtp
- 18.34 rtsp
- 18.35 sap
- 18.36 sctp
- 18.37 srt
- 18.38 srtp
- 18.39 subfile
- 18.40 tee
- 18.41 tcp
- 18.42 tls
- 18.43 udp
- 18.44 unix
- 18.45 zmq
- 19 Device Options
- 20 Input Devices
- 21 Resampler Options
- 22 Scaler Options
- 23 Filtering Introduction
- 24 graph2dot
- 25 Filtergraph description
- 26 Timeline editing
- 27 Changing options at runtime with a command
- 28 Options for filters with several inputs (framesync)
- 29 Audio Filters
- 29.1 aap
- 29.2 acompressor
- 29.3 acontrast
- 29.4 acopy
- 29.5 acrossfade
- 29.6 acrossover
- 29.7 acrusher
- 29.8 acue
- 29.9 adeclick
- 29.10 adeclip
- 29.11 adecorrelate
- 29.12 adelay
- 29.13 adenorm
- 29.14 aderivative, aintegral
- 29.15 adrc
- 29.16 adynamicequalizer
- 29.17 adynamicsmooth
- 29.18 aecho
- 29.19 aemphasis
- 29.20 aeval
- 29.21 aexciter
- 29.22 afade
- 29.23 afftdn
- 29.24 afftfilt
- 29.25 afir
- 29.26 aformat
- 29.27 afreqshift
- 29.28 afwtdn
- 29.29 agate
- 29.30 aiir
- 29.31 alimiter
- 29.32 allpass
- 29.33 aloop
- 29.34 amerge
- 29.35 amix
- 29.36 amultiply
- 29.37 anequalizer
- 29.38 anlmdn
- 29.39 anlmf, anlms
- 29.40 anull
- 29.41 apad
- 29.42 aphaser
- 29.43 aphaseshift
- 29.44 apsnr
- 29.45 apsyclip
- 29.46 apulsator
- 29.47 aresample
- 29.48 areverse
- 29.49 arls
- 29.50 arnndn
- 29.51 asdr
- 29.52 asetnsamples
- 29.53 asetrate
- 29.54 ashowinfo
- 29.55 asisdr
- 29.56 asoftclip
- 29.57 aspectralstats
- 29.58 asr
- 29.59 astats
- 29.60 asubboost
- 29.61 asubcut
- 29.62 asupercut
- 29.63 asuperpass
- 29.64 asuperstop
- 29.65 atempo
- 29.66 atilt
- 29.67 atrim
- 29.68 axcorrelate
- 29.69 bandpass
- 29.70 bandreject
- 29.71 bass, lowshelf
- 29.72 biquad
- 29.73 bs2b
- 29.74 channelmap
- 29.75 channelsplit
- 29.76 chorus
- 29.77 compand
- 29.78 compensationdelay
- 29.79 crossfeed
- 29.80 crystalizer
- 29.81 dcshift
- 29.82 deesser
- 29.83 dialoguenhance
- 29.84 drmeter
- 29.85 dynaudnorm
- 29.86 earwax
- 29.87 equalizer
- 29.88 extrastereo
- 29.89 firequalizer
- 29.90 flanger
- 29.91 haas
- 29.92 hdcd
- 29.93 headphone
- 29.94 highpass
- 29.95 join
- 29.96 ladspa
- 29.97 loudnorm
- 29.98 lowpass
- 29.99 lv2
- 29.100 mcompand
- 29.101 pan
- 29.102 replaygain
- 29.103 resample
- 29.104 rubberband
- 29.105 sidechaincompress
- 29.106 sidechaingate
- 29.107 silencedetect
- 29.108 silenceremove
- 29.109 sofalizer
- 29.110 speechnorm
- 29.111 stereotools
- 29.112 stereowiden
- 29.113 superequalizer
- 29.114 surround
- 29.115 tiltshelf
- 29.116 treble, highshelf
- 29.117 tremolo
- 29.118 vibrato
- 29.119 virtualbass
- 29.120 volume
- 29.121 volumedetect
- 30 Audio Sources
- 31 Audio Sinks
- 32 Video Filters
- 32.1 addroi
- 32.2 alphaextract
- 32.3 alphamerge
- 32.4 amplify
- 32.5 ass
- 32.6 atadenoise
- 32.7 avgblur
- 32.8 backgroundkey
- 32.9 bbox
- 32.10 bilateral
- 32.11 bilateral_cuda
- 32.12 bitplanenoise
- 32.13 blackdetect
- 32.14 blackframe
- 32.15 blend
- 32.16 blockdetect
- 32.17 blurdetect
- 32.18 bm3d
- 32.19 boxblur
- 32.20 bwdif
- 32.21 bwdif_cuda
- 32.22 ccrepack
- 32.23 cas
- 32.24 chromahold
- 32.25 chromakey
- 32.26 chromakey_cuda
- 32.27 chromanr
- 32.28 chromashift
- 32.29 ciescope
- 32.30 codecview
- 32.31 colorbalance
- 32.32 colorcontrast
- 32.33 colorcorrect
- 32.34 colorchannelmixer
- 32.35 colorize
- 32.36 colorkey
- 32.37 colorhold
- 32.38 colorlevels
- 32.39 colormap
- 32.40 colormatrix
- 32.41 colorspace
- 32.42 colorspace_cuda
- 32.43 colortemperature
- 32.44 convolution
- 32.45 convolve
- 32.46 copy
- 32.47 coreimage
- 32.48 corr
- 32.49 cover_rect
- 32.50 crop
- 32.51 cropdetect
- 32.52 cue
- 32.53 curves
- 32.54 datascope
- 32.55 dblur
- 32.56 dctdnoiz
- 32.57 deband
- 32.58 deblock
- 32.59 decimate
- 32.60 deconvolve
- 32.61 dedot
- 32.62 deflate
- 32.63 deflicker
- 32.64 dejudder
- 32.65 delogo
- 32.66 derain
- 32.67 deshake
- 32.68 despill
- 32.69 detelecine
- 32.70 dilation
- 32.71 displace
- 32.72 dnn_classify
- 32.73 dnn_detect
- 32.74 dnn_processing
- 32.75 drawbox
- 32.76 drawgraph
- 32.77 drawgrid
- 32.78 drawtext
- 32.79 edgedetect
- 32.80 elbg
- 32.81 entropy
- 32.82 epx
- 32.83 eq
- 32.84 erosion
- 32.85 estdif
- 32.86 exposure
- 32.87 extractplanes
- 32.88 fade
- 32.89 feedback
- 32.90 fftdnoiz
- 32.91 fftfilt
- 32.92 field
- 32.93 fieldhint
- 32.94 fieldmatch
- 32.95 fieldorder
- 32.96 fillborders
- 32.97 find_rect
- 32.98 floodfill
- 32.99 format
- 32.100 fps
- 32.101 framepack
- 32.102 framerate
- 32.103 framestep
- 32.104 freezedetect
- 32.105 freezeframes
- 32.106 frei0r
- 32.107 fspp
- 32.108 fsync
- 32.109 gblur
- 32.110 geq
- 32.111 gradfun
- 32.112 graphmonitor
- 32.113 grayworld
- 32.114 greyedge
- 32.115 guided
- 32.116 haldclut
- 32.117 hflip
- 32.118 histeq
- 32.119 histogram
- 32.120 hqdn3d
- 32.121 hwdownload
- 32.122 hwmap
- 32.123 hwupload
- 32.124 hwupload_cuda
- 32.125 hqx
- 32.126 hstack
- 32.127 hsvhold
- 32.128 hsvkey
- 32.129 hue
- 32.130 huesaturation
- 32.131 hysteresis
- 32.132 iccdetect
- 32.133 iccgen
- 32.134 identity
- 32.135 idet
- 32.136 il
- 32.137 inflate
- 32.138 interlace
- 32.139 kerndeint
- 32.140 kirsch
- 32.141 lagfun
- 32.142 lenscorrection
- 32.143 lensfun
- 32.144 libplacebo
- 32.145 libvmaf
- 32.146 libvmaf_cuda
- 32.147 limitdiff
- 32.148 limiter
- 32.149 loop
- 32.150 lut1d
- 32.151 lut3d
- 32.152 lumakey
- 32.153 lut, lutrgb, lutyuv
- 32.154 lut2, tlut2
- 32.155 maskedclamp
- 32.156 maskedmax
- 32.157 maskedmerge
- 32.158 maskedmin
- 32.159 maskedthreshold
- 32.160 maskfun
- 32.161 mcdeint
- 32.162 median
- 32.163 mergeplanes
- 32.164 mestimate
- 32.165 midequalizer
- 32.166 minterpolate
- 32.167 mix
- 32.168 monochrome
- 32.169 morpho
- 32.170 mpdecimate
- 32.171 msad
- 32.172 multiply
- 32.173 negate
- 32.174 nlmeans
- 32.175 nnedi
- 32.176 noformat
- 32.177 noise
- 32.178 normalize
- 32.179 null
- 32.180 ocr
- 32.181 ocv
- 32.182 oscilloscope
- 32.183 overlay
- 32.184 overlay_cuda
- 32.185 owdenoise
- 32.186 pad
- 32.187 palettegen
- 32.188 paletteuse
- 32.189 perspective
- 32.190 phase
- 32.191 photosensitivity
- 32.192 pixdesctest
- 32.193 pixelize
- 32.194 pixscope
- 32.195 pp
- 32.196 pp7
- 32.197 premultiply
- 32.198 prewitt
- 32.199 pseudocolor
- 32.200 psnr
- 32.201 pullup
- 32.202 qp
- 32.203 qrencode
- 32.204 quirc
- 32.205 random
- 32.206 readeia608
- 32.207 readvitc
- 32.208 remap
- 32.209 removegrain
- 32.210 removelogo
- 32.211 repeatfields
- 32.212 reverse
- 32.213 rgbashift
- 32.214 roberts
- 32.215 rotate
- 32.216 sab
- 32.217 scale
- 32.218 scale_cuda
- 32.219 scale_npp
- 32.220 scale2ref_npp
- 32.221 scale_vt
- 32.222 scharr
- 32.223 scroll
- 32.224 scdet
- 32.225 selectivecolor
- 32.226 separatefields
- 32.227 setdar, setsar
- 32.228 setfield
- 32.229 setparams
- 32.230 sharpen_npp
- 32.231 shear
- 32.232 showinfo
- 32.233 showpalette
- 32.234 shuffleframes
- 32.235 shufflepixels
- 32.236 shuffleplanes
- 32.237 signalstats
- 32.238 signature
- 32.239 siti
- 32.240 smartblur
- 32.241 sobel
- 32.242 spp
- 32.243 sr
- 32.244 ssim
- 32.245 stereo3d
- 32.246 streamselect, astreamselect
- 32.247 subtitles
- 32.248 super2xsai
- 32.249 swaprect
- 32.250 swapuv
- 32.251 tblend
- 32.252 telecine
- 32.253 thistogram
- 32.254 threshold
- 32.255 thumbnail
- 32.256 tile
- 32.257 tiltandshift
- 32.258 tinterlace
- 32.259 tmedian
- 32.260 tmidequalizer
- 32.261 tmix
- 32.262 tonemap
- 32.263 tpad
- 32.264 transpose
- 32.265 transpose_npp
- 32.266 trim
- 32.267 unpremultiply
- 32.268 unsharp
- 32.269 untile
- 32.270 uspp
- 32.271 v360
- 32.272 vaguedenoiser
- 32.273 varblur
- 32.274 vectorscope
- 32.275 vidstabdetect
- 32.276 vidstabtransform
- 32.277 vflip
- 32.278 vfrdet
- 32.279 vibrance
- 32.280 vif
- 32.281 vignette
- 32.282 vmafmotion
- 32.283 vstack
- 32.284 w3fdif
- 32.285 waveform
- 32.286 weave, doubleweave
- 32.287 xbr
- 32.288 xcorrelate
- 32.289 xfade
- 32.290 xmedian
- 32.291 xpsnr
- 32.292 xstack
- 32.293 yadif
- 32.294 yadif_cuda
- 32.295 yaepblur
- 32.296 zoompan
- 32.297 zscale
- 33 OpenCL Video Filters
- 33.1 avgblur_opencl
- 33.2 boxblur_opencl
- 33.3 colorkey_opencl
- 33.4 convolution_opencl
- 33.5 erosion_opencl
- 33.6 deshake_opencl
- 33.7 dilation_opencl
- 33.8 nlmeans_opencl
- 33.9 overlay_opencl
- 33.10 pad_opencl
- 33.11 prewitt_opencl
- 33.12 program_opencl
- 33.13 remap_opencl
- 33.14 roberts_opencl
- 33.15 sobel_opencl
- 33.16 tonemap_opencl
- 33.17 unsharp_opencl
- 33.18 xfade_opencl
- 34 VAAPI Video Filters
- 35 Vulkan Video Filters
- 36 QSV Video Filters
- 37 Video Sources
- 37.1 buffer
- 37.2 cellauto
- 37.3 coreimagesrc
- 37.4 ddagrab
- 37.5 gradients
- 37.6 mandelbrot
- 37.7 mptestsrc
- 37.8 frei0r_src
- 37.9 life
- 37.10 perlin
- 37.11 qrencodesrc
- 37.12 allrgb, allyuv, color, colorchart, colorspectrum, haldclutsrc, nullsrc, pal75bars, pal100bars, rgbtestsrc, smptebars, smptehdbars, testsrc, testsrc2, yuvtestsrc
- 37.13 openclsrc
- 37.14 sierpinski
- 37.15 zoneplate
- 38 Video Sinks
- 39 Multimedia Filters
- 39.1 a3dscope
- 39.2 abitscope
- 39.3 adrawgraph
- 39.4 agraphmonitor
- 39.5 ahistogram
- 39.6 aphasemeter
- 39.7 avectorscope
- 39.8 bench, abench
- 39.9 concat
- 39.10 ebur128
- 39.11 interleave, ainterleave
- 39.12 latency, alatency
- 39.13 metadata, ametadata
- 39.14 perms, aperms
- 39.15 realtime, arealtime
- 39.16 segment, asegment
- 39.17 select, aselect
- 39.18 sendcmd, asendcmd
- 39.19 setpts, asetpts
- 39.20 setrange
- 39.21 settb, asettb
- 39.22 showcqt
- 39.23 showcwt
- 39.24 showfreqs
- 39.25 showspatial
- 39.26 showspectrum
- 39.27 showspectrumpic
- 39.28 showvolume
- 39.29 showwaves
- 39.30 showwavespic
- 39.31 sidedata, asidedata
- 39.32 spectrumsynth
- 39.33 split, asplit
- 39.34 zmq, azmq
- 40 Multimedia Sources
- 41 External libraries
- 41.1 Alliance for Open Media (AOM)
- 41.2 AMD AMF/VCE
- 41.3 AviSynth
- 41.4 Chromaprint
- 41.5 codec2
- 41.6 dav1d
- 41.7 davs2
- 41.8 uavs3d
- 41.9 Game Music Emu
- 41.10 Intel QuickSync Video
- 41.11 Kvazaar
- 41.12 LAME
- 41.13 LCEVCdec
- 41.14 libilbc
- 41.15 libjxl
- 41.16 libvpx
- 41.17 ModPlug
- 41.18 OpenCORE, VisualOn, and Fraunhofer libraries
- 41.19 OpenH264
- 41.20 OpenJPEG
- 41.21 rav1e
- 41.22 SVT-AV1
- 41.23 TwoLAME
- 41.24 VapourSynth
- 41.25 x264
- 41.26 x265
- 41.27 xavs
- 41.28 xavs2
- 41.29 eXtra-fast Essential Video Encoder (XEVE)
- 41.30 eXtra-fast Essential Video Decoder (XEVD)
- 41.31 ZVBI
- 42 Supported File Formats, Codecs or Features
- 43 See Also
- 44 Authors
1 Synopsis
ffprobe [options] input_url
2 Description
ffprobe gathers information from multimedia streams and prints it in human- and machine-readable fashion.
For example it can be used to check the format of the container used by a multimedia stream and the format and type of each media stream contained in it.
If a url is specified in input, ffprobe will try to open and probe the url content. If the url cannot be opened or recognized as a multimedia file, a positive exit code is returned.
If no output is specified as output with o ffprobe will write to stdout.
ffprobe may be employed both as a standalone application or in combination with a textual filter, which may perform more sophisticated processing, e.g. statistical processing or plotting.
Options are used to list some of the formats supported by ffprobe or for specifying which information to display, and for setting how ffprobe will show it.
ffprobe output is designed to be easily parsable by a textual filter, and consists of one or more sections of a form defined by the selected writer, which is specified by the output_format option.
Sections may contain other nested sections, and are identified by a name (which may be shared by other sections), and an unique name. See the output of sections.
Metadata tags stored in the container or in the streams are recognized and printed in the corresponding "FORMAT", "STREAM", "STREAM_GROUP_STREAM" or "PROGRAM_STREAM" section.
3 Options
All the numerical options, if not specified otherwise, accept a string representing a number as input, which may be followed by one of the SI unit prefixes, for example: ’K’, ’M’, or ’G’.
If ’i’ is appended to the SI unit prefix, the complete prefix will be interpreted as a unit prefix for binary multiples, which are based on powers of 1024 instead of powers of 1000. Appending ’B’ to the SI unit prefix multiplies the value by 8. This allows using, for example: ’KB’, ’MiB’, ’G’ and ’B’ as number suffixes.
Options which do not take arguments are boolean options, and set the corresponding value to true. They can be set to false by prefixing the option name with "no". For example using "-nofoo" will set the boolean option with name "foo" to false.
Options that take arguments support a special syntax where the argument given on the command line is interpreted as a path to the file from which the actual argument value is loaded. To use this feature, add a forward slash ’/’ immediately before the option name (after the leading dash). E.g.
ffmpeg -i INPUT -/filter:v filter.script OUTPUT
will load a filtergraph description from the file named filter.script.
3.1 Stream specifiers
Some options are applied per-stream, e.g. bitrate or codec. Stream specifiers are used to precisely specify which stream(s) a given option belongs to.
A stream specifier is a string generally appended to the option name and
separated from it by a colon. E.g. -codec:a:1 ac3
contains the
a:1
stream specifier, which matches the second audio stream. Therefore, it
would select the ac3 codec for the second audio stream.
A stream specifier can match several streams, so that the option is applied to all
of them. E.g. the stream specifier in -b:a 128k
matches all audio
streams.
An empty stream specifier matches all streams. For example, -codec copy
or -codec: copy
would copy all the streams without reencoding.
Possible forms of stream specifiers are:
- stream_index
Matches the stream with this index. E.g.
-threads:1 4
would set the thread count for the second stream to 4. If stream_index is used as an additional stream specifier (see below), then it selects stream number stream_index from the matching streams. Stream numbering is based on the order of the streams as detected by libavformat except when a stream group specifier or program ID is also specified. In this case it is based on the ordering of the streams in the group or program.- stream_type[:additional_stream_specifier]
stream_type is one of following: ’v’ or ’V’ for video, ’a’ for audio, ’s’ for subtitle, ’d’ for data, and ’t’ for attachments. ’v’ matches all video streams, ’V’ only matches video streams which are not attached pictures, video thumbnails or cover arts. If additional_stream_specifier is used, then it matches streams which both have this type and match the additional_stream_specifier. Otherwise, it matches all streams of the specified type.
- g:group_specifier[:additional_stream_specifier]
Matches streams which are in the group with the specifier group_specifier. if additional_stream_specifier is used, then it matches streams which both are part of the group and match the additional_stream_specifier. group_specifier may be one of the following:
- group_index
Match the stream with this group index.
- #group_id or i:group_id
Match the stream with this group id.
- p:program_id[:additional_stream_specifier]
Matches streams which are in the program with the id program_id. If additional_stream_specifier is used, then it matches streams which both are part of the program and match the additional_stream_specifier.
- #stream_id or i:stream_id
Match the stream by stream id (e.g. PID in MPEG-TS container).
- m:key[:value]
Matches streams with the metadata tag key having the specified value. If value is not given, matches streams that contain the given tag with any value.
- disp:dispositions[:additional_stream_specifier]
Matches streams with the given disposition(s). dispositions is a list of one or more dispositions (as printed by the -dispositions option) joined with ’+’.
- u
Matches streams with usable configuration, the codec must be defined and the essential information such as video dimension or audio sample rate must be present.
Note that in
ffmpeg
, matching by metadata will only work properly for input files.
3.2 Generic options
These options are shared amongst the ff* tools.
- -L
Show license.
- -h, -?, -help, --help [arg]
Show help. An optional parameter may be specified to print help about a specific item. If no argument is specified, only basic (non advanced) tool options are shown.
Possible values of arg are:
- long
Print advanced tool options in addition to the basic tool options.
- full
Print complete list of options, including shared and private options for encoders, decoders, demuxers, muxers, filters, etc.
- decoder=decoder_name
Print detailed information about the decoder named decoder_name. Use the -decoders option to get a list of all decoders.
- encoder=encoder_name
Print detailed information about the encoder named encoder_name. Use the -encoders option to get a list of all encoders.
- demuxer=demuxer_name
Print detailed information about the demuxer named demuxer_name. Use the -formats option to get a list of all demuxers and muxers.
- muxer=muxer_name
Print detailed information about the muxer named muxer_name. Use the -formats option to get a list of all muxers and demuxers.
- filter=filter_name
Print detailed information about the filter named filter_name. Use the -filters option to get a list of all filters.
- bsf=bitstream_filter_name
Print detailed information about the bitstream filter named bitstream_filter_name. Use the -bsfs option to get a list of all bitstream filters.
- protocol=protocol_name
Print detailed information about the protocol named protocol_name. Use the -protocols option to get a list of all protocols.
- -version
Show version.
- -buildconf
Show the build configuration, one option per line.
- -formats
Show available formats (including devices).
- -demuxers
Show available demuxers.
- -muxers
Show available muxers.
- -devices
Show available devices.
- -codecs
Show all codecs known to libavcodec.
Note that the term ’codec’ is used throughout this documentation as a shortcut for what is more correctly called a media bitstream format.
- -decoders
Show available decoders.
- -encoders
Show all available encoders.
- -bsfs
Show available bitstream filters.
- -protocols
Show available protocols.
- -filters
Show available libavfilter filters.
- -pix_fmts
Show available pixel formats.
- -sample_fmts
Show available sample formats.
- -layouts
Show channel names and standard channel layouts.
- -dispositions
Show stream dispositions.
- -colors
Show recognized color names.
- -sources device[,opt1=val1[,opt2=val2]...]
Show autodetected sources of the input device. Some devices may provide system-dependent source names that cannot be autodetected. The returned list cannot be assumed to be always complete.
ffmpeg -sources pulse,server=192.168.0.4
- -sinks device[,opt1=val1[,opt2=val2]...]
Show autodetected sinks of the output device. Some devices may provide system-dependent sink names that cannot be autodetected. The returned list cannot be assumed to be always complete.
ffmpeg -sinks pulse,server=192.168.0.4
- -loglevel [flags+]loglevel | -v [flags+]loglevel
Set logging level and flags used by the library.
The optional flags prefix can consist of the following values:
- ‘repeat’
Indicates that repeated log output should not be compressed to the first line and the "Last message repeated n times" line will be omitted.
- ‘level’
Indicates that log output should add a
[level]
prefix to each message line. This can be used as an alternative to log coloring, e.g. when dumping the log to file.
Flags can also be used alone by adding a ’+’/’-’ prefix to set/reset a single flag without affecting other flags or changing loglevel. When setting both flags and loglevel, a ’+’ separator is expected between the last flags value and before loglevel.
loglevel is a string or a number containing one of the following values:
- ‘quiet, -8’
Show nothing at all; be silent.
- ‘panic, 0’
Only show fatal errors which could lead the process to crash, such as an assertion failure. This is not currently used for anything.
- ‘fatal, 8’
Only show fatal errors. These are errors after which the process absolutely cannot continue.
- ‘error, 16’
Show all errors, including ones which can be recovered from.
- ‘warning, 24’
Show all warnings and errors. Any message related to possibly incorrect or unexpected events will be shown.
- ‘info, 32’
Show informative messages during processing. This is in addition to warnings and errors. This is the default value.
- ‘verbose, 40’
Same as
info
, except more verbose.- ‘debug, 48’
Show everything, including debugging information.
- ‘trace, 56’
For example to enable repeated log output, add the
level
prefix, and set loglevel toverbose
:ffmpeg -loglevel repeat+level+verbose -i input output
Another example that enables repeated log output without affecting current state of
level
prefix flag or loglevel:ffmpeg [...] -loglevel +repeat
By default the program logs to stderr. If coloring is supported by the terminal, colors are used to mark errors and warnings. Log coloring can be disabled setting the environment variable
AV_LOG_FORCE_NOCOLOR
, or can be forced setting the environment variableAV_LOG_FORCE_COLOR
.- -report
Dump full command line and log output to a file named
program-YYYYMMDD-HHMMSS.log
in the current directory. This file can be useful for bug reports. It also implies-loglevel debug
.Setting the environment variable
FFREPORT
to any value has the same effect. If the value is a ’:’-separated key=value sequence, these options will affect the report; option values must be escaped if they contain special characters or the options delimiter ’:’ (see the “Quoting and escaping” section in the ffmpeg-utils manual).The following options are recognized:
- file
set the file name to use for the report;
%p
is expanded to the name of the program,%t
is expanded to a timestamp,%%
is expanded to a plain%
- level
set the log verbosity level using a numerical value (see
-loglevel
).
For example, to output a report to a file named ffreport.log using a log level of
32
(alias for log levelinfo
):FFREPORT=file=ffreport.log:level=32 ffmpeg -i input output
Errors in parsing the environment variable are not fatal, and will not appear in the report.
- -hide_banner
Suppress printing banner.
All FFmpeg tools will normally show a copyright notice, build options and library versions. This option can be used to suppress printing this information.
- -cpuflags flags (global)
Allows setting and clearing cpu flags. This option is intended for testing. Do not use it unless you know what you’re doing.
ffmpeg -cpuflags -sse+mmx ... ffmpeg -cpuflags mmx ... ffmpeg -cpuflags 0 ...
Possible flags for this option are:
- ‘x86’
- ‘mmx’
- ‘mmxext’
- ‘sse’
- ‘sse2’
- ‘sse2slow’
- ‘sse3’
- ‘sse3slow’
- ‘ssse3’
- ‘atom’
- ‘sse4.1’
- ‘sse4.2’
- ‘avx’
- ‘avx2’
- ‘xop’
- ‘fma3’
- ‘fma4’
- ‘3dnow’
- ‘3dnowext’
- ‘bmi1’
- ‘bmi2’
- ‘cmov’
- ‘ARM’
- ‘armv5te’
- ‘armv6’
- ‘armv6t2’
- ‘vfp’
- ‘vfpv3’
- ‘neon’
- ‘setend’
- ‘AArch64’
- ‘armv8’
- ‘vfp’
- ‘neon’
- ‘PowerPC’
- ‘altivec’
- ‘Specific Processors’
- ‘pentium2’
- ‘pentium3’
- ‘pentium4’
- ‘k6’
- ‘k62’
- ‘athlon’
- ‘athlonxp’
- ‘k8’
- -cpucount count (global)
Override detection of CPU count. This option is intended for testing. Do not use it unless you know what you’re doing.
ffmpeg -cpucount 2
- -max_alloc bytes
Set the maximum size limit for allocating a block on the heap by ffmpeg’s family of malloc functions. Exercise extreme caution when using this option. Don’t use if you do not understand the full consequence of doing so. Default is INT_MAX.
3.3 AVOptions
These options are provided directly by the libavformat, libavdevice and libavcodec libraries. To see the list of available AVOptions, use the -help option. They are separated into two categories:
- generic
These options can be set for any container, codec or device. Generic options are listed under AVFormatContext options for containers/devices and under AVCodecContext options for codecs.
- private
These options are specific to the given container, device or codec. Private options are listed under their corresponding containers/devices/codecs.
For example to write an ID3v2.3 header instead of a default ID3v2.4 to an MP3 file, use the id3v2_version private option of the MP3 muxer:
ffmpeg -i input.flac -id3v2_version 3 out.mp3
All codec AVOptions are per-stream, and thus a stream specifier should be attached to them:
ffmpeg -i multichannel.mxf -map 0:v:0 -map 0:a:0 -map 0:a:0 -c:a:0 ac3 -b:a:0 640k -ac:a:1 2 -c:a:1 aac -b:2 128k out.mp4
In the above example, a multichannel audio stream is mapped twice for output. The first instance is encoded with codec ac3 and bitrate 640k. The second instance is downmixed to 2 channels and encoded with codec aac. A bitrate of 128k is specified for it using absolute index of the output stream.
Note: the -nooption syntax cannot be used for boolean AVOptions, use -option 0/-option 1.
Note: the old undocumented way of specifying per-stream AVOptions by prepending v/a/s to the options name is now obsolete and will be removed soon.
3.4 Main options
- -f format
Force format to use.
- -unit
Show the unit of the displayed values.
- -prefix
Use SI prefixes for the displayed values. Unless the "-byte_binary_prefix" option is used all the prefixes are decimal.
- -byte_binary_prefix
Force the use of binary prefixes for byte values.
- -sexagesimal
Use sexagesimal format HH:MM:SS.MICROSECONDS for time values.
- -pretty
Prettify the format of the displayed values, it corresponds to the options "-unit -prefix -byte_binary_prefix -sexagesimal".
- -output_format, -of, -print_format writer_name[=writer_options]
Set the output printing format.
writer_name specifies the name of the writer, and writer_options specifies the options to be passed to the writer.
For example for printing the output in JSON format, specify:
-output_format json
For more details on the available output printing formats, see the Writers section below.
- -sections
Print sections structure and section information, and exit. The output is not meant to be parsed by a machine.
- -select_streams stream_specifier
Select only the streams specified by stream_specifier. This option affects only the options related to streams (e.g.
show_streams
,show_packets
, etc.).For example to show only audio streams, you can use the command:
ffprobe -show_streams -select_streams a INPUT
To show only video packets belonging to the video stream with index 1:
ffprobe -show_packets -select_streams v:1 INPUT
- -show_data
Show payload data, as a hexadecimal and ASCII dump. Coupled with -show_packets, it will dump the packets’ data. Coupled with -show_streams, it will dump the codec extradata.
The dump is printed as the "data" field. It may contain newlines.
- -show_data_hash algorithm
Show a hash of payload data, for packets with -show_packets and for codec extradata with -show_streams.
- -show_error
Show information about the error found when trying to probe the input.
The error information is printed within a section with name "ERROR".
- -show_format
Show information about the container format of the input multimedia stream.
All the container format information is printed within a section with name "FORMAT".
- -show_format_entry name
Like -show_format, but only prints the specified entry of the container format information, rather than all. This option may be given more than once, then all specified entries will be shown.
This option is deprecated, use
show_entries
instead.- -show_entries section_entries
Set list of entries to show.
Entries are specified according to the following syntax. section_entries contains a list of section entries separated by
:
. Each section entry is composed by a section name (or unique name), optionally followed by a list of entries local to that section, separated by,
.If section name is specified but is followed by no
=
, all entries are printed to output, together with all the contained sections. Otherwise only the entries specified in the local section entries list are printed. In particular, if=
is specified but the list of local entries is empty, then no entries will be shown for that section.Note that the order of specification of the local section entries is not honored in the output, and the usual display order will be retained.
The formal syntax is given by:
LOCAL_SECTION_ENTRIES ::= SECTION_ENTRY_NAME[,LOCAL_SECTION_ENTRIES] SECTION_ENTRY ::= SECTION_NAME[=[LOCAL_SECTION_ENTRIES]] SECTION_ENTRIES ::= SECTION_ENTRY[:SECTION_ENTRIES]
For example, to show only the index and type of each stream, and the PTS time, duration time, and stream index of the packets, you can specify the argument:
packet=pts_time,duration_time,stream_index : stream=index,codec_type
To show all the entries in the section "format", but only the codec type in the section "stream", specify the argument:
format : stream=codec_type
To show all the tags in the stream and format sections:
stream_tags : format_tags
To show only the
title
tag (if available) in the stream sections:stream_tags=title
- -show_packets
Show information about each packet contained in the input multimedia stream.
The information for each single packet is printed within a dedicated section with name "PACKET".
- -show_frames
Show information about each frame and subtitle contained in the input multimedia stream.
The information for each single frame is printed within a dedicated section with name "FRAME" or "SUBTITLE".
- -show_log loglevel
Show logging information from the decoder about each frame according to the value set in loglevel, (see
-loglevel
). This option requires-show_frames
.The information for each log message is printed within a dedicated section with name "LOG".
- -show_streams
Show information about each media stream contained in the input multimedia stream.
Each media stream information is printed within a dedicated section with name "STREAM".
- -show_programs
Show information about programs and their streams contained in the input multimedia stream.
Each media stream information is printed within a dedicated section with name "PROGRAM_STREAM".
- -show_stream_groups
Show information about stream groups and their streams contained in the input multimedia stream.
Each media stream information is printed within a dedicated section with name "STREAM_GROUP_STREAM".
- -show_chapters
Show information about chapters stored in the format.
Each chapter is printed within a dedicated section with name "CHAPTER".
- -count_frames
Count the number of frames per stream and report it in the corresponding stream section.
- -count_packets
Count the number of packets per stream and report it in the corresponding stream section.
- -read_intervals read_intervals
-
Read only the specified intervals. read_intervals must be a sequence of interval specifications separated by ",".
ffprobe
will seek to the interval starting point, and will continue reading from that.Each interval is specified by two optional parts, separated by "%".
The first part specifies the interval start position. It is interpreted as an absolute position, or as a relative offset from the current position if it is preceded by the "+" character. If this first part is not specified, no seeking will be performed when reading this interval.
The second part specifies the interval end position. It is interpreted as an absolute position, or as a relative offset from the current position if it is preceded by the "+" character. If the offset specification starts with "#", it is interpreted as the number of packets to read (not including the flushing packets) from the interval start. If no second part is specified, the program will read until the end of the input.
Note that seeking is not accurate, thus the actual interval start point may be different from the specified position. Also, when an interval duration is specified, the absolute end time will be computed by adding the duration to the interval start point found by seeking the file, rather than to the specified start value.
The formal syntax is given by:
INTERVAL ::= [START|+START_OFFSET][%[END|+END_OFFSET]] INTERVALS ::= INTERVAL[,INTERVALS]
A few examples follow.
- Seek to time 10, read packets until 20 seconds after the found seek
point, then seek to position
01:30
(1 minute and thirty seconds) and read packets until position01:45
.10%+20,01:30%01:45
- Read only 42 packets after seeking to position
01:23
:01:23%+#42
- Read only the first 20 seconds from the start:
%+20
- Read from the start until position
02:30
:%02:30
- Seek to time 10, read packets until 20 seconds after the found seek
point, then seek to position
- -show_private_data, -private
Show private data, that is data depending on the format of the particular shown element. This option is enabled by default, but you may need to disable it for specific uses, for example when creating XSD-compliant XML output.
- -show_program_version
Show information related to program version.
Version information is printed within a section with name "PROGRAM_VERSION".
- -show_library_versions
Show information related to library versions.
Version information for each library is printed within a section with name "LIBRARY_VERSION".
- -show_versions
Show information related to program and library versions. This is the equivalent of setting both -show_program_version and -show_library_versions options.
- -show_pixel_formats
Show information about all pixel formats supported by FFmpeg.
Pixel format information for each format is printed within a section with name "PIXEL_FORMAT".
- -show_optional_fields value
Some writers viz. JSON and XML, omit the printing of fields with invalid or non-applicable values, while other writers always print them. This option enables one to control this behaviour. Valid values are
always
/1
,never
/0
andauto
/-1
. Default is auto.- -bitexact
Force bitexact output, useful to produce output which is not dependent on the specific build.
- -i input_url
Read input_url.
- -o output_url
Write output to output_url. If not specified, the output is sent to stdout.
4 Writers
A writer defines the output format adopted by ffprobe
, and will be
used for printing all the parts of the output.
A writer may accept one or more arguments, which specify the options to adopt. The options are specified as a list of key=value pairs, separated by ":".
All writers support the following options:
- string_validation, sv
Set string validation mode.
The following values are accepted.
- ‘fail’
The writer will fail immediately in case an invalid string (UTF-8) sequence or code point is found in the input. This is especially useful to validate input metadata.
- ‘ignore’
Any validation error will be ignored. This will result in possibly broken output, especially with the json or xml writer.
- ‘replace’
The writer will substitute invalid UTF-8 sequences or code points with the string specified with the string_validation_replacement.
Default value is ‘replace’.
- string_validation_replacement, svr
Set replacement string to use in case string_validation is set to ‘replace’.
In case the option is not specified, the writer will assume the empty string, that is it will remove the invalid sequences from the input strings.
A description of the currently available writers follows.
4.1 default
Default format.
Print each section in the form:
[SECTION] key1=val1 ... keyN=valN [/SECTION]
Metadata tags are printed as a line in the corresponding FORMAT, STREAM, STREAM_GROUP_STREAM or PROGRAM_STREAM section, and are prefixed by the string "TAG:".
A description of the accepted options follows.
- nokey, nk
If set to 1 specify not to print the key of each field. Default value is 0.
- noprint_wrappers, nw
If set to 1 specify not to print the section header and footer. Default value is 0.
4.2 compact, csv
Compact and CSV format.
The csv
writer is equivalent to compact
, but supports
different defaults.
Each section is printed on a single line. If no option is specified, the output has the form:
section|key1=val1| ... |keyN=valN
Metadata tags are printed in the corresponding "format" or "stream" section. A metadata tag key, if printed, is prefixed by the string "tag:".
The description of the accepted options follows.
- item_sep, s
Specify the character to use for separating fields in the output line. It must be a single printable character, it is "|" by default ("," for the
csv
writer).- nokey, nk
If set to 1 specify not to print the key of each field. Its default value is 0 (1 for the
csv
writer).- escape, e
Set the escape mode to use, default to "c" ("csv" for the
csv
writer).It can assume one of the following values:
- c
Perform C-like escaping. Strings containing a newline (‘\n’), carriage return (‘\r’), a tab (‘\t’), a form feed (‘\f’), the escaping character (‘\’) or the item separator character SEP are escaped using C-like fashioned escaping, so that a newline is converted to the sequence ‘\n’, a carriage return to ‘\r’, ‘\’ to ‘\\’ and the separator SEP is converted to ‘\SEP’.
- csv
Perform CSV-like escaping, as described in RFC4180. Strings containing a newline (‘\n’), a carriage return (‘\r’), a double quote (‘"’), or SEP are enclosed in double-quotes.
- none
Perform no escaping.
- print_section, p
Print the section name at the beginning of each line if the value is
1
, disable it with value set to0
. Default value is1
.
4.3 flat
Flat format.
A free-form output where each line contains an explicit key=value, such as "streams.stream.3.tags.foo=bar". The output is shell escaped, so it can be directly embedded in sh scripts as long as the separator character is an alphanumeric character or an underscore (see sep_char option).
The description of the accepted options follows.
- sep_char, s
Separator character used to separate the chapter, the section name, IDs and potential tags in the printed field key.
Default value is ‘.’.
- hierarchical, h
Specify if the section name specification should be hierarchical. If set to 1, and if there is more than one section in the current chapter, the section name will be prefixed by the name of the chapter. A value of 0 will disable this behavior.
Default value is 1.
4.4 ini
INI format output.
Print output in an INI based format.
The following conventions are adopted:
- all key and values are UTF-8
- ‘.’ is the subgroup separator
- newline, ‘\t’, ‘\f’, ‘\b’ and the following characters are escaped
- ‘\’ is the escape character
- ‘#’ is the comment indicator
- ‘=’ is the key/value separator
- ‘:’ is not used but usually parsed as key/value separator
This writer accepts options as a list of key=value pairs, separated by ‘:’.
The description of the accepted options follows.
- hierarchical, h
Specify if the section name specification should be hierarchical. If set to 1, and if there is more than one section in the current chapter, the section name will be prefixed by the name of the chapter. A value of 0 will disable this behavior.
Default value is 1.
4.5 json
JSON based format.
Each section is printed using JSON notation.
The description of the accepted options follows.
- compact, c
If set to 1 enable compact output, that is each section will be printed on a single line. Default value is 0.
For more information about JSON, see http://www.json.org/.
4.6 xml
XML based format.
The XML output is described in the XML schema description file ffprobe.xsd installed in the FFmpeg datadir.
An updated version of the schema can be retrieved at the url http://www.ffmpeg.org/schema/ffprobe.xsd, which redirects to the latest schema committed into the FFmpeg development source code tree.
Note that the output issued will be compliant to the ffprobe.xsd schema only when no special global output options (unit, prefix, byte_binary_prefix, sexagesimal etc.) are specified.
The description of the accepted options follows.
- fully_qualified, q
If set to 1 specify if the output should be fully qualified. Default value is 0. This is required for generating an XML file which can be validated through an XSD file.
- xsd_strict, x
If set to 1 perform more checks for ensuring that the output is XSD compliant. Default value is 0. This option automatically sets fully_qualified to 1.
For more information about the XML format, see https://www.w3.org/XML/.
5 Timecode
ffprobe
supports Timecode extraction:
- MPEG1/2 timecode is extracted from the GOP, and is available in the video stream details (-show_streams, see timecode).
- MOV timecode is extracted from tmcd track, so is available in the tmcd stream metadata (-show_streams, see TAG:timecode).
- DV, GXF and AVI timecodes are available in format metadata (-show_format, see TAG:timecode).
6 Syntax
This section documents the syntax and formats employed by the FFmpeg libraries and tools.
6.1 Quoting and escaping
FFmpeg adopts the following quoting and escaping mechanism, unless explicitly specified. The following rules are applied:
- ‘'’ and ‘\’ are special characters (respectively used for quoting and escaping). In addition to them, there might be other special characters depending on the specific syntax where the escaping and quoting are employed.
- A special character is escaped by prefixing it with a ‘\’.
- All characters enclosed between ‘''’ are included literally in the parsed string. The quote character ‘'’ itself cannot be quoted, so you may need to close the quote and escape it.
- Leading and trailing whitespaces, unless escaped or quoted, are removed from the parsed string.
Note that you may need to add a second level of escaping when using the command line or a script, which depends on the syntax of the adopted shell language.
The function av_get_token
defined in
libavutil/avstring.h can be used to parse a token quoted or
escaped according to the rules defined above.
The tool tools/ffescape in the FFmpeg source tree can be used to automatically quote or escape a string in a script.
6.1.1 Examples
- Escape the string
Crime d'Amour
containing the'
special character:Crime d\'Amour
- The string above contains a quote, so the
'
needs to be escaped when quoting it:'Crime d'\''Amour'
- Include leading or trailing whitespaces using quoting:
' this string starts and ends with whitespaces '
- Escaping and quoting can be mixed together:
' The string '\'string\'' is a string '
- To include a literal ‘\’ you can use either escaping or quoting:
'c:\foo' can be written as c:\\foo
6.2 Date
The accepted syntax is:
[(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z] now
If the value is "now" it takes the current time.
Time is local time unless Z is appended, in which case it is interpreted as UTC. If the year-month-day part is not specified it takes the current year-month-day.
6.3 Time duration
There are two accepted syntaxes for expressing time duration.
[-][HH:]MM:SS[.m...]
HH expresses the number of hours, MM the number of minutes for a maximum of 2 digits, and SS the number of seconds for a maximum of 2 digits. The m at the end expresses decimal value for SS.
or
[-]S+[.m...][s|ms|us]
S expresses the number of seconds, with the optional decimal part m. The optional literal suffixes ‘s’, ‘ms’ or ‘us’ indicate to interpret the value as seconds, milliseconds or microseconds, respectively.
In both expressions, the optional ‘-’ indicates negative duration.
6.3.1 Examples
The following examples are all valid time duration:
- ‘55’
55 seconds
- ‘0.2’
0.2 seconds
- ‘200ms’
200 milliseconds, that’s 0.2s
- ‘200000us’
200000 microseconds, that’s 0.2s
- ‘12:03:45’
12 hours, 03 minutes and 45 seconds
- ‘23.189’
23.189 seconds
6.4 Video size
Specify the size of the sourced video, it may be a string of the form widthxheight, or the name of a size abbreviation.
The following abbreviations are recognized:
- ‘ntsc’
720x480
- ‘pal’
720x576
- ‘qntsc’
352x240
- ‘qpal’
352x288
- ‘sntsc’
640x480
- ‘spal’
768x576
- ‘film’
352x240
- ‘ntsc-film’
352x240
- ‘sqcif’
128x96
- ‘qcif’
176x144
- ‘cif’
352x288
- ‘4cif’
704x576
- ‘16cif’
1408x1152
- ‘qqvga’
160x120
- ‘qvga’
320x240
- ‘vga’
640x480
- ‘svga’
800x600
- ‘xga’
1024x768
- ‘uxga’
1600x1200
- ‘qxga’
2048x1536
- ‘sxga’
1280x1024
- ‘qsxga’
2560x2048
- ‘hsxga’
5120x4096
- ‘wvga’
852x480
- ‘wxga’
1366x768
- ‘wsxga’
1600x1024
- ‘wuxga’
1920x1200
- ‘woxga’
2560x1600
- ‘wqsxga’
3200x2048
- ‘wquxga’
3840x2400
- ‘whsxga’
6400x4096
- ‘whuxga’
7680x4800
- ‘cga’
320x200
- ‘ega’
640x350
- ‘hd480’
852x480
- ‘hd720’
1280x720
- ‘hd1080’
1920x1080
- ‘2k’
2048x1080
- ‘2kflat’
1998x1080
- ‘2kscope’
2048x858
- ‘4k’
4096x2160
- ‘4kflat’
3996x2160
- ‘4kscope’
4096x1716
- ‘nhd’
640x360
- ‘hqvga’
240x160
- ‘wqvga’
400x240
- ‘fwqvga’
432x240
- ‘hvga’
480x320
- ‘qhd’
960x540
- ‘2kdci’
2048x1080
- ‘4kdci’
4096x2160
- ‘uhd2160’
3840x2160
- ‘uhd4320’
7680x4320
6.5 Video rate
Specify the frame rate of a video, expressed as the number of frames generated per second. It has to be a string in the format frame_rate_num/frame_rate_den, an integer number, a float number or a valid video frame rate abbreviation.
The following abbreviations are recognized:
- ‘ntsc’
30000/1001
- ‘pal’
25/1
- ‘qntsc’
30000/1001
- ‘qpal’
25/1
- ‘sntsc’
30000/1001
- ‘spal’
25/1
- ‘film’
24/1
- ‘ntsc-film’
24000/1001
6.6 Ratio
A ratio can be expressed as an expression, or in the form numerator:denominator.
Note that a ratio with infinite (1/0) or negative value is considered valid, so you should check on the returned value if you want to exclude those values.
The undefined value can be expressed using the "0:0" string.
6.7 Color
It can be the name of a color as defined below (case insensitive match) or a
[0x|#]RRGGBB[AA]
sequence, possibly followed by @ and a string
representing the alpha component.
The alpha component may be a string composed by "0x" followed by an hexadecimal number or a decimal number between 0.0 and 1.0, which represents the opacity value (‘0x00’ or ‘0.0’ means completely transparent, ‘0xff’ or ‘1.0’ completely opaque). If the alpha component is not specified then ‘0xff’ is assumed.
The string ‘random’ will result in a random color.
The following names of colors are recognized:
- ‘AliceBlue’
0xF0F8FF
- ‘AntiqueWhite’
0xFAEBD7
- ‘Aqua’
0x00FFFF
- ‘Aquamarine’
0x7FFFD4
- ‘Azure’
0xF0FFFF
- ‘Beige’
0xF5F5DC
- ‘Bisque’
0xFFE4C4
- ‘Black’
0x000000
- ‘BlanchedAlmond’
0xFFEBCD
- ‘Blue’
0x0000FF
- ‘BlueViolet’
0x8A2BE2
- ‘Brown’
0xA52A2A
- ‘BurlyWood’
0xDEB887
- ‘CadetBlue’
0x5F9EA0
- ‘Chartreuse’
0x7FFF00
- ‘Chocolate’
0xD2691E
- ‘Coral’
0xFF7F50
- ‘CornflowerBlue’
0x6495ED
- ‘Cornsilk’
0xFFF8DC
- ‘Crimson’
0xDC143C
- ‘Cyan’
0x00FFFF
- ‘DarkBlue’
0x00008B
- ‘DarkCyan’
0x008B8B
- ‘DarkGoldenRod’
0xB8860B
- ‘DarkGray’
0xA9A9A9
- ‘DarkGreen’
0x006400
- ‘DarkKhaki’
0xBDB76B
- ‘DarkMagenta’
0x8B008B
- ‘DarkOliveGreen’
0x556B2F
- ‘Darkorange’
0xFF8C00
- ‘DarkOrchid’
0x9932CC
- ‘DarkRed’
0x8B0000
- ‘DarkSalmon’
0xE9967A
- ‘DarkSeaGreen’
0x8FBC8F
- ‘DarkSlateBlue’
0x483D8B
- ‘DarkSlateGray’
0x2F4F4F
- ‘DarkTurquoise’
0x00CED1
- ‘DarkViolet’
0x9400D3
- ‘DeepPink’
0xFF1493
- ‘DeepSkyBlue’
0x00BFFF
- ‘DimGray’
0x696969
- ‘DodgerBlue’
0x1E90FF
- ‘FireBrick’
0xB22222
- ‘FloralWhite’
0xFFFAF0
- ‘ForestGreen’
0x228B22
- ‘Fuchsia’
0xFF00FF
- ‘Gainsboro’
0xDCDCDC
- ‘GhostWhite’
0xF8F8FF
- ‘Gold’
0xFFD700
- ‘GoldenRod’
0xDAA520
- ‘Gray’
0x808080
- ‘Green’
0x008000
- ‘GreenYellow’
0xADFF2F
- ‘HoneyDew’
0xF0FFF0
- ‘HotPink’
0xFF69B4
- ‘IndianRed’
0xCD5C5C
- ‘Indigo’
0x4B0082
- ‘Ivory’
0xFFFFF0
- ‘Khaki’
0xF0E68C
- ‘Lavender’
0xE6E6FA
- ‘LavenderBlush’
0xFFF0F5
- ‘LawnGreen’
0x7CFC00
- ‘LemonChiffon’
0xFFFACD
- ‘LightBlue’
0xADD8E6
- ‘LightCoral’
0xF08080
- ‘LightCyan’
0xE0FFFF
- ‘LightGoldenRodYellow’
0xFAFAD2
- ‘LightGreen’
0x90EE90
- ‘LightGrey’
0xD3D3D3
- ‘LightPink’
0xFFB6C1
- ‘LightSalmon’
0xFFA07A
- ‘LightSeaGreen’
0x20B2AA
- ‘LightSkyBlue’
0x87CEFA
- ‘LightSlateGray’
0x778899
- ‘LightSteelBlue’
0xB0C4DE
- ‘LightYellow’
0xFFFFE0
- ‘Lime’
0x00FF00
- ‘LimeGreen’
0x32CD32
- ‘Linen’
0xFAF0E6
- ‘Magenta’
0xFF00FF
- ‘Maroon’
0x800000
- ‘MediumAquaMarine’
0x66CDAA
- ‘MediumBlue’
0x0000CD
- ‘MediumOrchid’
0xBA55D3
- ‘MediumPurple’
0x9370D8
- ‘MediumSeaGreen’
0x3CB371
- ‘MediumSlateBlue’
0x7B68EE
- ‘MediumSpringGreen’
0x00FA9A
- ‘MediumTurquoise’
0x48D1CC
- ‘MediumVioletRed’
0xC71585
- ‘MidnightBlue’
0x191970
- ‘MintCream’
0xF5FFFA
- ‘MistyRose’
0xFFE4E1
- ‘Moccasin’
0xFFE4B5
- ‘NavajoWhite’
0xFFDEAD
- ‘Navy’
0x000080
- ‘OldLace’
0xFDF5E6
- ‘Olive’
0x808000
- ‘OliveDrab’
0x6B8E23
- ‘Orange’
0xFFA500
- ‘OrangeRed’
0xFF4500
- ‘Orchid’
0xDA70D6
- ‘PaleGoldenRod’
0xEEE8AA
- ‘PaleGreen’
0x98FB98
- ‘PaleTurquoise’
0xAFEEEE
- ‘PaleVioletRed’
0xD87093
- ‘PapayaWhip’
0xFFEFD5
- ‘PeachPuff’
0xFFDAB9
- ‘Peru’
0xCD853F
- ‘Pink’
0xFFC0CB
- ‘Plum’
0xDDA0DD
- ‘PowderBlue’
0xB0E0E6
- ‘Purple’
0x800080
- ‘Red’
0xFF0000
- ‘RosyBrown’
0xBC8F8F
- ‘RoyalBlue’
0x4169E1
- ‘SaddleBrown’
0x8B4513
- ‘Salmon’
0xFA8072
- ‘SandyBrown’
0xF4A460
- ‘SeaGreen’
0x2E8B57
- ‘SeaShell’
0xFFF5EE
- ‘Sienna’
0xA0522D
- ‘Silver’
0xC0C0C0
- ‘SkyBlue’
0x87CEEB
- ‘SlateBlue’
0x6A5ACD
- ‘SlateGray’
0x708090
- ‘Snow’
0xFFFAFA
- ‘SpringGreen’
0x00FF7F
- ‘SteelBlue’
0x4682B4
- ‘Tan’
0xD2B48C
- ‘Teal’
0x008080
- ‘Thistle’
0xD8BFD8
- ‘Tomato’
0xFF6347
- ‘Turquoise’
0x40E0D0
- ‘Violet’
0xEE82EE
- ‘Wheat’
0xF5DEB3
- ‘White’
0xFFFFFF
- ‘WhiteSmoke’
0xF5F5F5
- ‘Yellow’
0xFFFF00
- ‘YellowGreen’
0x9ACD32
6.8 Channel Layout
A channel layout specifies the spatial disposition of the channels in a multi-channel audio stream. To specify a channel layout, FFmpeg makes use of a special syntax.
Individual channels are identified by an id, as given by the table below:
- ‘FL’
front left
- ‘FR’
front right
- ‘FC’
front center
- ‘LFE’
low frequency
- ‘BL’
back left
- ‘BR’
back right
- ‘FLC’
front left-of-center
- ‘FRC’
front right-of-center
- ‘BC’
back center
- ‘SL’
side left
- ‘SR’
side right
- ‘TC’
top center
- ‘TFL’
top front left
- ‘TFC’
top front center
- ‘TFR’
top front right
- ‘TBL’
top back left
- ‘TBC’
top back center
- ‘TBR’
top back right
- ‘DL’
downmix left
- ‘DR’
downmix right
- ‘WL’
wide left
- ‘WR’
wide right
- ‘SDL’
surround direct left
- ‘SDR’
surround direct right
- ‘LFE2’
low frequency 2
Standard channel layout compositions can be specified by using the following identifiers:
- ‘mono’
FC
- ‘stereo’
FL+FR
- ‘2.1’
FL+FR+LFE
- ‘3.0’
FL+FR+FC
- ‘3.0(back)’
FL+FR+BC
- ‘4.0’
FL+FR+FC+BC
- ‘quad’
FL+FR+BL+BR
- ‘quad(side)’
FL+FR+SL+SR
- ‘3.1’
FL+FR+FC+LFE
- ‘5.0’
FL+FR+FC+BL+BR
- ‘5.0(side)’
FL+FR+FC+SL+SR
- ‘4.1’
FL+FR+FC+LFE+BC
- ‘5.1’
FL+FR+FC+LFE+BL+BR
- ‘5.1(side)’
FL+FR+FC+LFE+SL+SR
- ‘6.0’
FL+FR+FC+BC+SL+SR
- ‘6.0(front)’
FL+FR+FLC+FRC+SL+SR
- ‘3.1.2’
FL+FR+FC+LFE+TFL+TFR
- ‘hexagonal’
FL+FR+FC+BL+BR+BC
- ‘6.1’
FL+FR+FC+LFE+BC+SL+SR
- ‘6.1’
FL+FR+FC+LFE+BL+BR+BC
- ‘6.1(front)’
FL+FR+LFE+FLC+FRC+SL+SR
- ‘7.0’
FL+FR+FC+BL+BR+SL+SR
- ‘7.0(front)’
FL+FR+FC+FLC+FRC+SL+SR
- ‘7.1’
FL+FR+FC+LFE+BL+BR+SL+SR
- ‘7.1(wide)’
FL+FR+FC+LFE+BL+BR+FLC+FRC
- ‘7.1(wide-side)’
FL+FR+FC+LFE+FLC+FRC+SL+SR
- ‘5.1.2’
FL+FR+FC+LFE+BL+BR+TFL+TFR
- ‘octagonal’
FL+FR+FC+BL+BR+BC+SL+SR
- ‘cube’
FL+FR+BL+BR+TFL+TFR+TBL+TBR
- ‘5.1.4’
FL+FR+FC+LFE+BL+BR+TFL+TFR+TBL+TBR
- ‘7.1.2’
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR
- ‘7.1.4’
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR+TBL+TBR
- ‘7.2.3’
FL+FR+FC+LFE+BL+BR+SL+SR+TFL+TFR+TBC+LFE2
- ‘9.1.4’
FL+FR+FC+LFE+BL+BR+FLC+FRC+SL+SR+TFL+TFR+TBL+TBR
- ‘hexadecagonal’
FL+FR+FC+BL+BR+BC+SL+SR+WL+WR+TBL+TBR+TBC+TFC+TFL+TFR
- ‘downmix’
DL+DR
- ‘22.2’
FL+FR+FC+LFE+BL+BR+FLC+FRC+BC+SL+SR+TC+TFL+TFC+TFR+TBL+TBC+TBR+LFE2+TSL+TSR+BFC+BFL+BFR
A custom channel layout can be specified as a sequence of terms, separated by ’+’. Each term can be:
- the name of a single channel (e.g. ‘FL’, ‘FR’, ‘FC’, ‘LFE’, etc.), each optionally containing a custom name after a ’@’, (e.g. ‘FL@Left’, ‘FR@Right’, ‘FC@Center’, ‘LFE@Low_Frequency’, etc.)
A standard channel layout can be specified by the following:
- the name of a single channel (e.g. ‘FL’, ‘FR’, ‘FC’, ‘LFE’, etc.)
- the name of a standard channel layout (e.g. ‘mono’, ‘stereo’, ‘4.0’, ‘quad’, ‘5.0’, etc.)
- a number of channels, in decimal, followed by ’c’, yielding the default channel
layout for that number of channels (see the function
av_channel_layout_default
). Note that not all channel counts have a default layout. - a number of channels, in decimal, followed by ’C’, yielding an unknown channel layout with the specified number of channels. Note that not all channel layout specification strings support unknown channel layouts.
- a channel layout mask, in hexadecimal starting with "0x" (see the
AV_CH_*
macros in libavutil/channel_layout.h.
Before libavutil version 53 the trailing character "c" to specify a number of channels was optional, but now it is required, while a channel layout mask can also be specified as a decimal number (if and only if not followed by "c" or "C").
See also the function av_channel_layout_from_string
defined in
libavutil/channel_layout.h.
7 Expression Evaluation
When evaluating an arithmetic expression, FFmpeg uses an internal formula evaluator, implemented through the libavutil/eval.h interface.
An expression may contain unary, binary operators, constants, and functions.
Two expressions expr1 and expr2 can be combined to form another expression "expr1;expr2". expr1 and expr2 are evaluated in turn, and the new expression evaluates to the value of expr2.
The following binary operators are available: +
, -
,
*
, /
, ^
.
The following unary operators are available: +
, -
.
Some internal variables can be used to store and load intermediary
results. They can be accessed using the ld
and st
functions with an index argument varying from 0 to 9 to specify which
internal variable to access.
The following functions are available:
- abs(x)
Compute absolute value of x.
- acos(x)
Compute arccosine of x.
- asin(x)
Compute arcsine of x.
- atan(x)
Compute arctangent of x.
- atan2(y, x)
Compute principal value of the arc tangent of y/x.
- between(x, min, max)
Return 1 if x is greater than or equal to min and lesser than or equal to max, 0 otherwise.
- bitand(x, y)
- bitor(x, y)
Compute bitwise and/or operation on x and y.
The results of the evaluation of x and y are converted to integers before executing the bitwise operation.
Note that both the conversion to integer and the conversion back to floating point can lose precision. Beware of unexpected results for large numbers (usually 2^53 and larger).
- ceil(expr)
Round the value of expression expr upwards to the nearest integer. For example, "ceil(1.5)" is "2.0".
- clip(x, min, max)
Return the value of x clipped between min and max.
- cos(x)
Compute cosine of x.
- cosh(x)
Compute hyperbolic cosine of x.
- eq(x, y)
Return 1 if x and y are equivalent, 0 otherwise.
- exp(x)
Compute exponential of x (with base
e
, the Euler’s number).- floor(expr)
Round the value of expression expr downwards to the nearest integer. For example, "floor(-1.5)" is "-2.0".
- gauss(x)
Compute Gauss function of x, corresponding to
exp(-x*x/2) / sqrt(2*PI)
.- gcd(x, y)
Return the greatest common divisor of x and y. If both x and y are 0 or either or both are less than zero then behavior is undefined.
- gt(x, y)
Return 1 if x is greater than y, 0 otherwise.
- gte(x, y)
Return 1 if x is greater than or equal to y, 0 otherwise.
- hypot(x, y)
This function is similar to the C function with the same name; it returns "sqrt(x*x + y*y)", the length of the hypotenuse of a right triangle with sides of length x and y, or the distance of the point (x, y) from the origin.
- if(x, y)
Evaluate x, and if the result is non-zero return the result of the evaluation of y, return 0 otherwise.
- if(x, y, z)
Evaluate x, and if the result is non-zero return the evaluation result of y, otherwise the evaluation result of z.
- ifnot(x, y)
Evaluate x, and if the result is zero return the result of the evaluation of y, return 0 otherwise.
- ifnot(x, y, z)
Evaluate x, and if the result is zero return the evaluation result of y, otherwise the evaluation result of z.
- isinf(x)
Return 1.0 if x is +/-INFINITY, 0.0 otherwise.
- isnan(x)
Return 1.0 if x is NAN, 0.0 otherwise.
- ld(idx)
Load the value of the internal variable with index idx, which was previously stored with st(idx, expr). The function returns the loaded value.
- lerp(x, y, z)
Return linear interpolation between x and y by amount of z.
- log(x)
Compute natural logarithm of x.
- lt(x, y)
Return 1 if x is lesser than y, 0 otherwise.
- lte(x, y)
Return 1 if x is lesser than or equal to y, 0 otherwise.
- max(x, y)
Return the maximum between x and y.
- min(x, y)
Return the minimum between x and y.
- mod(x, y)
Compute the remainder of division of x by y.
- not(expr)
Return 1.0 if expr is zero, 0.0 otherwise.
- pow(x, y)
Compute the power of x elevated y, it is equivalent to "(x)^(y)".
- print(t)
- print(t, l)
Print the value of expression t with loglevel l. If l is not specified then a default log level is used. Return the value of the expression printed.
- random(idx)
Return a pseudo random value between 0.0 and 1.0. idx is the index of the internal variable used to save the seed/state, which can be previously stored with
st(idx)
.To initialize the seed, you need to store the seed value as a 64-bit unsigned integer in the internal variable with index idx.
For example, to store the seed with value
42
in the internal variable with index0
and print a few random values:st(0,42); print(random(0)); print(random(0)); print(random(0))
- randomi(idx, min, max)
Return a pseudo random value in the interval between min and max. idx is the index of the internal variable which will be used to save the seed/state, which can be previously stored with
st(idx)
.To initialize the seed, you need to store the seed value as a 64-bit unsigned integer in the internal variable with index idx.
- root(expr, max)
Find an input value for which the function represented by expr with argument ld(0) is 0 in the interval 0..max.
The expression in expr must denote a continuous function or the result is undefined.
ld(0) is used to represent the function input value, which means that the given expression will be evaluated multiple times with various input values that the expression can access through
ld(0)
. When the expression evaluates to 0 then the corresponding input value will be returned.- round(expr)
Round the value of expression expr to the nearest integer. For example, "round(1.5)" is "2.0".
- sgn(x)
Compute sign of x.
- sin(x)
Compute sine of x.
- sinh(x)
Compute hyperbolic sine of x.
- sqrt(expr)
Compute the square root of expr. This is equivalent to "(expr)^.5".
- squish(x)
Compute expression
1/(1 + exp(4*x))
.- st(idx, expr)
Store the value of the expression expr in an internal variable. idx specifies the index of the variable where to store the value, and it is a value ranging from 0 to 9. The function returns the value stored in the internal variable.
The stored value can be retrieved with
ld(var)
.Note: variables are currently not shared between expressions.
- tan(x)
Compute tangent of x.
- tanh(x)
Compute hyperbolic tangent of x.
- taylor(expr, x)
- taylor(expr, x, idx)
Evaluate a Taylor series at x, given an expression representing the
ld(idx)
-th derivative of a function at 0.When the series does not converge the result is undefined.
ld(idx) is used to represent the derivative order in expr, which means that the given expression will be evaluated multiple times with various input values that the expression can access through
ld(idx)
. If idx is not specified then 0 is assumed.Note, when you have the derivatives at y instead of 0,
taylor(expr, x-y)
can be used.- time(0)
Return the current (wallclock) time in seconds.
- trunc(expr)
Round the value of expression expr towards zero to the nearest integer. For example, "trunc(-1.5)" is "-1.0".
- while(cond, expr)
Evaluate expression expr while the expression cond is non-zero, and returns the value of the last expr evaluation, or NAN if cond was always false.
The following constants are available:
- PI
area of the unit disc, approximately 3.14
- E
exp(1) (Euler’s number), approximately 2.718
- PHI
golden ratio (1+sqrt(5))/2, approximately 1.618
Assuming that an expression is considered "true" if it has a non-zero value, note that:
*
works like AND
+
works like OR
For example the construct:
if (A AND B) then C
is equivalent to:
if(A*B, C)
In your C code, you can extend the list of unary and binary functions, and define recognized constants, so that they are available for your expressions.
The evaluator also recognizes the International System unit prefixes. If ’i’ is appended after the prefix, binary prefixes are used, which are based on powers of 1024 instead of powers of 1000. The ’B’ postfix multiplies the value by 8, and can be appended after a unit prefix or used alone. This allows using for example ’KB’, ’MiB’, ’G’ and ’B’ as number postfix.
The list of available International System prefixes follows, with indication of the corresponding powers of 10 and of 2.
- y
10^-24 / 2^-80
- z
10^-21 / 2^-70
- a
10^-18 / 2^-60
- f
10^-15 / 2^-50
- p
10^-12 / 2^-40
- n
10^-9 / 2^-30
- u
10^-6 / 2^-20
- m
10^-3 / 2^-10
- c
10^-2
- d
10^-1
- h
10^2
- k
10^3 / 2^10
- K
10^3 / 2^10
- M
10^6 / 2^20
- G
10^9 / 2^30
- T
10^12 / 2^40
- P
10^15 / 2^50
- E
10^18 / 2^60
- Z
10^21 / 2^70
- Y
10^24 / 2^80
8 Codec Options
libavcodec provides some generic global options, which can be set on all the encoders and decoders. In addition, each codec may support so-called private options, which are specific for a given codec.
Sometimes, a global option may only affect a specific kind of codec, and may be nonsensical or ignored by another, so you need to be aware of the meaning of the specified options. Also some options are meant only for decoding or encoding.
Options may be set by specifying -option value in the
FFmpeg tools, or by setting the value explicitly in the
AVCodecContext
options or using the libavutil/opt.h API
for programmatic use.
The list of supported options follow:
- b integer (encoding,audio,video)
Set bitrate in bits/s. Default value is 200K.
- ab integer (encoding,audio)
Set audio bitrate (in bits/s). Default value is 128K.
- bt integer (encoding,video)
Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate tolerance specifies how far ratecontrol is willing to deviate from the target average bitrate value. This is not related to min/max bitrate. Lowering tolerance too much has an adverse effect on quality.
- flags flags (decoding/encoding,audio,video,subtitles)
Set generic flags.
Possible values:
- ‘mv4’
Use four motion vector by macroblock (mpeg4).
- ‘qpel’
Use 1/4 pel motion compensation.
- ‘loop’
Use loop filter.
- ‘qscale’
Use fixed qscale.
- ‘pass1’
Use internal 2pass ratecontrol in first pass mode.
- ‘pass2’
Use internal 2pass ratecontrol in second pass mode.
- ‘gray’
Only decode/encode grayscale.
- ‘psnr’
Set error[?] variables during encoding.
- ‘truncated’
Input bitstream might be randomly truncated.
- ‘drop_changed’
Don’t output frames whose parameters differ from first decoded frame in stream. Error AVERROR_INPUT_CHANGED is returned when a frame is dropped.
- ‘ildct’
Use interlaced DCT.
- ‘low_delay’
Force low delay.
- ‘global_header’
Place global headers in extradata instead of every keyframe.
- ‘bitexact’
Only write platform-, build- and time-independent data. (except (I)DCT). This ensures that file and data checksums are reproducible and match between platforms. Its primary use is for regression testing.
- ‘aic’
Apply H263 advanced intra coding / mpeg4 ac prediction.
- ‘ilme’
Apply interlaced motion estimation.
- ‘cgop’
Use closed gop.
- ‘output_corrupt’
Output even potentially corrupted frames.
- time_base rational number
Set codec time base.
It is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented. For fixed-fps content, timebase should be
1 / frame_rate
and timestamp increments should be identically 1.- g integer (encoding,video)
Set the group of picture (GOP) size. Default value is 12.
- ar integer (decoding/encoding,audio)
Set audio sampling rate (in Hz).
- ac integer (decoding/encoding,audio)
Set number of audio channels.
- cutoff integer (encoding,audio)
Set cutoff bandwidth. (Supported only by selected encoders, see their respective documentation sections.)
- frame_size integer (encoding,audio)
Set audio frame size.
Each submitted frame except the last must contain exactly frame_size samples per channel. May be 0 when the codec has CODEC_CAP_VARIABLE_FRAME_SIZE set, in that case the frame size is not restricted. It is set by some decoders to indicate constant frame size.
- frame_number integer
Set the frame number.
- delay integer
- qcomp float (encoding,video)
Set video quantizer scale compression (VBR). It is used as a constant in the ratecontrol equation. Recommended range for default rc_eq: 0.0-1.0.
- qblur float (encoding,video)
Set video quantizer scale blur (VBR).
- qmin integer (encoding,video)
Set min video quantizer scale (VBR). Must be included between -1 and 69, default value is 2.
- qmax integer (encoding,video)
Set max video quantizer scale (VBR). Must be included between -1 and 1024, default value is 31.
- qdiff integer (encoding,video)
Set max difference between the quantizer scale (VBR).
- bf integer (encoding,video)
Set max number of B frames between non-B-frames.
Must be an integer between -1 and 16. 0 means that B-frames are disabled. If a value of -1 is used, it will choose an automatic value depending on the encoder.
Default value is 0.
- b_qfactor float (encoding,video)
Set qp factor between P and B frames.
- codec_tag integer
- bug flags (decoding,video)
Workaround not auto detected encoder bugs.
Possible values:
- ‘autodetect’
- ‘xvid_ilace’
Xvid interlacing bug (autodetected if fourcc==XVIX)
- ‘ump4’
(autodetected if fourcc==UMP4)
- ‘no_padding’
padding bug (autodetected)
- ‘amv’
- ‘qpel_chroma’
- ‘std_qpel’
old standard qpel (autodetected per fourcc/version)
- ‘qpel_chroma2’
- ‘direct_blocksize’
direct-qpel-blocksize bug (autodetected per fourcc/version)
- ‘edge’
edge padding bug (autodetected per fourcc/version)
- ‘hpel_chroma’
- ‘dc_clip’
- ‘ms’
Workaround various bugs in microsoft broken decoders.
- ‘trunc’
trancated frames
- strict integer (decoding/encoding,audio,video)
Specify how strictly to follow the standards.
Possible values:
- ‘very’
strictly conform to an older more strict version of the spec or reference software
- ‘strict’
strictly conform to all the things in the spec no matter what consequences
- ‘normal’
- ‘unofficial’
allow unofficial extensions
- ‘experimental’
allow non standardized experimental things, experimental (unfinished/work in progress/not well tested) decoders and encoders. Note: experimental decoders can pose a security risk, do not use this for decoding untrusted input.
- b_qoffset float (encoding,video)
Set QP offset between P and B frames.
- err_detect flags (decoding,audio,video)
Set error detection flags.
Possible values:
- ‘crccheck’
verify embedded CRCs
- ‘bitstream’
detect bitstream specification deviations
- ‘buffer’
detect improper bitstream length
- ‘explode’
abort decoding on minor error detection
- ‘ignore_err’
ignore decoding errors, and continue decoding. This is useful if you want to analyze the content of a video and thus want everything to be decoded no matter what. This option will not result in a video that is pleasing to watch in case of errors.
- ‘careful’
consider things that violate the spec and have not been seen in the wild as errors
- ‘compliant’
consider all spec non compliancies as errors
- ‘aggressive’
consider things that a sane encoder should not do as an error
- has_b_frames integer
- block_align integer
- rc_override_count integer
- maxrate integer (encoding,audio,video)
Set max bitrate tolerance (in bits/s). Requires bufsize to be set.
- minrate integer (encoding,audio,video)
Set min bitrate tolerance (in bits/s). Most useful in setting up a CBR encode. It is of little use elsewise.
- bufsize integer (encoding,audio,video)
Set ratecontrol buffer size (in bits).
- i_qfactor float (encoding,video)
Set QP factor between P and I frames.
- i_qoffset float (encoding,video)
Set QP offset between P and I frames.
- dct integer (encoding,video)
Set DCT algorithm.
Possible values:
- ‘auto’
autoselect a good one (default)
- ‘fastint’
fast integer
- ‘int’
accurate integer
- ‘mmx’
- ‘altivec’
- ‘faan’
floating point AAN DCT
- lumi_mask float (encoding,video)
Compress bright areas stronger than medium ones.
- tcplx_mask float (encoding,video)
Set temporal complexity masking.
- scplx_mask float (encoding,video)
Set spatial complexity masking.
- p_mask float (encoding,video)
Set inter masking.
- dark_mask float (encoding,video)
Compress dark areas stronger than medium ones.
- idct integer (decoding/encoding,video)
Select IDCT implementation.
Possible values:
- ‘auto’
- ‘int’
- ‘simple’
- ‘simplemmx’
- ‘simpleauto’
Automatically pick a IDCT compatible with the simple one
- ‘arm’
- ‘altivec’
- ‘sh4’
- ‘simplearm’
- ‘simplearmv5te’
- ‘simplearmv6’
- ‘simpleneon’
- ‘xvid’
- ‘faani’
floating point AAN IDCT
- slice_count integer
- ec flags (decoding,video)
Set error concealment strategy.
Possible values:
- ‘guess_mvs’
iterative motion vector (MV) search (slow)
- ‘deblock’
use strong deblock filter for damaged MBs
- ‘favor_inter’
favor predicting from the previous frame instead of the current
- bits_per_coded_sample integer
- aspect rational number (encoding,video)
Set sample aspect ratio.
- sar rational number (encoding,video)
Set sample aspect ratio. Alias to aspect.
- debug flags (decoding/encoding,audio,video,subtitles)
Print specific debug info.
Possible values:
- ‘pict’
picture info
- ‘rc’
rate control
- ‘bitstream’
- ‘mb_type’
macroblock (MB) type
- ‘qp’
per-block quantization parameter (QP)
- ‘dct_coeff’
- ‘green_metadata’
display complexity metadata for the upcoming frame, GoP or for a given duration.
- ‘skip’
- ‘startcode’
- ‘er’
error recognition
- ‘mmco’
memory management control operations (H.264)
- ‘bugs’
- ‘buffers’
picture buffer allocations
- ‘thread_ops’
threading operations
- ‘nomc’
skip motion compensation
- cmp integer (encoding,video)
Set full pel me compare function.
Possible values:
- ‘sad’
sum of absolute differences, fast (default)
- ‘sse’
sum of squared errors
- ‘satd’
sum of absolute Hadamard transformed differences
- ‘dct’
sum of absolute DCT transformed differences
- ‘psnr’
sum of squared quantization errors (avoid, low quality)
- ‘bit’
number of bits needed for the block
- ‘rd’
rate distortion optimal, slow
- ‘zero’
0
- ‘vsad’
sum of absolute vertical differences
- ‘vsse’
sum of squared vertical differences
- ‘nsse’
noise preserving sum of squared differences
- ‘w53’
5/3 wavelet, only used in snow
- ‘w97’
9/7 wavelet, only used in snow
- ‘dctmax’
- ‘chroma’
- subcmp integer (encoding,video)
Set sub pel me compare function.
Possible values:
- ‘sad’
sum of absolute differences, fast (default)
- ‘sse’
sum of squared errors
- ‘satd’
sum of absolute Hadamard transformed differences
- ‘dct’
sum of absolute DCT transformed differences
- ‘psnr’
sum of squared quantization errors (avoid, low quality)
- ‘bit’
number of bits needed for the block
- ‘rd’
rate distortion optimal, slow
- ‘zero’
0
- ‘vsad’
sum of absolute vertical differences
- ‘vsse’
sum of squared vertical differences
- ‘nsse’
noise preserving sum of squared differences
- ‘w53’
5/3 wavelet, only used in snow
- ‘w97’
9/7 wavelet, only used in snow
- ‘dctmax’
- ‘chroma’
- mbcmp integer (encoding,video)
Set macroblock compare function.
Possible values:
- ‘sad’
sum of absolute differences, fast (default)
- ‘sse’
sum of squared errors
- ‘satd’
sum of absolute Hadamard transformed differences
- ‘dct’
sum of absolute DCT transformed differences
- ‘psnr’
sum of squared quantization errors (avoid, low quality)
- ‘bit’
number of bits needed for the block
- ‘rd’
rate distortion optimal, slow
- ‘zero’
0
- ‘vsad’
sum of absolute vertical differences
- ‘vsse’
sum of squared vertical differences
- ‘nsse’
noise preserving sum of squared differences
- ‘w53’
5/3 wavelet, only used in snow
- ‘w97’
9/7 wavelet, only used in snow
- ‘dctmax’
- ‘chroma’
- ildctcmp integer (encoding,video)
Set interlaced dct compare function.
Possible values:
- ‘sad’
sum of absolute differences, fast (default)
- ‘sse’
sum of squared errors
- ‘satd’
sum of absolute Hadamard transformed differences
- ‘dct’
sum of absolute DCT transformed differences
- ‘psnr’
sum of squared quantization errors (avoid, low quality)
- ‘bit’
number of bits needed for the block
- ‘rd’
rate distortion optimal, slow
- ‘zero’
0
- ‘vsad’
sum of absolute vertical differences
- ‘vsse’
sum of squared vertical differences
- ‘nsse’
noise preserving sum of squared differences
- ‘w53’
5/3 wavelet, only used in snow
- ‘w97’
9/7 wavelet, only used in snow
- ‘dctmax’
- ‘chroma’
- dia_size integer (encoding,video)
Set diamond type & size for motion estimation.
- ‘(1024, INT_MAX)’
full motion estimation(slowest)
- ‘(768, 1024]’
umh motion estimation
- ‘(512, 768]’
hex motion estimation
- ‘(256, 512]’
l2s diamond motion estimation
- ‘[2,256]’
var diamond motion estimation
- ‘(-1, 2)’
small diamond motion estimation
- ‘-1’
funny diamond motion estimation
- ‘(INT_MIN, -1)’
sab diamond motion estimation
- last_pred integer (encoding,video)
Set amount of motion predictors from the previous frame.
- precmp integer (encoding,video)
Set pre motion estimation compare function.
Possible values:
- ‘sad’
sum of absolute differences, fast (default)
- ‘sse’
sum of squared errors
- ‘satd’
sum of absolute Hadamard transformed differences
- ‘dct’
sum of absolute DCT transformed differences
- ‘psnr’
sum of squared quantization errors (avoid, low quality)
- ‘bit’
number of bits needed for the block
- ‘rd’
rate distortion optimal, slow
- ‘zero’
0
- ‘vsad’
sum of absolute vertical differences
- ‘vsse’
sum of squared vertical differences
- ‘nsse’
noise preserving sum of squared differences
- ‘w53’
5/3 wavelet, only used in snow
- ‘w97’
9/7 wavelet, only used in snow
- ‘dctmax’
- ‘chroma’
- pre_dia_size integer (encoding,video)
Set diamond type & size for motion estimation pre-pass.
- subq integer (encoding,video)
Set sub pel motion estimation quality.
- me_range integer (encoding,video)
Set limit motion vectors range (1023 for DivX player).
- global_quality integer (encoding,audio,video)
- slice_flags integer
- mbd integer (encoding,video)
Set macroblock decision algorithm (high quality mode).
Possible values:
- ‘simple’
use mbcmp (default)
- ‘bits’
use fewest bits
- ‘rd’
use best rate distortion
- rc_init_occupancy integer (encoding,video)
Set number of bits which should be loaded into the rc buffer before decoding starts.
- flags2 flags (decoding/encoding,audio,video,subtitles)
-
Possible values:
- ‘fast’
Allow non spec compliant speedup tricks.
- ‘noout’
Skip bitstream encoding.
- ‘ignorecrop’
Ignore cropping information from sps.
- ‘local_header’
Place global headers at every keyframe instead of in extradata.
- ‘chunks’
Frame data might be split into multiple chunks.
- ‘showall’
Show all frames before the first keyframe.
- ‘export_mvs’
Export motion vectors into frame side-data (see
AV_FRAME_DATA_MOTION_VECTORS
) for codecs that support it. See also doc/examples/export_mvs.c.- ‘skip_manual’
Do not skip samples and export skip information as frame side data.
- ‘ass_ro_flush_noop’
Do not reset ASS ReadOrder field on flush.
- ‘icc_profiles’
Generate/parse embedded ICC profiles from/to colorimetry tags.
- export_side_data flags (decoding/encoding,audio,video,subtitles)
-
Possible values:
- ‘mvs’
Export motion vectors into frame side-data (see
AV_FRAME_DATA_MOTION_VECTORS
) for codecs that support it. See also doc/examples/export_mvs.c.- ‘prft’
Export encoder Producer Reference Time into packet side-data (see
AV_PKT_DATA_PRFT
) for codecs that support it.- ‘venc_params’
Export video encoding parameters through frame side data (see
AV_FRAME_DATA_VIDEO_ENC_PARAMS
) for codecs that support it. At present, those are H.264 and VP9.- ‘film_grain’
Export film grain parameters through frame side data (see
AV_FRAME_DATA_FILM_GRAIN_PARAMS
). Supported at present by AV1 decoders.
- threads integer (decoding/encoding,video)
Set the number of threads to be used, in case the selected codec implementation supports multi-threading.
Possible values:
- ‘auto, 0’
automatically select the number of threads to set
Default value is ‘auto’.
- dc integer (encoding,video)
Set intra_dc_precision.
- nssew integer (encoding,video)
Set nsse weight.
- skip_top integer (decoding,video)
Set number of macroblock rows at the top which are skipped.
- skip_bottom integer (decoding,video)
Set number of macroblock rows at the bottom which are skipped.
- profile integer (encoding,audio,video)
-
Set encoder codec profile. Default value is ‘unknown’. Encoder specific profiles are documented in the relevant encoder documentation.
- level integer (encoding,audio,video)
-
Set the encoder level. This level depends on the specific codec, and might correspond to the profile level. It is set by default to ‘unknown’.
Possible values:
- ‘unknown’
- lowres integer (decoding,audio,video)
Decode at 1= 1/2, 2=1/4, 3=1/8 resolutions.
- mblmin integer (encoding,video)
Set min macroblock lagrange factor (VBR).
- mblmax integer (encoding,video)
Set max macroblock lagrange factor (VBR).
- skip_loop_filter integer (decoding,video)
- skip_idct integer (decoding,video)
- skip_frame integer (decoding,video)
-
Make decoder discard processing depending on the frame type selected by the option value.
skip_loop_filter skips frame loop filtering, skip_idct skips frame IDCT/dequantization, skip_frame skips decoding.
Possible values:
- ‘none’
Discard no frame.
- ‘default’
Discard useless frames like 0-sized frames.
- ‘noref’
Discard all non-reference frames.
- ‘bidir’
Discard all bidirectional frames.
- ‘nokey’
Discard all frames excepts keyframes.
- ‘nointra’
Discard all frames except I frames.
- ‘all’
Discard all frames.
Default value is ‘default’.
- bidir_refine integer (encoding,video)
Refine the two motion vectors used in bidirectional macroblocks.
- keyint_min integer (encoding,video)
Set minimum interval between IDR-frames.
- refs integer (encoding,video)
Set reference frames to consider for motion compensation.
- trellis integer (encoding,audio,video)
Set rate-distortion optimal quantization.
- mv0_threshold integer (encoding,video)
- compression_level integer (encoding,audio,video)
- bits_per_raw_sample integer
- channel_layout integer (decoding/encoding,audio)
See (ffmpeg-utils)the Channel Layout section in the ffmpeg-utils(1) manual for the required syntax.
- rc_max_vbv_use float (encoding,video)
- rc_min_vbv_use float (encoding,video)
- color_primaries integer (decoding/encoding,video)
Possible values:
- ‘bt709’
BT.709
- ‘bt470m’
BT.470 M
- ‘bt470bg’
BT.470 BG
- ‘smpte170m’
SMPTE 170 M
- ‘smpte240m’
SMPTE 240 M
- ‘film’
Film
- ‘bt2020’
BT.2020
- ‘smpte428’
- ‘smpte428_1’
SMPTE ST 428-1
- ‘smpte431’
SMPTE 431-2
- ‘smpte432’
SMPTE 432-1
- ‘jedec-p22’
JEDEC P22
- color_trc integer (decoding/encoding,video)
Possible values:
- ‘bt709’
BT.709
- ‘gamma22’
BT.470 M
- ‘gamma28’
BT.470 BG
- ‘smpte170m’
SMPTE 170 M
- ‘smpte240m’
SMPTE 240 M
- ‘linear’
Linear
- ‘log’
- ‘log100’
Log
- ‘log_sqrt’
- ‘log316’
Log square root
- ‘iec61966_2_4’
- ‘iec61966-2-4’
IEC 61966-2-4
- ‘bt1361’
- ‘bt1361e’
BT.1361
- ‘iec61966_2_1’
- ‘iec61966-2-1’
IEC 61966-2-1
- ‘bt2020_10’
- ‘bt2020_10bit’
BT.2020 - 10 bit
- ‘bt2020_12’
- ‘bt2020_12bit’
BT.2020 - 12 bit
- ‘smpte2084’
SMPTE ST 2084
- ‘smpte428’
- ‘smpte428_1’
SMPTE ST 428-1
- ‘arib-std-b67’
ARIB STD-B67
- colorspace integer (decoding/encoding,video)
Possible values:
- ‘rgb’
RGB
- ‘bt709’
BT.709
- ‘fcc’
FCC
- ‘bt470bg’
BT.470 BG
- ‘smpte170m’
SMPTE 170 M
- ‘smpte240m’
SMPTE 240 M
- ‘ycocg’
YCOCG
- ‘bt2020nc’
- ‘bt2020_ncl’
BT.2020 NCL
- ‘bt2020c’
- ‘bt2020_cl’
BT.2020 CL
- ‘smpte2085’
SMPTE 2085
- ‘chroma-derived-nc’
Chroma-derived NCL
- ‘chroma-derived-c’
Chroma-derived CL
- ‘ictcp’
ICtCp
- color_range integer (decoding/encoding,video)
If used as input parameter, it serves as a hint to the decoder, which color_range the input has. Possible values:
- ‘tv’
- ‘mpeg’
- ‘limited’
MPEG (219*2^(n-8))
- ‘pc’
- ‘jpeg’
- ‘full’
JPEG (2^n-1)
- chroma_sample_location integer (decoding/encoding,video)
Possible values:
- ‘left’
- ‘center’
- ‘topleft’
- ‘top’
- ‘bottomleft’
- ‘bottom’
- log_level_offset integer
Set the log level offset.
- slices integer (encoding,video)
Number of slices, used in parallelized encoding.
- thread_type flags (decoding/encoding,video)
Select which multithreading methods to use.
Use of ‘frame’ will increase decoding delay by one frame per thread, so clients which cannot provide future frames should not use it.
Possible values:
- ‘slice’
Decode more than one part of a single frame at once.
Multithreading using slices works only when the video was encoded with slices.
- ‘frame’
Decode more than one frame at once.
Default value is ‘slice+frame’.
- audio_service_type integer (encoding,audio)
Set audio service type.
Possible values:
- ‘ma’
Main Audio Service
- ‘ef’
Effects
- ‘vi’
Visually Impaired
- ‘hi’
Hearing Impaired
- ‘di’
Dialogue
- ‘co’
Commentary
- ‘em’
Emergency
- ‘vo’
Voice Over
- ‘ka’
Karaoke
- request_sample_fmt sample_fmt (decoding,audio)
Set sample format audio decoders should prefer. Default value is
none
.- pkt_timebase rational number
- sub_charenc encoding (decoding,subtitles)
Set the input subtitles character encoding.
- field_order field_order (video)
Set/override the field order of the video. Possible values:
- ‘progressive’
Progressive video
- ‘tt’
Interlaced video, top field coded and displayed first
- ‘bb’
Interlaced video, bottom field coded and displayed first
- ‘tb’
Interlaced video, top coded first, bottom displayed first
- ‘bt’
Interlaced video, bottom coded first, top displayed first
- skip_alpha bool (decoding,video)
Set to 1 to disable processing alpha (transparency). This works like the ‘gray’ flag in the flags option which skips chroma information instead of alpha. Default is 0.
- codec_whitelist list (input)
"," separated list of allowed decoders. By default all are allowed.
- dump_separator string (input)
Separator used to separate the fields printed on the command line about the Stream parameters. For example, to separate the fields with newlines and indentation:
ffprobe -dump_separator " " -i ~/videos/matrixbench_mpeg2.mpg
- max_pixels integer (decoding/encoding,video)
Maximum number of pixels per image. This value can be used to avoid out of memory failures due to large images.
- apply_cropping bool (decoding,video)
Enable cropping if cropping parameters are multiples of the required alignment for the left and top parameters. If the alignment is not met the cropping will be partially applied to maintain alignment. Default is 1 (enabled). Note: The required alignment depends on if
AV_CODEC_FLAG_UNALIGNED
is set and the CPU.AV_CODEC_FLAG_UNALIGNED
cannot be changed from the command line. Also hardware decoders will not apply left/top Cropping.
9 Decoders
Decoders are configured elements in FFmpeg which allow the decoding of multimedia streams.
When you configure your FFmpeg build, all the supported native decoders
are enabled by default. Decoders requiring an external library must be enabled
manually via the corresponding --enable-lib
option. You can list all
available decoders using the configure option --list-decoders
.
You can disable all the decoders with the configure option
--disable-decoders
and selectively enable / disable single decoders
with the options --enable-decoder=DECODER
/
--disable-decoder=DECODER
.
The option -decoders
of the ff* tools will display the list of
enabled decoders.
10 Video Decoders
A description of some of the currently available video decoders follows.
10.1 av1
AOMedia Video 1 (AV1) decoder.
10.1.1 Options
- operating_point
Select an operating point of a scalable AV1 bitstream (0 - 31). Default is 0.
10.2 hevc
HEVC (AKA ITU-T H.265 or ISO/IEC 23008-2) decoder.
The decoder supports MV-HEVC multiview streams with at most two views. Views to
be output are selected by supplying a list of view IDs to the decoder (the
view_ids option). This option may be set either statically before
decoder init, or from the get_format()
callback - useful for the case
when the view count or IDs change dynamically during decoding.
Only the base layer is decoded by default.
Note that if you are using the ffmpeg
CLI tool, you should be using view
specifiers as documented in its manual, rather than the options documented here.
10.2.1 Options
- view_ids (MV-HEVC)
Specify a list of view IDs that should be output. This option can also be set to a single ’-1’, which will cause all views defined in the VPS to be decoded and output.
- view_ids_available (MV-HEVC)
This option may be read by the caller to retrieve an array of view IDs available in the active VPS. The array is empty for single-layer video.
The value of this option is guaranteed to be accurate when read from the
get_format()
callback. It may also be set at other times (e.g. after opening the decoder), but the value is informational only and may be incorrect (e.g. when the stream contains multiple distinct VPS NALUs).- view_pos_available (MV-HEVC)
This option may be read by the caller to retrieve an array of view positions (left, right, or unspecified) available in the active VPS, as
AVStereo3DView
values. When the array is available, its elements apply to the corresponding elements of view_ids_available, i.e.view_pos_available[i]
contains the position of view with IDview_ids_available[i]
.Same validity restrictions as for view_ids_available apply to this option.
10.3 rawvideo
Raw video decoder.
This decoder decodes rawvideo streams.
10.3.1 Options
- top top_field_first
Specify the assumed field type of the input video.
- -1
the video is assumed to be progressive (default)
- 0
bottom-field-first is assumed
- 1
top-field-first is assumed
10.4 libdav1d
dav1d AV1 decoder.
libdav1d allows libavcodec to decode the AOMedia Video 1 (AV1) codec.
Requires the presence of the libdav1d headers and library during configuration.
You need to explicitly configure the build with --enable-libdav1d
.
10.4.1 Options
The following options are supported by the libdav1d wrapper.
- framethreads
Set amount of frame threads to use during decoding. The default value is 0 (autodetect). This option is deprecated for libdav1d >= 1.0 and will be removed in the future. Use the option
max_frame_delay
and the global optionthreads
instead.- tilethreads
Set amount of tile threads to use during decoding. The default value is 0 (autodetect). This option is deprecated for libdav1d >= 1.0 and will be removed in the future. Use the global option
threads
instead.- max_frame_delay
Set max amount of frames the decoder may buffer internally. The default value is 0 (autodetect).
- filmgrain
Apply film grain to the decoded video if present in the bitstream. Defaults to the internal default of the library. This option is deprecated and will be removed in the future. See the global option
export_side_data
to export Film Grain parameters instead of applying it.- oppoint
Select an operating point of a scalable AV1 bitstream (0 - 31). Defaults to the internal default of the library.
- alllayers
Output all spatial layers of a scalable AV1 bitstream. The default value is false.
10.5 libdavs2
AVS2-P2/IEEE1857.4 video decoder wrapper.
This decoder allows libavcodec to decode AVS2 streams with davs2 library.
10.6 libuavs3d
AVS3-P2/IEEE1857.10 video decoder.
libuavs3d allows libavcodec to decode AVS3 streams.
Requires the presence of the libuavs3d headers and library during configuration.
You need to explicitly configure the build with --enable-libuavs3d
.
10.6.1 Options
The following option is supported by the libuavs3d wrapper.
- frame_threads
Set amount of frame threads to use during decoding. The default value is 0 (autodetect).
10.7 libxevd
eXtra-fast Essential Video Decoder (XEVD) MPEG-5 EVC decoder wrapper.
This decoder requires the presence of the libxevd headers and library during configuration. You need to explicitly configure the build with --enable-libxevd.
The xevd project website is at https://github.com/mpeg5/xevd.
10.7.1 Options
The following options are supported by the libxevd wrapper. The xevd-equivalent options or values are listed in parentheses for easy migration.
To get a more accurate and extensive documentation of the libxevd options,
invoke the command xevd_app --help
or consult the libxevd documentation.
- threads (threads)
Force to use a specific number of threads
10.8 QSV Decoders
The family of Intel QuickSync Video decoders (VC1, MPEG-2, H.264, HEVC, JPEG/MJPEG, VP8, VP9, AV1, VVC).
10.8.1 Common Options
The following options are supported by all qsv decoders.
- async_depth
Internal parallelization depth, the higher the value the higher the latency.
- gpu_copy
A GPU-accelerated copy between video and system memory
- ‘default’
- ‘on’
- ‘off’
10.8.2 HEVC Options
Extra options for hevc_qsv.
- load_plugin
A user plugin to load in an internal session
- ‘none’
- ‘hevc_sw’
- ‘hevc_hw’
- load_plugins
A :-separate list of hexadecimal plugin UIDs to load in an internal session
10.9 v210
Uncompressed 4:2:2 10-bit decoder.
10.9.1 Options
- custom_stride
Set the line size of the v210 data in bytes. The default value is 0 (autodetect). You can use the special -1 value for a strideless v210 as seen in BOXX files.
11 Audio Decoders
A description of some of the currently available audio decoders follows.
11.1 ac3
AC-3 audio decoder.
This decoder implements part of ATSC A/52:2010 and ETSI TS 102 366, as well as the undocumented RealAudio 3 (a.k.a. dnet).
11.1.1 AC-3 Decoder Options
- -drc_scale value
Dynamic Range Scale Factor. The factor to apply to dynamic range values from the AC-3 stream. This factor is applied exponentially. The default value is 1. There are 3 notable scale factor ranges:
- drc_scale == 0
DRC disabled. Produces full range audio.
- 0 < drc_scale <= 1
DRC enabled. Applies a fraction of the stream DRC value. Audio reproduction is between full range and full compression.
- drc_scale > 1
DRC enabled. Applies drc_scale asymmetrically. Loud sounds are fully compressed. Soft sounds are enhanced.
11.2 flac
FLAC audio decoder.
This decoder aims to implement the complete FLAC specification from Xiph.
11.2.1 FLAC Decoder options
- -use_buggy_lpc
The lavc FLAC encoder used to produce buggy streams with high lpc values (like the default value). This option makes it possible to decode such streams correctly by using lavc’s old buggy lpc logic for decoding.
11.3 ffwavesynth
Internal wave synthesizer.
This decoder generates wave patterns according to predefined sequences. Its use is purely internal and the format of the data it accepts is not publicly documented.
11.4 libcelt
libcelt decoder wrapper.
libcelt allows libavcodec to decode the Xiph CELT ultra-low delay audio codec.
Requires the presence of the libcelt headers and library during configuration.
You need to explicitly configure the build with --enable-libcelt
.
11.5 libgsm
libgsm decoder wrapper.
libgsm allows libavcodec to decode the GSM full rate audio codec. Requires
the presence of the libgsm headers and library during configuration. You need
to explicitly configure the build with --enable-libgsm
.
This decoder supports both the ordinary GSM and the Microsoft variant.
11.6 libilbc
libilbc decoder wrapper.
libilbc allows libavcodec to decode the Internet Low Bitrate Codec (iLBC)
audio codec. Requires the presence of the libilbc headers and library during
configuration. You need to explicitly configure the build with
--enable-libilbc
.
11.6.1 Options
The following option is supported by the libilbc wrapper.
- enhance
-
Enable the enhancement of the decoded audio when set to 1. The default value is 0 (disabled).
11.7 libopencore-amrnb
libopencore-amrnb decoder wrapper.
libopencore-amrnb allows libavcodec to decode the Adaptive Multi-Rate
Narrowband audio codec. Using it requires the presence of the
libopencore-amrnb headers and library during configuration. You need to
explicitly configure the build with --enable-libopencore-amrnb
.
An FFmpeg native decoder for AMR-NB exists, so users can decode AMR-NB without this library.
11.8 libopencore-amrwb
libopencore-amrwb decoder wrapper.
libopencore-amrwb allows libavcodec to decode the Adaptive Multi-Rate
Wideband audio codec. Using it requires the presence of the
libopencore-amrwb headers and library during configuration. You need to
explicitly configure the build with --enable-libopencore-amrwb
.
An FFmpeg native decoder for AMR-WB exists, so users can decode AMR-WB without this library.
11.9 libopus
libopus decoder wrapper.
libopus allows libavcodec to decode the Opus Interactive Audio Codec.
Requires the presence of the libopus headers and library during
configuration. You need to explicitly configure the build with
--enable-libopus
.
An FFmpeg native decoder for Opus exists, so users can decode Opus without this library.
12 Subtitles Decoders
12.1 libaribb24
ARIB STD-B24 caption decoder.
Implements profiles A and C of the ARIB STD-B24 standard.
12.1.1 libaribb24 Decoder Options
- -aribb24-base-path path
Sets the base path for the libaribb24 library. This is utilized for reading of configuration files (for custom unicode conversions), and for dumping of non-text symbols as images under that location.
Unset by default.
- -aribb24-skip-ruby-text boolean
Tells the decoder wrapper to skip text blocks that contain half-height ruby text.
Enabled by default.
12.2 libaribcaption
Yet another ARIB STD-B24 caption decoder using external libaribcaption library.
Implements profiles A and C of the Japanse ARIB STD-B24 standard, Brazilian ABNT NBR 15606-1, and Philippines version of ISDB-T.
Requires the presence of the libaribcaption headers and library
(https://github.com/xqq/libaribcaption) during configuration.
You need to explicitly configure the build with --enable-libaribcaption
.
If both libaribb24 and libaribcaption are enabled, libaribcaption
decoder precedes.
12.2.1 libaribcaption Decoder Options
- -sub_type subtitle_type
Specifies the format of the decoded subtitles.
- ‘bitmap’
Graphical image.
- ‘ass’
ASS formatted text.
- ‘text’
Simple text based output without formatting.
The default is ass as same as libaribb24 decoder. Some present players (e.g., mpv) expect ASS format for ARIB caption.
- -caption_encoding encoding_scheme
Specifies the encoding scheme of input subtitle text.
- ‘auto’
Automatically detect text encoding (default).
- ‘jis’
8bit-char JIS encoding defined in ARIB STD B24. This encoding used in Japan for ISDB captions.
- ‘utf8’
UTF-8 encoding defined in ARIB STD B24. This encoding is used in Philippines for ISDB-T captions.
- ‘latin’
Latin character encoding defined in ABNT NBR 15606-1. This encoding is used in South America for SBTVD / ISDB-Tb captions.
- -font font_name[,font_name2,...]
Specify comma-separated list of font family names to be used for bitmap or ass type subtitle rendering. Only first font name is used for ass type subtitle.
If not specified, use internaly defined default font family.
- -ass_single_rect boolean
ARIB STD-B24 specifies that some captions may be displayed at different positions at a time (multi-rectangle subtitle). Since some players (e.g., old mpv) can’t handle multiple ASS rectangles in a single AVSubtitle, or multiple ASS rectangles of indeterminate duration with the same start timestamp, this option can change the behavior so that all the texts are displayed in a single ASS rectangle.
The default is false.
If your player cannot handle AVSubtitles with multiple ASS rectangles properly, set this option to true or define
ASS_SINGLE_RECT=1
to change default behavior at compilation.- -force_outline_text boolean
Specify whether always render outline text for all characters regardless of the indication by charactor style.
The default is false.
- -outline_width number (0.0 - 3.0)
Specify width for outline text, in dots (relative).
The default is 1.5.
- -ignore_background boolean
Specify whether to ignore background color rendering.
The default is false.
- -ignore_ruby boolean
Specify whether to ignore rendering for ruby-like (furigana) characters.
The default is false.
- -replace_drcs boolean
Specify whether to render replaced DRCS characters as Unicode characters.
The default is true.
- -replace_msz_ascii boolean
Specify whether to replace MSZ (Middle Size; half width) fullwidth alphanumerics with halfwidth alphanumerics.
The default is true.
- -replace_msz_japanese boolean
Specify whether to replace some MSZ (Middle Size; half width) fullwidth japanese special characters with halfwidth ones.
The default is true.
- -replace_msz_glyph boolean
Specify whether to replace MSZ (Middle Size; half width) characters with halfwidth glyphs if the fonts supports it. This option works under FreeType or DirectWrite renderer with Adobe-Japan1 compliant fonts. e.g., IBM Plex Sans JP, Morisawa BIZ UDGothic, Morisawa BIZ UDMincho, Yu Gothic, Yu Mincho, and Meiryo.
The default is true.
- -canvas_size image_size
Specify the resolution of the canvas to render subtitles to; usually, this should be frame size of input video. This only applies when
-subtitle_type
is set to bitmap.The libaribcaption decoder assumes input frame size for bitmap rendering as below:
- PROFILE_A : 1440 x 1080 with SAR (PAR) 4:3
- PROFILE_C : 320 x 180 with SAR (PAR) 1:1
If actual frame size of input video does not match above assumption, the rendered captions may be distorted. To make the captions undistorted, add
-canvas_size
option to specify actual input video size.Note that the
-canvas_size
option is not required for video with different size but same aspect ratio. In such cases, the caption will be stretched or shrunk to actual video size if-canvas_size
option is not specified. If-canvas_size
option is specified with different size, the caption will be stretched or shrunk as specified size with calculated SAR.
12.2.2 libaribcaption decoder usage examples
Display MPEG-TS file with ARIB subtitle by ffplay
tool:
ffplay -sub_type bitmap MPEG.TS
Display MPEG-TS file with input frame size 1920x1080 by ffplay
tool:
ffplay -sub_type bitmap -canvas_size 1920x1080 MPEG.TS
Embed ARIB subtitle in transcoded video:
ffmpeg -sub_type bitmap -i src.m2t -filter_complex "[0:v][0:s]overlay" -vcodec h264 dest.mp4
12.3 dvbsub
12.3.1 Options
- compute_clut
- -2
Compute clut once if no matching CLUT is in the stream.
- -1
Compute clut if no matching CLUT is in the stream.
- 0
Never compute CLUT
- 1
Always compute CLUT and override the one provided in the stream.
- dvb_substream
Selects the dvb substream, or all substreams if -1 which is default.
12.4 dvdsub
This codec decodes the bitmap subtitles used in DVDs; the same subtitles can also be found in VobSub file pairs and in some Matroska files.
12.4.1 Options
- palette
Specify the global palette used by the bitmaps. When stored in VobSub, the palette is normally specified in the index file; in Matroska, the palette is stored in the codec extra-data in the same format as in VobSub. In DVDs, the palette is stored in the IFO file, and therefore not available when reading from dumped VOB files.
The format for this option is a string containing 16 24-bits hexadecimal numbers (without 0x prefix) separated by commas, for example
0d00ee, ee450d, 101010, eaeaea, 0ce60b, ec14ed, ebff0b, 0d617a, 7b7b7b, d1d1d1, 7b2a0e, 0d950c, 0f007b, cf0dec, cfa80c, 7c127b
.- ifo_palette
Specify the IFO file from which the global palette is obtained. (experimental)
- forced_subs_only
Only decode subtitle entries marked as forced. Some titles have forced and non-forced subtitles in the same track. Setting this flag to
1
will only keep the forced subtitles. Default value is0
.
12.5 libzvbi-teletext
Libzvbi allows libavcodec to decode DVB teletext pages and DVB teletext
subtitles. Requires the presence of the libzvbi headers and library during
configuration. You need to explicitly configure the build with
--enable-libzvbi
.
12.5.1 Options
- txt_page
List of teletext page numbers to decode. Pages that do not match the specified list are dropped. You may use the special
*
string to match all pages, orsubtitle
to match all subtitle pages. Default value is *.- txt_default_region
Set default character set used for decoding, a value between 0 and 87 (see ETS 300 706, Section 15, Table 32). Default value is -1, which does not override the libzvbi default. This option is needed for some legacy level 1.0 transmissions which cannot signal the proper charset.
- txt_chop_top
Discards the top teletext line. Default value is 1.
- txt_format
Specifies the format of the decoded subtitles.
- bitmap
The default format, you should use this for teletext pages, because certain graphics and colors cannot be expressed in simple text or even ASS.
- text
Simple text based output without formatting.
- ass
Formatted ASS output, subtitle pages and teletext pages are returned in different styles, subtitle pages are stripped down to text, but an effort is made to keep the text alignment and the formatting.
- txt_left
X offset of generated bitmaps, default is 0.
- txt_top
Y offset of generated bitmaps, default is 0.
- txt_chop_spaces
Chops leading and trailing spaces and removes empty lines from the generated text. This option is useful for teletext based subtitles where empty spaces may be present at the start or at the end of the lines or empty lines may be present between the subtitle lines because of double-sized teletext characters. Default value is 1.
- txt_duration
Sets the display duration of the decoded teletext pages or subtitles in milliseconds. Default value is -1 which means infinity or until the next subtitle event comes.
- txt_transparent
Force transparent background of the generated teletext bitmaps. Default value is 0 which means an opaque background.
- txt_opacity
Sets the opacity (0-255) of the teletext background. If txt_transparent is not set, it only affects characters between a start box and an end box, typically subtitles. Default value is 0 if txt_transparent is set, 255 otherwise.
13 Bitstream Filters
When you configure your FFmpeg build, all the supported bitstream
filters are enabled by default. You can list all available ones using
the configure option --list-bsfs
.
You can disable all the bitstream filters using the configure option
--disable-bsfs
, and selectively enable any bitstream filter using
the option --enable-bsf=BSF
, or you can disable a particular
bitstream filter using the option --disable-bsf=BSF
.
The option -bsfs
of the ff* tools will display the list of
all the supported bitstream filters included in your build.
The ff* tools have a -bsf option applied per stream, taking a comma-separated list of filters, whose parameters follow the filter name after a ’=’.
ffmpeg -i INPUT -c:v copy -bsf:v filter1[=opt1=str1:opt2=str2][,filter2] OUTPUT
Below is a description of the currently available bitstream filters, with their parameters, if any.
13.1 aac_adtstoasc
Convert MPEG-2/4 AAC ADTS to an MPEG-4 Audio Specific Configuration bitstream.
This filter creates an MPEG-4 AudioSpecificConfig from an MPEG-2/4 ADTS header and removes the ADTS header.
This filter is required for example when copying an AAC stream from a raw ADTS AAC or an MPEG-TS container to MP4A-LATM, to an FLV file, or to MOV/MP4 files and related formats such as 3GP or M4A. Please note that it is auto-inserted for MP4A-LATM and MOV/MP4 and related formats.
13.2 av1_metadata
Modify metadata embedded in an AV1 stream.
- td
Insert or remove temporal delimiter OBUs in all temporal units of the stream.
- ‘insert’
Insert a TD at the beginning of every TU which does not already have one.
- ‘remove’
Remove the TD from the beginning of every TU which has one.
- color_primaries
- transfer_characteristics
- matrix_coefficients
Set the color description fields in the stream (see AV1 section 6.4.2).
- color_range
Set the color range in the stream (see AV1 section 6.4.2; note that this cannot be set for streams using BT.709 primaries, sRGB transfer characteristic and identity (RGB) matrix coefficients).
- ‘tv’
Limited range.
- ‘pc’
Full range.
- chroma_sample_position
Set the chroma sample location in the stream (see AV1 section 6.4.2). This can only be set for 4:2:0 streams.
- ‘vertical’
Left position (matching the default in MPEG-2 and H.264).
- ‘colocated’
Top-left position.
- tick_rate
Set the tick rate (time_scale / num_units_in_display_tick) in the timing info in the sequence header.
- num_ticks_per_picture
Set the number of ticks in each picture, to indicate that the stream has a fixed framerate. Ignored if tick_rate is not also set.
- delete_padding
Deletes Padding OBUs.
13.3 chomp
Remove zero padding at the end of a packet.
13.4 dca_core
Extract the core from a DCA/DTS stream, dropping extensions such as DTS-HD.
13.5 dovi_rpu
Manipulate Dolby Vision metadata in a HEVC/AV1 bitstream, optionally enabling metadata compression.
- strip
If enabled, strip all Dolby Vision metadata (configuration record + RPU data blocks) from the stream.
- compression
Which compression level to enable.
- ‘none’
No metadata compression.
- ‘limited’
Limited metadata compression scheme. Should be compatible with most devices. This is the default.
- ‘extended’
Extended metadata compression. Devices are not required to support this. Note that this level currently behaves the same as ‘limited’ in libavcodec.
13.6 dump_extra
Add extradata to the beginning of the filtered packets except when said packets already exactly begin with the extradata that is intended to be added.
- freq
The additional argument specifies which packets should be filtered. It accepts the values:
- ‘k’
- ‘keyframe’
add extradata to all key packets
- ‘e’
- ‘all’
add extradata to all packets
If not specified it is assumed ‘k’.
For example the following ffmpeg
command forces a global
header (thus disabling individual packet headers) in the H.264 packets
generated by the libx264
encoder, but corrects them by adding
the header stored in extradata to the key packets:
ffmpeg -i INPUT -map 0 -flags:v +global_header -c:v libx264 -bsf:v dump_extra out.ts
13.7 dv_error_marker
Blocks in DV which are marked as damaged are replaced by blocks of the specified color.
- color
The color to replace damaged blocks by
- sta
A 16 bit mask which specifies which of the 16 possible error status values are to be replaced by colored blocks. 0xFFFE is the default which replaces all non 0 error status values.
- ‘ok’
No error, no concealment
- ‘err’
Error, No concealment
- ‘res’
Reserved
- ‘notok’
Error or concealment
- ‘notres’
Not reserved
- ‘Aa, Ba, Ca, Ab, Bb, Cb, A, B, C, a, b, erri, erru’
The specific error status code
see page 44-46 or section 5.5 of http://web.archive.org/web/20060927044735/http://www.smpte.org/smpte_store/standards/pdf/s314m.pdf
13.8 eac3_core
Extract the core from a E-AC-3 stream, dropping extra channels.
13.9 extract_extradata
Extract the in-band extradata.
Certain codecs allow the long-term headers (e.g. MPEG-2 sequence headers, or H.264/HEVC (VPS/)SPS/PPS) to be transmitted either "in-band" (i.e. as a part of the bitstream containing the coded frames) or "out of band" (e.g. on the container level). This latter form is called "extradata" in FFmpeg terminology.
This bitstream filter detects the in-band headers and makes them available as extradata.
- remove
When this option is enabled, the long-term headers are removed from the bitstream after extraction.
13.10 filter_units
Remove units with types in or not in a given set from the stream.
- pass_types
List of unit types or ranges of unit types to pass through while removing all others. This is specified as a ’|’-separated list of unit type values or ranges of values with ’-’.
- remove_types
Identical to pass_types, except the units in the given set removed and all others passed through.
The types used by pass_types and remove_types correspond to NAL unit types (nal_unit_type) in H.264, HEVC and H.266 (see Table 7-1 in the H.264 and HEVC specifications or Table 5 in the H.266 specification), to marker values for JPEG (without 0xFF prefix) and to start codes without start code prefix (i.e. the byte following the 0x000001) for MPEG-2. For VP8 and VP9, every unit has type zero.
Extradata is unchanged by this transformation, but note that if the stream contains inline parameter sets then the output may be unusable if they are removed.
For example, to remove all non-VCL NAL units from an H.264 stream:
ffmpeg -i INPUT -c:v copy -bsf:v 'filter_units=pass_types=1-5' OUTPUT
To remove all AUDs, SEI and filler from an H.265 stream:
ffmpeg -i INPUT -c:v copy -bsf:v 'filter_units=remove_types=35|38-40' OUTPUT
To remove all user data from a MPEG-2 stream, including Closed Captions:
ffmpeg -i INPUT -c:v copy -bsf:v 'filter_units=remove_types=178' OUTPUT
To remove all SEI from a H264 stream, including Closed Captions:
ffmpeg -i INPUT -c:v copy -bsf:v 'filter_units=remove_types=6' OUTPUT
To remove all prefix and suffix SEI from a HEVC stream, including Closed Captions and dynamic HDR:
ffmpeg -i INPUT -c:v copy -bsf:v 'filter_units=remove_types=39|40' OUTPUT
13.11 hapqa_extract
Extract Rgb or Alpha part of an HAPQA file, without recompression, in order to create an HAPQ or an HAPAlphaOnly file.
- texture
Specifies the texture to keep.
- color
- alpha
Convert HAPQA to HAPQ
ffmpeg -i hapqa_inputfile.mov -c copy -bsf:v hapqa_extract=texture=color -tag:v HapY -metadata:s:v:0 encoder="HAPQ" hapq_file.mov
Convert HAPQA to HAPAlphaOnly
ffmpeg -i hapqa_inputfile.mov -c copy -bsf:v hapqa_extract=texture=alpha -tag:v HapA -metadata:s:v:0 encoder="HAPAlpha Only" hapalphaonly_file.mov
13.12 h264_metadata
Modify metadata embedded in an H.264 stream.
- aud
Insert or remove AUD NAL units in all access units of the stream.
- ‘pass’
- ‘insert’
- ‘remove’
Default is pass.
- sample_aspect_ratio
Set the sample aspect ratio of the stream in the VUI parameters. See H.264 table E-1.
- overscan_appropriate_flag
Set whether the stream is suitable for display using overscan or not (see H.264 section E.2.1).
- video_format
- video_full_range_flag
Set the video format in the stream (see H.264 section E.2.1 and table E-2).
- colour_primaries
- transfer_characteristics
- matrix_coefficients
Set the colour description in the stream (see H.264 section E.2.1 and tables E-3, E-4 and E-5).
- chroma_sample_loc_type
Set the chroma sample location in the stream (see H.264 section E.2.1 and figure E-1).
- tick_rate
Set the tick rate (time_scale / num_units_in_tick) in the VUI parameters. This is the smallest time unit representable in the stream, and in many cases represents the field rate of the stream (double the frame rate).
- fixed_frame_rate_flag
Set whether the stream has fixed framerate - typically this indicates that the framerate is exactly half the tick rate, but the exact meaning is dependent on interlacing and the picture structure (see H.264 section E.2.1 and table E-6).
- zero_new_constraint_set_flags
Zero constraint_set4_flag and constraint_set5_flag in the SPS. These bits were reserved in a previous version of the H.264 spec, and thus some hardware decoders require these to be zero. The result of zeroing this is still a valid bitstream.
- crop_left
- crop_right
- crop_top
- crop_bottom
Set the frame cropping offsets in the SPS. These values will replace the current ones if the stream is already cropped.
These fields are set in pixels. Note that some sizes may not be representable if the chroma is subsampled or the stream is interlaced (see H.264 section 7.4.2.1.1).
- sei_user_data
Insert a string as SEI unregistered user data. The argument must be of the form UUID+string, where the UUID is as hex digits possibly separated by hyphens, and the string can be anything.
For example, ‘086f3693-b7b3-4f2c-9653-21492feee5b8+hello’ will insert the string “hello” associated with the given UUID.
- delete_filler
Deletes both filler NAL units and filler SEI messages.
- display_orientation
Insert, extract or remove Display orientation SEI messages. See H.264 section D.1.27 and D.2.27 for syntax and semantics.
- ‘pass’
- ‘insert’
- ‘remove’
- ‘extract’
Default is pass.
Insert mode works in conjunction with
rotate
andflip
options. Any pre-existing Display orientation messages will be removed in insert or remove mode. Extract mode attaches the display matrix to the packet as side data.- rotate
Set rotation in display orientation SEI (anticlockwise angle in degrees). Range is -360 to +360. Default is NaN.
- flip
Set flip in display orientation SEI.
- ‘horizontal’
- ‘vertical’
Default is unset.
- level
Set the level in the SPS. Refer to H.264 section A.3 and tables A-1 to A-5.
The argument must be the name of a level (for example, ‘4.2’), a level_idc value (for example, ‘42’), or the special name ‘auto’ indicating that the filter should attempt to guess the level from the input stream properties.
13.13 h264_mp4toannexb
Convert an H.264 bitstream from length prefixed mode to start code prefixed mode (as defined in the Annex B of the ITU-T H.264 specification).
This is required by some streaming formats, typically the MPEG-2
transport stream format (muxer mpegts
).
For example to remux an MP4 file containing an H.264 stream to mpegts
format with ffmpeg
, you can use the command:
ffmpeg -i INPUT.mp4 -codec copy -bsf:v h264_mp4toannexb OUTPUT.ts
Please note that this filter is auto-inserted for MPEG-TS (muxer
mpegts
) and raw H.264 (muxer h264
) output formats.
13.14 h264_redundant_pps
This applies a specific fixup to some Blu-ray streams which contain redundant PPSs modifying irrelevant parameters of the stream which confuse other transformations which require correct extradata.
13.15 hevc_metadata
Modify metadata embedded in an HEVC stream.
- aud
Insert or remove AUD NAL units in all access units of the stream.
- ‘insert’
- ‘remove’
- sample_aspect_ratio
Set the sample aspect ratio in the stream in the VUI parameters.
- video_format
- video_full_range_flag
Set the video format in the stream (see H.265 section E.3.1 and table E.2).
- colour_primaries
- transfer_characteristics
- matrix_coefficients
Set the colour description in the stream (see H.265 section E.3.1 and tables E.3, E.4 and E.5).
- chroma_sample_loc_type
Set the chroma sample location in the stream (see H.265 section E.3.1 and figure E.1).
- tick_rate
Set the tick rate in the VPS and VUI parameters (time_scale / num_units_in_tick). Combined with num_ticks_poc_diff_one, this can set a constant framerate in the stream. Note that it is likely to be overridden by container parameters when the stream is in a container.
- num_ticks_poc_diff_one
Set poc_proportional_to_timing_flag in VPS and VUI and use this value to set num_ticks_poc_diff_one_minus1 (see H.265 sections 7.4.3.1 and E.3.1). Ignored if tick_rate is not also set.
- crop_left
- crop_right
- crop_top
- crop_bottom
Set the conformance window cropping offsets in the SPS. These values will replace the current ones if the stream is already cropped.
These fields are set in pixels. Note that some sizes may not be representable if the chroma is subsampled (H.265 section 7.4.3.2.1).
- width
- height
Set width and height after crop.
- level
Set the level in the VPS and SPS. See H.265 section A.4 and tables A.6 and A.7.
The argument must be the name of a level (for example, ‘5.1’), a general_level_idc value (for example, ‘153’ for level 5.1), or the special name ‘auto’ indicating that the filter should attempt to guess the level from the input stream properties.
13.16 hevc_mp4toannexb
Convert an HEVC/H.265 bitstream from length prefixed mode to start code prefixed mode (as defined in the Annex B of the ITU-T H.265 specification).
This is required by some streaming formats, typically the MPEG-2
transport stream format (muxer mpegts
).
For example to remux an MP4 file containing an HEVC stream to mpegts
format with ffmpeg
, you can use the command:
ffmpeg -i INPUT.mp4 -codec copy -bsf:v hevc_mp4toannexb OUTPUT.ts
Please note that this filter is auto-inserted for MPEG-TS (muxer
mpegts
) and raw HEVC/H.265 (muxer h265
or
hevc
) output formats.
13.17 imxdump
Modifies the bitstream to fit in MOV and to be usable by the Final Cut Pro decoder. This filter only applies to the mpeg2video codec, and is likely not needed for Final Cut Pro 7 and newer with the appropriate -tag:v.
For example, to remux 30 MB/sec NTSC IMX to MOV:
ffmpeg -i input.mxf -c copy -bsf:v imxdump -tag:v mx3n output.mov
13.18 mjpeg2jpeg
Convert MJPEG/AVI1 packets to full JPEG/JFIF packets.
MJPEG is a video codec wherein each video frame is essentially a JPEG image. The individual frames can be extracted without loss, e.g. by
ffmpeg -i ../some_mjpeg.avi -c:v copy frames_%d.jpg
Unfortunately, these chunks are incomplete JPEG images, because they lack the DHT segment required for decoding. Quoting from http://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml:
Avery Lee, writing in the rec.video.desktop newsgroup in 2001, commented that "MJPEG, or at least the MJPEG in AVIs having the MJPG fourcc, is restricted JPEG with a fixed – and *omitted* – Huffman table. The JPEG must be YCbCr colorspace, it must be 4:2:2, and it must use basic Huffman encoding, not arithmetic or progressive. . . . You can indeed extract the MJPEG frames and decode them with a regular JPEG decoder, but you have to prepend the DHT segment to them, or else the decoder won’t have any idea how to decompress the data. The exact table necessary is given in the OpenDML spec."
This bitstream filter patches the header of frames extracted from an MJPEG stream (carrying the AVI1 header ID and lacking a DHT segment) to produce fully qualified JPEG images.
ffmpeg -i mjpeg-movie.avi -c:v copy -bsf:v mjpeg2jpeg frame_%d.jpg exiftran -i -9 frame*.jpg ffmpeg -i frame_%d.jpg -c:v copy rotated.avi
13.19 mjpegadump
Add an MJPEG A header to the bitstream, to enable decoding by Quicktime.
13.20 mov2textsub
Extract a representable text file from MOV subtitles, stripping the metadata header from each subtitle packet.
See also the text2movsub filter.
13.21 mpeg2_metadata
Modify metadata embedded in an MPEG-2 stream.
- display_aspect_ratio
Set the display aspect ratio in the stream.
The following fixed values are supported:
- 4/3
- 16/9
- 221/100
Any other value will result in square pixels being signalled instead (see H.262 section 6.3.3 and table 6-3).
- frame_rate
Set the frame rate in the stream. This is constructed from a table of known values combined with a small multiplier and divisor - if the supplied value is not exactly representable, the nearest representable value will be used instead (see H.262 section 6.3.3 and table 6-4).
- video_format
Set the video format in the stream (see H.262 section 6.3.6 and table 6-6).
- colour_primaries
- transfer_characteristics
- matrix_coefficients
Set the colour description in the stream (see H.262 section 6.3.6 and tables 6-7, 6-8 and 6-9).
13.22 mpeg4_unpack_bframes
Unpack DivX-style packed B-frames.
DivX-style packed B-frames are not valid MPEG-4 and were only a workaround for the broken Video for Windows subsystem. They use more space, can cause minor AV sync issues, require more CPU power to decode (unless the player has some decoded picture queue to compensate the 2,0,2,0 frame per packet style) and cause trouble if copied into a standard container like mp4 or mpeg-ps/ts, because MPEG-4 decoders may not be able to decode them, since they are not valid MPEG-4.
For example to fix an AVI file containing an MPEG-4 stream with
DivX-style packed B-frames using ffmpeg
, you can use the command:
ffmpeg -i INPUT.avi -codec copy -bsf:v mpeg4_unpack_bframes OUTPUT.avi
13.23 noise
Damages the contents of packets or simply drops them without damaging the container. Can be used for fuzzing or testing error resilience/concealment.
Parameters:
- amount
Accepts an expression whose evaluation per-packet determines how often bytes in that packet will be modified. A value below 0 will result in a variable frequency. Default is 0 which results in no modification. However, if neither amount nor drop is specified, amount will be set to -1. See below for accepted variables.
- drop
Accepts an expression evaluated per-packet whose value determines whether that packet is dropped. Evaluation to a positive value results in the packet being dropped. Evaluation to a negative value results in a variable chance of it being dropped, roughly inverse in proportion to the magnitude of the value. Default is 0 which results in no drops. See below for accepted variables.
- dropamount
Accepts a non-negative integer, which assigns a variable chance of it being dropped, roughly inverse in proportion to the value. Default is 0 which results in no drops. This option is kept for backwards compatibility and is equivalent to setting drop to a negative value with the same magnitude i.e.
dropamount=4
is the same asdrop=-4
. Ignored if drop is also specified.
Both amount
and drop
accept expressions containing the following variables:
- ‘n’
The index of the packet, starting from zero.
- ‘tb’
The timebase for packet timestamps.
- ‘pts’
Packet presentation timestamp.
- ‘dts’
Packet decoding timestamp.
- ‘nopts’
Constant representing AV_NOPTS_VALUE.
- ‘startpts’
First non-AV_NOPTS_VALUE PTS seen in the stream.
- ‘startdts’
First non-AV_NOPTS_VALUE DTS seen in the stream.
- ‘duration’
- ‘d’
Packet duration, in timebase units.
- ‘pos’
Packet position in input; may be -1 when unknown or not set.
- ‘size’
Packet size, in bytes.
- ‘key’
Whether packet is marked as a keyframe.
- ‘state’
A pseudo random integer, primarily derived from the content of packet payload.
13.23.1 Examples
Apply modification to every byte but don’t drop any packets.
ffmpeg -i INPUT -c copy -bsf noise=1 output.mkv
Drop every video packet not marked as a keyframe after timestamp 30s but do not modify any of the remaining packets.
ffmpeg -i INPUT -c copy -bsf:v noise=drop='gt(t\,30)*not(key)' output.mkv
Drop one second of audio every 10 seconds and add some random noise to the rest.
ffmpeg -i INPUT -c copy -bsf:a noise=amount=-1:drop='between(mod(t\,10)\,9\,10)' output.mkv
13.24 null
This bitstream filter passes the packets through unchanged.
13.25 pcm_rechunk
Repacketize PCM audio to a fixed number of samples per packet or a fixed packet rate per second. This is similar to the (ffmpeg-filters)asetnsamples audio filter but works on audio packets instead of audio frames.
- nb_out_samples, n
Set the number of samples per each output audio packet. The number is intended as the number of samples per each channel. Default value is 1024.
- pad, p
If set to 1, the filter will pad the last audio packet with silence, so that it will contain the same number of samples (or roughly the same number of samples, see frame_rate) as the previous ones. Default value is 1.
- frame_rate, r
This option makes the filter output a fixed number of packets per second instead of a fixed number of samples per packet. If the audio sample rate is not divisible by the frame rate then the number of samples will not be constant but will vary slightly so that each packet will start as close to the frame boundary as possible. Using this option has precedence over nb_out_samples.
You can generate the well known 1602-1601-1602-1601-1602 pattern of 48kHz audio for NTSC frame rate using the frame_rate option.
ffmpeg -f lavfi -i sine=r=48000:d=1 -c pcm_s16le -bsf pcm_rechunk=r=30000/1001 -f framecrc -
13.26 pgs_frame_merge
Merge a sequence of PGS Subtitle segments ending with an "end of display set" segment into a single packet.
This is required by some containers that support PGS subtitles
(muxer matroska
).
13.27 prores_metadata
Modify color property metadata embedded in prores stream.
- color_primaries
Set the color primaries. Available values are:
- ‘auto’
Keep the same color primaries property (default).
- ‘unknown’
- ‘bt709’
- ‘bt470bg’
BT601 625
- ‘smpte170m’
BT601 525
- ‘bt2020’
- ‘smpte431’
DCI P3
- ‘smpte432’
P3 D65
- transfer_characteristics
Set the color transfer. Available values are:
- ‘auto’
Keep the same transfer characteristics property (default).
- ‘unknown’
- ‘bt709’
BT 601, BT 709, BT 2020
- ‘smpte2084’
SMPTE ST 2084
- ‘arib-std-b67’
ARIB STD-B67
- matrix_coefficients
Set the matrix coefficient. Available values are:
- ‘auto’
Keep the same colorspace property (default).
- ‘unknown’
- ‘bt709’
- ‘smpte170m’
BT 601
- ‘bt2020nc’
Set Rec709 colorspace for each frame of the file
ffmpeg -i INPUT -c copy -bsf:v prores_metadata=color_primaries=bt709:color_trc=bt709:colorspace=bt709 output.mov
Set Hybrid Log-Gamma parameters for each frame of the file
ffmpeg -i INPUT -c copy -bsf:v prores_metadata=color_primaries=bt2020:color_trc=arib-std-b67:colorspace=bt2020nc output.mov
13.28 remove_extra
Remove extradata from packets.
It accepts the following parameter:
- freq
Set which frame types to remove extradata from.
- ‘k’
Remove extradata from non-keyframes only.
- ‘keyframe’
Remove extradata from keyframes only.
- ‘e, all’
Remove extradata from all frames.
13.29 setts
Set PTS and DTS in packets.
It accepts the following parameters:
- ts
- pts
- dts
Set expressions for PTS, DTS or both.
- duration
Set expression for duration.
- time_base
Set output time base.
The expressions are evaluated through the eval API and can contain the following constants:
- N
The count of the input packet. Starting from 0.
- TS
The demux timestamp in input in case of
ts
ordts
option or presentation timestamp in case ofpts
option.- POS
The original position in the file of the packet, or undefined if undefined for the current packet
- DTS
The demux timestamp in input.
- PTS
The presentation timestamp in input.
- DURATION
The duration in input.
- STARTDTS
The DTS of the first packet.
- STARTPTS
The PTS of the first packet.
- PREV_INDTS
The previous input DTS.
- PREV_INPTS
The previous input PTS.
- PREV_INDURATION
The previous input duration.
- PREV_OUTDTS
The previous output DTS.
- PREV_OUTPTS
The previous output PTS.
- PREV_OUTDURATION
The previous output duration.
- NEXT_DTS
The next input DTS.
- NEXT_PTS
The next input PTS.
- NEXT_DURATION
The next input duration.
- TB
The timebase of stream packet belongs.
- TB_OUT
The output timebase.
- SR
The sample rate of stream packet belongs.
- NOPTS
The AV_NOPTS_VALUE constant.
For example, to set PTS equal to DTS (not recommended if B-frames are involved):
ffmpeg -i INPUT -c:a copy -bsf:a setts=pts=DTS out.mkv
13.30 showinfo
Log basic packet information. Mainly useful for testing, debugging, and development.
13.31 text2movsub
Convert text subtitles to MOV subtitles (as used by the mov_text
codec) with metadata headers.
See also the mov2textsub filter.
13.32 trace_headers
Log trace output containing all syntax elements in the coded stream headers (everything above the level of individual coded blocks). This can be useful for debugging low-level stream issues.
Supports AV1, H.264, H.265, (M)JPEG, MPEG-2 and VP9, but depending on the build only a subset of these may be available.
13.33 truehd_core
Extract the core from a TrueHD stream, dropping ATMOS data.
13.34 vp9_metadata
Modify metadata embedded in a VP9 stream.
- color_space
Set the color space value in the frame header. Note that any frame set to RGB will be implicitly set to PC range and that RGB is incompatible with profiles 0 and 2.
- ‘unknown’
- ‘bt601’
- ‘bt709’
- ‘smpte170’
- ‘smpte240’
- ‘bt2020’
- ‘rgb’
- color_range
Set the color range value in the frame header. Note that any value imposed by the color space will take precedence over this value.
- ‘tv’
- ‘pc’
13.35 vp9_superframe
Merge VP9 invisible (alt-ref) frames back into VP9 superframes. This fixes merging of split/segmented VP9 streams where the alt-ref frame was split from its visible counterpart.
13.36 vp9_superframe_split
Split VP9 superframes into single frames.
13.37 vp9_raw_reorder
Given a VP9 stream with correct timestamps but possibly out of order, insert additional show-existing-frame packets to correct the ordering.
14 Format Options
The libavformat library provides some generic global options, which can be set on all the muxers and demuxers. In addition each muxer or demuxer may support so-called private options, which are specific for that component.
Options may be set by specifying -option value in the
FFmpeg tools, or by setting the value explicitly in the
AVFormatContext
options or using the libavutil/opt.h API
for programmatic use.
The list of supported options follows:
- avioflags flags (input/output)
Possible values:
- ‘direct’
Reduce buffering.
- probesize integer (input)
Set probing size in bytes, i.e. the size of the data to analyze to get stream information. A higher value will enable detecting more information in case it is dispersed into the stream, but will increase latency. Must be an integer not lesser than 32. It is 5000000 by default.
- max_probe_packets integer (input)
Set the maximum number of buffered packets when probing a codec. Default is 2500 packets.
- packetsize integer (output)
Set packet size.
- fflags flags
Set format flags. Some are implemented for a limited number of formats.
Possible values for input files:
- ‘discardcorrupt’
Discard corrupted packets.
- ‘fastseek’
Enable fast, but inaccurate seeks for some formats.
- ‘genpts’
Generate missing PTS if DTS is present.
- ‘igndts’
Ignore DTS if PTS is also set. In case the PTS is set, the DTS value is set to NOPTS. This is ignored when the
nofillin
flag is set.- ‘ignidx’
Ignore index.
- ‘nobuffer’
Reduce the latency introduced by buffering during initial input streams analysis.
- ‘nofillin’
Do not fill in missing values in packet fields that can be exactly calculated.
- ‘noparse’
Disable AVParsers, this needs
+nofillin
too.- ‘sortdts’
Try to interleave output packets by DTS. At present, available only for AVIs with an index.
Possible values for output files:
- ‘autobsf’
Automatically apply bitstream filters as required by the output format. Enabled by default.
- ‘bitexact’
Only write platform-, build- and time-independent data. This ensures that file and data checksums are reproducible and match between platforms. Its primary use is for regression testing.
- ‘flush_packets’
Write out packets immediately.
- ‘shortest’
Stop muxing at the end of the shortest stream. It may be needed to increase max_interleave_delta to avoid flushing the longer streams before EOF.
- seek2any integer (input)
Allow seeking to non-keyframes on demuxer level when supported if set to 1. Default is 0.
- analyzeduration integer (input)
Specify how many microseconds are analyzed to probe the input. A higher value will enable detecting more accurate information, but will increase latency. It defaults to 5,000,000 microseconds = 5 seconds.
- cryptokey hexadecimal string (input)
Set decryption key.
- indexmem integer (input)
Set max memory used for timestamp index (per stream).
- rtbufsize integer (input)
Set max memory used for buffering real-time frames.
- fdebug flags (input/output)
Print specific debug info.
Possible values:
- ‘ts’
- max_delay integer (input/output)
Set maximum muxing or demuxing delay in microseconds.
- fpsprobesize integer (input)
Set number of frames used to probe fps.
- audio_preload integer (output)
Set microseconds by which audio packets should be interleaved earlier.
- chunk_duration integer (output)
Set microseconds for each chunk.
- chunk_size integer (output)
Set size in bytes for each chunk.
- err_detect, f_err_detect flags (input)
Set error detection flags.
f_err_detect
is deprecated and should be used only via theffmpeg
tool.Possible values:
- ‘crccheck’
Verify embedded CRCs.
- ‘bitstream’
Detect bitstream specification deviations.
- ‘buffer’
Detect improper bitstream length.
- ‘explode’
Abort decoding on minor error detection.
- ‘careful’
Consider things that violate the spec and have not been seen in the wild as errors.
- ‘compliant’
Consider all spec non compliancies as errors.
- ‘aggressive’
Consider things that a sane encoder should not do as an error.
- max_interleave_delta integer (output)
Set maximum buffering duration for interleaving. The duration is expressed in microseconds, and defaults to 10000000 (10 seconds).
To ensure all the streams are interleaved correctly, libavformat will wait until it has at least one packet for each stream before actually writing any packets to the output file. When some streams are "sparse" (i.e. there are large gaps between successive packets), this can result in excessive buffering.
This field specifies the maximum difference between the timestamps of the first and the last packet in the muxing queue, above which libavformat will output a packet regardless of whether it has queued a packet for all the streams.
If set to 0, libavformat will continue buffering packets until it has a packet for each stream, regardless of the maximum timestamp difference between the buffered packets.
- use_wallclock_as_timestamps integer (input)
Use wallclock as timestamps if set to 1. Default is 0.
- avoid_negative_ts integer (output)
-
Possible values:
- ‘make_non_negative’
Shift timestamps to make them non-negative. Also note that this affects only leading negative timestamps, and not non-monotonic negative timestamps.
- ‘make_zero’
Shift timestamps so that the first timestamp is 0.
- ‘auto (default)’
Enables shifting when required by the target format.
- ‘disabled’
Disables shifting of timestamp.
When shifting is enabled, all output timestamps are shifted by the same amount. Audio, video, and subtitles desynching and relative timestamp differences are preserved compared to how they would have been without shifting.
- skip_initial_bytes integer (input)
Set number of bytes to skip before reading header and frames if set to 1. Default is 0.
- correct_ts_overflow integer (input)
Correct single timestamp overflows if set to 1. Default is 1.
- flush_packets integer (output)
Flush the underlying I/O stream after each packet. Default is -1 (auto), which means that the underlying protocol will decide, 1 enables it, and has the effect of reducing the latency, 0 disables it and may increase IO throughput in some cases.
- output_ts_offset offset (output)
Set the output time offset.
offset must be a time duration specification, see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual.
The offset is added by the muxer to the output timestamps.
Specifying a positive offset means that the corresponding streams are delayed bt the time duration specified in offset. Default value is
0
(meaning that no offset is applied).- format_whitelist list (input)
"," separated list of allowed demuxers. By default all are allowed.
- dump_separator string (input)
Separator used to separate the fields printed on the command line about the Stream parameters. For example, to separate the fields with newlines and indentation:
ffprobe -dump_separator " " -i ~/videos/matrixbench_mpeg2.mpg
- max_streams integer (input)
Specifies the maximum number of streams. This can be used to reject files that would require too many resources due to a large number of streams.
- skip_estimate_duration_from_pts bool (input)
Skip estimation of input duration if it requires an additional probing for PTS at end of file. At present, applicable for MPEG-PS and MPEG-TS.
- duration_probesize integer (input)
Set probing size, in bytes, for input duration estimation when it actually requires an additional probing for PTS at end of file (at present: MPEG-PS and MPEG-TS). It is aimed at users interested in better durations probing for itself, or indirectly because using the concat demuxer, for example. The typical use case is an MPEG-TS CBR with a high bitrate, high video buffering and ending cleaning with similar PTS for video and audio: in such a scenario, the large physical gap between the last video packet and the last audio packet makes it necessary to read many bytes in order to get the video stream duration. Another use case is where the default probing behaviour only reaches a single video frame which is not the last one of the stream due to frame reordering, so the duration is not accurate. Setting this option has a performance impact even for small files because the probing size is fixed. Default behaviour is a general purpose trade-off, largely adaptive, but the probing size will not be extended to get streams durations at all costs. Must be an integer not lesser than 1, or 0 for default behaviour.
- strict, f_strict integer (input/output)
Specify how strictly to follow the standards.
f_strict
is deprecated and should be used only via theffmpeg
tool.Possible values:
- ‘very’
strictly conform to an older more strict version of the spec or reference software
- ‘strict’
strictly conform to all the things in the spec no matter what consequences
- ‘normal’
- ‘unofficial’
allow unofficial extensions
- ‘experimental’
allow non standardized experimental things, experimental (unfinished/work in progress/not well tested) decoders and encoders. Note: experimental decoders can pose a security risk, do not use this for decoding untrusted input.
14.1 Format stream specifiers
Format stream specifiers allow selection of one or more streams that match specific properties.
The exact semantics of stream specifiers is defined by the
avformat_match_stream_specifier()
function declared in the
libavformat/avformat.h header and documented in the
(ffmpeg)Stream specifiers section in the ffmpeg(1) manual.
15 Demuxers
Demuxers are configured elements in FFmpeg that can read the multimedia streams from a particular type of file.
When you configure your FFmpeg build, all the supported demuxers
are enabled by default. You can list all available ones using the
configure option --list-demuxers
.
You can disable all the demuxers using the configure option
--disable-demuxers
, and selectively enable a single demuxer with
the option --enable-demuxer=DEMUXER
, or disable it
with the option --disable-demuxer=DEMUXER
.
The option -demuxers
of the ff* tools will display the list of
enabled demuxers. Use -formats
to view a combined list of
enabled demuxers and muxers.
The description of some of the currently available demuxers follows.
15.1 aa
Audible Format 2, 3, and 4 demuxer.
This demuxer is used to demux Audible Format 2, 3, and 4 (.aa) files.
15.2 aac
Raw Audio Data Transport Stream AAC demuxer.
This demuxer is used to demux an ADTS input containing a single AAC stream alongwith any ID3v1/2 or APE tags in it.
15.3 apng
Animated Portable Network Graphics demuxer.
This demuxer is used to demux APNG files. All headers, but the PNG signature, up to (but not including) the first fcTL chunk are transmitted as extradata. Frames are then split as being all the chunks between two fcTL ones, or between the last fcTL and IEND chunks.
- -ignore_loop bool
Ignore the loop variable in the file if set. Default is enabled.
- -max_fps int
Maximum framerate in frames per second. Default of 0 imposes no limit.
- -default_fps int
Default framerate in frames per second when none is specified in the file (0 meaning as fast as possible). Default is 15.
15.4 asf
Advanced Systems Format demuxer.
This demuxer is used to demux ASF files and MMS network streams.
- -no_resync_search bool
Do not try to resynchronize by looking for a certain optional start code.
15.5 concat
Virtual concatenation script demuxer.
This demuxer reads a list of files and other directives from a text file and demuxes them one after the other, as if all their packets had been muxed together.
The timestamps in the files are adjusted so that the first file starts at 0 and each next file starts where the previous one finishes. Note that it is done globally and may cause gaps if all streams do not have exactly the same length.
All files must have the same streams (same codecs, same time base, etc.).
The duration of each file is used to adjust the timestamps of the next file:
if the duration is incorrect (because it was computed using the bit-rate or
because the file is truncated, for example), it can cause artifacts. The
duration
directive can be used to override the duration stored in
each file.
15.5.1 Syntax
The script is a text file in extended-ASCII, with one directive per line. Empty lines, leading spaces and lines starting with ’#’ are ignored. The following directive is recognized:
file path
Path to a file to read; special characters and spaces must be escaped with backslash or single quotes.
All subsequent file-related directives apply to that file.
ffconcat version 1.0
Identify the script type and version.
To make FFmpeg recognize the format automatically, this directive must appear exactly as is (no extra space or byte-order-mark) on the very first line of the script.
duration dur
Duration of the file. This information can be specified from the file; specifying it here may be more efficient or help if the information from the file is not available or accurate.
If the duration is set for all files, then it is possible to seek in the whole concatenated video.
inpoint timestamp
In point of the file. When the demuxer opens the file it instantly seeks to the specified timestamp. Seeking is done so that all streams can be presented successfully at In point.
This directive works best with intra frame codecs, because for non-intra frame ones you will usually get extra packets before the actual In point and the decoded content will most likely contain frames before In point too.
For each file, packets before the file In point will have timestamps less than the calculated start timestamp of the file (negative in case of the first file), and the duration of the files (if not specified by the
duration
directive) will be reduced based on their specified In point.Because of potential packets before the specified In point, packet timestamps may overlap between two concatenated files.
outpoint timestamp
Out point of the file. When the demuxer reaches the specified decoding timestamp in any of the streams, it handles it as an end of file condition and skips the current and all the remaining packets from all streams.
Out point is exclusive, which means that the demuxer will not output packets with a decoding timestamp greater or equal to Out point.
This directive works best with intra frame codecs and formats where all streams are tightly interleaved. For non-intra frame codecs you will usually get additional packets with presentation timestamp after Out point therefore the decoded content will most likely contain frames after Out point too. If your streams are not tightly interleaved you may not get all the packets from all streams before Out point and you may only will be able to decode the earliest stream until Out point.
The duration of the files (if not specified by the
duration
directive) will be reduced based on their specified Out point.file_packet_metadata key=value
Metadata of the packets of the file. The specified metadata will be set for each file packet. You can specify this directive multiple times to add multiple metadata entries. This directive is deprecated, use
file_packet_meta
instead.file_packet_meta key value
Metadata of the packets of the file. The specified metadata will be set for each file packet. You can specify this directive multiple times to add multiple metadata entries.
option key value
Option to access, open and probe the file. Can be present multiple times.
stream
Introduce a stream in the virtual file. All subsequent stream-related directives apply to the last introduced stream. Some streams properties must be set in order to allow identifying the matching streams in the subfiles. If no streams are defined in the script, the streams from the first file are copied.
exact_stream_id id
Set the id of the stream. If this directive is given, the string with the corresponding id in the subfiles will be used. This is especially useful for MPEG-PS (VOB) files, where the order of the streams is not reliable.
stream_meta key value
Metadata for the stream. Can be present multiple times.
stream_codec value
Codec for the stream.
stream_extradata hex_string
Extradata for the string, encoded in hexadecimal.
chapter id start end
Add a chapter. id is an unique identifier, possibly small and consecutive.
15.5.2 Options
This demuxer accepts the following option:
- safe
If set to 1, reject unsafe file paths and directives. A file path is considered safe if it does not contain a protocol specification and is relative and all components only contain characters from the portable character set (letters, digits, period, underscore and hyphen) and have no period at the beginning of a component.
If set to 0, any file name is accepted.
The default is 1.
- auto_convert
If set to 1, try to perform automatic conversions on packet data to make the streams concatenable. The default is 1.
Currently, the only conversion is adding the h264_mp4toannexb bitstream filter to H.264 streams in MP4 format. This is necessary in particular if there are resolution changes.
- segment_time_metadata
If set to 1, every packet will contain the lavf.concat.start_time and the lavf.concat.duration packet metadata values which are the start_time and the duration of the respective file segments in the concatenated output expressed in microseconds. The duration metadata is only set if it is known based on the concat file. The default is 0.
15.5.3 Examples
- Use absolute filenames and include some comments:
# my first filename file /mnt/share/file-1.wav # my second filename including whitespace file '/mnt/share/file 2.wav' # my third filename including whitespace plus single quote file '/mnt/share/file 3'\''.wav'
- Allow for input format auto-probing, use safe filenames and set the duration of
the first file:
ffconcat version 1.0 file file-1.wav duration 20.0 file subdir/file-2.wav
15.6 dash
Dynamic Adaptive Streaming over HTTP demuxer.
This demuxer presents all AVStreams found in the manifest.
By setting the discard flags on AVStreams the caller can decide
which streams to actually receive.
Each stream mirrors the id
and bandwidth
properties from the
<Representation>
as metadata keys named "id" and "variant_bitrate" respectively.
15.6.1 Options
This demuxer accepts the following option:
- cenc_decryption_key
16-byte key, in hex, to decrypt files encrypted using ISO Common Encryption (CENC/AES-128 CTR; ISO/IEC 23001-7).
15.7 dvdvideo
DVD-Video demuxer, powered by libdvdnav and libdvdread.
Can directly ingest DVD titles, specifically sequential PGCs, into a conversion pipeline. Menu assets, such as background video or audio, can also be demuxed given the menu’s coordinates (at best effort). Seeking is not supported at this time.
Block devices (DVD drives), ISO files, and directory structures are accepted.
Activate with -f dvdvideo
in front of one of these inputs.
This demuxer does NOT have decryption code of any kind. You are on your own working with encrypted DVDs, and should not expect support on the matter.
Underlying playback is handled by libdvdnav, and structure parsing by libdvdread.
FFmpeg must be built with GPL library support available as well as the
configure switches --enable-libdvdnav
and --enable-libdvdread
.
You will need to provide either the desired "title number" or exact PGC/PG coordinates. Many open-source DVD players and tools can aid in providing this information. If not specified, the demuxer will default to title 1 which works for many discs. However, due to the flexibility of the format, it is recommended to check manually. There are many discs that are authored strangely or with invalid headers.
If the input is a real DVD drive, please note that there are some drives which may silently fail on reading bad sectors from the disc, returning random bits instead which is effectively corrupt data. This is especially prominent on aging or rotting discs. A second pass and integrity checks would be needed to detect the corruption. This is not an FFmpeg issue.
15.7.1 Background
DVD-Video is not a directly accessible, linear container format in the traditional sense. Instead, it allows for complex and programmatic playback of carefully muxed MPEG-PS streams that are stored in headerless VOB files. To the end-user, these streams are known simply as "titles", but the actual logical playback sequence is defined by one or more "PGCs", or Program Group Chains, within the title. The PGC is in turn comprised of multiple "PGs", or Programs", which are the actual video segments (and for a typical video feature, sequentially ordered). The PGC structure, along with stream layout and metadata, are stored in IFO files that need to be parsed. PGCs can be thought of as playlists in easier terms.
An actual DVD player relies on user GUI interaction via menus and an internal VM to drive the direction of demuxing. Generally, the user would either navigate (via menus) or automatically be redirected to the PGC of their choice. During this process and the subsequent playback, the DVD player’s internal VM also maintains a state and executes instructions that can create jumps to different sectors during playback. This is why libdvdnav is involved, as a linear read of the MPEG-PS blobs on the disc (VOBs) is not enough to produce the right sequence in many cases.
There are many other DVD structures (a long subject) that will not be discussed here. NAV packets, in particular, are handled by this demuxer to build accurate timing but not emitted as a stream. For a good high-level understanding, refer to: https://code.videolan.org/videolan/libdvdnav/-/blob/master/doc/dvd_structures
15.7.2 Options
This demuxer accepts the following options:
- title int
The title number to play. Must be set if pgc and pg are not set. Not applicable to menus. Default is 0 (auto), which currently only selects the first available title (title 1) and notifies the user about the implications.
- chapter_start int
The chapter, or PTT (part-of-title), number to start at. Not applicable to menus. Default is 1.
- chapter_end int
The chapter, or PTT (part-of-title), number to end at. Not applicable to menus. Default is 0, which is a special value to signal end at the last possible chapter.
- angle int
The video angle number, referring to what is essentially an additional video stream that is composed from alternate frames interleaved in the VOBs. Not applicable to menus. Default is 1.
- region int
The region code to use for playback. Some discs may use this to default playback at a particular angle in different regions. This option will not affect the region code of a real DVD drive, if used as an input. Not applicable to menus. Default is 0, "world".
- menu bool
Demux menu assets instead of navigating a title. Requires exact coordinates of the menu (menu_lu, menu_vts, pgc, pg). Default is false.
- menu_lu int
The menu language to demux. In DVD, menus are grouped by language. Default is 0, the first language unit.
- menu_vts int
The VTS where the menu lives, or 0 if it is a VMG menu (root-level). Default is 0, VMG menu.
- pgc int
The entry PGC to start playback, in conjunction with pg. Alternative to setting title. Chapter markers are not supported at this time. Must be explicitly set for menus. Default is 0, automatically resolve from value of title.
- pg int
The entry PG to start playback, in conjunction with pgc. Alternative to setting title. Chapter markers are not supported at this time. Default is 0, automatically resolve from value of title, or start from the beginning (PG 1) of the menu.
- preindex bool
Enable this to have accurate chapter (PTT) markers and duration measurement, which requires a slow second pass read in order to index the chapter marker timestamps from NAV packets. This is non-ideal extra work for real optical drives. It is recommended and faster to use this option with a backup of the DVD structure stored on a hard drive. Not compatible with pgc and pg. Not applicable to menus. Default is 0, false.
- trim bool
Skip padding cells (i.e. cells shorter than 1 second) from the beginning. There exist many discs with filler segments at the beginning of the PGC, often with junk data intended for controlling a real DVD player’s buffering speed and with no other material data value. Not applicable to menus. Default is 1, true.
15.7.3 Examples
- Open title 3 from a given DVD structure:
ffmpeg -f dvdvideo -title 3 -i <path to DVD> ...
- Open chapters 3-6 from title 1 from a given DVD structure:
ffmpeg -f dvdvideo -chapter_start 3 -chapter_end 6 -title 1 -i <path to DVD> ...
- Open only chapter 5 from title 1 from a given DVD structure:
ffmpeg -f dvdvideo -chapter_start 5 -chapter_end 5 -title 1 -i <path to DVD> ...
- Demux menu with language 1 from VTS 1, PGC 1, starting at PG 1:
ffmpeg -f dvdvideo -menu 1 -menu_lu 1 -menu_vts 1 -pgc 1 -pg 1 -i <path to DVD> ...
15.8 ea
Electronic Arts Multimedia format demuxer.
This format is used by various Electronic Arts games.
15.8.1 Options
- merge_alpha bool
-
Normally the VP6 alpha channel (if exists) is returned as a secondary video stream, by setting this option you can make the demuxer return a single video stream which contains the alpha channel in addition to the ordinary video.
15.9 imf
Interoperable Master Format demuxer.
This demuxer presents audio and video streams found in an IMF Composition, as specified in SMPTE ST 2067-2.
ffmpeg [-assetmaps <path of ASSETMAP1>,<path of ASSETMAP2>,...] -i <path of CPL> ...
If -assetmaps
is not specified, the demuxer looks for a file called
ASSETMAP.xml in the same directory as the CPL.
15.10 flv, live_flv, kux
Adobe Flash Video Format demuxer.
This demuxer is used to demux FLV files and RTMP network streams. In case of live network streams, if you force format, you may use live_flv option instead of flv to survive timestamp discontinuities. KUX is a flv variant used on the Youku platform.
ffmpeg -f flv -i myfile.flv ... ffmpeg -f live_flv -i rtmp://<any.server>/anything/key ....
- -flv_metadata bool
Allocate the streams according to the onMetaData array content.
- -flv_ignore_prevtag bool
Ignore the size of previous tag value.
- -flv_full_metadata bool
Output all context of the onMetadata.
15.11 gif
Animated GIF demuxer.
It accepts the following options:
- min_delay
Set the minimum valid delay between frames in hundredths of seconds. Range is 0 to 6000. Default value is 2.
- max_gif_delay
Set the maximum valid delay between frames in hundredth of seconds. Range is 0 to 65535. Default value is 65535 (nearly eleven minutes), the maximum value allowed by the specification.
- default_delay
Set the default delay between frames in hundredths of seconds. Range is 0 to 6000. Default value is 10.
- ignore_loop
GIF files can contain information to loop a certain number of times (or infinitely). If ignore_loop is set to 1, then the loop setting from the input will be ignored and looping will not occur. If set to 0, then looping will occur and will cycle the number of times according to the GIF. Default value is 1.
For example, with the overlay filter, place an infinitely looping GIF over another video:
ffmpeg -i input.mp4 -ignore_loop 0 -i input.gif -filter_complex overlay=shortest=1 out.mkv
Note that in the above example the shortest option for overlay filter is used to end the output video at the length of the shortest input file, which in this case is input.mp4 as the GIF in this example loops infinitely.
15.12 hls
HLS demuxer
Apple HTTP Live Streaming demuxer.
This demuxer presents all AVStreams from all variant streams. The id field is set to the bitrate variant index number. By setting the discard flags on AVStreams (by pressing ’a’ or ’v’ in ffplay), the caller can decide which variant streams to actually receive. The total bitrate of the variant that the stream belongs to is available in a metadata key named "variant_bitrate".
It accepts the following options:
- live_start_index
segment index to start live streams at (negative values are from the end).
- prefer_x_start
prefer to use #EXT-X-START if it’s in playlist instead of live_start_index.
- allowed_extensions
’,’ separated list of file extensions that hls is allowed to access.
- max_reload
Maximum number of times a insufficient list is attempted to be reloaded. Default value is 1000.
- m3u8_hold_counters
The maximum number of times to load m3u8 when it refreshes without new segments. Default value is 1000.
- http_persistent
Use persistent HTTP connections. Applicable only for HTTP streams. Enabled by default.
- http_multiple
Use multiple HTTP connections for downloading HTTP segments. Enabled by default for HTTP/1.1 servers.
- http_seekable
Use HTTP partial requests for downloading HTTP segments. 0 = disable, 1 = enable, -1 = auto, Default is auto.
- seg_format_options
Set options for the demuxer of media segments using a list of key=value pairs separated by
:
.- seg_max_retry
Maximum number of times to reload a segment on error, useful when segment skip on network error is not desired. Default value is 0.
15.13 image2
Image file demuxer.
This demuxer reads from a list of image files specified by a pattern. The syntax and meaning of the pattern is specified by the option pattern_type.
The pattern may contain a suffix which is used to automatically determine the format of the images contained in the files.
The size, the pixel format, and the format of each image must be the same for all the files in the sequence.
This demuxer accepts the following options:
- framerate
Set the frame rate for the video stream. It defaults to 25.
- loop
If set to 1, loop over the input. Default value is 0.
- pattern_type
Select the pattern type used to interpret the provided filename.
pattern_type accepts one of the following values.
- none
Disable pattern matching, therefore the video will only contain the specified image. You should use this option if you do not want to create sequences from multiple images and your filenames may contain special pattern characters.
- sequence
Select a sequence pattern type, used to specify a sequence of files indexed by sequential numbers.
A sequence pattern may contain the string "%d" or "%0Nd", which specifies the position of the characters representing a sequential number in each filename matched by the pattern. If the form "%d0Nd" is used, the string representing the number in each filename is 0-padded and N is the total number of 0-padded digits representing the number. The literal character ’%’ can be specified in the pattern with the string "%%".
If the sequence pattern contains "%d" or "%0Nd", the first filename of the file list specified by the pattern must contain a number inclusively contained between start_number and start_number+start_number_range-1, and all the following numbers must be sequential.
For example the pattern "img-%03d.bmp" will match a sequence of filenames of the form img-001.bmp, img-002.bmp, ..., img-010.bmp, etc.; the pattern "i%%m%%g-%d.jpg" will match a sequence of filenames of the form i%m%g-1.jpg, i%m%g-2.jpg, ..., i%m%g-10.jpg, etc.
Note that the pattern must not necessarily contain "%d" or "%0Nd", for example to convert a single image file img.jpeg you can employ the command:
ffmpeg -i img.jpeg img.png
- glob
Select a glob wildcard pattern type.
The pattern is interpreted like a
glob()
pattern. This is only selectable if libavformat was compiled with globbing support.- glob_sequence (deprecated, will be removed)
Select a mixed glob wildcard/sequence pattern.
If your version of libavformat was compiled with globbing support, and the provided pattern contains at least one glob meta character among
%*?[]{}
that is preceded by an unescaped "%", the pattern is interpreted like aglob()
pattern, otherwise it is interpreted like a sequence pattern.All glob special characters
%*?[]{}
must be prefixed with "%". To escape a literal "%" you shall use "%%".For example the pattern
foo-%*.jpeg
will match all the filenames prefixed by "foo-" and terminating with ".jpeg", andfoo-%?%?%?.jpeg
will match all the filenames prefixed with "foo-", followed by a sequence of three characters, and terminating with ".jpeg".This pattern type is deprecated in favor of glob and sequence.
Default value is glob_sequence.
- pixel_format
Set the pixel format of the images to read. If not specified the pixel format is guessed from the first image file in the sequence.
- start_number
Set the index of the file matched by the image file pattern to start to read from. Default value is 0.
- start_number_range
Set the index interval range to check when looking for the first image file in the sequence, starting from start_number. Default value is 5.
- ts_from_file
If set to 1, will set frame timestamp to modification time of image file. Note that monotonity of timestamps is not provided: images go in the same order as without this option. Default value is 0. If set to 2, will set frame timestamp to the modification time of the image file in nanosecond precision.
- video_size
Set the video size of the images to read. If not specified the video size is guessed from the first image file in the sequence.
- export_path_metadata
If set to 1, will add two extra fields to the metadata found in input, making them also available for other filters (see drawtext filter for examples). Default value is 0. The extra fields are described below:
- lavf.image2dec.source_path
Corresponds to the full path to the input file being read.
- lavf.image2dec.source_basename
Corresponds to the name of the file being read.
15.13.1 Examples
- Use
ffmpeg
for creating a video from the images in the file sequence img-001.jpeg, img-002.jpeg, ..., assuming an input frame rate of 10 frames per second:ffmpeg -framerate 10 -i 'img-%03d.jpeg' out.mkv
- As above, but start by reading from a file with index 100 in the sequence:
ffmpeg -framerate 10 -start_number 100 -i 'img-%03d.jpeg' out.mkv
- Read images matching the "*.png" glob pattern , that is all the files
terminating with the ".png" suffix:
ffmpeg -framerate 10 -pattern_type glob -i "*.png" out.mkv
15.14 libgme
The Game Music Emu library is a collection of video game music file emulators.
See https://bitbucket.org/mpyne/game-music-emu/overview for more information.
It accepts the following options:
- track_index
Set the index of which track to demux. The demuxer can only export one track. Track indexes start at 0. Default is to pick the first track. Number of tracks is exported as tracks metadata entry.
- sample_rate
Set the sampling rate of the exported track. Range is 1000 to 999999. Default is 44100.
- max_size (bytes)
The demuxer buffers the entire file into memory. Adjust this value to set the maximum buffer size, which in turn, acts as a ceiling for the size of files that can be read. Default is 50 MiB.
15.15 libmodplug
ModPlug based module demuxer
See https://github.com/Konstanty/libmodplug
It will export one 2-channel 16-bit 44.1 kHz audio stream.
Optionally, a pal8
16-color video stream can be exported with or without printed metadata.
It accepts the following options:
- noise_reduction
Apply a simple low-pass filter. Can be 1 (on) or 0 (off). Default is 0.
- reverb_depth
Set amount of reverb. Range 0-100. Default is 0.
- reverb_delay
Set delay in ms, clamped to 40-250 ms. Default is 0.
- bass_amount
Apply bass expansion a.k.a. XBass or megabass. Range is 0 (quiet) to 100 (loud). Default is 0.
- bass_range
Set cutoff i.e. upper-bound for bass frequencies. Range is 10-100 Hz. Default is 0.
- surround_depth
Apply a Dolby Pro-Logic surround effect. Range is 0 (quiet) to 100 (heavy). Default is 0.
- surround_delay
Set surround delay in ms, clamped to 5-40 ms. Default is 0.
- max_size
The demuxer buffers the entire file into memory. Adjust this value to set the maximum buffer size, which in turn, acts as a ceiling for the size of files that can be read. Range is 0 to 100 MiB. 0 removes buffer size limit (not recommended). Default is 5 MiB.
- video_stream_expr
String which is evaluated using the eval API to assign colors to the generated video stream. Variables which can be used are
x
,y
,w
,h
,t
,speed
,tempo
,order
,pattern
androw
.- video_stream
Generate video stream. Can be 1 (on) or 0 (off). Default is 0.
- video_stream_w
Set video frame width in ’chars’ where one char indicates 8 pixels. Range is 20-512. Default is 30.
- video_stream_h
Set video frame height in ’chars’ where one char indicates 8 pixels. Range is 20-512. Default is 30.
- video_stream_ptxt
Print metadata on video stream. Includes
speed
,tempo
,order
,pattern
,row
andts
(time in ms). Can be 1 (on) or 0 (off). Default is 1.
15.16 libopenmpt
libopenmpt based module demuxer
See https://lib.openmpt.org/libopenmpt/ for more information.
Some files have multiple subsongs (tracks) this can be set with the subsong option.
It accepts the following options:
- subsong
Set the subsong index. This can be either ’all’, ’auto’, or the index of the subsong. Subsong indexes start at 0. The default is ’auto’.
The default value is to let libopenmpt choose.
- layout
Set the channel layout. Valid values are 1, 2, and 4 channel layouts. The default value is STEREO.
- sample_rate
Set the sample rate for libopenmpt to output. Range is from 1000 to INT_MAX. The value default is 48000.
15.17 mov/mp4/3gp
Demuxer for Quicktime File Format & ISO/IEC Base Media File Format (ISO/IEC 14496-12 or MPEG-4 Part 12, ISO/IEC 15444-12 or JPEG 2000 Part 12).
Registered extensions: mov, mp4, m4a, 3gp, 3g2, mj2, psp, m4b, ism, ismv, isma, f4v
15.17.1 Options
This demuxer accepts the following options:
- enable_drefs
Enable loading of external tracks, disabled by default. Enabling this can theoretically leak information in some use cases.
- use_absolute_path
Allows loading of external tracks via absolute paths, disabled by default. Enabling this poses a security risk. It should only be enabled if the source is known to be non-malicious.
- seek_streams_individually
When seeking, identify the closest point in each stream individually and demux packets in that stream from identified point. This can lead to a different sequence of packets compared to demuxing linearly from the beginning. Default is true.
- ignore_editlist
Ignore any edit list atoms. The demuxer, by default, modifies the stream index to reflect the timeline described by the edit list. Default is false.
- advanced_editlist
Modify the stream index to reflect the timeline described by the edit list.
ignore_editlist
must be set to false for this option to be effective. If bothignore_editlist
and this option are set to false, then only the start of the stream index is modified to reflect initial dwell time or starting timestamp described by the edit list. Default is true.- ignore_chapters
Don’t parse chapters. This includes GoPro ’HiLight’ tags/moments. Note that chapters are only parsed when input is seekable. Default is false.
- use_mfra_for
For seekable fragmented input, set fragment’s starting timestamp from media fragment random access box, if present.
Following options are available:
- ‘auto’
Auto-detect whether to set mfra timestamps as PTS or DTS (default)
- ‘dts’
Set mfra timestamps as DTS
- ‘pts’
Set mfra timestamps as PTS
- ‘0’
Don’t use mfra box to set timestamps
- use_tfdt
For fragmented input, set fragment’s starting timestamp to
baseMediaDecodeTime
from thetfdt
box. Default is enabled, which will prefer to use thetfdt
box to set DTS. Disable to use theearliest_presentation_time
from thesidx
box. In either case, the timestamp from themfra
box will be used if it’s available anduse_mfra_for
is set to pts or dts.- export_all
Export unrecognized boxes within the udta box as metadata entries. The first four characters of the box type are set as the key. Default is false.
- export_xmp
Export entire contents of XMP_ box and uuid box as a string with key
xmp
. Note that ifexport_all
is set and this option isn’t, the contents of XMP_ box are still exported but with keyXMP_
. Default is false.- activation_bytes
4-byte key required to decrypt Audible AAX and AAX+ files. See Audible AAX subsection below.
- audible_fixed_key
Fixed key used for handling Audible AAX/AAX+ files. It has been pre-set so should not be necessary to specify.
- decryption_key
16-byte key, in hex, to decrypt files encrypted using ISO Common Encryption (CENC/AES-128 CTR; ISO/IEC 23001-7).
- max_stts_delta
Very high sample deltas written in a trak’s stts box may occasionally be intended but usually they are written in error or used to store a negative value for dts correction when treated as signed 32-bit integers. This option lets the user set an upper limit, beyond which the delta is clamped to 1. Values greater than the limit if negative when cast to int32 are used to adjust onward dts.
Unit is the track time scale. Range is 0 to UINT_MAX. Default is
UINT_MAX - 48000*10
which allows up to a 10 second dts correction for 48 kHz audio streams while accommodating 99.9% ofuint32
range.- interleaved_read
Interleave packets from multiple tracks at demuxer level. For badly interleaved files, this prevents playback issues caused by large gaps between packets in different tracks, as MOV/MP4 do not have packet placement requirements. However, this can cause excessive seeking on very badly interleaved files, due to seeking between tracks, so disabling it may prevent I/O issues, at the expense of playback.
15.17.2 Audible AAX
Audible AAX files are encrypted M4B files, and they can be decrypted by specifying a 4 byte activation secret.
ffmpeg -activation_bytes 1CEB00DA -i test.aax -vn -c:a copy output.mp4
15.18 mpegts
MPEG-2 transport stream demuxer.
This demuxer accepts the following options:
- resync_size
Set size limit for looking up a new synchronization. Default value is 65536.
- skip_unknown_pmt
Skip PMTs for programs not defined in the PAT. Default value is 0.
- fix_teletext_pts
Override teletext packet PTS and DTS values with the timestamps calculated from the PCR of the first program which the teletext stream is part of and is not discarded. Default value is 1, set this option to 0 if you want your teletext packet PTS and DTS values untouched.
- ts_packetsize
Output option carrying the raw packet size in bytes. Show the detected raw packet size, cannot be set by the user.
- scan_all_pmts
Scan and combine all PMTs. The value is an integer with value from -1 to 1 (-1 means automatic setting, 1 means enabled, 0 means disabled). Default value is -1.
- merge_pmt_versions
Re-use existing streams when a PMT’s version is updated and elementary streams move to different PIDs. Default value is 0.
- max_packet_size
Set maximum size, in bytes, of packet emitted by the demuxer. Payloads above this size are split across multiple packets. Range is 1 to INT_MAX/2. Default is 204800 bytes.
15.19 mpjpeg
MJPEG encapsulated in multi-part MIME demuxer.
This demuxer allows reading of MJPEG, where each frame is represented as a part of multipart/x-mixed-replace stream.
- strict_mime_boundary
Default implementation applies a relaxed standard to multi-part MIME boundary detection, to prevent regression with numerous existing endpoints not generating a proper MIME MJPEG stream. Turning this option on by setting it to 1 will result in a stricter check of the boundary value.
15.20 rawvideo
Raw video demuxer.
This demuxer allows one to read raw video data. Since there is no header specifying the assumed video parameters, the user must specify them in order to be able to decode the data correctly.
This demuxer accepts the following options:
- framerate
Set input video frame rate. Default value is 25.
- pixel_format
Set the input video pixel format. Default value is
yuv420p
.- video_size
Set the input video size. This value must be specified explicitly.
For example to read a rawvideo file input.raw with
ffplay
, assuming a pixel format of rgb24
, a video
size of 320x240
, and a frame rate of 10 images per second, use
the command:
ffplay -f rawvideo -pixel_format rgb24 -video_size 320x240 -framerate 10 input.raw
15.21 rcwt
RCWT (Raw Captions With Time) is a format native to ccextractor, a commonly used open source tool for processing 608/708 Closed Captions (CC) sources. For more information on the format, see (ffmpeg-formats)rcwtenc.
This demuxer implements the specification as of March 2024, which has been stable and unchanged since April 2014.
15.21.1 Examples
- Render CC to ASS using the built-in decoder:
ffmpeg -i CC.rcwt.bin CC.ass
Note that if your output appears to be empty, you may have to manually set the decoder’s data_field option to pick the desired CC substream.
- Convert an RCWT backup to Scenarist (SCC) format:
ffmpeg -i CC.rcwt.bin -c:s copy CC.scc
Note that the SCC format does not support all of the possible CC extensions that can be stored in RCWT (such as EIA-708).
15.22 sbg
SBaGen script demuxer.
This demuxer reads the script language used by SBaGen http://uazu.net/sbagen/ to generate binaural beats sessions. A SBG script looks like that:
-SE a: 300-2.5/3 440+4.5/0 b: 300-2.5/0 440+4.5/3 off: - NOW == a +0:07:00 == b +0:14:00 == a +0:21:00 == b +0:30:00 off
A SBG script can mix absolute and relative timestamps. If the script uses either only absolute timestamps (including the script start time) or only relative ones, then its layout is fixed, and the conversion is straightforward. On the other hand, if the script mixes both kind of timestamps, then the NOW reference for relative timestamps will be taken from the current time of day at the time the script is read, and the script layout will be frozen according to that reference. That means that if the script is directly played, the actual times will match the absolute timestamps up to the sound controller’s clock accuracy, but if the user somehow pauses the playback or seeks, all times will be shifted accordingly.
15.23 tedcaptions
JSON captions used for TED Talks.
TED does not provide links to the captions, but they can be guessed from the page. The file tools/bookmarklets.html from the FFmpeg source tree contains a bookmarklet to expose them.
This demuxer accepts the following option:
- start_time
Set the start time of the TED talk, in milliseconds. The default is 15000 (15s). It is used to sync the captions with the downloadable videos, because they include a 15s intro.
Example: convert the captions to a format most players understand:
ffmpeg -i http://www.ted.com/talks/subtitles/id/1/lang/en talk1-en.srt
15.24 vapoursynth
Vapoursynth wrapper.
Due to security concerns, Vapoursynth scripts will not
be autodetected so the input format has to be forced. For ff* CLI tools,
add -f vapoursynth
before the input -i yourscript.vpy
.
This demuxer accepts the following option:
- max_script_size
The demuxer buffers the entire script into memory. Adjust this value to set the maximum buffer size, which in turn, acts as a ceiling for the size of scripts that can be read. Default is 1 MiB.
15.25 w64
Sony Wave64 Audio demuxer.
This demuxer accepts the following options:
- max_size
See the same option for the wav demuxer.
15.26 wav
RIFF Wave Audio demuxer.
This demuxer accepts the following options:
- max_size
Specify the maximum packet size in bytes for the demuxed packets. By default this is set to 0, which means that a sensible value is chosen based on the input format.
16 Metadata
FFmpeg is able to dump metadata from media files into a simple UTF-8-encoded INI-like text file and then load it back using the metadata muxer/demuxer.
The file format is as follows:
- A file consists of a header and a number of metadata tags divided into sections, each on its own line.
- The header is a ‘;FFMETADATA’ string, followed by a version number (now 1).
- Metadata tags are of the form ‘key=value’
- Immediately after header follows global metadata
- After global metadata there may be sections with per-stream/per-chapter metadata.
- A section starts with the section name in uppercase (i.e. STREAM or CHAPTER) in brackets (‘[’, ‘]’) and ends with next section or end of file.
- At the beginning of a chapter section there may be an optional timebase to be
used for start/end values. It must be in form
‘TIMEBASE=num/den’, where num and den are
integers. If the timebase is missing then start/end times are assumed to
be in nanoseconds.
Next a chapter section must contain chapter start and end times in form ‘START=num’, ‘END=num’, where num is a positive integer.
- Empty lines and lines starting with ‘;’ or ‘#’ are ignored.
- Metadata keys or values containing special characters (‘=’, ‘;’, ‘#’, ‘\’ and a newline) must be escaped with a backslash ‘\’.
- Note that whitespace in metadata (e.g. ‘foo = bar’) is considered to be a part of the tag (in the example above key is ‘foo ’, value is ‘ bar’).
A ffmetadata file might look like this:
;FFMETADATA1 title=bike\\shed ;this is a comment artist=FFmpeg troll team [CHAPTER] TIMEBASE=1/1000 START=0 #chapter ends at 0:01:00 END=60000 title=chapter \#1 [STREAM] title=multi\ line
By using the ffmetadata muxer and demuxer it is possible to extract metadata from an input file to an ffmetadata file, and then transcode the file into an output file with the edited ffmetadata file.
Extracting an ffmetadata file with ffmpeg goes as follows:
ffmpeg -i INPUT -f ffmetadata FFMETADATAFILE
Reinserting edited metadata information from the FFMETADATAFILE file can be done as:
ffmpeg -i INPUT -i FFMETADATAFILE -map_metadata 1 -codec copy OUTPUT
17 Protocol Options
The libavformat library provides some generic global options, which can be set on all the protocols. In addition each protocol may support so-called private options, which are specific for that component.
Options may be set by specifying -option value in the
FFmpeg tools, or by setting the value explicitly in the
AVFormatContext
options or using the libavutil/opt.h API
for programmatic use.
The list of supported options follows:
- protocol_whitelist list (input)
Set a ","-separated list of allowed protocols. "ALL" matches all protocols. Protocols prefixed by "-" are disabled. All protocols are allowed by default but protocols used by an another protocol (nested protocols) are restricted to a per protocol subset.
18 Protocols
Protocols are configured elements in FFmpeg that enable access to resources that require specific protocols.
When you configure your FFmpeg build, all the supported protocols are enabled by default. You can list all available ones using the configure option "–list-protocols".
You can disable all the protocols using the configure option "–disable-protocols", and selectively enable a protocol using the option "–enable-protocol=PROTOCOL", or you can disable a particular protocol using the option "–disable-protocol=PROTOCOL".
The option "-protocols" of the ff* tools will display the list of supported protocols.
All protocols accept the following options:
- rw_timeout
Maximum time to wait for (network) read/write operations to complete, in microseconds.
A description of the currently available protocols follows.
18.1 amqp
Advanced Message Queueing Protocol (AMQP) version 0-9-1 is a broker based publish-subscribe communication protocol.
FFmpeg must be compiled with –enable-librabbitmq to support AMQP. A separate AMQP broker must also be run. An example open-source AMQP broker is RabbitMQ.
After starting the broker, an FFmpeg client may stream data to the broker using the command:
ffmpeg -re -i input -f mpegts amqp://[[user]:[password]@]hostname[:port][/vhost]
Where hostname and port (default is 5672) is the address of the broker. The client may also set a user/password for authentication. The default for both fields is "guest". Name of virtual host on broker can be set with vhost. The default value is "/".
Muliple subscribers may stream from the broker using the command:
ffplay amqp://[[user]:[password]@]hostname[:port][/vhost]
In RabbitMQ all data published to the broker flows through a specific exchange, and each subscribing client has an assigned queue/buffer. When a packet arrives at an exchange, it may be copied to a client’s queue depending on the exchange and routing_key fields.
The following options are supported:
- exchange
Sets the exchange to use on the broker. RabbitMQ has several predefined exchanges: "amq.direct" is the default exchange, where the publisher and subscriber must have a matching routing_key; "amq.fanout" is the same as a broadcast operation (i.e. the data is forwarded to all queues on the fanout exchange independent of the routing_key); and "amq.topic" is similar to "amq.direct", but allows for more complex pattern matching (refer to the RabbitMQ documentation).
- routing_key
Sets the routing key. The default value is "amqp". The routing key is used on the "amq.direct" and "amq.topic" exchanges to decide whether packets are written to the queue of a subscriber.
- pkt_size
Maximum size of each packet sent/received to the broker. Default is 131072. Minimum is 4096 and max is any large value (representable by an int). When receiving packets, this sets an internal buffer size in FFmpeg. It should be equal to or greater than the size of the published packets to the broker. Otherwise the received message may be truncated causing decoding errors.
- connection_timeout
The timeout in seconds during the initial connection to the broker. The default value is rw_timeout, or 5 seconds if rw_timeout is not set.
- delivery_mode mode
Sets the delivery mode of each message sent to broker. The following values are accepted:
- ‘persistent’
Delivery mode set to "persistent" (2). This is the default value. Messages may be written to the broker’s disk depending on its setup.
- ‘non-persistent’
Delivery mode set to "non-persistent" (1). Messages will stay in broker’s memory unless the broker is under memory pressure.
18.2 async
Asynchronous data filling wrapper for input stream.
Fill data in a background thread, to decouple I/O operation from demux thread.
async:URL async:http://host/resource async:cache:http://host/resource
18.3 bluray
Read BluRay playlist.
The accepted options are:
- angle
BluRay angle
- chapter
Start chapter (1...N)
- playlist
Playlist to read (BDMV/PLAYLIST/?????.mpls)
Examples:
Read longest playlist from BluRay mounted to /mnt/bluray:
bluray:/mnt/bluray
Read angle 2 of playlist 4 from BluRay mounted to /mnt/bluray, start from chapter 2:
-playlist 4 -angle 2 -chapter 2 bluray:/mnt/bluray
18.4 cache
Caching wrapper for input stream.
Cache the input stream to temporary file. It brings seeking capability to live streams.
The accepted options are:
- read_ahead_limit
Amount in bytes that may be read ahead when seeking isn’t supported. Range is -1 to INT_MAX. -1 for unlimited. Default is 65536.
URL Syntax is
cache:URL
18.5 concat
Physical concatenation protocol.
Read and seek from many resources in sequence as if they were a unique resource.
A URL accepted by this protocol has the syntax:
concat:URL1|URL2|...|URLN
where URL1, URL2, ..., URLN are the urls of the resource to be concatenated, each one possibly specifying a distinct protocol.
For example to read a sequence of files split1.mpeg,
split2.mpeg, split3.mpeg with ffplay
use the
command:
ffplay concat:split1.mpeg\|split2.mpeg\|split3.mpeg
Note that you may need to escape the character "|" which is special for many shells.
18.6 concatf
Physical concatenation protocol using a line break delimited list of resources.
Read and seek from many resources in sequence as if they were a unique resource.
A URL accepted by this protocol has the syntax:
concatf:URL
where URL is the url containing a line break delimited list of resources to be concatenated, each one possibly specifying a distinct protocol. Special characters must be escaped with backslash or single quotes. See (ffmpeg-utils)the "Quoting and escaping" section in the ffmpeg-utils(1) manual.
For example to read a sequence of files split1.mpeg,
split2.mpeg, split3.mpeg listed in separate lines within
a file split.txt with ffplay
use the command:
ffplay concatf:split.txt
Where split.txt contains the lines:
split1.mpeg split2.mpeg split3.mpeg
18.7 crypto
AES-encrypted stream reading protocol.
The accepted options are:
- key
Set the AES decryption key binary block from given hexadecimal representation.
- iv
Set the AES decryption initialization vector binary block from given hexadecimal representation.
Accepted URL formats:
crypto:URL crypto+URL
18.8 data
Data in-line in the URI. See http://en.wikipedia.org/wiki/Data_URI_scheme.
For example, to convert a GIF file given inline with ffmpeg
:
ffmpeg -i "data:image/gif;base64,R0lGODdhCAAIAMIEAAAAAAAA//8AAP//AP///////////////ywAAAAACAAIAAADF0gEDLojDgdGiJdJqUX02iB4E8Q9jUMkADs=" smiley.png
18.9 fd
File descriptor access protocol.
The accepted syntax is:
fd: -fd file_descriptor
If fd is not specified, by default the stdout file descriptor will be used for writing, stdin for reading. Unlike the pipe protocol, fd protocol has seek support if it corresponding to a regular file. fd protocol doesn’t support pass file descriptor via URL for security.
This protocol accepts the following options:
- blocksize
Set I/O operation maximum block size, in bytes. Default value is
INT_MAX
, which results in not limiting the requested block size. Setting this value reasonably low improves user termination request reaction time, which is valuable if data transmission is slow.- fd
Set file descriptor.
18.10 file
File access protocol.
Read from or write to a file.
A file URL can have the form:
file:filename
where filename is the path of the file to read.
An URL that does not have a protocol prefix will be assumed to be a file URL. Depending on the build, an URL that looks like a Windows path with the drive letter at the beginning will also be assumed to be a file URL (usually not the case in builds for unix-like systems).
For example to read from a file input.mpeg with ffmpeg
use the command:
ffmpeg -i file:input.mpeg output.mpeg
This protocol accepts the following options:
- truncate
Truncate existing files on write, if set to 1. A value of 0 prevents truncating. Default value is 1.
- blocksize
Set I/O operation maximum block size, in bytes. Default value is
INT_MAX
, which results in not limiting the requested block size. Setting this value reasonably low improves user termination request reaction time, which is valuable for files on slow medium.- follow
If set to 1, the protocol will retry reading at the end of the file, allowing reading files that still are being written. In order for this to terminate, you either need to use the rw_timeout option, or use the interrupt callback (for API users).
- seekable
Controls if seekability is advertised on the file. 0 means non-seekable, -1 means auto (seekable for normal files, non-seekable for named pipes).
Many demuxers handle seekable and non-seekable resources differently, overriding this might speed up opening certain files at the cost of losing some features (e.g. accurate seeking).
18.11 ftp
FTP (File Transfer Protocol).
Read from or write to remote resources using FTP protocol.
Following syntax is required.
ftp://[user[:password]@]server[:port]/path/to/remote/resource.mpeg
This protocol accepts the following options.
- timeout
Set timeout in microseconds of socket I/O operations used by the underlying low level operation. By default it is set to -1, which means that the timeout is not specified.
- ftp-user
Set a user to be used for authenticating to the FTP server. This is overridden by the user in the FTP URL.
- ftp-password
Set a password to be used for authenticating to the FTP server. This is overridden by the password in the FTP URL, or by ftp-anonymous-password if no user is set.
- ftp-anonymous-password
Password used when login as anonymous user. Typically an e-mail address should be used.
- ftp-write-seekable
Control seekability of connection during encoding. If set to 1 the resource is supposed to be seekable, if set to 0 it is assumed not to be seekable. Default value is 0.
NOTE: Protocol can be used as output, but it is recommended to not do it, unless special care is taken (tests, customized server configuration etc.). Different FTP servers behave in different way during seek operation. ff* tools may produce incomplete content due to server limitations.
18.12 gopher
Gopher protocol.
18.13 gophers
Gophers protocol.
The Gopher protocol with TLS encapsulation.
18.14 hls
Read Apple HTTP Live Streaming compliant segmented stream as a uniform one. The M3U8 playlists describing the segments can be remote HTTP resources or local files, accessed using the standard file protocol. The nested protocol is declared by specifying "+proto" after the hls URI scheme name, where proto is either "file" or "http".
hls+http://host/path/to/remote/resource.m3u8 hls+file://path/to/local/resource.m3u8
Using this protocol is discouraged - the hls demuxer should work just as well (if not, please report the issues) and is more complete. To use the hls demuxer instead, simply use the direct URLs to the m3u8 files.
18.15 http
HTTP (Hyper Text Transfer Protocol).
This protocol accepts the following options:
- seekable
Control seekability of connection. If set to 1 the resource is supposed to be seekable, if set to 0 it is assumed not to be seekable, if set to -1 it will try to autodetect if it is seekable. Default value is -1.
- chunked_post
If set to 1 use chunked Transfer-Encoding for posts, default is 1.
- http_proxy
set HTTP proxy to tunnel through e.g. http://example.com:1234
- headers
Set custom HTTP headers, can override built in default headers. The value must be a string encoding the headers.
- content_type
Set a specific content type for the POST messages or for listen mode.
- user_agent
Override the User-Agent header. If not specified the protocol will use a string describing the libavformat build. ("Lavf/<version>")
- referer
Set the Referer header. Include ’Referer: URL’ header in HTTP request.
- multiple_requests
Use persistent connections if set to 1, default is 0.
- post_data
Set custom HTTP post data.
- mime_type
Export the MIME type.
- http_version
Exports the HTTP response version number. Usually "1.0" or "1.1".
- cookies
Set the cookies to be sent in future requests. The format of each cookie is the same as the value of a Set-Cookie HTTP response field. Multiple cookies can be delimited by a newline character.
- icy
If set to 1 request ICY (SHOUTcast) metadata from the server. If the server supports this, the metadata has to be retrieved by the application by reading the icy_metadata_headers and icy_metadata_packet options. The default is 1.
- icy_metadata_headers
If the server supports ICY metadata, this contains the ICY-specific HTTP reply headers, separated by newline characters.
- icy_metadata_packet
If the server supports ICY metadata, and icy was set to 1, this contains the last non-empty metadata packet sent by the server. It should be polled in regular intervals by applications interested in mid-stream metadata updates.
- metadata
Set an exported dictionary containing Icecast metadata from the bitstream, if present. Only useful with the C API.
- auth_type
-
Set HTTP authentication type. No option for Digest, since this method requires getting nonce parameters from the server first and can’t be used straight away like Basic.
- none
Choose the HTTP authentication type automatically. This is the default.
- basic
-
Choose the HTTP basic authentication.
Basic authentication sends a Base64-encoded string that contains a user name and password for the client. Base64 is not a form of encryption and should be considered the same as sending the user name and password in clear text (Base64 is a reversible encoding). If a resource needs to be protected, strongly consider using an authentication scheme other than basic authentication. HTTPS/TLS should be used with basic authentication. Without these additional security enhancements, basic authentication should not be used to protect sensitive or valuable information.
- send_expect_100
Send an Expect: 100-continue header for POST. If set to 1 it will send, if set to 0 it won’t, if set to -1 it will try to send if it is applicable. Default value is -1.
- location
An exported dictionary containing the content location. Only useful with the C API.
- offset
Set initial byte offset.
- end_offset
Try to limit the request to bytes preceding this offset.
- method
When used as a client option it sets the HTTP method for the request.
When used as a server option it sets the HTTP method that is going to be expected from the client(s). If the expected and the received HTTP method do not match the client will be given a Bad Request response. When unset the HTTP method is not checked for now. This will be replaced by autodetection in the future.
- reconnect
Reconnect automatically when disconnected before EOF is hit.
- reconnect_at_eof
If set then eof is treated like an error and causes reconnection, this is useful for live / endless streams.
- reconnect_on_network_error
Reconnect automatically in case of TCP/TLS errors during connect.
- reconnect_on_http_error
A comma separated list of HTTP status codes to reconnect on. The list can include specific status codes (e.g. ’503’) or the strings ’4xx’ / ’5xx’.
- reconnect_streamed
If set then even streamed/non seekable streams will be reconnected on errors.
- reconnect_delay_max
Set the maximum delay in seconds after which to give up reconnecting.
- reconnect_max_retries
Set the maximum number of times to retry a connection. Default unset.
- reconnect_delay_total_max
Set the maximum total delay in seconds after which to give up reconnecting.
- respect_retry_after
If enabled, and a Retry-After header is encountered, its requested reconnection delay will be honored, rather than using exponential backoff. Useful for 429 and 503 errors. Default enabled.
- listen
If set to 1 enables experimental HTTP server. This can be used to send data when used as an output option, or read data from a client with HTTP POST when used as an input option. If set to 2 enables experimental multi-client HTTP server. This is not yet implemented in ffmpeg.c and thus must not be used as a command line option.
# Server side (sending): ffmpeg -i somefile.ogg -c copy -listen 1 -f ogg http://server:port # Client side (receiving): ffmpeg -i http://server:port -c copy somefile.ogg # Client can also be done with wget: wget http://server:port -O somefile.ogg # Server side (receiving): ffmpeg -listen 1 -i http://server:port -c copy somefile.ogg # Client side (sending): ffmpeg -i somefile.ogg -chunked_post 0 -c copy -f ogg http://server:port # Client can also be done with wget: wget --post-file=somefile.ogg http://server:port
- resource
The resource requested by a client, when the experimental HTTP server is in use.
- reply_code
The HTTP code returned to the client, when the experimental HTTP server is in use.
- short_seek_size
Set the threshold, in bytes, for when a readahead should be prefered over a seek and new HTTP request. This is useful, for example, to make sure the same connection is used for reading large video packets with small audio packets in between.
18.15.1 HTTP Cookies
Some HTTP requests will be denied unless cookie values are passed in with the request. The cookies option allows these cookies to be specified. At the very least, each cookie must specify a value along with a path and domain. HTTP requests that match both the domain and path will automatically include the cookie value in the HTTP Cookie header field. Multiple cookies can be delimited by a newline.
The required syntax to play a stream specifying a cookie is:
ffplay -cookies "nlqptid=nltid=tsn; path=/; domain=somedomain.com;" http://somedomain.com/somestream.m3u8
18.16 Icecast
Icecast protocol (stream to Icecast servers)
This protocol accepts the following options:
- ice_genre
Set the stream genre.
- ice_name
Set the stream name.
- ice_description
Set the stream description.
- ice_url
Set the stream website URL.
- ice_public
Set if the stream should be public. The default is 0 (not public).
- user_agent
Override the User-Agent header. If not specified a string of the form "Lavf/<version>" will be used.
- password
Set the Icecast mountpoint password.
- content_type
Set the stream content type. This must be set if it is different from audio/mpeg.
- legacy_icecast
This enables support for Icecast versions < 2.4.0, that do not support the HTTP PUT method but the SOURCE method.
- tls
Establish a TLS (HTTPS) connection to Icecast.
icecast://[username[:password]@]server:port/mountpoint
18.17 ipfs
InterPlanetary File System (IPFS) protocol support. One can access files stored on the IPFS network through so-called gateways. These are http(s) endpoints. This protocol wraps the IPFS native protocols (ipfs:// and ipns://) to be sent to such a gateway. Users can (and should) host their own node which means this protocol will use one’s local gateway to access files on the IPFS network.
This protocol accepts the following options:
- gateway
Defines the gateway to use. When not set, the protocol will first try locating the local gateway by looking at
$IPFS_GATEWAY
,$IPFS_PATH
and$HOME/.ipfs/
, in that order.
One can use this protocol in 2 ways. Using IPFS:
ffplay ipfs://<hash>
Or the IPNS protocol (IPNS is mutable IPFS):
ffplay ipns://<hash>
18.18 mmst
MMS (Microsoft Media Server) protocol over TCP.
18.19 mmsh
MMS (Microsoft Media Server) protocol over HTTP.
The required syntax is:
mmsh://server[:port][/app][/playpath]
18.20 md5
MD5 output protocol.
Computes the MD5 hash of the data to be written, and on close writes this to the designated output or stdout if none is specified. It can be used to test muxers without writing an actual file.
Some examples follow.
# Write the MD5 hash of the encoded AVI file to the file output.avi.md5. ffmpeg -i input.flv -f avi -y md5:output.avi.md5 # Write the MD5 hash of the encoded AVI file to stdout. ffmpeg -i input.flv -f avi -y md5:
Note that some formats (typically MOV) require the output protocol to be seekable, so they will fail with the MD5 output protocol.
18.21 pipe
UNIX pipe access protocol.
Read and write from UNIX pipes.
The accepted syntax is:
pipe:[number]
If fd isn’t specified, number is the number corresponding to the file descriptor of the pipe (e.g. 0 for stdin, 1 for stdout, 2 for stderr). If number is not specified, by default the stdout file descriptor will be used for writing, stdin for reading.
For example to read from stdin with ffmpeg
:
cat test.wav | ffmpeg -i pipe:0 # ...this is the same as... cat test.wav | ffmpeg -i pipe:
For writing to stdout with ffmpeg
:
ffmpeg -i test.wav -f avi pipe:1 | cat > test.avi # ...this is the same as... ffmpeg -i test.wav -f avi pipe: | cat > test.avi
This protocol accepts the following options:
- blocksize
Set I/O operation maximum block size, in bytes. Default value is
INT_MAX
, which results in not limiting the requested block size. Setting this value reasonably low improves user termination request reaction time, which is valuable if data transmission is slow.- fd
Set file descriptor.
Note that some formats (typically MOV), require the output protocol to be seekable, so they will fail with the pipe output protocol.
18.22 prompeg
Pro-MPEG Code of Practice #3 Release 2 FEC protocol.
The Pro-MPEG CoP#3 FEC is a 2D parity-check forward error correction mechanism for MPEG-2 Transport Streams sent over RTP.
This protocol must be used in conjunction with the rtp_mpegts
muxer and
the rtp
protocol.
The required syntax is:
-f rtp_mpegts -fec prompeg=option=val... rtp://hostname:port
The destination UDP ports are port + 2
for the column FEC stream
and port + 4
for the row FEC stream.
This protocol accepts the following options:
- l=n
The number of columns (4-20, LxD <= 100)
- d=n
The number of rows (4-20, LxD <= 100)
Example usage:
-f rtp_mpegts -fec prompeg=l=8:d=4 rtp://hostname:port
18.23 rist
Reliable Internet Streaming Transport protocol
The accepted options are:
- rist_profile
Supported values:
- ‘simple’
- ‘main’
This one is default.
- ‘advanced’
- buffer_size
Set internal RIST buffer size in milliseconds for retransmission of data. Default value is 0 which means the librist default (1 sec). Maximum value is 30 seconds.
- fifo_size
Size of the librist receiver output fifo in number of packets. This must be a power of 2. Defaults to 8192 (vs the librist default of 1024).
- overrun_nonfatal=1|0
Survive in case of librist fifo buffer overrun. Default value is 0.
- pkt_size
Set maximum packet size for sending data. 1316 by default.
- log_level
Set loglevel for RIST logging messages. You only need to set this if you explicitly want to enable debug level messages or packet loss simulation, otherwise the regular loglevel is respected.
- secret
Set override of encryption secret, by default is unset.
- encryption
Set encryption type, by default is disabled. Acceptable values are 128 and 256.
18.24 rtmp
Real-Time Messaging Protocol.
The Real-Time Messaging Protocol (RTMP) is used for streaming multimedia content across a TCP/IP network.
The required syntax is:
rtmp://[username:password@]server[:port][/app][/instance][/playpath]
The accepted parameters are:
- username
An optional username (mostly for publishing).
- password
An optional password (mostly for publishing).
- server
The address of the RTMP server.
- port
The number of the TCP port to use (by default is 1935).
- app
It is the name of the application to access. It usually corresponds to the path where the application is installed on the RTMP server (e.g. /ondemand/, /flash/live/, etc.). You can override the value parsed from the URI through the
rtmp_app
option, too.- playpath
It is the path or name of the resource to play with reference to the application specified in app, may be prefixed by "mp4:". You can override the value parsed from the URI through the
rtmp_playpath
option, too.- listen
Act as a server, listening for an incoming connection.
- timeout
Maximum time to wait for the incoming connection. Implies listen.
Additionally, the following parameters can be set via command line options
(or in code via AVOption
s):
- rtmp_app
Name of application to connect on the RTMP server. This option overrides the parameter specified in the URI.
- rtmp_buffer
Set the client buffer time in milliseconds. The default is 3000.
- rtmp_conn
Extra arbitrary AMF connection parameters, parsed from a string, e.g. like
B:1 S:authMe O:1 NN:code:1.23 NS:flag:ok O:0
. Each value is prefixed by a single character denoting the type, B for Boolean, N for number, S for string, O for object, or Z for null, followed by a colon. For Booleans the data must be either 0 or 1 for FALSE or TRUE, respectively. Likewise for Objects the data must be 0 or 1 to end or begin an object, respectively. Data items in subobjects may be named, by prefixing the type with ’N’ and specifying the name before the value (i.e.NB:myFlag:1
). This option may be used multiple times to construct arbitrary AMF sequences.- rtmp_enhanced_codecs
Specify the list of codecs the client advertises to support in an enhanced RTMP stream. This option should be set to a comma separated list of fourcc values, like
hvc1,av01,vp09
for multiple codecs orhvc1
for only one codec. The specified list will be presented in the "fourCcLive" property of the Connect Command Message.- rtmp_flashver
Version of the Flash plugin used to run the SWF player. The default is LNX 9,0,124,2. (When publishing, the default is FMLE/3.0 (compatible; <libavformat version>).)
- rtmp_flush_interval
Number of packets flushed in the same request (RTMPT only). The default is 10.
- rtmp_live
Specify that the media is a live stream. No resuming or seeking in live streams is possible. The default value is
any
, which means the subscriber first tries to play the live stream specified in the playpath. If a live stream of that name is not found, it plays the recorded stream. The other possible values arelive
andrecorded
.- rtmp_pageurl
URL of the web page in which the media was embedded. By default no value will be sent.
- rtmp_playpath
Stream identifier to play or to publish. This option overrides the parameter specified in the URI.
- rtmp_subscribe
Name of live stream to subscribe to. By default no value will be sent. It is only sent if the option is specified or if rtmp_live is set to live.
- rtmp_swfhash
SHA256 hash of the decompressed SWF file (32 bytes).
- rtmp_swfsize
Size of the decompressed SWF file, required for SWFVerification.
- rtmp_swfurl
URL of the SWF player for the media. By default no value will be sent.
- rtmp_swfverify
URL to player swf file, compute hash/size automatically.
- rtmp_tcurl
URL of the target stream. Defaults to proto://host[:port]/app.
- tcp_nodelay=1|0
Set TCP_NODELAY to disable Nagle’s algorithm. Default value is 0.
Remark: Writing to the socket is currently not optimized to minimize system calls and reduces the efficiency / effect of TCP_NODELAY.
For example to read with ffplay
a multimedia resource named
"sample" from the application "vod" from an RTMP server "myserver":
ffplay rtmp://myserver/vod/sample
To publish to a password protected server, passing the playpath and app names separately:
ffmpeg -re -i <input> -f flv -rtmp_playpath some/long/path -rtmp_app long/app/name rtmp://username:password@myserver/
18.25 rtmpe
Encrypted Real-Time Messaging Protocol.
The Encrypted Real-Time Messaging Protocol (RTMPE) is used for streaming multimedia content within standard cryptographic primitives, consisting of Diffie-Hellman key exchange and HMACSHA256, generating a pair of RC4 keys.
18.26 rtmps
Real-Time Messaging Protocol over a secure SSL connection.
The Real-Time Messaging Protocol (RTMPS) is used for streaming multimedia content across an encrypted connection.
18.27 rtmpt
Real-Time Messaging Protocol tunneled through HTTP.
The Real-Time Messaging Protocol tunneled through HTTP (RTMPT) is used for streaming multimedia content within HTTP requests to traverse firewalls.
18.28 rtmpte
Encrypted Real-Time Messaging Protocol tunneled through HTTP.
The Encrypted Real-Time Messaging Protocol tunneled through HTTP (RTMPTE) is used for streaming multimedia content within HTTP requests to traverse firewalls.
18.29 rtmpts
Real-Time Messaging Protocol tunneled through HTTPS.
The Real-Time Messaging Protocol tunneled through HTTPS (RTMPTS) is used for streaming multimedia content within HTTPS requests to traverse firewalls.
18.30 libsmbclient
libsmbclient permits one to manipulate CIFS/SMB network resources.
Following syntax is required.
smb://[[domain:]user[:password@]]server[/share[/path[/file]]]
This protocol accepts the following options.
- timeout
Set timeout in milliseconds of socket I/O operations used by the underlying low level operation. By default it is set to -1, which means that the timeout is not specified.
- truncate
Truncate existing files on write, if set to 1. A value of 0 prevents truncating. Default value is 1.
- workgroup
Set the workgroup used for making connections. By default workgroup is not specified.
For more information see: http://www.samba.org/.
18.31 libssh
Secure File Transfer Protocol via libssh
Read from or write to remote resources using SFTP protocol.
Following syntax is required.
sftp://[user[:password]@]server[:port]/path/to/remote/resource.mpeg
This protocol accepts the following options.
- timeout
Set timeout of socket I/O operations used by the underlying low level operation. By default it is set to -1, which means that the timeout is not specified.
- truncate
Truncate existing files on write, if set to 1. A value of 0 prevents truncating. Default value is 1.
- private_key
Specify the path of the file containing private key to use during authorization. By default libssh searches for keys in the ~/.ssh/ directory.
Example: Play a file stored on remote server.
ffplay sftp://user:password@server_address:22/home/user/resource.mpeg
18.32 librtmp rtmp, rtmpe, rtmps, rtmpt, rtmpte
Real-Time Messaging Protocol and its variants supported through librtmp.
Requires the presence of the librtmp headers and library during configuration. You need to explicitly configure the build with "–enable-librtmp". If enabled this will replace the native RTMP protocol.
This protocol provides most client functions and a few server functions needed to support RTMP, RTMP tunneled in HTTP (RTMPT), encrypted RTMP (RTMPE), RTMP over SSL/TLS (RTMPS) and tunneled variants of these encrypted types (RTMPTE, RTMPTS).
The required syntax is:
rtmp_proto://server[:port][/app][/playpath] options
where rtmp_proto is one of the strings "rtmp", "rtmpt", "rtmpe", "rtmps", "rtmpte", "rtmpts" corresponding to each RTMP variant, and server, port, app and playpath have the same meaning as specified for the RTMP native protocol. options contains a list of space-separated options of the form key=val.
See the librtmp manual page (man 3 librtmp) for more information.
For example, to stream a file in real-time to an RTMP server using
ffmpeg
:
ffmpeg -re -i myfile -f flv rtmp://myserver/live/mystream
To play the same stream using ffplay
:
ffplay "rtmp://myserver/live/mystream live=1"
18.33 rtp
Real-time Transport Protocol.
The required syntax for an RTP URL is: rtp://hostname[:port][?option=val...]
port specifies the RTP port to use.
The following URL options are supported:
- ttl=n
Set the TTL (Time-To-Live) value (for multicast only).
- rtcpport=n
Set the remote RTCP port to n.
- localrtpport=n
Set the local RTP port to n.
- localrtcpport=n'
Set the local RTCP port to n.
- pkt_size=n
Set max packet size (in bytes) to n.
- buffer_size=size
Set the maximum UDP socket buffer size in bytes.
- connect=0|1
Do a
connect()
on the UDP socket (if set to 1) or not (if set to 0).- sources=ip[,ip]
List allowed source IP addresses.
- block=ip[,ip]
List disallowed (blocked) source IP addresses.
- write_to_source=0|1
Send packets to the source address of the latest received packet (if set to 1) or to a default remote address (if set to 0).
- localport=n
Set the local RTP port to n.
- localaddr=addr
Local IP address of a network interface used for sending packets or joining multicast groups.
- timeout=n
Set timeout (in microseconds) of socket I/O operations to n.
This is a deprecated option. Instead, localrtpport should be used.
Important notes:
- If rtcpport is not set the RTCP port will be set to the RTP port value plus 1.
- If localrtpport (the local RTP port) is not set any available port will be used for the local RTP and RTCP ports.
- If localrtcpport (the local RTCP port) is not set it will be set to the local RTP port value plus 1.
18.34 rtsp
Real-Time Streaming Protocol.
RTSP is not technically a protocol handler in libavformat, it is a demuxer and muxer. The demuxer supports both normal RTSP (with data transferred over RTP; this is used by e.g. Apple and Microsoft) and Real-RTSP (with data transferred over RDT).
The muxer can be used to send a stream using RTSP ANNOUNCE to a server supporting it (currently Darwin Streaming Server and Mischa Spiegelmock’s RTSP server).
The required syntax for a RTSP url is:
rtsp://hostname[:port]/path
Options can be set on the ffmpeg
/ffplay
command
line, or set in code via AVOption
s or in
avformat_open_input
.
18.34.1 Muxer
The following options are supported.
- rtsp_transport
Set RTSP transport protocols.
It accepts the following values:
- ‘udp’
Use UDP as lower transport protocol.
- ‘tcp’
Use TCP (interleaving within the RTSP control channel) as lower transport protocol.
Default value is ‘0’.
- rtsp_flags
Set RTSP flags.
The following values are accepted:
- ‘latm’
Use MP4A-LATM packetization instead of MPEG4-GENERIC for AAC.
- ‘rfc2190’
Use RFC 2190 packetization instead of RFC 4629 for H.263.
- ‘skip_rtcp’
Don’t send RTCP sender reports.
- ‘h264_mode0’
Use mode 0 for H.264 in RTP.
- ‘send_bye’
Send RTCP BYE packets when finishing.
Default value is ‘0’.
- min_port
Set minimum local UDP port. Default value is 5000.
- max_port
Set maximum local UDP port. Default value is 65000.
- buffer_size
Set the maximum socket buffer size in bytes.
- pkt_size
Set max send packet size (in bytes). Default value is 1472.
18.34.2 Demuxer
The following options are supported.
- initial_pause
Do not start playing the stream immediately if set to 1. Default value is 0.
- rtsp_transport
Set RTSP transport protocols.
It accepts the following values:
- ‘udp’
Use UDP as lower transport protocol.
- ‘tcp’
Use TCP (interleaving within the RTSP control channel) as lower transport protocol.
- ‘udp_multicast’
Use UDP multicast as lower transport protocol.
- ‘http’
Use HTTP tunneling as lower transport protocol, which is useful for passing proxies.
- ‘https’
Use HTTPs tunneling as lower transport protocol, which is useful for passing proxies and widely used for security consideration.
Multiple lower transport protocols may be specified, in that case they are tried one at a time (if the setup of one fails, the next one is tried). For the muxer, only the ‘tcp’ and ‘udp’ options are supported.
- rtsp_flags
Set RTSP flags.
The following values are accepted:
- ‘filter_src’
Accept packets only from negotiated peer address and port.
- ‘listen’
Act as a server, listening for an incoming connection.
- ‘prefer_tcp’
Try TCP for RTP transport first, if TCP is available as RTSP RTP transport.
- ‘satip_raw’
Export raw MPEG-TS stream instead of demuxing. The flag will simply write out the raw stream, with the original PAT/PMT/PIDs intact.
Default value is ‘none’.
- allowed_media_types
Set media types to accept from the server.
The following flags are accepted:
- ‘video’
- ‘audio’
- ‘data’
- ‘subtitle’
By default it accepts all media types.
- min_port
Set minimum local UDP port. Default value is 5000.
- max_port
Set maximum local UDP port. Default value is 65000.
- listen_timeout
Set maximum timeout (in seconds) to establish an initial connection. Setting listen_timeout > 0 sets rtsp_flags to ‘listen’. Default is -1 which means an infinite timeout when ‘listen’ mode is set.
- reorder_queue_size
Set number of packets to buffer for handling of reordered packets.
- timeout
Set socket TCP I/O timeout in microseconds.
- user_agent
Override User-Agent header. If not specified, it defaults to the libavformat identifier string.
- buffer_size
Set the maximum socket buffer size in bytes.
When receiving data over UDP, the demuxer tries to reorder received packets
(since they may arrive out of order, or packets may get lost totally). This
can be disabled by setting the maximum demuxing delay to zero (via
the max_delay
field of AVFormatContext).
When watching multi-bitrate Real-RTSP streams with ffplay
, the
streams to display can be chosen with -vst
n and
-ast
n for video and audio respectively, and can be switched
on the fly by pressing v
and a
.
18.34.3 Examples
The following examples all make use of the ffplay
and
ffmpeg
tools.
- Watch a stream over UDP, with a max reordering delay of 0.5 seconds:
ffplay -max_delay 500000 -rtsp_transport udp rtsp://server/video.mp4
- Watch a stream tunneled over HTTP:
ffplay -rtsp_transport http rtsp://server/video.mp4
- Send a stream in realtime to a RTSP server, for others to watch:
ffmpeg -re -i input -f rtsp -muxdelay 0.1 rtsp://server/live.sdp
- Receive a stream in realtime:
ffmpeg -rtsp_flags listen -i rtsp://ownaddress/live.sdp output
18.35 sap
Session Announcement Protocol (RFC 2974). This is not technically a protocol handler in libavformat, it is a muxer and demuxer. It is used for signalling of RTP streams, by announcing the SDP for the streams regularly on a separate port.
18.35.1 Muxer
The syntax for a SAP url given to the muxer is:
sap://destination[:port][?options]
The RTP packets are sent to destination on port port,
or to port 5004 if no port is specified.
options is a &
-separated list. The following options
are supported:
- announce_addr=address
Specify the destination IP address for sending the announcements to. If omitted, the announcements are sent to the commonly used SAP announcement multicast address 224.2.127.254 (sap.mcast.net), or ff0e::2:7ffe if destination is an IPv6 address.
- announce_port=port
Specify the port to send the announcements on, defaults to 9875 if not specified.
- ttl=ttl
Specify the time to live value for the announcements and RTP packets, defaults to 255.
- same_port=0|1
If set to 1, send all RTP streams on the same port pair. If zero (the default), all streams are sent on unique ports, with each stream on a port 2 numbers higher than the previous. VLC/Live555 requires this to be set to 1, to be able to receive the stream. The RTP stack in libavformat for receiving requires all streams to be sent on unique ports.
Example command lines follow.
To broadcast a stream on the local subnet, for watching in VLC:
ffmpeg -re -i input -f sap sap://224.0.0.255?same_port=1
Similarly, for watching in ffplay
:
ffmpeg -re -i input -f sap sap://224.0.0.255
And for watching in ffplay
, over IPv6:
ffmpeg -re -i input -f sap sap://[ff0e::1:2:3:4]
18.35.2 Demuxer
The syntax for a SAP url given to the demuxer is:
sap://[address][:port]
address is the multicast address to listen for announcements on, if omitted, the default 224.2.127.254 (sap.mcast.net) is used. port is the port that is listened on, 9875 if omitted.
The demuxers listens for announcements on the given address and port. Once an announcement is received, it tries to receive that particular stream.
Example command lines follow.
To play back the first stream announced on the normal SAP multicast address:
ffplay sap://
To play back the first stream announced on one the default IPv6 SAP multicast address:
ffplay sap://[ff0e::2:7ffe]
18.36 sctp
Stream Control Transmission Protocol.
The accepted URL syntax is:
sctp://host:port[?options]
The protocol accepts the following options:
- listen
If set to any value, listen for an incoming connection. Outgoing connection is done by default.
- max_streams
Set the maximum number of streams. By default no limit is set.
18.37 srt
Haivision Secure Reliable Transport Protocol via libsrt.
The supported syntax for a SRT URL is:
srt://hostname:port[?options]
options contains a list of &-separated options of the form key=val.
or
options srt://hostname:port
options contains a list of ’-key val’ options.
This protocol accepts the following options.
- connect_timeout=milliseconds
Connection timeout; SRT cannot connect for RTT > 1500 msec (2 handshake exchanges) with the default connect timeout of 3 seconds. This option applies to the caller and rendezvous connection modes. The connect timeout is 10 times the value set for the rendezvous mode (which can be used as a workaround for this connection problem with earlier versions).
- ffs=bytes
Flight Flag Size (Window Size), in bytes. FFS is actually an internal parameter and you should set it to not less than recv_buffer_size and mss. The default value is relatively large, therefore unless you set a very large receiver buffer, you do not need to change this option. Default value is 25600.
- inputbw=bytes/seconds
Sender nominal input rate, in bytes per seconds. Used along with oheadbw, when maxbw is set to relative (0), to calculate maximum sending rate when recovery packets are sent along with the main media stream: inputbw * (100 + oheadbw) / 100 if inputbw is not set while maxbw is set to relative (0), the actual input rate is evaluated inside the library. Default value is 0.
- iptos=tos
IP Type of Service. Applies to sender only. Default value is 0xB8.
- ipttl=ttl
IP Time To Live. Applies to sender only. Default value is 64.
- latency=microseconds
Timestamp-based Packet Delivery Delay. Used to absorb bursts of missed packet retransmissions. This flag sets both rcvlatency and peerlatency to the same value. Note that prior to version 1.3.0 this is the only flag to set the latency, however this is effectively equivalent to setting peerlatency, when side is sender and rcvlatency when side is receiver, and the bidirectional stream sending is not supported.
- listen_timeout=microseconds
Set socket listen timeout.
- maxbw=bytes/seconds
Maximum sending bandwidth, in bytes per seconds. -1 infinite (CSRTCC limit is 30mbps) 0 relative to input rate (see inputbw) >0 absolute limit value Default value is 0 (relative)
- mode=caller|listener|rendezvous
Connection mode. caller opens client connection. listener starts server to listen for incoming connections. rendezvous use Rendez-Vous connection mode. Default value is caller.
- mss=bytes
Maximum Segment Size, in bytes. Used for buffer allocation and rate calculation using a packet counter assuming fully filled packets. The smallest MSS between the peers is used. This is 1500 by default in the overall internet. This is the maximum size of the UDP packet and can be only decreased, unless you have some unusual dedicated network settings. Default value is 1500.
- nakreport=1|0
If set to 1, Receiver will send ‘UMSG_LOSSREPORT‘ messages periodically until a lost packet is retransmitted or intentionally dropped. Default value is 1.
- oheadbw=percents
Recovery bandwidth overhead above input rate, in percents. See inputbw. Default value is 25%.
- passphrase=string
HaiCrypt Encryption/Decryption Passphrase string, length from 10 to 79 characters. The passphrase is the shared secret between the sender and the receiver. It is used to generate the Key Encrypting Key using PBKDF2 (Password-Based Key Derivation Function). It is used only if pbkeylen is non-zero. It is used on the receiver only if the received data is encrypted. The configured passphrase cannot be recovered (write-only).
- enforced_encryption=1|0
If true, both connection parties must have the same password set (including empty, that is, with no encryption). If the password doesn’t match or only one side is unencrypted, the connection is rejected. Default is true.
- kmrefreshrate=packets
The number of packets to be transmitted after which the encryption key is switched to a new key. Default is -1. -1 means auto (0x1000000 in srt library). The range for this option is integers in the 0 -
INT_MAX
.- kmpreannounce=packets
The interval between when a new encryption key is sent and when switchover occurs. This value also applies to the subsequent interval between when switchover occurs and when the old encryption key is decommissioned. Default is -1. -1 means auto (0x1000 in srt library). The range for this option is integers in the 0 -
INT_MAX
.- snddropdelay=microseconds
The sender’s extra delay before dropping packets. This delay is added to the default drop delay time interval value.
Special value -1: Do not drop packets on the sender at all.
- payload_size=bytes
Sets the maximum declared size of a packet transferred during the single call to the sending function in Live mode. Use 0 if this value isn’t used (which is default in file mode). Default is -1 (automatic), which typically means MPEG-TS; if you are going to use SRT to send any different kind of payload, such as, for example, wrapping a live stream in very small frames, then you can use a bigger maximum frame size, though not greater than 1456 bytes.
- pkt_size=bytes
Alias for ‘payload_size’.
- peerlatency=microseconds
The latency value (as described in rcvlatency) that is set by the sender side as a minimum value for the receiver.
- pbkeylen=bytes
Sender encryption key length, in bytes. Only can be set to 0, 16, 24 and 32. Enable sender encryption if not 0. Not required on receiver (set to 0), key size obtained from sender in HaiCrypt handshake. Default value is 0.
- rcvlatency=microseconds
The time that should elapse since the moment when the packet was sent and the moment when it’s delivered to the receiver application in the receiving function. This time should be a buffer time large enough to cover the time spent for sending, unexpectedly extended RTT time, and the time needed to retransmit the lost UDP packet. The effective latency value will be the maximum of this options’ value and the value of peerlatency set by the peer side. Before version 1.3.0 this option is only available as latency.
- recv_buffer_size=bytes
Set UDP receive buffer size, expressed in bytes.
- send_buffer_size=bytes
Set UDP send buffer size, expressed in bytes.
- timeout=microseconds
Set raise error timeouts for read, write and connect operations. Note that the SRT library has internal timeouts which can be controlled separately, the value set here is only a cap on those.
- tlpktdrop=1|0
Too-late Packet Drop. When enabled on receiver, it skips missing packets that have not been delivered in time and delivers the following packets to the application when their time-to-play has come. It also sends a fake ACK to the sender. When enabled on sender and enabled on the receiving peer, the sender drops the older packets that have no chance of being delivered in time. It was automatically enabled in the sender if the receiver supports it.
- sndbuf=bytes
Set send buffer size, expressed in bytes.
- rcvbuf=bytes
Set receive buffer size, expressed in bytes.
Receive buffer must not be greater than ffs.
- lossmaxttl=packets
The value up to which the Reorder Tolerance may grow. When Reorder Tolerance is > 0, then packet loss report is delayed until that number of packets come in. Reorder Tolerance increases every time a "belated" packet has come, but it wasn’t due to retransmission (that is, when UDP packets tend to come out of order), with the difference between the latest sequence and this packet’s sequence, and not more than the value of this option. By default it’s 0, which means that this mechanism is turned off, and the loss report is always sent immediately upon experiencing a "gap" in sequences.
- minversion
The minimum SRT version that is required from the peer. A connection to a peer that does not satisfy the minimum version requirement will be rejected.
The version format in hex is 0xXXYYZZ for x.y.z in human readable form.
- streamid=string
A string limited to 512 characters that can be set on the socket prior to connecting. This stream ID will be able to be retrieved by the listener side from the socket that is returned from srt_accept and was connected by a socket with that set stream ID. SRT does not enforce any special interpretation of the contents of this string. This option doesn’t make sense in Rendezvous connection; the result might be that simply one side will override the value from the other side and it’s the matter of luck which one would win
- srt_streamid=string
Alias for ‘streamid’ to avoid conflict with ffmpeg command line option.
- smoother=live|file
The type of Smoother used for the transmission for that socket, which is responsible for the transmission and congestion control. The Smoother type must be exactly the same on both connecting parties, otherwise the connection is rejected.
- messageapi=1|0
When set, this socket uses the Message API, otherwise it uses Buffer API. Note that in live mode (see transtype) there’s only message API available. In File mode you can chose to use one of two modes:
Stream API (default, when this option is false). In this mode you may send as many data as you wish with one sending instruction, or even use dedicated functions that read directly from a file. The internal facility will take care of any speed and congestion control. When receiving, you can also receive as many data as desired, the data not extracted will be waiting for the next call. There is no boundary between data portions in the Stream mode.
Message API. In this mode your single sending instruction passes exactly one piece of data that has boundaries (a message). Contrary to Live mode, this message may span across multiple UDP packets and the only size limitation is that it shall fit as a whole in the sending buffer. The receiver shall use as large buffer as necessary to receive the message, otherwise the message will not be given up. When the message is not complete (not all packets received or there was a packet loss) it will not be given up.
- transtype=live|file
Sets the transmission type for the socket, in particular, setting this option sets multiple other parameters to their default values as required for a particular transmission type.
live: Set options as for live transmission. In this mode, you should send by one sending instruction only so many data that fit in one UDP packet, and limited to the value defined first in payload_size (1316 is default in this mode). There is no speed control in this mode, only the bandwidth control, if configured, in order to not exceed the bandwidth with the overhead transmission (retransmitted and control packets).
file: Set options as for non-live transmission. See messageapi for further explanations
- linger=seconds
The number of seconds that the socket waits for unsent data when closing. Default is -1. -1 means auto (off with 0 seconds in live mode, on with 180 seconds in file mode). The range for this option is integers in the 0 -
INT_MAX
.- tsbpd=1|0
When true, use Timestamp-based Packet Delivery mode. The default behavior depends on the transmission type: enabled in live mode, disabled in file mode.
For more information see: https://github.com/Haivision/srt.
18.38 srtp
Secure Real-time Transport Protocol.
The accepted options are:
- srtp_in_suite
- srtp_out_suite
Select input and output encoding suites.
Supported values:
- ‘AES_CM_128_HMAC_SHA1_80’
- ‘SRTP_AES128_CM_HMAC_SHA1_80’
- ‘AES_CM_128_HMAC_SHA1_32’
- ‘SRTP_AES128_CM_HMAC_SHA1_32’
- srtp_in_params
- srtp_out_params
Set input and output encoding parameters, which are expressed by a base64-encoded representation of a binary block. The first 16 bytes of this binary block are used as master key, the following 14 bytes are used as master salt.
18.39 subfile
Virtually extract a segment of a file or another stream. The underlying stream must be seekable.
Accepted options:
- start
Start offset of the extracted segment, in bytes.
- end
End offset of the extracted segment, in bytes. If set to 0, extract till end of file.
Examples:
Extract a chapter from a DVD VOB file (start and end sectors obtained externally and multiplied by 2048):
subfile,,start,153391104,end,268142592,,:/media/dvd/VIDEO_TS/VTS_08_1.VOB
Play an AVI file directly from a TAR archive:
subfile,,start,183241728,end,366490624,,:archive.tar
Play a MPEG-TS file from start offset till end:
subfile,,start,32815239,end,0,,:video.ts
18.40 tee
Writes the output to multiple protocols. The individual outputs are separated by |
tee:file://path/to/local/this.avi|file://path/to/local/that.avi
18.41 tcp
Transmission Control Protocol.
The required syntax for a TCP url is:
tcp://hostname:port[?options]
options contains a list of &-separated options of the form key=val.
The list of supported options follows.
- listen=2|1|0
Listen for an incoming connection. 0 disables listen, 1 enables listen in single client mode, 2 enables listen in multi-client mode. Default value is 0.
- local_addr=addr
Local IP address of a network interface used for tcp socket connect.
- local_port=port
Local port used for tcp socket connect.
- timeout=microseconds
Set raise error timeout, expressed in microseconds.
This option is only relevant in read mode: if no data arrived in more than this time interval, raise error.
- listen_timeout=milliseconds
Set listen timeout, expressed in milliseconds.
- recv_buffer_size=bytes
Set receive buffer size, expressed bytes.
- send_buffer_size=bytes
Set send buffer size, expressed bytes.
- tcp_nodelay=1|0
Set TCP_NODELAY to disable Nagle’s algorithm. Default value is 0.
Remark: Writing to the socket is currently not optimized to minimize system calls and reduces the efficiency / effect of TCP_NODELAY.
- tcp_mss=bytes
Set maximum segment size for outgoing TCP packets, expressed in bytes.
The following example shows how to setup a listening TCP connection
with ffmpeg
, which is then accessed with ffplay
:
ffmpeg -i input -f format tcp://hostname:port?listen ffplay tcp://hostname:port
18.42 tls
Transport Layer Security (TLS) / Secure Sockets Layer (SSL)
The required syntax for a TLS/SSL url is:
tls://hostname:port[?options]
The following parameters can be set via command line options
(or in code via AVOption
s):
- ca_file, cafile=filename
A file containing certificate authority (CA) root certificates to treat as trusted. If the linked TLS library contains a default this might not need to be specified for verification to work, but not all libraries and setups have defaults built in. The file must be in OpenSSL PEM format.
- tls_verify=1|0
If enabled, try to verify the peer that we are communicating with. Note, if using OpenSSL, this currently only makes sure that the peer certificate is signed by one of the root certificates in the CA database, but it does not validate that the certificate actually matches the host name we are trying to connect to. (With other backends, the host name is validated as well.)
This is disabled by default since it requires a CA database to be provided by the caller in many cases.
- cert_file, cert=filename
A file containing a certificate to use in the handshake with the peer. (When operating as server, in listen mode, this is more often required by the peer, while client certificates only are mandated in certain setups.)
- key_file, key=filename
A file containing the private key for the certificate.
- listen=1|0
If enabled, listen for connections on the provided port, and assume the server role in the handshake instead of the client role.
- http_proxy
The HTTP proxy to tunnel through, e.g.
http://example.com:1234
. The proxy must support the CONNECT method.
Example command lines:
To create a TLS/SSL server that serves an input stream.
ffmpeg -i input -f format tls://hostname:port?listen&cert=server.crt&key=server.key
To play back a stream from the TLS/SSL server using ffplay
:
ffplay tls://hostname:port
18.43 udp
User Datagram Protocol.
The required syntax for an UDP URL is:
udp://hostname:port[?options]
options contains a list of &-separated options of the form key=val.
In case threading is enabled on the system, a circular buffer is used to store the incoming data, which allows one to reduce loss of data due to UDP socket buffer overruns. The fifo_size and overrun_nonfatal options are related to this buffer.
The list of supported options follows.
- buffer_size=size
Set the UDP maximum socket buffer size in bytes. This is used to set either the receive or send buffer size, depending on what the socket is used for. Default is 32 KB for output, 384 KB for input. See also fifo_size.
- bitrate=bitrate
If set to nonzero, the output will have the specified constant bitrate if the input has enough packets to sustain it.
- burst_bits=bits
When using bitrate this specifies the maximum number of bits in packet bursts.
- localport=port
Override the local UDP port to bind with.
- localaddr=addr
Local IP address of a network interface used for sending packets or joining multicast groups.
- pkt_size=size
Set the size in bytes of UDP packets.
- reuse=1|0
Explicitly allow or disallow reusing UDP sockets.
- ttl=ttl
Set the time to live value (for multicast only).
- connect=1|0
Initialize the UDP socket with
connect()
. In this case, the destination address can’t be changed with ff_udp_set_remote_url later. If the destination address isn’t known at the start, this option can be specified in ff_udp_set_remote_url, too. This allows finding out the source address for the packets with getsockname, and makes writes return with AVERROR(ECONNREFUSED) if "destination unreachable" is received. For receiving, this gives the benefit of only receiving packets from the specified peer address/port.- sources=address[,address]
Only receive packets sent from the specified addresses. In case of multicast, also subscribe to multicast traffic coming from these addresses only.
- block=address[,address]
Ignore packets sent from the specified addresses. In case of multicast, also exclude the source addresses in the multicast subscription.
- fifo_size=units
Set the UDP receiving circular buffer size, expressed as a number of packets with size of 188 bytes. If not specified defaults to 7*4096.
- overrun_nonfatal=1|0
Survive in case of UDP receiving circular buffer overrun. Default value is 0.
- timeout=microseconds
Set raise error timeout, expressed in microseconds.
This option is only relevant in read mode: if no data arrived in more than this time interval, raise error.
- broadcast=1|0
Explicitly allow or disallow UDP broadcasting.
Note that broadcasting may not work properly on networks having a broadcast storm protection.
18.43.1 Examples
- Use
ffmpeg
to stream over UDP to a remote endpoint:ffmpeg -i input -f format udp://hostname:port
- Use
ffmpeg
to stream in mpegts format over UDP using 188 sized UDP packets, using a large input buffer:ffmpeg -i input -f mpegts udp://hostname:port?pkt_size=188&buffer_size=65535
- Use
ffmpeg
to receive over UDP from a remote endpoint:ffmpeg -i udp://[multicast-address]:port ...
18.44 unix
Unix local socket
The required syntax for a Unix socket URL is:
unix://filepath
The following parameters can be set via command line options
(or in code via AVOption
s):
- timeout
Timeout in ms.
- listen
Create the Unix socket in listening mode.
18.45 zmq
ZeroMQ asynchronous messaging using the libzmq library.
This library supports unicast streaming to multiple clients without relying on an external server.
The required syntax for streaming or connecting to a stream is:
zmq:tcp://ip-address:port
Example: Create a localhost stream on port 5555:
ffmpeg -re -i input -f mpegts zmq:tcp://127.0.0.1:5555
Multiple clients may connect to the stream using:
ffplay zmq:tcp://127.0.0.1:5555
Streaming to multiple clients is implemented using a ZeroMQ Pub-Sub pattern. The server side binds to a port and publishes data. Clients connect to the server (via IP address/port) and subscribe to the stream. The order in which the server and client start generally does not matter.
ffmpeg must be compiled with the –enable-libzmq option to support this protocol.
Options can be set on the ffmpeg
/ffplay
command
line. The following options are supported:
- pkt_size
Forces the maximum packet size for sending/receiving data. The default value is 131,072 bytes. On the server side, this sets the maximum size of sent packets via ZeroMQ. On the clients, it sets an internal buffer size for receiving packets. Note that pkt_size on the clients should be equal to or greater than pkt_size on the server. Otherwise the received message may be truncated causing decoding errors.
19 Device Options
The libavdevice library provides the same interface as libavformat. Namely, an input device is considered like a demuxer, and an output device like a muxer, and the interface and generic device options are the same provided by libavformat (see the ffmpeg-formats manual).
In addition each input or output device may support so-called private options, which are specific for that component.
Options may be set by specifying -option value in the
FFmpeg tools, or by setting the value explicitly in the device
AVFormatContext
options or using the libavutil/opt.h API
for programmatic use.
20 Input Devices
Input devices are configured elements in FFmpeg which enable accessing the data coming from a multimedia device attached to your system.
When you configure your FFmpeg build, all the supported input devices are enabled by default. You can list all available ones using the configure option "–list-indevs".
You can disable all the input devices using the configure option "–disable-indevs", and selectively enable an input device using the option "–enable-indev=INDEV", or you can disable a particular input device using the option "–disable-indev=INDEV".
The option "-devices" of the ff* tools will display the list of supported input devices.
A description of the currently available input devices follows.
20.1 alsa
ALSA (Advanced Linux Sound Architecture) input device.
To enable this input device during configuration you need libasound installed on your system.
This device allows capturing from an ALSA device. The name of the device to capture has to be an ALSA card identifier.
An ALSA identifier has the syntax:
hw:CARD[,DEV[,SUBDEV]]
where the DEV and SUBDEV components are optional.
The three arguments (in order: CARD,DEV,SUBDEV) specify card number or identifier, device number and subdevice number (-1 means any).
To see the list of cards currently recognized by your system check the files /proc/asound/cards and /proc/asound/devices.
For example to capture with ffmpeg
from an ALSA device with
card id 0, you may run the command:
ffmpeg -f alsa -i hw:0 alsaout.wav
For more information see: http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html
20.1.1 Options
- sample_rate
Set the sample rate in Hz. Default is 48000.
- channels
Set the number of channels. Default is 2.
20.2 android_camera
Android camera input device.
This input devices uses the Android Camera2 NDK API which is available on devices with API level 24+. The availability of android_camera is autodetected during configuration.
This device allows capturing from all cameras on an Android device, which are integrated into the Camera2 NDK API.
The available cameras are enumerated internally and can be selected with the camera_index parameter. The input file string is discarded.
Generally the back facing camera has index 0 while the front facing camera has index 1.
20.2.1 Options
- video_size
Set the video size given as a string such as 640x480 or hd720. Falls back to the first available configuration reported by Android if requested video size is not available or by default.
- framerate
Set the video framerate. Falls back to the first available configuration reported by Android if requested framerate is not available or by default (-1).
- camera_index
Set the index of the camera to use. Default is 0.
- input_queue_size
Set the maximum number of frames to buffer. Default is 5.
20.3 avfoundation
AVFoundation input device.
AVFoundation is the currently recommended framework by Apple for streamgrabbing on OSX >= 10.7 as well as on iOS.
The input filename has to be given in the following syntax:
-i "[[VIDEO]:[AUDIO]]"
The first entry selects the video input while the latter selects the audio input. The stream has to be specified by the device name or the device index as shown by the device list. Alternatively, the video and/or audio input device can be chosen by index using the -video_device_index <INDEX> and/or -audio_device_index <INDEX> , overriding any device name or index given in the input filename.
All available devices can be enumerated by using -list_devices true, listing all device names and corresponding indices.
There are two device name aliases:
default
Select the AVFoundation default device of the corresponding type.
none
Do not record the corresponding media type. This is equivalent to specifying an empty device name or index.
20.3.1 Options
AVFoundation supports the following options:
- -list_devices <TRUE|FALSE>
If set to true, a list of all available input devices is given showing all device names and indices.
- -video_device_index <INDEX>
Specify the video device by its index. Overrides anything given in the input filename.
- -audio_device_index <INDEX>
Specify the audio device by its index. Overrides anything given in the input filename.
- -pixel_format <FORMAT>
Request the video device to use a specific pixel format. If the specified format is not supported, a list of available formats is given and the first one in this list is used instead. Available pixel formats are:
monob, rgb555be, rgb555le, rgb565be, rgb565le, rgb24, bgr24, 0rgb, bgr0, 0bgr, rgb0, bgr48be, uyvy422, yuva444p, yuva444p16le, yuv444p, yuv422p16, yuv422p10, yuv444p10, yuv420p, nv12, yuyv422, gray
- -framerate
Set the grabbing frame rate. Default is
ntsc
, corresponding to a frame rate of30000/1001
.- -video_size
Set the video frame size.
- -capture_cursor
Capture the mouse pointer. Default is 0.
- -capture_mouse_clicks
Capture the screen mouse clicks. Default is 0.
- -capture_raw_data
Capture the raw device data. Default is 0. Using this option may result in receiving the underlying data delivered to the AVFoundation framework. E.g. for muxed devices that sends raw DV data to the framework (like tape-based camcorders), setting this option to false results in extracted video frames captured in the designated pixel format only. Setting this option to true results in receiving the raw DV stream untouched.
20.3.2 Examples
- Print the list of AVFoundation supported devices and exit:
$ ffmpeg -f avfoundation -list_devices true -i ""
- Record video from video device 0 and audio from audio device 0 into out.avi:
$ ffmpeg -f avfoundation -i "0:0" out.avi
- Record video from video device 2 and audio from audio device 1 into out.avi:
$ ffmpeg -f avfoundation -video_device_index 2 -i ":1" out.avi
- Record video from the system default video device using the pixel format bgr0 and do not record any audio into out.avi:
$ ffmpeg -f avfoundation -pixel_format bgr0 -i "default:none" out.avi
- Record raw DV data from a suitable input device and write the output into out.dv:
$ ffmpeg -f avfoundation -capture_raw_data true -i "zr100:none" out.dv
20.4 bktr
BSD video input device. Deprecated and will be removed - please contact the developers if you are interested in maintaining it.
20.4.1 Options
- framerate
Set the frame rate.
- video_size
Set the video frame size. Default is
vga
.- standard
-
Available values are:
- ‘pal’
- ‘ntsc’
- ‘secam’
- ‘paln’
- ‘palm’
- ‘ntscj’
20.5 decklink
The decklink input device provides capture capabilities for Blackmagic DeckLink devices.
To enable this input device, you need the Blackmagic DeckLink SDK and you
need to configure with the appropriate --extra-cflags
and --extra-ldflags
.
On Windows, you need to run the IDL files through widl
.
DeckLink is very picky about the formats it supports. Pixel format of the
input can be set with raw_format.
Framerate and video size must be determined for your device with
-list_formats 1
. Audio sample rate is always 48 kHz and the number
of channels can be 2, 8 or 16. Note that all audio channels are bundled in one single
audio track.
20.5.1 Options
- list_devices
If set to true, print a list of devices and exit. Defaults to false. This option is deprecated, please use the
-sources
option of ffmpeg to list the available input devices.- list_formats
If set to true, print a list of supported formats and exit. Defaults to false.
- format_code <FourCC>
This sets the input video format to the format given by the FourCC. To see the supported values of your device(s) use list_formats. Note that there is a FourCC 'pal ' that can also be used as pal (3 letters). Default behavior is autodetection of the input video format, if the hardware supports it.
- raw_format
Set the pixel format of the captured video. Available values are:
- ‘auto’
-
This is the default which means 8-bit YUV 422 or 8-bit ARGB if format autodetection is used, 8-bit YUV 422 otherwise.
- ‘uyvy422’
-
8-bit YUV 422.
- ‘yuv422p10’
-
10-bit YUV 422.
- ‘argb’
-
8-bit RGB.
- ‘bgra’
-
8-bit RGB.
- ‘rgb10’
-
10-bit RGB.
- teletext_lines
If set to nonzero, an additional teletext stream will be captured from the vertical ancillary data. Both SD PAL (576i) and HD (1080i or 1080p) sources are supported. In case of HD sources, OP47 packets are decoded.
This option is a bitmask of the SD PAL VBI lines captured, specifically lines 6 to 22, and lines 318 to 335. Line 6 is the LSB in the mask. Selected lines which do not contain teletext information will be ignored. You can use the special all constant to select all possible lines, or standard to skip lines 6, 318 and 319, which are not compatible with all receivers.
For SD sources, ffmpeg needs to be compiled with
--enable-libzvbi
. For HD sources, on older (pre-4K) DeckLink card models you have to capture in 10 bit mode.- channels
Defines number of audio channels to capture. Must be ‘2’, ‘8’ or ‘16’. Defaults to ‘2’.
- duplex_mode
Sets the decklink device duplex/profile mode. Must be ‘unset’, ‘half’, ‘full’, ‘one_sub_device_full’, ‘one_sub_device_half’, ‘two_sub_device_full’, ‘four_sub_device_half’ Defaults to ‘unset’.
Note: DeckLink SDK 11.0 have replaced the duplex property by a profile property. For the DeckLink Duo 2 and DeckLink Quad 2, a profile is shared between any 2 sub-devices that utilize the same connectors. For the DeckLink 8K Pro, a profile is shared between all 4 sub-devices. So DeckLink 8K Pro support four profiles.
Valid profile modes for DeckLink 8K Pro(with DeckLink SDK >= 11.0): ‘one_sub_device_full’, ‘one_sub_device_half’, ‘two_sub_device_full’, ‘four_sub_device_half’
Valid profile modes for DeckLink Quad 2 and DeckLink Duo 2: ‘half’, ‘full’
- timecode_format
Timecode type to include in the frame and video stream metadata. Must be ‘none’, ‘rp188vitc’, ‘rp188vitc2’, ‘rp188ltc’, ‘rp188hfr’, ‘rp188any’, ‘vitc’, ‘vitc2’, or ‘serial’. Defaults to ‘none’ (not included).
In order to properly support 50/60 fps timecodes, the ordering of the queried timecode types for ‘rp188any’ is HFR, VITC1, VITC2 and LTC for >30 fps content. Note that this is slightly different to the ordering used by the DeckLink API, which is HFR, VITC1, LTC, VITC2.
- video_input
Sets the video input source. Must be ‘unset’, ‘sdi’, ‘hdmi’, ‘optical_sdi’, ‘component’, ‘composite’ or ‘s_video’. Defaults to ‘unset’.
- audio_input
Sets the audio input source. Must be ‘unset’, ‘embedded’, ‘aes_ebu’, ‘analog’, ‘analog_xlr’, ‘analog_rca’ or ‘microphone’. Defaults to ‘unset’.
- video_pts
Sets the video packet timestamp source. Must be ‘video’, ‘audio’, ‘reference’, ‘wallclock’ or ‘abs_wallclock’. Defaults to ‘video’.
- audio_pts
Sets the audio packet timestamp source. Must be ‘video’, ‘audio’, ‘reference’, ‘wallclock’ or ‘abs_wallclock’. Defaults to ‘audio’.
- draw_bars
If set to ‘true’, color bars are drawn in the event of a signal loss. Defaults to ‘true’. This option is deprecated, please use the
signal_loss_action
option.- signal_loss_action
Sets the action to take in the event of a signal loss. Accepts one of the following values:
- 1, none
Do nothing on signal loss. This usually results in black frames.
- 2, bars
Draw color bars on signal loss. Only supported for 8-bit input signals.
- 3, repeat
Repeat the last video frame on signal loss.
Defaults to ‘bars’.
- queue_size
Sets maximum input buffer size in bytes. If the buffering reaches this value, incoming frames will be dropped. Defaults to ‘1073741824’.
- audio_depth
Sets the audio sample bit depth. Must be ‘16’ or ‘32’. Defaults to ‘16’.
- decklink_copyts
If set to true, timestamps are forwarded as they are without removing the initial offset. Defaults to false.
- timestamp_align
Capture start time alignment in seconds. If set to nonzero, input frames are dropped till the system timestamp aligns with configured value. Alignment difference of up to one frame duration is tolerated. This is useful for maintaining input synchronization across N different hardware devices deployed for ’N-way’ redundancy. The system time of different hardware devices should be synchronized with protocols such as NTP or PTP, before using this option. Note that this method is not foolproof. In some border cases input synchronization may not happen due to thread scheduling jitters in the OS. Either sync could go wrong by 1 frame or in a rarer case timestamp_align seconds. Defaults to ‘0’.
- wait_for_tc (bool)
Drop frames till a frame with timecode is received. Sometimes serial timecode isn’t received with the first input frame. If that happens, the stored stream timecode will be inaccurate. If this option is set to true, input frames are dropped till a frame with timecode is received. Option timecode_format must be specified. Defaults to false.
- enable_klv(bool)
If set to true, extracts KLV data from VANC and outputs KLV packets. KLV VANC packets are joined based on MID and PSC fields and aggregated into one KLV packet. Defaults to false.
20.5.2 Examples
- List input devices:
ffmpeg -sources decklink
- List supported formats:
ffmpeg -f decklink -list_formats 1 -i 'Intensity Pro'
- Capture video clip at 1080i50:
ffmpeg -format_code Hi50 -f decklink -i 'Intensity Pro' -c:a copy -c:v copy output.avi
- Capture video clip at 1080i50 10 bit:
ffmpeg -raw_format yuv422p10 -format_code Hi50 -f decklink -i 'UltraStudio Mini Recorder' -c:a copy -c:v copy output.avi
- Capture video clip at 1080i50 with 16 audio channels:
ffmpeg -channels 16 -format_code Hi50 -f decklink -i 'UltraStudio Mini Recorder' -c:a copy -c:v copy output.avi
20.6 dshow
Windows DirectShow input device.
DirectShow support is enabled when FFmpeg is built with the mingw-w64 project. Currently only audio and video devices are supported.
Multiple devices may be opened as separate inputs, but they may also be opened on the same input, which should improve synchronism between them.
The input name should be in the format:
TYPE=NAME[:TYPE=NAME]
where TYPE can be either audio or video, and NAME is the device’s name or alternative name..
20.6.1 Options
If no options are specified, the device’s defaults are used. If the device does not support the requested options, it will fail to open.
- video_size
Set the video size in the captured video.
- framerate
Set the frame rate in the captured video.
- sample_rate
Set the sample rate (in Hz) of the captured audio.
- sample_size
Set the sample size (in bits) of the captured audio.
- channels
Set the number of channels in the captured audio.
- list_devices
If set to true, print a list of devices and exit.
- list_options
If set to true, print a list of selected device’s options and exit.
- video_device_number
Set video device number for devices with the same name (starts at 0, defaults to 0).
- audio_device_number
Set audio device number for devices with the same name (starts at 0, defaults to 0).
- pixel_format
Select pixel format to be used by DirectShow. This may only be set when the video codec is not set or set to rawvideo.
- audio_buffer_size
Set audio device buffer size in milliseconds (which can directly impact latency, depending on the device). Defaults to using the audio device’s default buffer size (typically some multiple of 500ms). Setting this value too low can degrade performance. See also http://msdn.microsoft.com/en-us/library/windows/desktop/dd377582(v=vs.85).aspx
- video_pin_name
Select video capture pin to use by name or alternative name.
- audio_pin_name
Select audio capture pin to use by name or alternative name.
- crossbar_video_input_pin_number
Select video input pin number for crossbar device. This will be routed to the crossbar device’s Video Decoder output pin. Note that changing this value can affect future invocations (sets a new default) until system reboot occurs.
- crossbar_audio_input_pin_number
Select audio input pin number for crossbar device. This will be routed to the crossbar device’s Audio Decoder output pin. Note that changing this value can affect future invocations (sets a new default) until system reboot occurs.
- show_video_device_dialog
If set to true, before capture starts, popup a display dialog to the end user, allowing them to change video filter properties and configurations manually. Note that for crossbar devices, adjusting values in this dialog may be needed at times to toggle between PAL (25 fps) and NTSC (29.97) input frame rates, sizes, interlacing, etc. Changing these values can enable different scan rates/frame rates and avoiding green bars at the bottom, flickering scan lines, etc. Note that with some devices, changing these properties can also affect future invocations (sets new defaults) until system reboot occurs.
- show_audio_device_dialog
If set to true, before capture starts, popup a display dialog to the end user, allowing them to change audio filter properties and configurations manually.
- show_video_crossbar_connection_dialog
If set to true, before capture starts, popup a display dialog to the end user, allowing them to manually modify crossbar pin routings, when it opens a video device.
- show_audio_crossbar_connection_dialog
If set to true, before capture starts, popup a display dialog to the end user, allowing them to manually modify crossbar pin routings, when it opens an audio device.
- show_analog_tv_tuner_dialog
If set to true, before capture starts, popup a display dialog to the end user, allowing them to manually modify TV channels and frequencies.
- show_analog_tv_tuner_audio_dialog
If set to true, before capture starts, popup a display dialog to the end user, allowing them to manually modify TV audio (like mono vs. stereo, Language A,B or C).
- audio_device_load
Load an audio capture filter device from file instead of searching it by name. It may load additional parameters too, if the filter supports the serialization of its properties to. To use this an audio capture source has to be specified, but it can be anything even fake one.
- audio_device_save
Save the currently used audio capture filter device and its parameters (if the filter supports it) to a file. If a file with the same name exists it will be overwritten.
- video_device_load
Load a video capture filter device from file instead of searching it by name. It may load additional parameters too, if the filter supports the serialization of its properties to. To use this a video capture source has to be specified, but it can be anything even fake one.
- video_device_save
Save the currently used video capture filter device and its parameters (if the filter supports it) to a file. If a file with the same name exists it will be overwritten.
- use_video_device_timestamps
If set to false, the timestamp for video frames will be derived from the wallclock instead of the timestamp provided by the capture device. This allows working around devices that provide unreliable timestamps.
20.6.2 Examples
- Print the list of DirectShow supported devices and exit:
$ ffmpeg -list_devices true -f dshow -i dummy
- Open video device Camera:
$ ffmpeg -f dshow -i video="Camera"
- Open second video device with name Camera:
$ ffmpeg -f dshow -video_device_number 1 -i video="Camera"
- Open video device Camera and audio device Microphone:
$ ffmpeg -f dshow -i video="Camera":audio="Microphone"
- Print the list of supported options in selected device and exit:
$ ffmpeg -list_options true -f dshow -i video="Camera"
- Specify pin names to capture by name or alternative name, specify alternative device name:
$ ffmpeg -f dshow -audio_pin_name "Audio Out" -video_pin_name 2 -i video=video="@device_pnp_\\?\pci#ven_1a0a&dev_6200&subsys_62021461&rev_01#4&e2c7dd6&0&00e1#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\{ca465100-deb0-4d59-818f-8c477184adf6}":audio="Microphone"
- Configure a crossbar device, specifying crossbar pins, allow user to adjust video capture properties at startup:
$ ffmpeg -f dshow -show_video_device_dialog true -crossbar_video_input_pin_number 0 -crossbar_audio_input_pin_number 3 -i video="AVerMedia BDA Analog Capture":audio="AVerMedia BDA Analog Capture"
20.7 fbdev
Linux framebuffer input device.
The Linux framebuffer is a graphic hardware-independent abstraction layer to show graphics on a computer monitor, typically on the console. It is accessed through a file device node, usually /dev/fb0.
For more detailed information read the file Documentation/fb/framebuffer.txt included in the Linux source tree.
See also http://linux-fbdev.sourceforge.net/, and fbset(1).
To record from the framebuffer device /dev/fb0 with
ffmpeg
:
ffmpeg -f fbdev -framerate 10 -i /dev/fb0 out.avi
You can take a single screenshot image with the command:
ffmpeg -f fbdev -framerate 1 -i /dev/fb0 -frames:v 1 screenshot.jpeg
20.7.1 Options
- framerate
Set the frame rate. Default is 25.
20.8 gdigrab
Win32 GDI-based screen capture device.
This device allows you to capture a region of the display on Windows.
Amongst options for the imput filenames are such elements as:
desktop
or
title=window_title
or
hwnd=window_hwnd
The first option will capture the entire desktop, or a fixed region of the desktop. The second and third options will instead capture the contents of a single window, regardless of its position on the screen.
For example, to grab the entire desktop using ffmpeg
:
ffmpeg -f gdigrab -framerate 6 -i desktop out.mpg
Grab a 640x480 region at position 10,20
:
ffmpeg -f gdigrab -framerate 6 -offset_x 10 -offset_y 20 -video_size vga -i desktop out.mpg
Grab the contents of the window named "Calculator"
ffmpeg -f gdigrab -framerate 6 -i title=Calculator out.mpg
20.8.1 Options
- draw_mouse
Specify whether to draw the mouse pointer. Use the value
0
to not draw the pointer. Default value is1
.- framerate
Set the grabbing frame rate. Default value is
ntsc
, corresponding to a frame rate of30000/1001
.- show_region
Show grabbed region on screen.
If show_region is specified with
1
, then the grabbing region will be indicated on screen. With this option, it is easy to know what is being grabbed if only a portion of the screen is grabbed.Note that show_region is incompatible with grabbing the contents of a single window.
For example:
ffmpeg -f gdigrab -show_region 1 -framerate 6 -video_size cif -offset_x 10 -offset_y 20 -i desktop out.mpg
- video_size
Set the video frame size. The default is to capture the full screen if desktop is selected, or the full window size if title=window_title is selected.
- offset_x
When capturing a region with video_size, set the distance from the left edge of the screen or desktop.
Note that the offset calculation is from the top left corner of the primary monitor on Windows. If you have a monitor positioned to the left of your primary monitor, you will need to use a negative offset_x value to move the region to that monitor.
- offset_y
When capturing a region with video_size, set the distance from the top edge of the screen or desktop.
Note that the offset calculation is from the top left corner of the primary monitor on Windows. If you have a monitor positioned above your primary monitor, you will need to use a negative offset_y value to move the region to that monitor.
20.9 iec61883
FireWire DV/HDV input device using libiec61883.
To enable this input device, you need libiec61883, libraw1394 and
libavc1394 installed on your system. Use the configure option
--enable-libiec61883
to compile with the device enabled.
The iec61883 capture device supports capturing from a video device connected via IEEE1394 (FireWire), using libiec61883 and the new Linux FireWire stack (juju). This is the default DV/HDV input method in Linux Kernel 2.6.37 and later, since the old FireWire stack was removed.
Specify the FireWire port to be used as input file, or "auto" to choose the first port connected.
20.9.1 Options
- dvtype
Override autodetection of DV/HDV. This should only be used if auto detection does not work, or if usage of a different device type should be prohibited. Treating a DV device as HDV (or vice versa) will not work and result in undefined behavior. The values auto, dv and hdv are supported.
- dvbuffer
Set maximum size of buffer for incoming data, in frames. For DV, this is an exact value. For HDV, it is not frame exact, since HDV does not have a fixed frame size.
- dvguid
Select the capture device by specifying its GUID. Capturing will only be performed from the specified device and fails if no device with the given GUID is found. This is useful to select the input if multiple devices are connected at the same time. Look at /sys/bus/firewire/devices to find out the GUIDs.
20.9.2 Examples
- Grab and show the input of a FireWire DV/HDV device.
ffplay -f iec61883 -i auto
- Grab and record the input of a FireWire DV/HDV device,
using a packet buffer of 100000 packets if the source is HDV.
ffmpeg -f iec61883 -i auto -dvbuffer 100000 out.mpg
20.10 jack
JACK input device.
To enable this input device during configuration you need libjack installed on your system.
A JACK input device creates one or more JACK writable clients, one for each audio channel, with name client_name:input_N, where client_name is the name provided by the application, and N is a number which identifies the channel. Each writable client will send the acquired data to the FFmpeg input device.
Once you have created one or more JACK readable clients, you need to connect them to one or more JACK writable clients.
To connect or disconnect JACK clients you can use the jack_connect
and jack_disconnect
programs, or do it through a graphical interface,
for example with qjackctl
.
To list the JACK clients and their properties you can invoke the command
jack_lsp
.
Follows an example which shows how to capture a JACK readable client
with ffmpeg
.
# Create a JACK writable client with name "ffmpeg". $ ffmpeg -f jack -i ffmpeg -y out.wav # Start the sample jack_metro readable client. $ jack_metro -b 120 -d 0.2 -f 4000 # List the current JACK clients. $ jack_lsp -c system:capture_1 system:capture_2 system:playback_1 system:playback_2 ffmpeg:input_1 metro:120_bpm # Connect metro to the ffmpeg writable client. $ jack_connect metro:120_bpm ffmpeg:input_1
For more information read: http://jackaudio.org/
20.10.1 Options
- channels
Set the number of channels. Default is 2.
20.11 kmsgrab
KMS video input device.
Captures the KMS scanout framebuffer associated with a specified CRTC or plane as a DRM object that can be passed to other hardware functions.
Requires either DRM master or CAP_SYS_ADMIN to run.
If you don’t understand what all of that means, you probably don’t want this. Look at x11grab instead.
20.11.1 Options
- device
DRM device to capture on. Defaults to /dev/dri/card0.
- format
Pixel format of the framebuffer. This can be autodetected if you are running Linux 5.7 or later, but needs to be provided for earlier versions. Defaults to bgr0, which is the most common format used by the Linux console and Xorg X server.
- format_modifier
Format modifier to signal on output frames. This is necessary to import correctly into some APIs. It can be autodetected if you are running Linux 5.7 or later, but will need to be provided explicitly when needed in earlier versions. See the libdrm documentation for possible values.
- crtc_id
KMS CRTC ID to define the capture source. The first active plane on the given CRTC will be used.
- plane_id
KMS plane ID to define the capture source. Defaults to the first active plane found if neither crtc_id nor plane_id are specified.
- framerate
Framerate to capture at. This is not synchronised to any page flipping or framebuffer changes - it just defines the interval at which the framebuffer is sampled. Sampling faster than the framebuffer update rate will generate independent frames with the same content. Defaults to
30
.
20.11.2 Examples
- Capture from the first active plane, download the result to normal frames and encode.
This will only work if the framebuffer is both linear and mappable - if not, the result
may be scrambled or fail to download.
ffmpeg -f kmsgrab -i - -vf 'hwdownload,format=bgr0' output.mp4
- Capture from CRTC ID 42 at 60fps, map the result to VAAPI, convert to NV12 and encode as H.264.
ffmpeg -crtc_id 42 -framerate 60 -f kmsgrab -i - -vf 'hwmap=derive_device=vaapi,scale_vaapi=w=1920:h=1080:format=nv12' -c:v h264_vaapi output.mp4
- To capture only part of a plane the output can be cropped - this can be used to capture
a single window, as long as it has a known absolute position and size. For example, to
capture and encode the middle quarter of a 1920x1080 plane:
ffmpeg -f kmsgrab -i - -vf 'hwmap=derive_device=vaapi,crop=960:540:480:270,scale_vaapi=960:540:nv12' -c:v h264_vaapi output.mp4
20.12 lavfi
Libavfilter input virtual device.
This input device reads data from the open output pads of a libavfilter filtergraph.
For each filtergraph open output, the input device will create a corresponding stream which is mapped to the generated output. The filtergraph is specified through the option graph.
20.12.1 Options
- graph
Specify the filtergraph to use as input. Each video open output must be labelled by a unique string of the form "outN", where N is a number starting from 0 corresponding to the mapped input stream generated by the device. The first unlabelled output is automatically assigned to the "out0" label, but all the others need to be specified explicitly.
The suffix "+subcc" can be appended to the output label to create an extra stream with the closed captions packets attached to that output (experimental; only for EIA-608 / CEA-708 for now). The subcc streams are created after all the normal streams, in the order of the corresponding stream. For example, if there is "out19+subcc", "out7+subcc" and up to "out42", the stream #43 is subcc for stream #7 and stream #44 is subcc for stream #19.
If not specified defaults to the filename specified for the input device.
- graph_file
Set the filename of the filtergraph to be read and sent to the other filters. Syntax of the filtergraph is the same as the one specified by the option graph.
- dumpgraph
Dump graph to stderr.
20.12.2 Examples
- Create a color video stream and play it back with
ffplay
:ffplay -f lavfi -graph "color=c=pink [out0]" dummy
- As the previous example, but use filename for specifying the graph
description, and omit the "out0" label:
ffplay -f lavfi color=c=pink
- Create three different video test filtered sources and play them:
ffplay -f lavfi -graph "testsrc [out0]; testsrc,hflip [out1]; testsrc,negate [out2]" test3
- Read an audio stream from a file using the amovie source and play it
back with
ffplay
:ffplay -f lavfi "amovie=test.wav"
- Read an audio stream and a video stream and play it back with
ffplay
:ffplay -f lavfi "movie=test.avi[out0];amovie=test.wav[out1]"
- Dump decoded frames to images and Closed Captions to an RCWT backup:
ffmpeg -f lavfi -i "movie=test.ts[out0+subcc]" -map v frame%08d.png -map s -c copy -f rcwt subcc.bin
20.13 libcdio
Audio-CD input device based on libcdio.
To enable this input device during configuration you need libcdio
installed on your system. It requires the configure option
--enable-libcdio
.
This device allows playing and grabbing from an Audio-CD.
For example to copy with ffmpeg
the entire Audio-CD in /dev/sr0,
you may run the command:
ffmpeg -f libcdio -i /dev/sr0 cd.wav
20.13.1 Options
- speed
Set drive reading speed. Default value is 0.
The speed is specified CD-ROM speed units. The speed is set through the libcdio
cdio_cddap_speed_set
function. On many CD-ROM drives, specifying a value too large will result in using the fastest speed.- paranoia_mode
Set paranoia recovery mode flags. It accepts one of the following values:
- ‘disable’
- ‘verify’
- ‘overlap’
- ‘neverskip’
- ‘full’
Default value is ‘disable’.
For more information about the available recovery modes, consult the paranoia project documentation.
20.14 libdc1394
IIDC1394 input device, based on libdc1394 and libraw1394.
Requires the configure option --enable-libdc1394
.
20.14.1 Options
- framerate
Set the frame rate. Default is
ntsc
, corresponding to a frame rate of30000/1001
.- pixel_format
Select the pixel format. Default is
uyvy422
.- video_size
Set the video size given as a string such as
640x480
orhd720
. Default isqvga
.
20.15 openal
The OpenAL input device provides audio capture on all systems with a working OpenAL 1.1 implementation.
To enable this input device during configuration, you need OpenAL
headers and libraries installed on your system, and need to configure
FFmpeg with --enable-openal
.
OpenAL headers and libraries should be provided as part of your OpenAL
implementation, or as an additional download (an SDK). Depending on your
installation you may need to specify additional flags via the
--extra-cflags
and --extra-ldflags
for allowing the build
system to locate the OpenAL headers and libraries.
An incomplete list of OpenAL implementations follows:
- Creative
The official Windows implementation, providing hardware acceleration with supported devices and software fallback. See http://openal.org/.
- OpenAL Soft
Portable, open source (LGPL) software implementation. Includes backends for the most common sound APIs on the Windows, Linux, Solaris, and BSD operating systems. See http://kcat.strangesoft.net/openal.html.
- Apple
OpenAL is part of Core Audio, the official Mac OS X Audio interface. See http://developer.apple.com/technologies/mac/audio-and-video.html
This device allows one to capture from an audio input device handled through OpenAL.
You need to specify the name of the device to capture in the provided filename. If the empty string is provided, the device will automatically select the default device. You can get the list of the supported devices by using the option list_devices.
20.15.1 Options
- channels
Set the number of channels in the captured audio. Only the values 1 (monaural) and 2 (stereo) are currently supported. Defaults to 2.
- sample_size
Set the sample size (in bits) of the captured audio. Only the values 8 and 16 are currently supported. Defaults to 16.
- sample_rate
Set the sample rate (in Hz) of the captured audio. Defaults to 44.1k.
- list_devices
If set to true, print a list of devices and exit. Defaults to false.
20.15.2 Examples
Print the list of OpenAL supported devices and exit:
$ ffmpeg -list_devices true -f openal -i dummy out.ogg
Capture from the OpenAL device DR-BT101 via PulseAudio:
$ ffmpeg -f openal -i 'DR-BT101 via PulseAudio' out.ogg
Capture from the default device (note the empty string ” as filename):
$ ffmpeg -f openal -i '' out.ogg
Capture from two devices simultaneously, writing to two different files,
within the same ffmpeg
command:
$ ffmpeg -f openal -i 'DR-BT101 via PulseAudio' out1.ogg -f openal -i 'ALSA Default' out2.ogg
Note: not all OpenAL implementations support multiple simultaneous capture - try the latest OpenAL Soft if the above does not work.
20.16 oss
Open Sound System input device.
The filename to provide to the input device is the device node representing the OSS input device, and is usually set to /dev/dsp.
For example to grab from /dev/dsp using ffmpeg
use the
command:
ffmpeg -f oss -i /dev/dsp /tmp/oss.wav
For more information about OSS see: http://manuals.opensound.com/usersguide/dsp.html
20.16.1 Options
- sample_rate
Set the sample rate in Hz. Default is 48000.
- channels
Set the number of channels. Default is 2.
20.17 pulse
PulseAudio input device.
To enable this output device you need to configure FFmpeg with --enable-libpulse
.
The filename to provide to the input device is a source device or the string "default"
To list the PulseAudio source devices and their properties you can invoke
the command pactl list sources
.
More information about PulseAudio can be found on http://www.pulseaudio.org.
20.17.1 Options
- server
Connect to a specific PulseAudio server, specified by an IP address. Default server is used when not provided.
- name
Specify the application name PulseAudio will use when showing active clients, by default it is the
LIBAVFORMAT_IDENT
string.- stream_name
Specify the stream name PulseAudio will use when showing active streams, by default it is "record".
- sample_rate
Specify the samplerate in Hz, by default 48kHz is used.
- channels
Specify the channels in use, by default 2 (stereo) is set.
- frame_size
This option does nothing and is deprecated.
- fragment_size
Specify the size in bytes of the minimal buffering fragment in PulseAudio, it will affect the audio latency. By default it is set to 50 ms amount of data.
- wallclock
Set the initial PTS using the current time. Default is 1.
20.17.2 Examples
Record a stream from default device:
ffmpeg -f pulse -i default /tmp/pulse.wav
20.18 sndio
sndio input device.
To enable this input device during configuration you need libsndio installed on your system.
The filename to provide to the input device is the device node representing the sndio input device, and is usually set to /dev/audio0.
For example to grab from /dev/audio0 using ffmpeg
use the
command:
ffmpeg -f sndio -i /dev/audio0 /tmp/oss.wav
20.18.1 Options
- sample_rate
Set the sample rate in Hz. Default is 48000.
- channels
Set the number of channels. Default is 2.
20.19 video4linux2, v4l2
Video4Linux2 input video device.
"v4l2" can be used as alias for "video4linux2".
If FFmpeg is built with v4l-utils support (by using the
--enable-libv4l2
configure option), it is possible to use it with the
-use_libv4l2
input device option.
The name of the device to grab is a file device node, usually Linux systems tend to automatically create such nodes when the device (e.g. an USB webcam) is plugged into the system, and has a name of the kind /dev/videoN, where N is a number associated to the device.
Video4Linux2 devices usually support a limited set of
widthxheight sizes and frame rates. You can check which are
supported using -list_formats all
for Video4Linux2 devices.
Some devices, like TV cards, support one or more standards. It is possible
to list all the supported standards using -list_standards all
.
The time base for the timestamps is 1 microsecond. Depending on the kernel version and configuration, the timestamps may be derived from the real time clock (origin at the Unix Epoch) or the monotonic clock (origin usually at boot time, unaffected by NTP or manual changes to the clock). The -timestamps abs or -ts abs option can be used to force conversion into the real time clock.
Some usage examples of the video4linux2 device with ffmpeg
and ffplay
:
- List supported formats for a video4linux2 device:
ffplay -f video4linux2 -list_formats all /dev/video0
- Grab and show the input of a video4linux2 device:
ffplay -f video4linux2 -framerate 30 -video_size hd720 /dev/video0
- Grab and record the input of a video4linux2 device, leave the
frame rate and size as previously set:
ffmpeg -f video4linux2 -input_format mjpeg -i /dev/video0 out.mpeg
For more information about Video4Linux, check http://linuxtv.org/.
20.19.1 Options
- standard
Set the standard. Must be the name of a supported standard. To get a list of the supported standards, use the list_standards option.
- channel
Set the input channel number. Default to -1, which means using the previously selected channel.
- video_size
Set the video frame size. The argument must be a string in the form WIDTHxHEIGHT or a valid size abbreviation.
- pixel_format
Select the pixel format (only valid for raw video input).
- input_format
Set the preferred pixel format (for raw video) or a codec name. This option allows one to select the input format, when several are available.
- framerate
Set the preferred video frame rate.
- list_formats
List available formats (supported pixel formats, codecs, and frame sizes) and exit.
Available values are:
- ‘all’
Show all available (compressed and non-compressed) formats.
- ‘raw’
Show only raw video (non-compressed) formats.
- ‘compressed’
Show only compressed formats.
- list_standards
List supported standards and exit.
Available values are:
- ‘all’
Show all supported standards.
- timestamps, ts
Set type of timestamps for grabbed frames.
Available values are:
- ‘default’
Use timestamps from the kernel.
- ‘abs’
Use absolute timestamps (wall clock).
- ‘mono2abs’
Force conversion from monotonic to absolute timestamps.
Default value is
default
.- use_libv4l2
Use libv4l2 (v4l-utils) conversion functions. Default is 0.
20.20 vfwcap
VfW (Video for Windows) capture input device.
The filename passed as input is the capture driver number, ranging from 0 to 9. You may use "list" as filename to print a list of drivers. Any other filename will be interpreted as device number 0.
20.20.1 Options
- video_size
Set the video frame size.
- framerate
Set the grabbing frame rate. Default value is
ntsc
, corresponding to a frame rate of30000/1001
.
20.21 x11grab
X11 video input device.
To enable this input device during configuration you need libxcb installed on your system. It will be automatically detected during configuration.
This device allows one to capture a region of an X11 display.
The filename passed as input has the syntax:
[hostname]:display_number.screen_number[+x_offset,y_offset]
hostname:display_number.screen_number specifies the
X11 display name of the screen to grab from. hostname can be
omitted, and defaults to "localhost". The environment variable
DISPLAY
contains the default display name.
x_offset and y_offset specify the offsets of the grabbed area with respect to the top-left border of the X11 screen. They default to 0.
Check the X11 documentation (e.g. man X
) for more detailed
information.
Use the xdpyinfo
program for getting basic information about
the properties of your X11 display (e.g. grep for "name" or
"dimensions").
For example to grab from :0.0 using ffmpeg
:
ffmpeg -f x11grab -framerate 25 -video_size cif -i :0.0 out.mpg
Grab at position 10,20
:
ffmpeg -f x11grab -framerate 25 -video_size cif -i :0.0+10,20 out.mpg
20.21.1 Options
- select_region
Specify whether to select the grabbing area graphically using the pointer. A value of
1
prompts the user to select the grabbing area graphically by clicking and dragging. A single click with no dragging will select the whole screen. A region with zero width or height will also select the whole screen. This option overwrites the video_size, grab_x, and grab_y options. Default value is0
.- draw_mouse
Specify whether to draw the mouse pointer. A value of
0
specifies not to draw the pointer. Default value is1
.- follow_mouse
Make the grabbed area follow the mouse. The argument can be
centered
or a number of pixels PIXELS.When it is specified with "centered", the grabbing region follows the mouse pointer and keeps the pointer at the center of region; otherwise, the region follows only when the mouse pointer reaches within PIXELS (greater than zero) to the edge of region.
For example:
ffmpeg -f x11grab -follow_mouse centered -framerate 25 -video_size cif -i :0.0 out.mpg
To follow only when the mouse pointer reaches within 100 pixels to edge:
ffmpeg -f x11grab -follow_mouse 100 -framerate 25 -video_size cif -i :0.0 out.mpg
- framerate
Set the grabbing frame rate. Default value is
ntsc
, corresponding to a frame rate of30000/1001
.- show_region
Show grabbed region on screen.
If show_region is specified with
1
, then the grabbing region will be indicated on screen. With this option, it is easy to know what is being grabbed if only a portion of the screen is grabbed.- region_border
Set the region border thickness if -show_region 1 is used. Range is 1 to 128 and default is 3 (XCB-based x11grab only).
For example:
ffmpeg -f x11grab -show_region 1 -framerate 25 -video_size cif -i :0.0+10,20 out.mpg
With follow_mouse:
ffmpeg -f x11grab -follow_mouse centered -show_region 1 -framerate 25 -video_size cif -i :0.0 out.mpg
- window_id
Grab this window, instead of the whole screen. Default value is 0, which maps to the whole screen (root window).
The id of a window can be found using the
xwininfo
program, possibly with options -tree and -root.If the window is later enlarged, the new area is not recorded. Video ends when the window is closed, unmapped (i.e., iconified) or shrunk beyond the video size (which defaults to the initial window size).
This option disables options follow_mouse and select_region.
- video_size
Set the video frame size. Default is the full desktop or window.
- grab_x
- grab_y
Set the grabbing region coordinates. They are expressed as offset from the top left corner of the X11 window and correspond to the x_offset and y_offset parameters in the device name. The default value for both options is 0.
21 Resampler Options
The audio resampler supports the following named options.
Options may be set by specifying -option value in the
FFmpeg tools, option=value for the aresample filter,
by setting the value explicitly in the
SwrContext
options or using the libavutil/opt.h API for
programmatic use.
- uchl, used_chlayout
Set used input channel layout. Default is unset. This option is only used for special remapping.
- isr, in_sample_rate
Set the input sample rate. Default value is 0.
- osr, out_sample_rate
Set the output sample rate. Default value is 0.
- isf, in_sample_fmt
Specify the input sample format. It is set by default to
none
.- osf, out_sample_fmt
Specify the output sample format. It is set by default to
none
.- tsf, internal_sample_fmt
Set the internal sample format. Default value is
none
. This will automatically be chosen when it is not explicitly set.- ichl, in_chlayout
- ochl, out_chlayout
Set the input/output channel layout.
See (ffmpeg-utils)the Channel Layout section in the ffmpeg-utils(1) manual for the required syntax.
- clev, center_mix_level
Set the center mix level. It is a value expressed in deciBel, and must be in the interval [-32,32].
- slev, surround_mix_level
Set the surround mix level. It is a value expressed in deciBel, and must be in the interval [-32,32].
- lfe_mix_level
Set LFE mix into non LFE level. It is used when there is a LFE input but no LFE output. It is a value expressed in deciBel, and must be in the interval [-32,32].
- rmvol, rematrix_volume
Set rematrix volume. Default value is 1.0.
- rematrix_maxval
Set maximum output value for rematrixing. This can be used to prevent clipping vs. preventing volume reduction. A value of 1.0 prevents clipping.
- flags, swr_flags
Set flags used by the converter. Default value is 0.
It supports the following individual flags:
- res
force resampling, this flag forces resampling to be used even when the input and output sample rates match.
- dither_scale
Set the dither scale. Default value is 1.
- dither_method
Set dither method. Default value is 0.
Supported values:
- ‘rectangular’
select rectangular dither
- ‘triangular’
select triangular dither
- ‘triangular_hp’
select triangular dither with high pass
- ‘lipshitz’
select Lipshitz noise shaping dither.
- ‘shibata’
select Shibata noise shaping dither.
- ‘low_shibata’
select low Shibata noise shaping dither.
- ‘high_shibata’
select high Shibata noise shaping dither.
- ‘f_weighted’
select f-weighted noise shaping dither
- ‘modified_e_weighted’
select modified-e-weighted noise shaping dither
- ‘improved_e_weighted’
select improved-e-weighted noise shaping dither
- resampler
Set resampling engine. Default value is swr.
Supported values:
- ‘swr’
select the native SW Resampler; filter options precision and cheby are not applicable in this case.
- ‘soxr’
select the SoX Resampler (where available); compensation, and filter options filter_size, phase_shift, exact_rational, filter_type & kaiser_beta, are not applicable in this case.
- filter_size
For swr only, set resampling filter size, default value is 32.
- phase_shift
For swr only, set resampling phase shift, default value is 10, and must be in the interval [0,30].
- linear_interp
Use linear interpolation when enabled (the default). Disable it if you want to preserve speed instead of quality when exact_rational fails.
- exact_rational
For swr only, when enabled, try to use exact phase_count based on input and output sample rate. However, if it is larger than
1 << phase_shift
, the phase_count will be1 << phase_shift
as fallback. Default is enabled.- cutoff
Set cutoff frequency (swr: 6dB point; soxr: 0dB point) ratio; must be a float value between 0 and 1. Default value is 0.97 with swr, and 0.91 with soxr (which, with a sample-rate of 44100, preserves the entire audio band to 20kHz).
- precision
For soxr only, the precision in bits to which the resampled signal will be calculated. The default value of 20 (which, with suitable dithering, is appropriate for a destination bit-depth of 16) gives SoX’s ’High Quality’; a value of 28 gives SoX’s ’Very High Quality’.
- cheby
For soxr only, selects passband rolloff none (Chebyshev) & higher-precision approximation for ’irrational’ ratios. Default value is 0.
- async
For swr only, simple 1 parameter audio sync to timestamps using stretching, squeezing, filling and trimming. Setting this to 1 will enable filling and trimming, larger values represent the maximum amount in samples that the data may be stretched or squeezed for each second. Default value is 0, thus no compensation is applied to make the samples match the audio timestamps.
- first_pts
For swr only, assume the first pts should be this value. The time unit is 1 / sample rate. This allows for padding/trimming at the start of stream. By default, no assumption is made about the first frame’s expected pts, so no padding or trimming is done. For example, this could be set to 0 to pad the beginning with silence if an audio stream starts after the video stream or to trim any samples with a negative pts due to encoder delay.
- min_comp
For swr only, set the minimum difference between timestamps and audio data (in seconds) to trigger stretching/squeezing/filling or trimming of the data to make it match the timestamps. The default is that stretching/squeezing/filling and trimming is disabled (min_comp =
FLT_MAX
).- min_hard_comp
For swr only, set the minimum difference between timestamps and audio data (in seconds) to trigger adding/dropping samples to make it match the timestamps. This option effectively is a threshold to select between hard (trim/fill) and soft (squeeze/stretch) compensation. Note that all compensation is by default disabled through min_comp. The default is 0.1.
- comp_duration
For swr only, set duration (in seconds) over which data is stretched/squeezed to make it match the timestamps. Must be a non-negative double float value, default value is 1.0.
- max_soft_comp
For swr only, set maximum factor by which data is stretched/squeezed to make it match the timestamps. Must be a non-negative double float value, default value is 0.
- matrix_encoding
Select matrixed stereo encoding.
It accepts the following values:
- ‘none’
select none
- ‘dolby’
select Dolby
- ‘dplii’
select Dolby Pro Logic II
Default value is
none
.- filter_type
For swr only, select resampling filter type. This only affects resampling operations.
It accepts the following values:
- ‘cubic’
select cubic
- ‘blackman_nuttall’
select Blackman Nuttall windowed sinc
- ‘kaiser’
select Kaiser windowed sinc
- kaiser_beta
For swr only, set Kaiser window beta value. Must be a double float value in the interval [2,16], default value is 9.
- output_sample_bits
For swr only, set number of used output sample bits for dithering. Must be an integer in the interval [0,64], default value is 0, which means it’s not used.
22 Scaler Options
The video scaler supports the following named options.
Options may be set by specifying -option value in the
FFmpeg tools, with a few API-only exceptions noted below.
For programmatic use, they can be set explicitly in the
SwsContext
options or through the libavutil/opt.h API.
- sws_flags
Set the scaler flags. This is also used to set the scaling algorithm. Only a single algorithm should be selected. Default value is ‘bicubic’.
It accepts the following values:
- ‘fast_bilinear’
Select fast bilinear scaling algorithm.
- ‘bilinear’
Select bilinear scaling algorithm.
- ‘bicubic’
Select bicubic scaling algorithm.
- ‘experimental’
Select experimental scaling algorithm.
- ‘neighbor’
Select nearest neighbor rescaling algorithm.
- ‘area’
Select averaging area rescaling algorithm.
- ‘bicublin’
Select bicubic scaling algorithm for the luma component, bilinear for chroma components.
- ‘gauss’
Select Gaussian rescaling algorithm.
- ‘sinc’
Select sinc rescaling algorithm.
- ‘lanczos’
Select Lanczos rescaling algorithm. The default width (alpha) is 3 and can be changed by setting
param0
.- ‘spline’
Select natural bicubic spline rescaling algorithm.
- ‘print_info’
Enable printing/debug logging.
- ‘accurate_rnd’
Enable accurate rounding.
- ‘full_chroma_int’
Enable full chroma interpolation.
- ‘full_chroma_inp’
Select full chroma input.
- ‘bitexact’
Enable bitexact output.
- srcw (API only)
Set source width.
- srch (API only)
Set source height.
- dstw (API only)
Set destination width.
- dsth (API only)
Set destination height.
- src_format (API only)
Set source pixel format (must be expressed as an integer).
- dst_format (API only)
Set destination pixel format (must be expressed as an integer).
- src_range (boolean)
If value is set to
1
, indicates source is full range. Default value is0
, which indicates source is limited range.- dst_range (boolean)
If value is set to
1
, enable full range for destination. Default value is0
, which enables limited range.- param0, param1
Set scaling algorithm parameters. The specified values are specific of some scaling algorithms and ignored by others. The specified values are floating point number values.
- sws_dither
Set the dithering algorithm. Accepts one of the following values. Default value is ‘auto’.
- ‘auto’
automatic choice
- ‘none’
no dithering
- ‘bayer’
bayer dither
- ‘ed’
error diffusion dither
- ‘a_dither’
arithmetic dither, based using addition
- ‘x_dither’
arithmetic dither, based using xor (more random/less apparent patterning that a_dither).
- alphablend
Set the alpha blending to use when the input has alpha but the output does not. Default value is ‘none’.
- ‘uniform_color’
Blend onto a uniform background color
- ‘checkerboard’
Blend onto a checkerboard
- ‘none’
No blending
23 Filtering Introduction
Filtering in FFmpeg is enabled through the libavfilter library.
In libavfilter, a filter can have multiple inputs and multiple outputs. To illustrate the sorts of things that are possible, we consider the following filtergraph.
[main] input --> split ---------------------> overlay --> output | ^ |[tmp] [flip]| +-----> crop --> vflip -------+
This filtergraph splits the input stream in two streams, then sends one stream through the crop filter and the vflip filter, before merging it back with the other stream by overlaying it on top. You can use the following command to achieve this:
ffmpeg -i INPUT -vf "split [main][tmp]; [tmp] crop=iw:ih/2:0:0, vflip [flip]; [main][flip] overlay=0:H/2" OUTPUT
The result will be that the top half of the video is mirrored onto the bottom half of the output video.
Filters in the same linear chain are separated by commas, and distinct linear chains of filters are separated by semicolons. In our example, crop,vflip are in one linear chain, split and overlay are separately in another. The points where the linear chains join are labelled by names enclosed in square brackets. In the example, the split filter generates two outputs that are associated to the labels [main] and [tmp].
The stream sent to the second output of split, labelled as [tmp], is processed through the crop filter, which crops away the lower half part of the video, and then vertically flipped. The overlay filter takes in input the first unchanged output of the split filter (which was labelled as [main]), and overlay on its lower half the output generated by the crop,vflip filterchain.
Some filters take in input a list of parameters: they are specified after the filter name and an equal sign, and are separated from each other by a colon.
There exist so-called source filters that do not have an audio/video input, and sink filters that will not have audio/video output.
24 graph2dot
The graph2dot program included in the FFmpeg tools directory can be used to parse a filtergraph description and issue a corresponding textual representation in the dot language.
Invoke the command:
graph2dot -h
to see how to use graph2dot.
You can then pass the dot description to the dot program (from the graphviz suite of programs) and obtain a graphical representation of the filtergraph.
For example the sequence of commands:
echo GRAPH_DESCRIPTION | \ tools/graph2dot -o graph.tmp && \ dot -Tpng graph.tmp -o graph.png && \ display graph.png
can be used to create and display an image representing the graph described by the GRAPH_DESCRIPTION string. Note that this string must be a complete self-contained graph, with its inputs and outputs explicitly defined. For example if your command line is of the form:
ffmpeg -i infile -vf scale=640:360 outfile
your GRAPH_DESCRIPTION string will need to be of the form:
nullsrc,scale=640:360,nullsink
you may also need to set the nullsrc parameters and add a format filter in order to simulate a specific input file.
25 Filtergraph description
A filtergraph is a directed graph of connected filters. It can contain cycles, and there can be multiple links between a pair of filters. Each link has one input pad on one side connecting it to one filter from which it takes its input, and one output pad on the other side connecting it to one filter accepting its output.
Each filter in a filtergraph is an instance of a filter class registered in the application, which defines the features and the number of input and output pads of the filter.
A filter with no input pads is called a "source", and a filter with no output pads is called a "sink".
25.1 Filtergraph syntax
A filtergraph has a textual representation, which is recognized by the
-filter/-vf/-af and
-filter_complex options in ffmpeg
and
-vf/-af in ffplay
, and by the
avfilter_graph_parse_ptr()
function defined in
libavfilter/avfilter.h.
A filterchain consists of a sequence of connected filters, each one connected to the previous one in the sequence. A filterchain is represented by a list of ","-separated filter descriptions.
A filtergraph consists of a sequence of filterchains. A sequence of filterchains is represented by a list of ";"-separated filterchain descriptions.
A filter is represented by a string of the form: [in_link_1]...[in_link_N]filter_name@id=arguments[out_link_1]...[out_link_M]
filter_name is the name of the filter class of which the described filter is an instance of, and has to be the name of one of the filter classes registered in the program optionally followed by "@id". The name of the filter class is optionally followed by a string "=arguments".
arguments is a string which contains the parameters used to initialize the filter instance. It may have one of two forms:
- A ’:’-separated list of key=value pairs.
- A ’:’-separated list of value. In this case, the keys are assumed to be
the option names in the order they are declared. E.g. the
fade
filter declares three options in this order – type, start_frame and nb_frames. Then the parameter list in:0:30 means that the value in is assigned to the option type, 0 to start_frame and 30 to nb_frames. - A ’:’-separated list of mixed direct value and long key=value pairs. The direct value must precede the key=value pairs, and follow the same constraints order of the previous point. The following key=value pairs can be set in any preferred order.
If the option value itself is a list of items (e.g. the format
filter
takes a list of pixel formats), the items in the list are usually separated by
‘|’.
The list of arguments can be quoted using the character ‘'’ as initial and ending mark, and the character ‘\’ for escaping the characters within the quoted text; otherwise the argument string is considered terminated when the next special character (belonging to the set ‘[]=;,’) is encountered.
A special syntax implemented in the ffmpeg
CLI tool allows loading
option values from files. This is done be prepending a slash ’/’ to the option
name, then the supplied value is interpreted as a path from which the actual
value is loaded. E.g.
ffmpeg -i <INPUT> -vf drawtext=/text=/tmp/some_text <OUTPUT>
will load the text to be drawn from /tmp/some_text. API users wishing to
implement a similar feature should use the avfilter_graph_segment_*()
functions together with custom IO code.
The name and arguments of the filter are optionally preceded and followed by a list of link labels. A link label allows one to name a link and associate it to a filter output or input pad. The preceding labels in_link_1 ... in_link_N, are associated to the filter input pads, the following labels out_link_1 ... out_link_M, are associated to the output pads.
When two link labels with the same name are found in the filtergraph, a link between the corresponding input and output pad is created.
If an output pad is not labelled, it is linked by default to the first unlabelled input pad of the next filter in the filterchain. For example in the filterchain
nullsrc, split[L1], [L2]overlay, nullsink
the split filter instance has two output pads, and the overlay filter instance two input pads. The first output pad of split is labelled "L1", the first input pad of overlay is labelled "L2", and the second output pad of split is linked to the second input pad of overlay, which are both unlabelled.
In a filter description, if the input label of the first filter is not specified, "in" is assumed; if the output label of the last filter is not specified, "out" is assumed.
In a complete filterchain all the unlabelled filter input and output pads must be connected. A filtergraph is considered valid if all the filter input and output pads of all the filterchains are connected.
Leading and trailing whitespaces (space, tabs, or line feeds) separating tokens in the filtergraph specification are ignored. This means that the filtergraph can be expressed using empty lines and spaces to improve redability.
For example, the filtergraph:
testsrc,split[L1],hflip[L2];[L1][L2] hstack
can be represented as:
testsrc, split [L1], hflip [L2]; [L1][L2] hstack
Libavfilter will automatically insert scale filters where format
conversion is required. It is possible to specify swscale flags
for those automatically inserted scalers by prepending
sws_flags=flags;
to the filtergraph description.
Here is a BNF description of the filtergraph syntax:
NAME ::= sequence of alphanumeric characters and '_' FILTER_NAME ::= NAME["@"NAME] LINKLABEL ::= "[" NAME "]" LINKLABELS ::= LINKLABEL [LINKLABELS] FILTER_ARGUMENTS ::= sequence of chars (possibly quoted) FILTER ::= [LINKLABELS] FILTER_NAME ["=" FILTER_ARGUMENTS] [LINKLABELS] FILTERCHAIN ::= FILTER [,FILTERCHAIN] FILTERGRAPH ::= [sws_flags=flags;] FILTERCHAIN [;FILTERGRAPH]
25.2 Notes on filtergraph escaping
Filtergraph description composition entails several levels of escaping. See (ffmpeg-utils)the "Quoting and escaping" section in the ffmpeg-utils(1) manual for more information about the employed escaping procedure.
A first level escaping affects the content of each filter option
value, which may contain the special character :
used to
separate values, or one of the escaping characters \'
.
A second level escaping affects the whole filter description, which
may contain the escaping characters \'
or the special
characters [],;
used by the filtergraph description.
Finally, when you specify a filtergraph on a shell commandline, you need to perform a third level escaping for the shell special characters contained within it.
For example, consider the following string to be embedded in the drawtext filter description text value:
this is a 'string': may contain one, or more, special characters
This string contains the '
special escaping character, and the
:
special character, so it needs to be escaped in this way:
text=this is a \'string\'\: may contain one, or more, special characters
A second level of escaping is required when embedding the filter description in a filtergraph description, in order to escape all the filtergraph special characters. Thus the example above becomes:
drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters
(note that in addition to the \'
escaping special characters,
also ,
needs to be escaped).
Finally an additional level of escaping is needed when writing the
filtergraph description in a shell command, which depends on the
escaping rules of the adopted shell. For example, assuming that
\
is special and needs to be escaped with another \
, the
previous string will finally result in:
-vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"
In order to avoid cumbersome escaping when using a commandline tool accepting a filter specification as input, it is advisable to avoid direct inclusion of the filter or options specification in the shell.
For example, in case of the drawtext filter, you might prefer to use the textfile option in place of text to specify the text to render.
26 Timeline editing
Some filters support a generic enable option. For the filters supporting timeline editing, this option can be set to an expression which is evaluated before sending a frame to the filter. If the evaluation is non-zero, the filter will be enabled, otherwise the frame will be sent unchanged to the next filter in the filtergraph.
The expression accepts the following values:
- ‘t’
timestamp expressed in seconds, NAN if the input timestamp is unknown
- ‘n’
sequential number of the input frame, starting from 0
- ‘pos’
the position in the file of the input frame, NAN if unknown; deprecated, do not use
- ‘w’
- ‘h’
width and height of the input frame if video
Additionally, these filters support an enable command that can be used to re-define the expression.
Like any other filtering option, the enable option follows the same rules.
For example, to enable a blur filter (smartblur) from 10 seconds to 3 minutes, and a curves filter starting at 3 seconds:
smartblur = enable='between(t,10,3*60)', curves = enable='gte(t,3)' : preset=cross_process
See ffmpeg -filters
to view which filters have timeline support.
27 Changing options at runtime with a command
Some options can be changed during the operation of the filter using
a command. These options are marked ’T’ on the output of
ffmpeg
-h filter=<name of filter>.
The name of the command is the name of the option and the argument is
the new value.
28 Options for filters with several inputs (framesync)
Some filters with several inputs support a common set of options. These options can only be set by name, not with the short notation.
- eof_action
The action to take when EOF is encountered on the secondary input; it accepts one of the following values:
- repeat
Repeat the last frame (the default).
- endall
End both streams.
- pass
Pass the main input through.
- shortest
If set to 1, force the output to terminate when the shortest input terminates. Default value is 0.
- repeatlast
If set to 1, force the filter to extend the last frame of secondary streams until the end of the primary stream. A value of 0 disables this behavior. Default value is 1.
- ts_sync_mode
How strictly to sync streams based on secondary input timestamps; it accepts one of the following values:
- default
Frame from secondary input with the nearest lower or equal timestamp to the primary input frame.
- nearest
Frame from secondary input with the absolute nearest timestamp to the primary input frame.
29 Audio Filters
When you configure your FFmpeg build, you can disable any of the
existing filters using --disable-filters
.
The configure output will show the audio filters included in your
build.
Below is a description of the currently available audio filters.
29.1 aap
Apply Affine Projection algorithm to the first audio stream using the second audio stream.
This adaptive filter is used to estimate unknown audio based on multiple input audio samples. Affine projection algorithm can make trade-offs between computation complexity with convergence speed.
A description of the accepted options follows.
- order
Set the filter order.
- projection
Set the projection order.
- mu
Set the filter mu.
- delta
Set the coefficient to initialize internal covariance matrix.
- out_mode
Set the filter output samples. It accepts the following values:
- i
Pass the 1st input.
- d
Pass the 2nd input.
- o
Pass difference between desired, 2nd input and error signal estimate.
- n
Pass difference between input, 1st input and error signal estimate.
- e
Pass error signal estimated samples.
Default value is o.
- precision
Set which precision to use when processing samples.
- auto
Auto pick internal sample format depending on other filters.
- float
Always use single-floating point precision sample format.
- double
Always use double-floating point precision sample format.
29.2 acompressor
A compressor is mainly used to reduce the dynamic range of a signal. Especially modern music is mostly compressed at a high ratio to improve the overall loudness. It’s done to get the highest attention of a listener, "fatten" the sound and bring more "power" to the track. If a signal is compressed too much it may sound dull or "dead" afterwards or it may start to "pump" (which could be a powerful effect but can also destroy a track completely). The right compression is the key to reach a professional sound and is the high art of mixing and mastering. Because of its complex settings it may take a long time to get the right feeling for this kind of effect.
Compression is done by detecting the volume above a chosen level
threshold
and dividing it by the factor set with ratio
.
So if you set the threshold to -12dB and your signal reaches -6dB a ratio
of 2:1 will result in a signal at -9dB. Because an exact manipulation of
the signal would cause distortion of the waveform the reduction can be
levelled over the time. This is done by setting "Attack" and "Release".
attack
determines how long the signal has to rise above the threshold
before any reduction will occur and release
sets the time the signal
has to fall below the threshold to reduce the reduction again. Shorter signals
than the chosen attack time will be left untouched.
The overall reduction of the signal can be made up afterwards with the
makeup
setting. So compressing the peaks of a signal about 6dB and
raising the makeup to this level results in a signal twice as loud than the
source. To gain a softer entry in the compression the knee
flattens the
hard edge at the threshold in the range of the chosen decibels.
The filter accepts the following options:
- level_in
Set input gain. Default is 1. Range is between 0.015625 and 64.
- mode
Set mode of compressor operation. Can be
upward
ordownward
. Default isdownward
.- threshold
If a signal of stream rises above this level it will affect the gain reduction. By default it is 0.125. Range is between 0.00097563 and 1.
- ratio
Set a ratio by which the signal is reduced. 1:2 means that if the level rose 4dB above the threshold, it will be only 2dB above after the reduction. Default is 2. Range is between 1 and 20.
- attack
Amount of milliseconds the signal has to rise above the threshold before gain reduction starts. Default is 20. Range is between 0.01 and 2000.
- release
Amount of milliseconds the signal has to fall below the threshold before reduction is decreased again. Default is 250. Range is between 0.01 and 9000.
- makeup
Set the amount by how much signal will be amplified after processing. Default is 1. Range is from 1 to 64.
- knee
Curve the sharp knee around the threshold to enter gain reduction more softly. Default is 2.82843. Range is between 1 and 8.
- link
Choose if the
average
level between all channels of input stream or the louder(maximum
) channel of input stream affects the reduction. Default isaverage
.- detection
Should the exact signal be taken in case of
peak
or an RMS one in case ofrms
. Default isrms
which is mostly smoother.- mix
How much to use compressed signal in output. Default is 1. Range is between 0 and 1.
29.2.1 Commands
This filter supports the all above options as commands.
29.3 acontrast
Simple audio dynamic range compression/expansion filter.
The filter accepts the following options:
- contrast
Set contrast. Default is 33. Allowed range is between 0 and 100.
29.4 acopy
Copy the input audio source unchanged to the output. This is mainly useful for testing purposes.
29.5 acrossfade
Apply cross fade from one input audio stream to another input audio stream. The cross fade is applied for specified duration near the end of first stream.
The filter accepts the following options:
- nb_samples, ns
Specify the number of samples for which the cross fade effect has to last. At the end of the cross fade effect the first input audio will be completely silent. Default is 44100.
- duration, d
Specify the duration of the cross fade effect. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. By default the duration is determined by nb_samples. If set this option is used instead of nb_samples.
- overlap, o
Should first stream end overlap with second stream start. Default is enabled.
- curve1
Set curve for cross fade transition for first stream.
- curve2
Set curve for cross fade transition for second stream.
For description of available curve types see afade filter description.
29.5.1 Examples
- Cross fade from one input to another:
ffmpeg -i first.flac -i second.flac -filter_complex acrossfade=d=10:c1=exp:c2=exp output.flac
- Cross fade from one input to another but without overlapping:
ffmpeg -i first.flac -i second.flac -filter_complex acrossfade=d=10:o=0:c1=exp:c2=exp output.flac
29.6 acrossover
Split audio stream into several bands.
This filter splits audio stream into two or more frequency ranges. Summing all streams back will give flat output.
The filter accepts the following options:
- split
Set split frequencies. Those must be positive and increasing.
- order
Set filter order for each band split. This controls filter roll-off or steepness of filter transfer function. Available values are:
- ‘2nd’
12 dB per octave.
- ‘4th’
24 dB per octave.
- ‘6th’
36 dB per octave.
- ‘8th’
48 dB per octave.
- ‘10th’
60 dB per octave.
- ‘12th’
72 dB per octave.
- ‘14th’
84 dB per octave.
- ‘16th’
96 dB per octave.
- ‘18th’
108 dB per octave.
- ‘20th’
120 dB per octave.
Default is 4th.
- level
Set input gain level. Allowed range is from 0 to 1. Default value is 1.
- gains
Set output gain for each band. Default value is 1 for all bands.
- precision
Set which precision to use when processing samples.
- auto
Auto pick internal sample format depending on other filters.
- float
Always use single-floating point precision sample format.
- double
Always use double-floating point precision sample format.
Default value is
auto
.
29.6.1 Examples
- Split input audio stream into two bands (low and high) with split frequency of 1500 Hz,
each band will be in separate stream:
ffmpeg -i in.flac -filter_complex 'acrossover=split=1500[LOW][HIGH]' -map '[LOW]' low.wav -map '[HIGH]' high.wav
- Same as above, but with higher filter order:
ffmpeg -i in.flac -filter_complex 'acrossover=split=1500:order=8th[LOW][HIGH]' -map '[LOW]' low.wav -map '[HIGH]' high.wav
- Same as above, but also with additional middle band (frequencies between 1500 and 8000):
ffmpeg -i in.flac -filter_complex 'acrossover=split=1500 8000:order=8th[LOW][MID][HIGH]' -map '[LOW]' low.wav -map '[MID]' mid.wav -map '[HIGH]' high.wav
29.7 acrusher
Reduce audio bit resolution.
This filter is bit crusher with enhanced functionality. A bit crusher is used to audibly reduce number of bits an audio signal is sampled with. This doesn’t change the bit depth at all, it just produces the effect. Material reduced in bit depth sounds more harsh and "digital". This filter is able to even round to continuous values instead of discrete bit depths. Additionally it has a D/C offset which results in different crushing of the lower and the upper half of the signal. An Anti-Aliasing setting is able to produce "softer" crushing sounds.
Another feature of this filter is the logarithmic mode. This setting switches from linear distances between bits to logarithmic ones. The result is a much more "natural" sounding crusher which doesn’t gate low signals for example. The human ear has a logarithmic perception, so this kind of crushing is much more pleasant. Logarithmic crushing is also able to get anti-aliased.
The filter accepts the following options:
- level_in
Set level in.
- level_out
Set level out.
- bits
Set bit reduction.
- mix
Set mixing amount.
- mode
Can be linear:
lin
or logarithmic:log
.- dc
Set DC.
- aa
Set anti-aliasing.
- samples
Set sample reduction.
- lfo
Enable LFO. By default disabled.
- lforange
Set LFO range.
- lforate
Set LFO rate.
29.7.1 Commands
This filter supports the all above options as commands.
29.8 acue
Delay audio filtering until a given wallclock timestamp. See the cue filter.
29.9 adeclick
Remove impulsive noise from input audio.
Samples detected as impulsive noise are replaced by interpolated samples using autoregressive modelling.
- window, w
Set window size, in milliseconds. Allowed range is from
10
to100
. Default value is55
milliseconds. This sets size of window which will be processed at once.- overlap, o
Set window overlap, in percentage of window size. Allowed range is from
50
to95
. Default value is75
percent. Setting this to a very high value increases impulsive noise removal but makes whole process much slower.- arorder, a
Set autoregression order, in percentage of window size. Allowed range is from
0
to25
. Default value is2
percent. This option also controls quality of interpolated samples using neighbour good samples.- threshold, t
Set threshold value. Allowed range is from
1
to100
. Default value is2
. This controls the strength of impulsive noise which is going to be removed. The lower value, the more samples will be detected as impulsive noise.- burst, b
Set burst fusion, in percentage of window size. Allowed range is
0
to10
. Default value is2
. If any two samples detected as noise are spaced less than this value then any sample between those two samples will be also detected as noise.- method, m
Set overlap method.
It accepts the following values:
- add, a
Select overlap-add method. Even not interpolated samples are slightly changed with this method.
- save, s
Select overlap-save method. Not interpolated samples remain unchanged.
Default value is
a
.
29.10 adeclip
Remove clipped samples from input audio.
Samples detected as clipped are replaced by interpolated samples using autoregressive modelling.
- window, w
Set window size, in milliseconds. Allowed range is from
10
to100
. Default value is55
milliseconds. This sets size of window which will be processed at once.- overlap, o
Set window overlap, in percentage of window size. Allowed range is from
50
to95
. Default value is75
percent.- arorder, a
Set autoregression order, in percentage of window size. Allowed range is from
0
to25
. Default value is8
percent. This option also controls quality of interpolated samples using neighbour good samples.- threshold, t
Set threshold value. Allowed range is from
1
to100
. Default value is10
. Higher values make clip detection less aggressive.- hsize, n
Set size of histogram used to detect clips. Allowed range is from
100
to9999
. Default value is1000
. Higher values make clip detection less aggressive.- method, m
Set overlap method.
It accepts the following values:
- add, a
Select overlap-add method. Even not interpolated samples are slightly changed with this method.
- save, s
Select overlap-save method. Not interpolated samples remain unchanged.
Default value is
a
.
29.11 adecorrelate
Apply decorrelation to input audio stream.
The filter accepts the following options:
- stages
Set decorrelation stages of filtering. Allowed range is from 1 to 16. Default value is 6.
- seed
Set random seed used for setting delay in samples across channels.
29.12 adelay
Delay one or more audio channels.
Samples in delayed channel are filled with silence.
The filter accepts the following option:
- delays
Set list of delays in milliseconds for each channel separated by ’|’. Unused delays will be silently ignored. If number of given delays is smaller than number of channels all remaining channels will not be delayed. If you want to delay exact number of samples, append ’S’ to number. If you want instead to delay in seconds, append ’s’ to number.
- all
Use last set delay for all remaining channels. By default is disabled. This option if enabled changes how option
delays
is interpreted.
29.12.1 Examples
- Delay first channel by 1.5 seconds, the third channel by 0.5 seconds and leave
the second channel (and any other channels that may be present) unchanged.
adelay=1500|0|500
- Delay second channel by 500 samples, the third channel by 700 samples and leave
the first channel (and any other channels that may be present) unchanged.
adelay=0|500S|700S
- Delay all channels by same number of samples:
adelay=delays=64S:all=1
29.13 adenorm
Remedy denormals in audio by adding extremely low-level noise.
This filter shall be placed before any filter that can produce denormals.
A description of the accepted parameters follows.
- level
Set level of added noise in dB. Default is
-351
. Allowed range is from -451 to -90.- type
Set type of added noise.
- dc
Add DC signal.
- ac
Add AC signal.
- square
Add square signal.
- pulse
Add pulse signal.
Default is
dc
.
29.13.1 Commands
This filter supports the all above options as commands.
29.14 aderivative, aintegral
Compute derivative/integral of audio stream.
Applying both filters one after another produces original audio.
29.15 adrc
Apply spectral dynamic range controller filter to input audio stream.
A description of the accepted options follows.
- transfer
Set the transfer expression.
The expression can contain the following constants:
- ch
current channel number
- sn
current sample number
- nb_channels
number of channels
- t
timestamp expressed in seconds
- sr
sample rate
- p
current frequency power value, in dB
- f
current frequency in Hz
Default value is
p
.- attack
Set the attack in milliseconds. Default is
50
milliseconds. Allowed range is from 1 to 1000 milliseconds.- release
Set the release in milliseconds. Default is
100
milliseconds. Allowed range is from 5 to 2000 milliseconds.- channels
Set which channels to filter, by default
all
channels in audio stream are filtered.
29.15.1 Commands
This filter supports the all above options as commands.
29.15.2 Examples
- Apply spectral compression to all frequencies with threshold of -50 dB and 1:6 ratio:
adrc=transfer='if(gt(p,-50),-50+(p-(-50))/6,p)':attack=50:release=100
- Similar to above but with 1:2 ratio and filtering only front center channel:
adrc=transfer='if(gt(p,-50),-50+(p-(-50))/2,p)':attack=50:release=100:channels=FC
- Apply spectral noise gate to all frequencies with threshold of -85 dB and with short attack time and short release time:
adrc=transfer='if(lte(p,-85),p-800,p)':attack=1:release=5
- Apply spectral expansion to all frequencies with threshold of -10 dB and 1:2 ratio:
adrc=transfer='if(lt(p,-10),-10+(p-(-10))*2,p)':attack=50:release=100
- Apply limiter to max -60 dB to all frequencies, with attack of 2 ms and release of 10 ms:
adrc=transfer='min(p,-60)':attack=2:release=10
29.16 adynamicequalizer
Apply dynamic equalization to input audio stream.
A description of the accepted options follows.
- threshold
Set the detection threshold used to trigger equalization. Threshold detection is using detection filter. Default value is 0. Allowed range is from 0 to 100.
- dfrequency
Set the detection frequency in Hz used for detection filter used to trigger equalization. Default value is 1000 Hz. Allowed range is between 2 and 1000000 Hz.
- dqfactor
Set the detection resonance factor for detection filter used to trigger equalization. Default value is 1. Allowed range is from 0.001 to 1000.
- tfrequency
Set the target frequency of equalization filter. Default value is 1000 Hz. Allowed range is between 2 and 1000000 Hz.
- tqfactor
Set the target resonance factor for target equalization filter. Default value is 1. Allowed range is from 0.001 to 1000.
- attack
Set the amount of milliseconds the signal from detection has to rise above the detection threshold before equalization starts. Default is 20. Allowed range is between 1 and 2000.
- release
Set the amount of milliseconds the signal from detection has to fall below the detection threshold before equalization ends. Default is 200. Allowed range is between 1 and 2000.
- ratio
Set the ratio by which the equalization gain is raised. Default is 1. Allowed range is between 0 and 30.
- makeup
Set the makeup offset by which the equalization gain is raised. Default is 0. Allowed range is between 0 and 100.
- range
Set the max allowed cut/boost amount. Default is 50. Allowed range is from 1 to 200.
- mode
Set the mode of filter operation, can be one of the following:
- ‘listen’
Output only isolated detection signal.
- ‘cutbelow’
Cut frequencies below detection threshold.
- ‘cutabove’
Cut frequencies above detection threshold.
- ‘boostbelow’
Boost frequencies below detection threshold.
- ‘boostabove’
Boost frequencies above detection threshold.
Default mode is ‘cutbelow’.
- dftype
Set the type of detection filter, can be one of the following:
- ‘bandpass’
- ‘lowpass’
- ‘highpass’
- ‘peak’
Default type is ‘bandpass’.
- tftype
Set the type of target filter, can be one of the following:
- ‘bell’
- ‘lowshelf’
- ‘highshelf’
Default type is ‘bell’.
- auto
Automatically gather threshold from detection filter. By default is ‘disabled’. This option is useful to detect threshold in certain time frame of input audio stream, in such case option value is changed at runtime.
Available values are:
- ‘disabled’
Disable using automatically gathered threshold value.
- ‘off’
Stop picking threshold value.
- ‘on’
Start picking threshold value.
- ‘adaptive’
Adaptively pick threshold value, by calculating sliding window entropy.
- precision
Set which precision to use when processing samples.
- auto
Auto pick internal sample format depending on other filters.
- float
Always use single-floating point precision sample format.
- double
Always use double-floating point precision sample format.
29.16.1 Commands
This filter supports the all above options as commands.
29.17 adynamicsmooth
Apply dynamic smoothing to input audio stream.
A description of the accepted options follows.
- sensitivity
Set an amount of sensitivity to frequency fluctations. Default is 2. Allowed range is from 0 to 1e+06.
- basefreq
Set a base frequency for smoothing. Default value is 22050. Allowed range is from 2 to 1e+06.
29.17.1 Commands
This filter supports the all above options as commands.
29.18 aecho
Apply echoing to the input audio.
Echoes are reflected sound and can occur naturally amongst mountains
(and sometimes large buildings) when talking or shouting; digital echo
effects emulate this behaviour and are often used to help fill out the
sound of a single instrument or vocal. The time difference between the
original signal and the reflection is the delay
, and the
loudness of the reflected signal is the decay
.
Multiple echoes can have different delays and decays.
A description of the accepted parameters follows.
- in_gain
Set input gain of reflected signal. Default is
0.6
.- out_gain
Set output gain of reflected signal. Default is
0.3
.- delays
Set list of time intervals in milliseconds between original signal and reflections separated by ’|’. Allowed range for each
delay
is(0 - 90000.0]
. Default is1000
.- decays
Set list of loudness of reflected signals separated by ’|’. Allowed range for each
decay
is(0 - 1.0]
. Default is0.5
.
29.18.1 Examples
- Make it sound as if there are twice as many instruments as are actually playing:
aecho=0.8:0.88:60:0.4
- If delay is very short, then it sounds like a (metallic) robot playing music:
aecho=0.8:0.88:6:0.4
- A longer delay will sound like an open air concert in the mountains:
aecho=0.8:0.9:1000:0.3
- Same as above but with one more mountain:
aecho=0.8:0.9:1000|1800:0.3|0.25
29.19 aemphasis
Audio emphasis filter creates or restores material directly taken from LPs or emphased CDs with different filter curves. E.g. to store music on vinyl the signal has to be altered by a filter first to even out the disadvantages of this recording medium. Once the material is played back the inverse filter has to be applied to restore the distortion of the frequency response.
The filter accepts the following options:
- level_in
Set input gain.
- level_out
Set output gain.
- mode
Set filter mode. For restoring material use
reproduction
mode, otherwise useproduction
mode. Default isreproduction
mode.- type
Set filter type. Selects medium. Can be one of the following:
- col
select Columbia.
- emi
select EMI.
- bsi
select BSI (78RPM).
- riaa
select RIAA.
- cd
select Compact Disc (CD).
- 50fm
select 50µs (FM).
- 75fm
select 75µs (FM).
- 50kf
select 50µs (FM-KF).
- 75kf
select 75µs (FM-KF).
29.19.1 Commands
This filter supports the all above options as commands.
29.20 aeval
Modify an audio signal according to the specified expressions.
This filter accepts one or more expressions (one for each channel), which are evaluated and used to modify a corresponding audio signal.
It accepts the following parameters:
- exprs
Set the ’|’-separated expressions list for each separate channel. If the number of input channels is greater than the number of expressions, the last specified expression is used for the remaining output channels.
- channel_layout, c
Set output channel layout. If not specified, the channel layout is specified by the number of expressions. If set to ‘same’, it will use by default the same input channel layout.
Each expression in exprs can contain the following constants and functions:
- ch
channel number of the current expression
- n
number of the evaluated sample, starting from 0
- s
sample rate
- t
time of the evaluated sample expressed in seconds
- nb_in_channels
- nb_out_channels
input and output number of channels
- val(CH)
the value of input channel with number CH
Note: this filter is slow. For faster processing you should use a dedicated filter.
29.20.1 Examples
- Half volume:
aeval=val(ch)/2:c=same
- Invert phase of the second channel:
aeval=val(0)|-val(1)
29.21 aexciter
An exciter is used to produce high sound that is not present in the original signal. This is done by creating harmonic distortions of the signal which are restricted in range and added to the original signal. An Exciter raises the upper end of an audio signal without simply raising the higher frequencies like an equalizer would do to create a more "crisp" or "brilliant" sound.
The filter accepts the following options:
- level_in
Set input level prior processing of signal. Allowed range is from 0 to 64. Default value is 1.
- level_out
Set output level after processing of signal. Allowed range is from 0 to 64. Default value is 1.
- amount
Set the amount of harmonics added to original signal. Allowed range is from 0 to 64. Default value is 1.
- drive
Set the amount of newly created harmonics. Allowed range is from 0.1 to 10. Default value is 8.5.
- blend
Set the octave of newly created harmonics. Allowed range is from -10 to 10. Default value is 0.
- freq
Set the lower frequency limit of producing harmonics in Hz. Allowed range is from 2000 to 12000 Hz. Default is 7500 Hz.
- ceil
Set the upper frequency limit of producing harmonics. Allowed range is from 9999 to 20000 Hz. If value is lower than 10000 Hz no limit is applied.
- listen
Mute the original signal and output only added harmonics. By default is disabled.
29.21.1 Commands
This filter supports the all above options as commands.
29.22 afade
Apply fade-in/out effect to input audio.
A description of the accepted parameters follows.
- type, t
Specify the effect type, can be either
in
for fade-in, orout
for a fade-out effect. Default isin
.- start_sample, ss
Specify the number of the start sample for starting to apply the fade effect. Default is 0.
- nb_samples, ns
Specify the number of samples for which the fade effect has to last. At the end of the fade-in effect the output audio will have the same volume as the input audio, at the end of the fade-out transition the output audio will be silence. Default is 44100.
- start_time, st
Specify the start time of the fade effect. Default is 0. The value must be specified as a time duration; see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. If set this option is used instead of start_sample.
- duration, d
Specify the duration of the fade effect. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. At the end of the fade-in effect the output audio will have the same volume as the input audio, at the end of the fade-out transition the output audio will be silence. By default the duration is determined by nb_samples. If set this option is used instead of nb_samples.
- curve
Set curve for fade transition.
It accepts the following values:
- tri
select triangular, linear slope (default)
- qsin
select quarter of sine wave
- hsin
select half of sine wave
- esin
select exponential sine wave
- log
select logarithmic
- ipar
select inverted parabola
- qua
select quadratic
- cub
select cubic
- squ
select square root
- cbr
select cubic root
- par
select parabola
- exp
select exponential
- iqsin
select inverted quarter of sine wave
- ihsin
select inverted half of sine wave
- dese
select double-exponential seat
- desi
select double-exponential sigmoid
- losi
select logistic sigmoid
- sinc
select sine cardinal function
- isinc
select inverted sine cardinal function
- quat
select quartic
- quatr
select quartic root
- qsin2
select squared quarter of sine wave
- hsin2
select squared half of sine wave
- nofade
no fade applied
- silence
Set the initial gain for fade-in or final gain for fade-out. Default value is
0.0
.- unity
Set the initial gain for fade-out or final gain for fade-in. Default value is
1.0
.
29.22.1 Commands
This filter supports the all above options as commands.
29.22.2 Examples
- Fade in first 15 seconds of audio:
afade=t=in:ss=0:d=15
- Fade out last 25 seconds of a 900 seconds audio:
afade=t=out:st=875:d=25
29.23 afftdn
Denoise audio samples with FFT.
A description of the accepted parameters follows.
- noise_reduction, nr
Set the noise reduction in dB, allowed range is 0.01 to 97. Default value is 12 dB.
- noise_floor, nf
Set the noise floor in dB, allowed range is -80 to -20. Default value is -50 dB.
- noise_type, nt
Set the noise type.
It accepts the following values:
- white, w
Select white noise.
- vinyl, v
Select vinyl noise.
- shellac, s
Select shellac noise.
- custom, c
Select custom noise, defined in
bn
option.Default value is white noise.
- band_noise, bn
Set custom band noise profile for every one of 15 bands. Bands are separated by ’ ’ or ’|’.
- residual_floor, rf
Set the residual floor in dB, allowed range is -80 to -20. Default value is -38 dB.
- track_noise, tn
Enable noise floor tracking. By default is disabled. With this enabled, noise floor is automatically adjusted.
- track_residual, tr
Enable residual tracking. By default is disabled.
- output_mode, om
Set the output mode.
It accepts the following values:
- input, i
Pass input unchanged.
- output, o
Pass noise filtered out.
- noise, n
Pass only noise.
Default value is output.
- adaptivity, ad
Set the adaptivity factor, used how fast to adapt gains adjustments per each frequency bin. Value 0 enables instant adaptation, while higher values react much slower. Allowed range is from 0 to 1. Default value is 0.5.
- floor_offset, fo
Set the noise floor offset factor. This option is used to adjust offset applied to measured noise floor. It is only effective when noise floor tracking is enabled. Allowed range is from -2.0 to 2.0. Default value is 1.0.
- noise_link, nl
Set the noise link used for multichannel audio.
It accepts the following values:
- none
Use unchanged channel’s noise floor.
- min
Use measured min noise floor of all channels.
- max
Use measured max noise floor of all channels.
- average
Use measured average noise floor of all channels.
Default value is min.
- band_multiplier, bm
Set the band multiplier factor, used how much to spread bands across frequency bins. Allowed range is from 0.2 to 5. Default value is 1.25.
- sample_noise, sn
Toggle capturing and measurement of noise profile from input audio.
It accepts the following values:
- start, begin
Start sample noise capture.
- stop, end
Stop sample noise capture and measure new noise band profile.
Default value is
none
.
- gain_smooth, gs
Set gain smooth spatial radius, used to smooth gains applied to each frequency bin. Useful to reduce random music noise artefacts. Higher values increases smoothing of gains. Allowed range is from
0
to50
. Default value is0
.
29.23.1 Commands
This filter supports the some above mentioned options as commands.
29.23.2 Examples
- Reduce white noise by 10dB, and use previously measured noise floor of -40dB:
afftdn=nr=10:nf=-40
- Reduce white noise by 10dB, also set initial noise floor to -80dB and enable automatic
tracking of noise floor so noise floor will gradually change during processing:
afftdn=nr=10:nf=-80:tn=1
- Reduce noise by 20dB, using noise floor of -40dB and using commands to take noise profile
of first 0.4 seconds of input audio:
asendcmd=0.0 afftdn sn start,asendcmd=0.4 afftdn sn stop,afftdn=nr=20:nf=-40
29.24 afftfilt
Apply arbitrary expressions to samples in frequency domain.
- real
Set frequency domain real expression for each separate channel separated by ’|’. Default is "re". If the number of input channels is greater than the number of expressions, the last specified expression is used for the remaining output channels.
- imag
Set frequency domain imaginary expression for each separate channel separated by ’|’. Default is "im".
Each expression in real and imag can contain the following constants and functions:
- sr
sample rate
- b
current frequency bin number
- nb
number of available bins
- ch
channel number of the current expression
- chs
number of channels
- pts
current frame pts
- re
current real part of frequency bin of current channel
- im
current imaginary part of frequency bin of current channel
- real(b, ch)
Return the value of real part of frequency bin at location (bin,channel)
- imag(b, ch)
Return the value of imaginary part of frequency bin at location (bin,channel)
- win_size
Set window size. Allowed range is from 16 to 131072. Default is
4096
- win_func
Set window function.
It accepts the following values:
- ‘rect’
- ‘bartlett’
- ‘hann, hanning’
- ‘hamming’
- ‘blackman’
- ‘welch’
- ‘flattop’
- ‘bharris’
- ‘bnuttall’
- ‘bhann’
- ‘sine’
- ‘nuttall’
- ‘lanczos’
- ‘gauss’
- ‘tukey’
- ‘dolph’
- ‘cauchy’
- ‘parzen’
- ‘poisson’
- ‘bohman’
- ‘kaiser’
Default is
hann
.- overlap
Set window overlap. If set to 1, the recommended overlap for selected window function will be picked. Default is
0.75
.
29.24.1 Examples
- Leave almost only low frequencies in audio:
afftfilt="'real=re * (1-clip((b/nb)*b,0,1))':imag='im * (1-clip((b/nb)*b,0,1))'"
- Apply robotize effect:
afftfilt="real='hypot(re,im)*sin(0)':imag='hypot(re,im)*cos(0)':win_size=512:overlap=0.75"
- Apply whisper effect:
afftfilt="real='hypot(re,im)*cos((random(0)*2-1)*2*3.14)':imag='hypot(re,im)*sin((random(1)*2-1)*2*3.14)':win_size=128:overlap=0.8"
- Apply phase shift:
afftfilt="real=re*cos(1)-im*sin(1):imag=re*sin(1)+im*cos(1)"
29.25 afir
Apply an arbitrary Finite Impulse Response filter.
This filter is designed for applying long FIR filters, up to 60 seconds long.
It can be used as component for digital crossover filters, room equalization, cross talk cancellation, wavefield synthesis, auralization, ambiophonics, ambisonics and spatialization.
This filter uses the streams higher than first one as FIR coefficients. If the non-first stream holds a single channel, it will be used for all input channels in the first stream, otherwise the number of channels in the non-first stream must be same as the number of channels in the first stream.
It accepts the following parameters:
- dry
Set dry gain. This sets input gain.
- wet
Set wet gain. This sets final output gain.
- length
Set Impulse Response filter length. Default is 1, which means whole IR is processed.
- gtype
This option is deprecated, and does nothing.
- irnorm
Set norm to be applied to IR coefficients before filtering. Allowed range is from -1 to 2. IR coefficients are normalized with calculated vector norm set by this option. For negative values, no norm is calculated, and IR coefficients are not modified at all. Default is 1.
- irlink
For multichannel IR if this option is set to true, all IR channels will be normalized with maximal measured gain of all IR channels coefficients as set by
irnorm
option. When disabled, all IR coefficients in each IR channel will be normalized independently. Default is true.- irgain
Set gain to be applied to IR coefficients before filtering. Allowed range is 0 to 1. This gain is applied after any gain applied with irnorm option.
- irfmt
Set format of IR stream. Can be
mono
orinput
. Default isinput
.- maxir
Set max allowed Impulse Response filter duration in seconds. Default is 30 seconds. Allowed range is 0.1 to 60 seconds.
- response
This option is deprecated, and does nothing.
- channel
This option is deprecated, and does nothing.
- size
This option is deprecated, and does nothing.
- rate
This option is deprecated, and does nothing.
- minp
Set minimal partition size used for convolution. Default is 8192. Allowed range is from 1 to 65536. Lower values decreases latency at cost of higher CPU usage.
- maxp
Set maximal partition size used for convolution. Default is 8192. Allowed range is from 8 to 65536. Lower values may increase CPU usage.
- nbirs
Set number of input impulse responses streams which will be switchable at runtime. Allowed range is from 1 to 32. Default is 1.
- ir
Set IR stream which will be used for convolution, starting from 0, should always be lower than supplied value by
nbirs
option. Default is 0. This option can be changed at runtime via commands.- precision
Set which precision to use when processing samples.
- auto
Auto pick internal sample format depending on other filters.
- float
Always use single-floating point precision sample format.
- double
Always use double-floating point precision sample format.
Default value is auto.
- irload
Set when to load IR stream. Can be
init
oraccess
. First one load and prepares all IRs on initialization, second one once on first access of specific IR. Default isinit
.
29.25.1 Examples
- Apply reverb to stream using mono IR file as second input, complete command using ffmpeg:
ffmpeg -i input.wav -i middle_tunnel_1way_mono.wav -lavfi afir output.wav
- Apply true stereo processing given input stereo stream, and two stereo impulse responses for left and right channel,
the impulse response files are files with names l_ir.wav and r_ir.wav, and setting irnorm option value:
"pan=4C|c0=FL|c1=FL|c2=FR|c3=FR[a];amovie=l_ir.wav[LIR];amovie=r_ir.wav[RIR];[LIR][RIR]amerge[ir];[a][ir]afir=irfmt=input:irnorm=1.2,pan=stereo|FL<c0+c2|FR<c1+c3"
- Similar to above example, but with
irgain
explicitly set to estimated value and withirnorm
disabled:"pan=4C|c0=FL|c1=FL|c2=FR|c3=FR[a];amovie=l_ir.wav[LIR];amovie=r_ir.wav[RIR];[LIR][RIR]amerge[ir];[a][ir]afir=irfmt=input:irgain=-5dB:irnom=-1,pan=stereo|FL<c0+c2|FR<c1+c3"
29.26 aformat
Set output format constraints for the input audio. The framework will negotiate the most appropriate format to minimize conversions.
It accepts the following parameters:
- sample_fmts, f
A ’|’-separated list of requested sample formats.
- sample_rates, r
A ’|’-separated list of requested sample rates.
- channel_layouts, cl
A ’|’-separated list of requested channel layouts.
See (ffmpeg-utils)the Channel Layout section in the ffmpeg-utils(1) manual for the required syntax.
If a parameter is omitted, all values are allowed.
Force the output to either unsigned 8-bit or signed 16-bit stereo
aformat=sample_fmts=u8|s16:channel_layouts=stereo
29.27 afreqshift
Apply frequency shift to input audio samples.
The filter accepts the following options:
- shift
Specify frequency shift. Allowed range is -INT_MAX to INT_MAX. Default value is 0.0.
- level
Set output gain applied to final output. Allowed range is from 0.0 to 1.0. Default value is 1.0.
- order
Set filter order used for filtering. Allowed range is from 1 to 16. Default value is 8.
29.27.1 Commands
This filter supports the all above options as commands.
29.28 afwtdn
Reduce broadband noise from input samples using Wavelets.
A description of the accepted options follows.
- sigma
Set the noise sigma, allowed range is from 0 to 1. Default value is 0. This option controls strength of denoising applied to input samples. Most useful way to set this option is via decibels, eg. -45dB.
- levels
Set the number of wavelet levels of decomposition. Allowed range is from 1 to 12. Default value is 10. Setting this too low make denoising performance very poor.
- wavet
Set wavelet type for decomposition of input frame. They are sorted by number of coefficients, from lowest to highest. More coefficients means worse filtering speed, but overall better quality. Available wavelets are:
- ‘sym2’
- ‘sym4’
- ‘rbior68’
- ‘deb10’
- ‘sym10’
- ‘coif5’
- ‘bl3’
- percent
Set percent of full denoising. Allowed range is from 0 to 100 percent. Default value is 85 percent or partial denoising.
- profile
If enabled, first input frame will be used as noise profile. If first frame samples contain non-noise performance will be very poor.
- adaptive
If enabled, input frames are analyzed for presence of noise. If noise is detected with high possibility then input frame profile will be used for processing following frames, until new noise frame is detected.
- samples
Set size of single frame in number of samples. Allowed range is from 512 to 65536. Default frame size is 8192 samples.
- softness
Set softness applied inside thresholding function. Allowed range is from 0 to 10. Default softness is 1.
29.28.1 Commands
This filter supports the all above options as commands.
29.29 agate
A gate is mainly used to reduce lower parts of a signal. This kind of signal processing reduces disturbing noise between useful signals.
Gating is done by detecting the volume below a chosen level threshold and dividing it by the factor set with ratio. The bottom of the noise floor is set via range. Because an exact manipulation of the signal would cause distortion of the waveform the reduction can be levelled over time. This is done by setting attack and release.
attack determines how long the signal has to fall below the threshold before any reduction will occur and release sets the time the signal has to rise above the threshold to reduce the reduction again. Shorter signals than the chosen attack time will be left untouched.
- level_in
Set input level before filtering. Default is 1. Allowed range is from 0.015625 to 64.
- mode
Set the mode of operation. Can be
upward
ordownward
. Default isdownward
. If set toupward
mode, higher parts of signal will be amplified, expanding dynamic range in upward direction. Otherwise, in case ofdownward
lower parts of signal will be reduced.- range
Set the level of gain reduction when the signal is below the threshold. Default is 0.06125. Allowed range is from 0 to 1. Setting this to 0 disables reduction and then filter behaves like expander.
- threshold
If a signal rises above this level the gain reduction is released. Default is 0.125. Allowed range is from 0 to 1.
- ratio
Set a ratio by which the signal is reduced. Default is 2. Allowed range is from 1 to 9000.
- attack
Amount of milliseconds the signal has to rise above the threshold before gain reduction stops. Default is 20 milliseconds. Allowed range is from 0.01 to 9000.
- release
Amount of milliseconds the signal has to fall below the threshold before the reduction is increased again. Default is 250 milliseconds. Allowed range is from 0.01 to 9000.
- makeup
Set amount of amplification of signal after processing. Default is 1. Allowed range is from 1 to 64.
- knee
Curve the sharp knee around the threshold to enter gain reduction more softly. Default is 2.828427125. Allowed range is from 1 to 8.
- detection
Choose if exact signal should be taken for detection or an RMS like one. Default is
rms
. Can bepeak
orrms
.- link
Choose if the average level between all channels or the louder channel affects the reduction. Default is
average
. Can beaverage
ormaximum
.
29.29.1 Commands
This filter supports the all above options as commands.
29.30 aiir
Apply an arbitrary Infinite Impulse Response filter.
It accepts the following parameters:
- zeros, z
Set B/numerator/zeros/reflection coefficients.
- poles, p
Set A/denominator/poles/ladder coefficients.
- gains, k
Set channels gains.
- dry_gain
Set input gain.
- wet_gain
Set output gain.
- format, f
Set coefficients format.
- ‘ll’
lattice-ladder function
- ‘sf’
analog transfer function
- ‘tf’
digital transfer function
- ‘zp’
Z-plane zeros/poles, cartesian (default)
- ‘pr’
Z-plane zeros/poles, polar radians
- ‘pd’
Z-plane zeros/poles, polar degrees
- ‘sp’
S-plane zeros/poles
- process, r
Set type of processing.
- ‘d’
direct processing
- ‘s’
serial processing
- ‘p’
parallel processing
- precision, e
Set filtering precision.
- ‘dbl’
double-precision floating-point (default)
- ‘flt’
single-precision floating-point
- ‘i32’
32-bit integers
- ‘i16’
16-bit integers
- normalize, n
Normalize filter coefficients, by default is enabled. Enabling it will normalize magnitude response at DC to 0dB.
- mix
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- response
Show IR frequency response, magnitude(magenta), phase(green) and group delay(yellow) in additional video stream. By default it is disabled.
- channel
Set for which IR channel to display frequency response. By default is first channel displayed. This option is used only when response is enabled.
- size
Set video stream size. This option is used only when response is enabled.
Coefficients in tf
and sf
format are separated by spaces and are in ascending
order.
Coefficients in zp
format are separated by spaces and order of coefficients
doesn’t matter. Coefficients in zp
format are complex numbers with i
imaginary unit.
Different coefficients and gains can be provided for every channel, in such case use ’|’ to separate coefficients or gains. Last provided coefficients will be used for all remaining channels.
29.30.1 Examples
- Apply 2 pole elliptic notch at around 5000Hz for 48000 Hz sample rate:
aiir=k=1:z=7.957584807809675810E-1 -2.575128568908332300 3.674839853930788710 -2.57512875289799137 7.957586296317130880E-1:p=1 -2.86950072432325953 3.63022088054647218 -2.28075678147272232 6.361362326477423500E-1:f=tf:r=d
- Same as above but in
zp
format:aiir=k=0.79575848078096756:z=0.80918701+0.58773007i 0.80918701-0.58773007i 0.80884700+0.58784055i 0.80884700-0.58784055i:p=0.63892345+0.59951235i 0.63892345-0.59951235i 0.79582691+0.44198673i 0.79582691-0.44198673i:f=zp:r=s
- Apply 3-rd order analog normalized Butterworth low-pass filter, using analog transfer function format:
aiir=z=1.3057 0 0 0:p=1.3057 2.3892 2.1860 1:f=sf:r=d
29.31 alimiter
The limiter prevents an input signal from rising over a desired threshold. This limiter uses lookahead technology to prevent your signal from distorting. It means that there is a small delay after the signal is processed. Keep in mind that the delay it produces is the attack time you set.
The filter accepts the following options:
- level_in
Set input gain. Default is 1.
- level_out
Set output gain. Default is 1.
- limit
Don’t let signals above this level pass the limiter. Default is 1.
- attack
The limiter will reach its attenuation level in this amount of time in milliseconds. Default is 5 milliseconds.
- release
Come back from limiting to attenuation 1.0 in this amount of milliseconds. Default is 50 milliseconds.
- asc
When gain reduction is always needed ASC takes care of releasing to an average reduction level rather than reaching a reduction of 0 in the release time.
- asc_level
Select how much the release time is affected by ASC, 0 means nearly no changes in release time while 1 produces higher release times.
- level
Auto level output signal. Default is enabled. This normalizes audio back to 0dB if enabled.
- latency
Compensate the delay introduced by using the lookahead buffer set with attack parameter. Also flush the valid audio data in the lookahead buffer when the stream hits EOF.
Depending on picked setting it is recommended to upsample input 2x or 4x times with aresample before applying this filter.
29.32 allpass
Apply a two-pole all-pass filter with central frequency (in Hz) frequency, and filter-width width. An all-pass filter changes the audio’s frequency to phase relationship without changing its frequency to amplitude relationship.
The filter accepts the following options:
- frequency, f
Set frequency in Hz.
- width_type, t
Set method to specify band-width of filter.
- h
Hz
- q
Q-Factor
- o
octave
- s
slope
- k
kHz
- width, w
Specify the band-width of a filter in width_type units.
- mix, m
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- channels, c
Specify which channels to filter, by default all available are filtered.
- normalize, n
Normalize biquad coefficients, by default is disabled. Enabling it will normalize magnitude response at DC to 0dB.
- order, o
Set the filter order, can be 1 or 2. Default is 2.
- transform, a
Set transform type of IIR filter.
- di
- dii
- tdi
- tdii
- latt
- svf
- zdf
- precision, r
Set precision of filtering.
- auto
Pick automatic sample format depending on surround filters.
- s16
Always use signed 16-bit.
- s32
Always use signed 32-bit.
- f32
Always use float 32-bit.
- f64
Always use float 64-bit.
29.32.1 Commands
This filter supports the following commands:
- frequency, f
Change allpass frequency. Syntax for the command is : "frequency"
- width_type, t
Change allpass width_type. Syntax for the command is : "width_type"
- width, w
Change allpass width. Syntax for the command is : "width"
- mix, m
Change allpass mix. Syntax for the command is : "mix"
29.33 aloop
Loop audio samples.
The filter accepts the following options:
- loop
Set the number of loops. Setting this value to -1 will result in infinite loops. Default is 0.
- size
Set maximal number of samples. Default is 0.
- start
Set first sample of loop. Default is 0.
- time
Set the time of loop start in seconds. Only used if option named start is set to
-1
.
29.34 amerge
Merge two or more audio streams into a single multi-channel stream.
The filter accepts the following options:
- inputs
Set the number of inputs. Default is 2.
If the channel layouts of the inputs are disjoint, and therefore compatible, the channel layout of the output will be set accordingly and the channels will be reordered as necessary. If the channel layouts of the inputs are not disjoint, the output will have all the channels of the first input then all the channels of the second input, in that order, and the channel layout of the output will be the default value corresponding to the total number of channels.
For example, if the first input is in 2.1 (FL+FR+LF) and the second input is FC+BL+BR, then the output will be in 5.1, with the channels in the following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the first input, b1 is the first channel of the second input).
On the other hand, if both input are in stereo, the output channels will be in the default order: a1, a2, b1, b2, and the channel layout will be arbitrarily set to 4.0, which may or may not be the expected value.
All inputs must have the same sample rate, and format.
If inputs do not have the same duration, the output will stop with the shortest.
29.34.1 Examples
- Merge two mono files into a stereo stream:
amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
- Multiple merges assuming 1 video stream and 6 audio streams in input.mkv:
ffmpeg -i input.mkv -filter_complex "[0:1][0:2][0:3][0:4][0:5][0:6] amerge=inputs=6" -c:a pcm_s16le output.mkv
29.35 amix
Mixes multiple audio inputs into a single output.
Note that this filter only supports float samples (the amerge and pan audio filters support many formats). If the amix input has integer samples then aresample will be automatically inserted to perform the conversion to float samples.
It accepts the following parameters:
- inputs
The number of inputs. If unspecified, it defaults to 2.
- duration
How to determine the end-of-stream.
- longest
The duration of the longest input. (default)
- shortest
The duration of the shortest input.
- first
The duration of the first input.
- dropout_transition
The transition time, in seconds, for volume renormalization when an input stream ends. The default value is 2 seconds.
- weights
Specify weight of each input audio stream as a sequence of numbers separated by a space. If fewer weights are specified compared to number of inputs, the last weight is assigned to the remaining inputs. Default weight for each input is 1.
- normalize
Always scale inputs instead of only doing summation of samples. Beware of heavy clipping if inputs are not normalized prior or after filtering by this filter if this option is disabled. By default is enabled.
29.35.1 Examples
- This will mix 3 input audio streams to a single output with the same duration as the
first input and a dropout transition time of 3 seconds:
ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
- This will mix one vocal and one music input audio stream to a single output with the same duration as the
longest input. The music will have quarter the weight as the vocals, and the inputs are not normalized:
ffmpeg -i VOCALS -i MUSIC -filter_complex amix=inputs=2:duration=longest:dropout_transition=0:weights="1 0.25":normalize=0 OUTPUT
29.35.2 Commands
This filter supports the following commands:
- weights
- normalize
Syntax is same as option with same name.
29.36 amultiply
Multiply first audio stream with second audio stream and store result in output audio stream. Multiplication is done by multiplying each sample from first stream with sample at same position from second stream.
With this element-wise multiplication one can create amplitude fades and amplitude modulations.
29.37 anequalizer
High-order parametric multiband equalizer for each channel.
It accepts the following parameters:
- params
-
This option string is in format: "cchn f=cf w=w g=g t=f | ..." Each equalizer band is separated by ’|’.
- chn
Set channel number to which equalization will be applied. If input doesn’t have that channel the entry is ignored.
- f
Set central frequency for band. If input doesn’t have that frequency the entry is ignored.
- w
Set band width in Hertz.
- g
Set band gain in dB.
- t
Set filter type for band, optional, can be:
- ‘0’
Butterworth, this is default.
- ‘1’
Chebyshev type 1.
- ‘2’
Chebyshev type 2.
- curves
With this option activated frequency response of anequalizer is displayed in video stream.
- size
Set video stream size. Only useful if curves option is activated.
- mgain
Set max gain that will be displayed. Only useful if curves option is activated. Setting this to a reasonable value makes it possible to display gain which is derived from neighbour bands which are too close to each other and thus produce higher gain when both are activated.
- fscale
Set frequency scale used to draw frequency response in video output. Can be linear or logarithmic. Default is logarithmic.
- colors
Set color for each channel curve which is going to be displayed in video stream. This is list of color names separated by space or by ’|’. Unrecognised or missing colors will be replaced by white color.
29.37.1 Examples
- Lower gain by 10 of central frequency 200Hz and width 100 Hz
for first 2 channels using Chebyshev type 1 filter:
anequalizer=c0 f=200 w=100 g=-10 t=1|c1 f=200 w=100 g=-10 t=1
29.37.2 Commands
This filter supports the following commands:
- change
Alter existing filter parameters. Syntax for the commands is : "fN|f=freq|w=width|g=gain"
fN is existing filter number, starting from 0, if no such filter is available error is returned. freq set new frequency parameter. width set new width parameter in Hertz. gain set new gain parameter in dB.
Full filter invocation with asendcmd may look like this: asendcmd=c=’4.0 anequalizer change 0|f=200|w=50|g=1’,anequalizer=...
29.38 anlmdn
Reduce broadband noise in audio samples using Non-Local Means algorithm.
Each sample is adjusted by looking for other samples with similar contexts. This context similarity is defined by comparing their surrounding patches of size p. Patches are searched in an area of r around the sample.
The filter accepts the following options:
- strength, s
Set denoising strength. Allowed range is from 0.00001 to 10000. Default value is 0.00001.
- patch, p
Set patch radius duration. Allowed range is from 1 to 100 milliseconds. Default value is 2 milliseconds.
- research, r
Set research radius duration. Allowed range is from 2 to 300 milliseconds. Default value is 6 milliseconds.
- output, o
Set the output mode.
It accepts the following values:
- i
Pass input unchanged.
- o
Pass noise filtered out.
- n
Pass only noise.
Default value is o.
- smooth, m
Set smooth factor. Default value is 11. Allowed range is from 1 to 1000.
29.38.1 Commands
This filter supports the all above options as commands.
29.39 anlmf, anlms
Apply Normalized Least-Mean-(Squares|Fourth) algorithm to the first audio stream using the second audio stream.
This adaptive filter is used to mimic a desired filter by finding the filter coefficients that relate to producing the least mean square of the error signal (difference between the desired, 2nd input audio stream and the actual signal, the 1st input audio stream).
A description of the accepted options follows.
- order
Set filter order.
- mu
Set filter mu.
- eps
Set the filter eps.
- leakage
Set the filter leakage.
- out_mode
It accepts the following values:
- i
Pass the 1st input.
- d
Pass the 2nd input.
- o
Pass difference between desired, 2nd input and error signal estimate.
- n
Pass difference between input, 1st input and error signal estimate.
- e
Pass error signal estimated samples.
Default value is o.
- precision
Set which precision to use when processing samples.
- auto
Auto pick internal sample format depending on other filters.
- float
Always use single-floating point precision sample format.
- double
Always use double-floating point precision sample format.
29.39.1 Examples
- One of many usages of this filter is noise reduction, input audio is filtered
with same samples that are delayed by fixed amount, one such example for stereo audio is:
asplit[a][b],[a]adelay=32S|32S[a],[b][a]anlms=order=128:leakage=0.0005:mu=.5:out_mode=o
29.39.2 Commands
This filter supports the same commands as options, excluding option order
.
29.40 anull
Pass the audio source unchanged to the output.
29.41 apad
Pad the end of an audio stream with silence.
This can be used together with ffmpeg
-shortest to
extend audio streams to the same length as the video stream.
A description of the accepted options follows.
- packet_size
Set silence packet size. Default value is 4096.
- pad_len
Set the number of samples of silence to add to the end. After the value is reached, the stream is terminated. This option is mutually exclusive with whole_len.
- whole_len
Set the minimum total number of samples in the output audio stream. If the value is longer than the input audio length, silence is added to the end, until the value is reached. This option is mutually exclusive with pad_len.
- pad_dur
Specify the duration of samples of silence to add. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. Used only if set to non-negative value.
- whole_dur
Specify the minimum total duration in the output audio stream. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. Used only if set to non-negative value. If the value is longer than the input audio length, silence is added to the end, until the value is reached. This option is mutually exclusive with pad_dur
If neither the pad_len nor the whole_len nor pad_dur nor whole_dur option is set, the filter will add silence to the end of the input stream indefinitely.
Note that for ffmpeg 4.4 and earlier a zero pad_dur or whole_dur also caused the filter to add silence indefinitely.
29.41.1 Examples
- Add 1024 samples of silence to the end of the input:
apad=pad_len=1024
- Make sure the audio output will contain at least 10000 samples, pad
the input with silence if required:
apad=whole_len=10000
- Use
ffmpeg
to pad the audio input with silence, so that the video stream will always result the shortest and will be converted until the end in the output file when using the shortest option:ffmpeg -i VIDEO -i AUDIO -filter_complex "[1:0]apad" -shortest OUTPUT
29.42 aphaser
Add a phasing effect to the input audio.
A phaser filter creates series of peaks and troughs in the frequency spectrum. The position of the peaks and troughs are modulated so that they vary over time, creating a sweeping effect.
A description of the accepted parameters follows.
- in_gain
Set input gain. Default is 0.4.
- out_gain
Set output gain. Default is 0.74
- delay
Set delay in milliseconds. Default is 3.0.
- decay
Set decay. Default is 0.4.
- speed
Set modulation speed in Hz. Default is 0.5.
- type
Set modulation type. Default is triangular.
It accepts the following values:
- ‘triangular, t’
- ‘sinusoidal, s’
29.43 aphaseshift
Apply phase shift to input audio samples.
The filter accepts the following options:
- shift
Specify phase shift. Allowed range is from -1.0 to 1.0. Default value is 0.0.
- level
Set output gain applied to final output. Allowed range is from 0.0 to 1.0. Default value is 1.0.
- order
Set filter order used for filtering. Allowed range is from 1 to 16. Default value is 8.
29.43.1 Commands
This filter supports the all above options as commands.
29.44 apsnr
Measure Audio Peak Signal-to-Noise Ratio.
This filter takes two audio streams for input, and outputs first audio stream. Results are in dB per channel at end of either input.
29.45 apsyclip
Apply Psychoacoustic clipper to input audio stream.
The filter accepts the following options:
- level_in
Set input gain. By default it is 1. Range is [0.015625 - 64].
- level_out
Set output gain. By default it is 1. Range is [0.015625 - 64].
- clip
Set the clipping start value. Default value is 0dBFS or 1.
- diff
Output only difference samples, useful to hear introduced distortions. By default is disabled.
- adaptive
Set strength of adaptive distortion applied. Default value is 0.5. Allowed range is from 0 to 1.
- iterations
Set number of iterations of psychoacoustic clipper. Allowed range is from 1 to 20. Default value is 10.
- level
Auto level output signal. Default is disabled. This normalizes audio back to 0dBFS if enabled.
29.45.1 Commands
This filter supports the all above options as commands.
29.46 apulsator
Audio pulsator is something between an autopanner and a tremolo. But it can produce funny stereo effects as well. Pulsator changes the volume of the left and right channel based on a LFO (low frequency oscillator) with different waveforms and shifted phases. This filter have the ability to define an offset between left and right channel. An offset of 0 means that both LFO shapes match each other. The left and right channel are altered equally - a conventional tremolo. An offset of 50% means that the shape of the right channel is exactly shifted in phase (or moved backwards about half of the frequency) - pulsator acts as an autopanner. At 1 both curves match again. Every setting in between moves the phase shift gapless between all stages and produces some "bypassing" sounds with sine and triangle waveforms. The more you set the offset near 1 (starting from the 0.5) the faster the signal passes from the left to the right speaker.
The filter accepts the following options:
- level_in
Set input gain. By default it is 1. Range is [0.015625 - 64].
- level_out
Set output gain. By default it is 1. Range is [0.015625 - 64].
- mode
Set waveform shape the LFO will use. Can be one of: sine, triangle, square, sawup or sawdown. Default is sine.
- amount
Set modulation. Define how much of original signal is affected by the LFO.
- offset_l
Set left channel offset. Default is 0. Allowed range is [0 - 1].
- offset_r
Set right channel offset. Default is 0.5. Allowed range is [0 - 1].
- width
Set pulse width. Default is 1. Allowed range is [0 - 2].
- timing
Set possible timing mode. Can be one of: bpm, ms or hz. Default is hz.
- bpm
Set bpm. Default is 120. Allowed range is [30 - 300]. Only used if timing is set to bpm.
- ms
Set ms. Default is 500. Allowed range is [10 - 2000]. Only used if timing is set to ms.
- hz
Set frequency in Hz. Default is 2. Allowed range is [0.01 - 100]. Only used if timing is set to hz.
29.47 aresample
Resample the input audio to the specified parameters, using the libswresample library. If none are specified then the filter will automatically convert between its input and output.
This filter is also able to stretch/squeeze the audio data to make it match the timestamps or to inject silence / cut out audio to make it match the timestamps, do a combination of both or do neither.
The filter accepts the syntax [sample_rate:]resampler_options, where sample_rate expresses a sample rate and resampler_options is a list of key=value pairs, separated by ":". See the (ffmpeg-resampler)"Resampler Options" section in the ffmpeg-resampler(1) manual for the complete list of supported options.
29.47.1 Examples
- Resample the input audio to 44100Hz:
aresample=44100
- Stretch/squeeze samples to the given timestamps, with a maximum of 1000
samples per second compensation:
aresample=async=1000
29.48 areverse
Reverse an audio clip.
Warning: This filter requires memory to buffer the entire clip, so trimming is suggested.
29.48.1 Examples
- Take the first 5 seconds of a clip, and reverse it.
atrim=end=5,areverse
29.49 arls
Apply Recursive Least Squares algorithm to the first audio stream using the second audio stream.
This adaptive filter is used to mimic a desired filter by recursively finding the filter coefficients that relate to producing the minimal weighted linear least squares cost function of the error signal (difference between the desired, 2nd input audio stream and the actual signal, the 1st input audio stream).
A description of the accepted options follows.
- order
Set the filter order.
- lambda
Set the forgetting factor.
- delta
Set the coefficient to initialize internal covariance matrix.
- out_mode
Set the filter output samples. It accepts the following values:
- i
Pass the 1st input.
- d
Pass the 2nd input.
- o
Pass difference between desired, 2nd input and error signal estimate.
- n
Pass difference between input, 1st input and error signal estimate.
- e
Pass error signal estimated samples.
Default value is o.
- precision
Set which precision to use when processing samples.
- auto
Auto pick internal sample format depending on other filters.
- float
Always use single-floating point precision sample format.
- double
Always use double-floating point precision sample format.
29.50 arnndn
Reduce noise from speech using Recurrent Neural Networks.
This filter accepts the following options:
- model, m
Set train model file to load. This option is always required.
- mix
Set how much to mix filtered samples into final output. Allowed range is from -1 to 1. Default value is 1. Negative values are special, they set how much to keep filtered noise in the final filter output. Set this option to -1 to hear actual noise removed from input signal.
29.50.1 Commands
This filter supports the all above options as commands.
29.51 asdr
Measure Audio Signal-to-Distortion Ratio.
This filter takes two audio streams for input, and outputs first audio stream. Results are in dB per channel at end of either input.
29.52 asetnsamples
Set the number of samples per each output audio frame.
The last output packet may contain a different number of samples, as the filter will flush all the remaining samples when the input audio signals its end.
The filter accepts the following options:
- nb_out_samples, n
Set the number of frames per each output audio frame. The number is intended as the number of samples per each channel. Default value is 1024.
- pad, p
If set to 1, the filter will pad the last audio frame with zeroes, so that the last frame will contain the same number of samples as the previous ones. Default value is 1.
For example, to set the number of per-frame samples to 1234 and disable padding for the last frame, use:
asetnsamples=n=1234:p=0
29.53 asetrate
Set the sample rate without altering the PCM data. This will result in a change of speed and pitch.
The filter accepts the following options:
- sample_rate, r
Set the output sample rate. Default is 44100 Hz.
29.54 ashowinfo
Show a line containing various information for each input audio frame. The input audio is not modified.
The shown line contains a sequence of key/value pairs of the form key:value.
The following values are shown in the output:
- n
The (sequential) number of the input frame, starting from 0.
- pts
The presentation timestamp of the input frame, in time base units; the time base depends on the filter input pad, and is usually 1/sample_rate.
- pts_time
The presentation timestamp of the input frame in seconds.
- fmt
The sample format.
- chlayout
The channel layout.
- rate
The sample rate for the audio frame.
- nb_samples
The number of samples (per channel) in the frame.
- checksum
The Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio, the data is treated as if all the planes were concatenated.
- plane_checksums
A list of Adler-32 checksums for each data plane.
29.55 asisdr
Measure Audio Scaled-Invariant Signal-to-Distortion Ratio.
This filter takes two audio streams for input, and outputs first audio stream. Results are in dB per channel at end of either input.
29.56 asoftclip
Apply audio soft clipping.
Soft clipping is a type of distortion effect where the amplitude of a signal is saturated along a smooth curve, rather than the abrupt shape of hard-clipping.
This filter accepts the following options:
- type
Set type of soft-clipping.
It accepts the following values:
- hard
- tanh
- atan
- cubic
- exp
- alg
- quintic
- sin
- erf
- threshold
Set threshold from where to start clipping. Default value is 0dB or 1.
- output
Set gain applied to output. Default value is 0dB or 1.
- param
Set additional parameter which controls sigmoid function.
- oversample
Set oversampling factor.
29.56.1 Commands
This filter supports the all above options as commands.
29.57 aspectralstats
Display frequency domain statistical information about the audio channels. Statistics are calculated and stored as metadata for each audio channel and for each audio frame.
It accepts the following option:
- win_size
Set the window length in samples. Default value is 2048. Allowed range is from 32 to 65536.
- win_func
Set window function.
It accepts the following values:
- ‘rect’
- ‘bartlett’
- ‘hann, hanning’
- ‘hamming’
- ‘blackman’
- ‘welch’
- ‘flattop’
- ‘bharris’
- ‘bnuttall’
- ‘bhann’
- ‘sine’
- ‘nuttall’
- ‘lanczos’
- ‘gauss’
- ‘tukey’
- ‘dolph’
- ‘cauchy’
- ‘parzen’
- ‘poisson’
- ‘bohman’
- ‘kaiser’
Default is
hann
.- overlap
Set window overlap. Allowed range is from
0
to1
. Default value is0.5
.- measure
Select the parameters which are measured. The metadata keys can be used as flags, default is all which measures everything. none disables all measurement.
A list of each metadata key follows:
- mean
- variance
- centroid
- spread
- skewness
- kurtosis
- entropy
- flatness
- crest
- flux
- slope
- decrease
- rolloff
29.58 asr
Automatic Speech Recognition
This filter uses PocketSphinx for speech recognition. To enable
compilation of this filter, you need to configure FFmpeg with
--enable-pocketsphinx
.
It accepts the following options:
- rate
Set sampling rate of input audio. Defaults is
16000
. This need to match speech models, otherwise one will get poor results.- hmm
Set dictionary containing acoustic model files.
- dict
Set pronunciation dictionary.
- lm
Set language model file.
- lmctl
Set language model set.
- lmname
Set which language model to use.
- logfn
Set output for log messages.
The filter exports recognized speech as the frame metadata lavfi.asr.text
.
29.59 astats
Display time domain statistical information about the audio channels. Statistics are calculated and displayed for each audio channel and, where applicable, an overall figure is also given.
It accepts the following option:
- length
Short window length in seconds, used for peak and trough RMS measurement. Default is
0.05
(50 milliseconds). Allowed range is[0 - 10]
.- metadata
-
Set metadata injection. All the metadata keys are prefixed with
lavfi.astats.X
, whereX
is channel number starting from 1 or stringOverall
. Default is disabled.Available keys for each channel are: Bit_depth Crest_factor DC_offset Dynamic_range Entropy Flat_factor Max_difference Max_level Mean_difference Min_difference Min_level Noise_floor Noise_floor_count Number_of_Infs Number_of_NaNs Number_of_denormals Peak_count Abs_Peak_count Peak_level RMS_difference RMS_peak RMS_trough Zero_crossings Zero_crossings_rate
and for
Overall
: Bit_depth DC_offset Entropy Flat_factor Max_difference Max_level Mean_difference Min_difference Min_level Noise_floor Noise_floor_count Number_of_Infs Number_of_NaNs Number_of_denormals Number_of_samples Peak_count Abs_Peak_count Peak_level RMS_difference RMS_level RMS_peak RMS_troughFor example, a full key looks like
lavfi.astats.1.DC_offset
orlavfi.astats.Overall.Peak_count
.Read below for the description of the keys.
- reset
Set the number of frames over which cumulative stats are calculated before being reset. Default is disabled.
- measure_perchannel
Select the parameters which are measured per channel. The metadata keys can be used as flags, default is all which measures everything. none disables all per channel measurement.
- measure_overall
Select the parameters which are measured overall. The metadata keys can be used as flags, default is all which measures everything. none disables all overall measurement.
A description of the measure keys follow:
- none
no measures
- all
all measures
- Bit_depth
overall bit depth of audio, i.e. number of bits used for each sample
- Crest_factor
standard ratio of peak to RMS level (note: not in dB)
- DC_offset
mean amplitude displacement from zero
- Dynamic_range
measured dynamic range of audio in dB
- Entropy
entropy measured across whole audio, entropy of value near 1.0 is typically measured for white noise
- Flat_factor
flatness (i.e. consecutive samples with the same value) of the signal at its peak levels (i.e. either Min_level or Max_level)
- Max_difference
maximal difference between two consecutive samples
- Max_level
maximal sample level
- Mean_difference
mean difference between two consecutive samples, i.e. the average of each difference between two consecutive samples
- Min_difference
minimal difference between two consecutive samples
- Min_level
minimal sample level
- Noise_floor
minimum local peak measured in dBFS over a short window
- Noise_floor_count
number of occasions (not the number of samples) that the signal attained Noise floor
- Number_of_Infs
number of samples with an infinite value
- Number_of_NaNs
number of samples with a NaN (not a number) value
- Number_of_denormals
number of samples with a subnormal value
- Number_of_samples
number of samples
- Peak_count
number of occasions (not the number of samples) that the signal attained either Min_level or Max_level
- Abs_Peak_count
number of occasions that the absolute samples taken from the signal attained max absolute value of Min_level and Max_level
- Peak_level
standard peak level measured in dBFS
- RMS_difference
Root Mean Square difference between two consecutive samples
- RMS_level
standard RMS level measured in dBFS
- RMS_peak
- RMS_trough
peak and trough values for RMS level measured over a short window, measured in dBFS.
- Zero crossings
number of points where the waveform crosses the zero level axis
- Zero crossings rate
rate of Zero crossings and number of audio samples
29.60 asubboost
Boost subwoofer frequencies.
The filter accepts the following options:
- dry
Set dry gain, how much of original signal is kept. Allowed range is from 0 to 1. Default value is 1.0.
- wet
Set wet gain, how much of filtered signal is kept. Allowed range is from 0 to 1. Default value is 1.0.
- boost
Set max boost factor. Allowed range is from 1 to 12. Default value is 2.
- decay
Set delay line decay gain value. Allowed range is from 0 to 1. Default value is 0.0.
- feedback
Set delay line feedback gain value. Allowed range is from 0 to 1. Default value is 0.9.
- cutoff
Set cutoff frequency in Hertz. Allowed range is 50 to 900. Default value is 100.
- slope
Set slope amount for cutoff frequency. Allowed range is 0.0001 to 1. Default value is 0.5.
- delay
Set delay. Allowed range is from 1 to 100. Default value is 20.
- channels
Set the channels to process. Default value is all available.
29.60.1 Commands
This filter supports the all above options as commands.
29.61 asubcut
Cut subwoofer frequencies.
This filter allows to set custom, steeper roll off than highpass filter, and thus is able to more attenuate frequency content in stop-band.
The filter accepts the following options:
- cutoff
Set cutoff frequency in Hertz. Allowed range is 2 to 200. Default value is 20.
- order
Set filter order. Available values are from 3 to 20. Default value is 10.
- level
Set input gain level. Allowed range is from 0 to 1. Default value is 1.
29.61.1 Commands
This filter supports the all above options as commands.
29.62 asupercut
Cut super frequencies.
The filter accepts the following options:
- cutoff
Set cutoff frequency in Hertz. Allowed range is 20000 to 192000. Default value is 20000.
- order
Set filter order. Available values are from 3 to 20. Default value is 10.
- level
Set input gain level. Allowed range is from 0 to 1. Default value is 1.
29.62.1 Commands
This filter supports the all above options as commands.
29.63 asuperpass
Apply high order Butterworth band-pass filter.
The filter accepts the following options:
- centerf
Set center frequency in Hertz. Allowed range is 2 to 999999. Default value is 1000.
- order
Set filter order. Available values are from 4 to 20. Default value is 4.
- qfactor
Set Q-factor. Allowed range is from 0.01 to 100. Default value is 1.
- level
Set input gain level. Allowed range is from 0 to 2. Default value is 1.
29.63.1 Commands
This filter supports the all above options as commands.
29.64 asuperstop
Apply high order Butterworth band-stop filter.
The filter accepts the following options:
- centerf
Set center frequency in Hertz. Allowed range is 2 to 999999. Default value is 1000.
- order
Set filter order. Available values are from 4 to 20. Default value is 4.
- qfactor
Set Q-factor. Allowed range is from 0.01 to 100. Default value is 1.
- level
Set input gain level. Allowed range is from 0 to 2. Default value is 1.
29.64.1 Commands
This filter supports the all above options as commands.
29.65 atempo
Adjust audio tempo.
The filter accepts exactly one parameter, the audio tempo. If not specified then the filter will assume nominal 1.0 tempo. Tempo must be in the [0.5, 100.0] range.
Note that tempo greater than 2 will skip some samples rather than blend them in. If for any reason this is a concern it is always possible to daisy-chain several instances of atempo to achieve the desired product tempo.
29.65.1 Examples
- Slow down audio to 80% tempo:
atempo=0.8
- To speed up audio to 300% tempo:
atempo=3
- To speed up audio to 300% tempo by daisy-chaining two atempo instances:
atempo=sqrt(3),atempo=sqrt(3)
29.65.2 Commands
This filter supports the following commands:
- tempo
Change filter tempo scale factor. Syntax for the command is : "tempo"
29.66 atilt
Apply spectral tilt filter to audio stream.
This filter apply any spectral roll-off slope over any specified frequency band.
The filter accepts the following options:
- freq
Set central frequency of tilt in Hz. Default is 10000 Hz.
- slope
Set slope direction of tilt. Default is 0. Allowed range is from -1 to 1.
- width
Set width of tilt. Default is 1000. Allowed range is from 100 to 10000.
- order
Set order of tilt filter.
- level
Set input volume level. Allowed range is from 0 to 4. Default is 1.
29.66.1 Commands
This filter supports the all above options as commands.
29.67 atrim
Trim the input so that the output contains one continuous subpart of the input.
It accepts the following parameters:
- start
Timestamp (in seconds) of the start of the section to keep. I.e. the audio sample with the timestamp start will be the first sample in the output.
- end
Specify time of the first audio sample that will be dropped, i.e. the audio sample immediately preceding the one with the timestamp end will be the last sample in the output.
- start_pts
Same as start, except this option sets the start timestamp in samples instead of seconds.
- end_pts
Same as end, except this option sets the end timestamp in samples instead of seconds.
- duration
The maximum duration of the output in seconds.
- start_sample
The number of the first sample that should be output.
- end_sample
The number of the first sample that should be dropped.
start, end, and duration are expressed as time duration specifications; see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual.
Note that the first two sets of the start/end options and the duration option look at the frame timestamp, while the _sample options simply count the samples that pass through the filter. So start/end_pts and start/end_sample will give different results when the timestamps are wrong, inexact or do not start at zero. Also note that this filter does not modify the timestamps. If you wish to have the output timestamps start at zero, insert the asetpts filter after the atrim filter.
If multiple start or end options are set, this filter tries to be greedy and keep all samples that match at least one of the specified constraints. To keep only the part that matches all the constraints at once, chain multiple atrim filters.
The defaults are such that all the input is kept. So it is possible to set e.g. just the end values to keep everything before the specified time.
Examples:
- Drop everything except the second minute of input:
ffmpeg -i INPUT -af atrim=60:120
- Keep only the first 1000 samples:
ffmpeg -i INPUT -af atrim=end_sample=1000
29.68 axcorrelate
Calculate normalized windowed cross-correlation between two input audio streams.
Resulted samples are always between -1 and 1 inclusive. If result is 1 it means two input samples are highly correlated in that selected segment. Result 0 means they are not correlated at all. If result is -1 it means two input samples are out of phase, which means they cancel each other.
The filter accepts the following options:
- size
Set size of segment over which cross-correlation is calculated. Default is 256. Allowed range is from 2 to 131072.
- algo
Set algorithm for cross-correlation. Can be
slow
orfast
orbest
. Default isbest
. Fast algorithm assumes mean values over any given segment are always zero and thus need much less calculations to make. This is generally not true, but is valid for typical audio streams.
29.68.1 Examples
- Calculate correlation between channels in stereo audio stream:
ffmpeg -i stereo.wav -af channelsplit,axcorrelate=size=1024:algo=fast correlation.wav
29.69 bandpass
Apply a two-pole Butterworth band-pass filter with central frequency frequency, and (3dB-point) band-width width. The csg option selects a constant skirt gain (peak gain = Q) instead of the default: constant 0dB peak gain. The filter roll off at 6dB per octave (20dB per decade).
The filter accepts the following options:
- frequency, f
Set the filter’s central frequency. Default is
3000
.- csg
Constant skirt gain if set to 1. Defaults to 0.
- width_type, t
Set method to specify band-width of filter.
- h
Hz
- q
Q-Factor
- o
octave
- s
slope
- k
kHz
- width, w
Specify the band-width of a filter in width_type units.
- mix, m
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- channels, c
Specify which channels to filter, by default all available are filtered.
- normalize, n
Normalize biquad coefficients, by default is disabled. Enabling it will normalize magnitude response at DC to 0dB.
- transform, a
Set transform type of IIR filter.
- di
- dii
- tdi
- tdii
- latt
- svf
- zdf
- precision, r
Set precision of filtering.
- auto
Pick automatic sample format depending on surround filters.
- s16
Always use signed 16-bit.
- s32
Always use signed 32-bit.
- f32
Always use float 32-bit.
- f64
Always use float 64-bit.
- block_size, b
Set block size used for reverse IIR processing. If this value is set to high enough value (higher than impulse response length truncated when reaches near zero values) filtering will become linear phase otherwise if not big enough it will just produce nasty artifacts.
Note that filter delay will be exactly this many samples when set to non-zero value.
29.69.1 Commands
This filter supports the following commands:
- frequency, f
Change bandpass frequency. Syntax for the command is : "frequency"
- width_type, t
Change bandpass width_type. Syntax for the command is : "width_type"
- width, w
Change bandpass width. Syntax for the command is : "width"
- mix, m
Change bandpass mix. Syntax for the command is : "mix"
29.70 bandreject
Apply a two-pole Butterworth band-reject filter with central frequency frequency, and (3dB-point) band-width width. The filter roll off at 6dB per octave (20dB per decade).
The filter accepts the following options:
- frequency, f
Set the filter’s central frequency. Default is
3000
.- width_type, t
Set method to specify band-width of filter.
- h
Hz
- q
Q-Factor
- o
octave
- s
slope
- k
kHz
- width, w
Specify the band-width of a filter in width_type units.
- mix, m
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- channels, c
Specify which channels to filter, by default all available are filtered.
- normalize, n
Normalize biquad coefficients, by default is disabled. Enabling it will normalize magnitude response at DC to 0dB.
- transform, a
Set transform type of IIR filter.
- di
- dii
- tdi
- tdii
- latt
- svf
- zdf
- precision, r
Set precision of filtering.
- auto
Pick automatic sample format depending on surround filters.
- s16
Always use signed 16-bit.
- s32
Always use signed 32-bit.
- f32
Always use float 32-bit.
- f64
Always use float 64-bit.
- block_size, b
Set block size used for reverse IIR processing. If this value is set to high enough value (higher than impulse response length truncated when reaches near zero values) filtering will become linear phase otherwise if not big enough it will just produce nasty artifacts.
Note that filter delay will be exactly this many samples when set to non-zero value.
29.70.1 Commands
This filter supports the following commands:
- frequency, f
Change bandreject frequency. Syntax for the command is : "frequency"
- width_type, t
Change bandreject width_type. Syntax for the command is : "width_type"
- width, w
Change bandreject width. Syntax for the command is : "width"
- mix, m
Change bandreject mix. Syntax for the command is : "mix"
29.71 bass, lowshelf
Boost or cut the bass (lower) frequencies of the audio using a two-pole shelving filter with a response similar to that of a standard hi-fi’s tone-controls. This is also known as shelving equalisation (EQ).
The filter accepts the following options:
- gain, g
Give the gain at 0 Hz. Its useful range is about -20 (for a large cut) to +20 (for a large boost). Beware of clipping when using a positive gain.
- frequency, f
Set the filter’s central frequency and so can be used to extend or reduce the frequency range to be boosted or cut. The default value is
100
Hz.- width_type, t
Set method to specify band-width of filter.
- h
Hz
- q
Q-Factor
- o
octave
- s
slope
- k
kHz
- width, w
Determine how steep is the filter’s shelf transition.
- poles, p
Set number of poles. Default is 2.
- mix, m
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- channels, c
Specify which channels to filter, by default all available are filtered.
- normalize, n
Normalize biquad coefficients, by default is disabled. Enabling it will normalize magnitude response at DC to 0dB.
- transform, a
Set transform type of IIR filter.
- di
- dii
- tdi
- tdii
- latt
- svf
- zdf
- precision, r
Set precision of filtering.
- auto
Pick automatic sample format depending on surround filters.
- s16
Always use signed 16-bit.
- s32
Always use signed 32-bit.
- f32
Always use float 32-bit.
- f64
Always use float 64-bit.
- block_size, b
Set block size used for reverse IIR processing. If this value is set to high enough value (higher than impulse response length truncated when reaches near zero values) filtering will become linear phase otherwise if not big enough it will just produce nasty artifacts.
Note that filter delay will be exactly this many samples when set to non-zero value.
29.71.1 Commands
This filter supports the following commands:
- frequency, f
Change bass frequency. Syntax for the command is : "frequency"
- width_type, t
Change bass width_type. Syntax for the command is : "width_type"
- width, w
Change bass width. Syntax for the command is : "width"
- gain, g
Change bass gain. Syntax for the command is : "gain"
- mix, m
Change bass mix. Syntax for the command is : "mix"
29.72 biquad
Apply a biquad IIR filter with the given coefficients. Where b0, b1, b2 and a0, a1, a2 are the numerator and denominator coefficients respectively. and channels, c specify which channels to filter, by default all available are filtered.
29.72.1 Commands
This filter supports the following commands:
- a0
- a1
- a2
- b0
- b1
- b2
Change biquad parameter. Syntax for the command is : "value"
- mix, m
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- channels, c
Specify which channels to filter, by default all available are filtered.
- normalize, n
Normalize biquad coefficients, by default is disabled. Enabling it will normalize magnitude response at DC to 0dB.
- transform, a
Set transform type of IIR filter.
- di
- dii
- tdi
- tdii
- latt
- svf
- zdf
- precision, r
Set precision of filtering.
- auto
Pick automatic sample format depending on surround filters.
- s16
Always use signed 16-bit.
- s32
Always use signed 32-bit.
- f32
Always use float 32-bit.
- f64
Always use float 64-bit.
- block_size, b
Set block size used for reverse IIR processing. If this value is set to high enough value (higher than impulse response length truncated when reaches near zero values) filtering will become linear phase otherwise if not big enough it will just produce nasty artifacts.
Note that filter delay will be exactly this many samples when set to non-zero value.
29.73 bs2b
Bauer stereo to binaural transformation, which improves headphone listening of stereo audio records.
To enable compilation of this filter you need to configure FFmpeg with
--enable-libbs2b
.
It accepts the following parameters:
- profile
Pre-defined crossfeed level.
- default
Default level (fcut=700, feed=50).
- cmoy
Chu Moy circuit (fcut=700, feed=60).
- jmeier
Jan Meier circuit (fcut=650, feed=95).
- fcut
Cut frequency (in Hz).
- feed
Feed level (in Hz).
29.74 channelmap
Remap input channels to new locations.
It accepts the following parameters:
- map
Map channels from input to output. The argument is a ’|’-separated list of mappings, each in the
in_channel-out_channel
orin_channel
form. in_channel can be either the name of the input channel (e.g. FL for front left) or its index in the input channel layout. out_channel is the name of the output channel or its index in the output channel layout. If out_channel is not given then it is implicitly an index, starting with zero and increasing by one for each mapping. Mixing different types of mappings is not allowed and will result in a parse error.- channel_layout
The channel layout of the output stream. If not specified, then filter will guess it based on the out_channel names or the number of mappings. Guessed layouts will not necessarily contain channels in the order of the mappings.
If no mapping is present, the filter will implicitly map input channels to output channels, preserving indices.
29.74.1 Examples
- For example, assuming a 5.1+downmix input MOV file,
ffmpeg -i in.mov -filter 'channelmap=map=DL-FL|DR-FR' out.wav
will create an output WAV file tagged as stereo from the downmix channels of the input.
- To fix a 5.1 WAV improperly encoded in AAC’s native channel order
ffmpeg -i in.wav -filter 'channelmap=1|2|0|5|3|4:5.1' out.wav
29.75 channelsplit
Split each channel from an input audio stream into a separate output stream.
It accepts the following parameters:
- channel_layout
The channel layout of the input stream. The default is "stereo".
- channels
A channel layout describing the channels to be extracted as separate output streams or "all" to extract each input channel as a separate stream. The default is "all".
Choosing channels not present in channel layout in the input will result in an error.
29.75.1 Examples
- For example, assuming a stereo input MP3 file,
ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
will create an output Matroska file with two audio streams, one containing only the left channel and the other the right channel.
- Split a 5.1 WAV file into per-channel files:
ffmpeg -i in.wav -filter_complex 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]' -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]' front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]' side_right.wav
- Extract only LFE from a 5.1 WAV file:
ffmpeg -i in.wav -filter_complex 'channelsplit=channel_layout=5.1:channels=LFE[LFE]' -map '[LFE]' lfe.wav
29.76 chorus
Add a chorus effect to the audio.
Can make a single vocal sound like a chorus, but can also be applied to instrumentation.
Chorus resembles an echo effect with a short delay, but whereas with echo the delay is constant, with chorus, it is varied using using sinusoidal or triangular modulation. The modulation depth defines the range the modulated delay is played before or after the delay. Hence the delayed sound will sound slower or faster, that is the delayed sound tuned around the original one, like in a chorus where some vocals are slightly off key.
It accepts the following parameters:
- in_gain
Set input gain. Default is 0.4.
- out_gain
Set output gain. Default is 0.4.
- delays
Set delays. A typical delay is around 40ms to 60ms.
- decays
Set decays.
- speeds
Set speeds.
- depths
Set depths.
29.76.1 Examples
- A single delay:
chorus=0.7:0.9:55:0.4:0.25:2
- Two delays:
chorus=0.6:0.9:50|60:0.4|0.32:0.25|0.4:2|1.3
- Fuller sounding chorus with three delays:
chorus=0.5:0.9:50|60|40:0.4|0.32|0.3:0.25|0.4|0.3:2|2.3|1.3
29.77 compand
Compress or expand the audio’s dynamic range.
It accepts the following parameters:
- attacks
- decays
A list of times in seconds for each channel over which the instantaneous level of the input signal is averaged to determine its volume. attacks refers to increase of volume and decays refers to decrease of volume. For most situations, the attack time (response to the audio getting louder) should be shorter than the decay time, because the human ear is more sensitive to sudden loud audio than sudden soft audio. A typical value for attack is 0.3 seconds and a typical value for decay is 0.8 seconds. If specified number of attacks & decays is lower than number of channels, the last set attack/decay will be used for all remaining channels.
- points
A list of points for the transfer function, specified in dB relative to the maximum possible signal amplitude. Each key points list must be defined using the following syntax:
x0/y0|x1/y1|x2/y2|....
orx0/y0 x1/y1 x2/y2 ....
The input values must be in strictly increasing order but the transfer function does not have to be monotonically rising. The point
0/0
is assumed but may be overridden (by0/out-dBn
). Typical values for the transfer function are-70/-70|-60/-20|1/0
.- soft-knee
Set the curve radius in dB for all joints. It defaults to 0.01.
- gain
Set the additional gain in dB to be applied at all points on the transfer function. This allows for easy adjustment of the overall gain. It defaults to 0.
- volume
Set an initial volume, in dB, to be assumed for each channel when filtering starts. This permits the user to supply a nominal level initially, so that, for example, a very large gain is not applied to initial signal levels before the companding has begun to operate. A typical value for audio which is initially quiet is -90 dB. It defaults to 0.
- delay
Set a delay, in seconds. The input audio is analyzed immediately, but audio is delayed before being fed to the volume adjuster. Specifying a delay approximately equal to the attack/decay times allows the filter to effectively operate in predictive rather than reactive mode. It defaults to 0.
29.77.1 Examples
- Make music with both quiet and loud passages suitable for listening to in a
noisy environment:
compand=.3|.3:1|1:-90/-60|-60/-40|-40/-30|-20/-20:6:0:-90:0.2
Another example for audio with whisper and explosion parts:
compand=0|0:1|1:-90/-900|-70/-70|-30/-9|0/-3:6:0:0:0
- A noise gate for when the noise is at a lower level than the signal:
compand=.1|.1:.2|.2:-900/-900|-50.1/-900|-50/-50:.01:0:-90:.1
- Here is another noise gate, this time for when the noise is at a higher level
than the signal (making it, in some ways, similar to squelch):
compand=.1|.1:.1|.1:-45.1/-45.1|-45/-900|0/-900:.01:45:-90:.1
- 2:1 compression starting at -6dB:
compand=points=-80/-80|-6/-6|0/-3.8|20/3.5
- 2:1 compression starting at -9dB:
compand=points=-80/-80|-9/-9|0/-5.3|20/2.9
- 2:1 compression starting at -12dB:
compand=points=-80/-80|-12/-12|0/-6.8|20/1.9
- 2:1 compression starting at -18dB:
compand=points=-80/-80|-18/-18|0/-9.8|20/0.7
- 3:1 compression starting at -15dB:
compand=points=-80/-80|-15/-15|0/-10.8|20/-5.2
- Compressor/Gate:
compand=points=-80/-105|-62/-80|-15.4/-15.4|0/-12|20/-7.6
- Expander:
compand=attacks=0:points=-80/-169|-54/-80|-49.5/-64.6|-41.1/-41.1|-25.8/-15|-10.8/-4.5|0/0|20/8.3
- Hard limiter at -6dB:
compand=attacks=0:points=-80/-80|-6/-6|20/-6
- Hard limiter at -12dB:
compand=attacks=0:points=-80/-80|-12/-12|20/-12
- Hard noise gate at -35 dB:
compand=attacks=0:points=-80/-115|-35.1/-80|-35/-35|20/20
- Soft limiter:
compand=attacks=0:points=-80/-80|-12.4/-12.4|-6/-8|0/-6.8|20/-2.8
29.78 compensationdelay
Compensation Delay Line is a metric based delay to compensate differing positions of microphones or speakers.
For example, you have recorded guitar with two microphones placed in different locations. Because the front of sound wave has fixed speed in normal conditions, the phasing of microphones can vary and depends on their location and interposition. The best sound mix can be achieved when these microphones are in phase (synchronized). Note that a distance of ~30 cm between microphones makes one microphone capture the signal in antiphase to the other microphone. That makes the final mix sound moody. This filter helps to solve phasing problems by adding different delays to each microphone track and make them synchronized.
The best result can be reached when you take one track as base and synchronize other tracks one by one with it. Remember that synchronization/delay tolerance depends on sample rate, too. Higher sample rates will give more tolerance.
The filter accepts the following parameters:
- mm
Set millimeters distance. This is compensation distance for fine tuning. Default is 0.
- cm
Set cm distance. This is compensation distance for tightening distance setup. Default is 0.
- m
Set meters distance. This is compensation distance for hard distance setup. Default is 0.
- dry
Set dry amount. Amount of unprocessed (dry) signal. Default is 0.
- wet
Set wet amount. Amount of processed (wet) signal. Default is 1.
- temp
Set temperature in degrees Celsius. This is the temperature of the environment. Default is 20.
29.78.1 Commands
This filter supports the all above options as commands.
29.79 crossfeed
Apply headphone crossfeed filter.
Crossfeed is the process of blending the left and right channels of stereo audio recording. It is mainly used to reduce extreme stereo separation of low frequencies.
The intent is to produce more speaker like sound to the listener.
The filter accepts the following options:
- strength
Set strength of crossfeed. Default is 0.2. Allowed range is from 0 to 1. This sets gain of low shelf filter for side part of stereo image. Default is -6dB. Max allowed is -30db when strength is set to 1.
- range
Set soundstage wideness. Default is 0.5. Allowed range is from 0 to 1. This sets cut off frequency of low shelf filter. Default is cut off near 1550 Hz. With range set to 1 cut off frequency is set to 2100 Hz.
- slope
Set curve slope of low shelf filter. Default is 0.5. Allowed range is from 0.01 to 1.
- level_in
Set input gain. Default is 0.9.
- level_out
Set output gain. Default is 1.
- block_size
Set block size used for reverse IIR processing. If this value is set to high enough value (higher than impulse response length truncated when reaches near zero values) filtering will become linear phase otherwise if not big enough it will just produce nasty artifacts.
Note that filter delay will be exactly this many samples when set to non-zero value.
29.79.1 Commands
This filter supports the all above options as commands.
29.80 crystalizer
Simple algorithm for audio noise sharpening.
This filter linearly increases differences between each audio sample.
The filter accepts the following options:
- i
Sets the intensity of effect (default: 2.0). Must be in range between -10.0 to 0 (unchanged sound) to 10.0 (maximum effect). To inverse filtering use negative value.
- c
Enable clipping. By default is enabled.
29.80.1 Commands
This filter supports the all above options as commands.
29.81 dcshift
Apply a DC shift to the audio.
This can be useful to remove a DC offset (caused perhaps by a hardware problem in the recording chain) from the audio. The effect of a DC offset is reduced headroom and hence volume. The astats filter can be used to determine if a signal has a DC offset.
- shift
Set the DC shift, allowed range is [-1, 1]. It indicates the amount to shift the audio.
- limitergain
Optional. It should have a value much less than 1 (e.g. 0.05 or 0.02) and is used to prevent clipping.
29.82 deesser
Apply de-essing to the audio samples.
- i
Set intensity for triggering de-essing. Allowed range is from 0 to 1. Default is 0.
- m
Set amount of ducking on treble part of sound. Allowed range is from 0 to 1. Default is 0.5.
- f
How much of original frequency content to keep when de-essing. Allowed range is from 0 to 1. Default is 0.5.
- s
Set the output mode.
It accepts the following values:
- i
Pass input unchanged.
- o
Pass ess filtered out.
- e
Pass only ess.
Default value is o.
29.83 dialoguenhance
Enhance dialogue in stereo audio.
This filter accepts stereo input and produce surround (3.0) channels output. The newly produced front center channel have enhanced speech dialogue originally available in both stereo channels. This filter outputs front left and front right channels same as available in stereo input.
The filter accepts the following options:
- original
Set the original center factor to keep in front center channel output. Allowed range is from 0 to 1. Default value is 1.
- enhance
Set the dialogue enhance factor to put in front center channel output. Allowed range is from 0 to 3. Default value is 1.
- voice
Set the voice detection factor. Allowed range is from 2 to 32. Default value is 2.
29.83.1 Commands
This filter supports the all above options as commands.
29.84 drmeter
Measure audio dynamic range.
DR values of 14 and higher is found in very dynamic material. DR of 8 to 13 is found in transition material. And anything less that 8 have very poor dynamics and is very compressed.
The filter accepts the following options:
- length
Set window length in seconds used to split audio into segments of equal length. Default is 3 seconds.
29.85 dynaudnorm
Dynamic Audio Normalizer.
This filter applies a certain amount of gain to the input audio in order to bring its peak magnitude to a target level (e.g. 0 dBFS). However, in contrast to more "simple" normalization algorithms, the Dynamic Audio Normalizer *dynamically* re-adjusts the gain factor to the input audio. This allows for applying extra gain to the "quiet" sections of the audio while avoiding distortions or clipping the "loud" sections. In other words: The Dynamic Audio Normalizer will "even out" the volume of quiet and loud sections, in the sense that the volume of each section is brought to the same target level. Note, however, that the Dynamic Audio Normalizer achieves this goal *without* applying "dynamic range compressing". It will retain 100% of the dynamic range *within* each section of the audio file.
- framelen, f
Set the frame length in milliseconds. In range from 10 to 8000 milliseconds. Default is 500 milliseconds. The Dynamic Audio Normalizer processes the input audio in small chunks, referred to as frames. This is required, because a peak magnitude has no meaning for just a single sample value. Instead, we need to determine the peak magnitude for a contiguous sequence of sample values. While a "standard" normalizer would simply use the peak magnitude of the complete file, the Dynamic Audio Normalizer determines the peak magnitude individually for each frame. The length of a frame is specified in milliseconds. By default, the Dynamic Audio Normalizer uses a frame length of 500 milliseconds, which has been found to give good results with most files. Note that the exact frame length, in number of samples, will be determined automatically, based on the sampling rate of the individual input audio file.
- gausssize, g
Set the Gaussian filter window size. In range from 3 to 301, must be odd number. Default is 31. Probably the most important parameter of the Dynamic Audio Normalizer is the
window size
of the Gaussian smoothing filter. The filter’s window size is specified in frames, centered around the current frame. For the sake of simplicity, this must be an odd number. Consequently, the default value of 31 takes into account the current frame, as well as the 15 preceding frames and the 15 subsequent frames. Using a larger window results in a stronger smoothing effect and thus in less gain variation, i.e. slower gain adaptation. Conversely, using a smaller window results in a weaker smoothing effect and thus in more gain variation, i.e. faster gain adaptation. In other words, the more you increase this value, the more the Dynamic Audio Normalizer will behave like a "traditional" normalization filter. On the contrary, the more you decrease this value, the more the Dynamic Audio Normalizer will behave like a dynamic range compressor.- peak, p
Set the target peak value. This specifies the highest permissible magnitude level for the normalized audio input. This filter will try to approach the target peak magnitude as closely as possible, but at the same time it also makes sure that the normalized signal will never exceed the peak magnitude. A frame’s maximum local gain factor is imposed directly by the target peak magnitude. The default value is 0.95 and thus leaves a headroom of 5%*. It is not recommended to go above this value.
- maxgain, m
Set the maximum gain factor. In range from 1.0 to 100.0. Default is 10.0. The Dynamic Audio Normalizer determines the maximum possible (local) gain factor for each input frame, i.e. the maximum gain factor that does not result in clipping or distortion. The maximum gain factor is determined by the frame’s highest magnitude sample. However, the Dynamic Audio Normalizer additionally bounds the frame’s maximum gain factor by a predetermined (global) maximum gain factor. This is done in order to avoid excessive gain factors in "silent" or almost silent frames. By default, the maximum gain factor is 10.0, For most inputs the default value should be sufficient and it usually is not recommended to increase this value. Though, for input with an extremely low overall volume level, it may be necessary to allow even higher gain factors. Note, however, that the Dynamic Audio Normalizer does not simply apply a "hard" threshold (i.e. cut off values above the threshold). Instead, a "sigmoid" threshold function will be applied. This way, the gain factors will smoothly approach the threshold value, but never exceed that value.
- targetrms, r
Set the target RMS. In range from 0.0 to 1.0. Default is 0.0 - disabled. By default, the Dynamic Audio Normalizer performs "peak" normalization. This means that the maximum local gain factor for each frame is defined (only) by the frame’s highest magnitude sample. This way, the samples can be amplified as much as possible without exceeding the maximum signal level, i.e. without clipping. Optionally, however, the Dynamic Audio Normalizer can also take into account the frame’s root mean square, abbreviated RMS. In electrical engineering, the RMS is commonly used to determine the power of a time-varying signal. It is therefore considered that the RMS is a better approximation of the "perceived loudness" than just looking at the signal’s peak magnitude. Consequently, by adjusting all frames to a constant RMS value, a uniform "perceived loudness" can be established. If a target RMS value has been specified, a frame’s local gain factor is defined as the factor that would result in exactly that RMS value. Note, however, that the maximum local gain factor is still restricted by the frame’s highest magnitude sample, in order to prevent clipping.
- coupling, n
Enable channels coupling. By default is enabled. By default, the Dynamic Audio Normalizer will amplify all channels by the same amount. This means the same gain factor will be applied to all channels, i.e. the maximum possible gain factor is determined by the "loudest" channel. However, in some recordings, it may happen that the volume of the different channels is uneven, e.g. one channel may be "quieter" than the other one(s). In this case, this option can be used to disable the channel coupling. This way, the gain factor will be determined independently for each channel, depending only on the individual channel’s highest magnitude sample. This allows for harmonizing the volume of the different channels.
- correctdc, c
Enable DC bias correction. By default is disabled. An audio signal (in the time domain) is a sequence of sample values. In the Dynamic Audio Normalizer these sample values are represented in the -1.0 to 1.0 range, regardless of the original input format. Normally, the audio signal, or "waveform", should be centered around the zero point. That means if we calculate the mean value of all samples in a file, or in a single frame, then the result should be 0.0 or at least very close to that value. If, however, there is a significant deviation of the mean value from 0.0, in either positive or negative direction, this is referred to as a DC bias or DC offset. Since a DC bias is clearly undesirable, the Dynamic Audio Normalizer provides optional DC bias correction. With DC bias correction enabled, the Dynamic Audio Normalizer will determine the mean value, or "DC correction" offset, of each input frame and subtract that value from all of the frame’s sample values which ensures those samples are centered around 0.0 again. Also, in order to avoid "gaps" at the frame boundaries, the DC correction offset values will be interpolated smoothly between neighbouring frames.
- altboundary, b
Enable alternative boundary mode. By default is disabled. The Dynamic Audio Normalizer takes into account a certain neighbourhood around each frame. This includes the preceding frames as well as the subsequent frames. However, for the "boundary" frames, located at the very beginning and at the very end of the audio file, not all neighbouring frames are available. In particular, for the first few frames in the audio file, the preceding frames are not known. And, similarly, for the last few frames in the audio file, the subsequent frames are not known. Thus, the question arises which gain factors should be assumed for the missing frames in the "boundary" region. The Dynamic Audio Normalizer implements two modes to deal with this situation. The default boundary mode assumes a gain factor of exactly 1.0 for the missing frames, resulting in a smooth "fade in" and "fade out" at the beginning and at the end of the input, respectively.
- compress, s
Set the compress factor. In range from 0.0 to 30.0. Default is 0.0. By default, the Dynamic Audio Normalizer does not apply "traditional" compression. This means that signal peaks will not be pruned and thus the full dynamic range will be retained within each local neighbourhood. However, in some cases it may be desirable to combine the Dynamic Audio Normalizer’s normalization algorithm with a more "traditional" compression. For this purpose, the Dynamic Audio Normalizer provides an optional compression (thresholding) function. If (and only if) the compression feature is enabled, all input frames will be processed by a soft knee thresholding function prior to the actual normalization process. Put simply, the thresholding function is going to prune all samples whose magnitude exceeds a certain threshold value. However, the Dynamic Audio Normalizer does not simply apply a fixed threshold value. Instead, the threshold value will be adjusted for each individual frame. In general, smaller parameters result in stronger compression, and vice versa. Values below 3.0 are not recommended, because audible distortion may appear.
- threshold, t
Set the target threshold value. This specifies the lowest permissible magnitude level for the audio input which will be normalized. If input frame volume is above this value frame will be normalized. Otherwise frame may not be normalized at all. The default value is set to 0, which means all input frames will be normalized. This option is mostly useful if digital noise is not wanted to be amplified.
- channels, h
Specify which channels to filter, by default all available channels are filtered.
- overlap, o
Specify overlap for frames. If set to 0 (default) no frame overlapping is done. Using >0 and <1 values will make less conservative gain adjustments, like when framelen option is set to smaller value, if framelen option value is compensated for non-zero overlap then gain adjustments will be smoother across time compared to zero overlap case.
- curve, v
Specify the peak mapping curve expression which is going to be used when calculating gain applied to frames. The max output frame gain will still be limited by other options mentioned previously for this filter.
The expression can contain the following constants:
- ch
current channel number
- sn
current sample number
- nb_channels
number of channels
- t
timestamp expressed in seconds
- sr
sample rate
- p
current frame peak value
29.85.1 Commands
This filter supports the all above options as commands.
29.86 earwax
Make audio easier to listen to on headphones.
This filter adds ‘cues’ to 44.1kHz stereo (i.e. audio CD format) audio so that when listened to on headphones the stereo image is moved from inside your head (standard for headphones) to outside and in front of the listener (standard for speakers).
Ported from SoX.
29.87 equalizer
Apply a two-pole peaking equalisation (EQ) filter. With this filter, the signal-level at and around a selected frequency can be increased or decreased, whilst (unlike bandpass and bandreject filters) that at all other frequencies is unchanged.
In order to produce complex equalisation curves, this filter can be given several times, each with a different central frequency.
The filter accepts the following options:
- frequency, f
Set the filter’s central frequency in Hz.
- width_type, t
Set method to specify band-width of filter.
- h
Hz
- q
Q-Factor
- o
octave
- s
slope
- k
kHz
- width, w
Specify the band-width of a filter in width_type units.
- gain, g
Set the required gain or attenuation in dB. Beware of clipping when using a positive gain.
- mix, m
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- channels, c
Specify which channels to filter, by default all available are filtered.
- normalize, n
Normalize biquad coefficients, by default is disabled. Enabling it will normalize magnitude response at DC to 0dB.
- transform, a
Set transform type of IIR filter.
- di
- dii
- tdi
- tdii
- latt
- svf
- zdf
- precision, r
Set precision of filtering.
- auto
Pick automatic sample format depending on surround filters.
- s16
Always use signed 16-bit.
- s32
Always use signed 32-bit.
- f32
Always use float 32-bit.
- f64
Always use float 64-bit.
- block_size, b
Set block size used for reverse IIR processing. If this value is set to high enough value (higher than impulse response length truncated when reaches near zero values) filtering will become linear phase otherwise if not big enough it will just produce nasty artifacts.
Note that filter delay will be exactly this many samples when set to non-zero value.
29.87.1 Examples
- Attenuate 10 dB at 1000 Hz, with a bandwidth of 200 Hz:
equalizer=f=1000:t=h:width=200:g=-10
- Apply 2 dB gain at 1000 Hz with Q 1 and attenuate 5 dB at 100 Hz with Q 2:
equalizer=f=1000:t=q:w=1:g=2,equalizer=f=100:t=q:w=2:g=-5
29.87.2 Commands
This filter supports the following commands:
- frequency, f
Change equalizer frequency. Syntax for the command is : "frequency"
- width_type, t
Change equalizer width_type. Syntax for the command is : "width_type"
- width, w
Change equalizer width. Syntax for the command is : "width"
- gain, g
Change equalizer gain. Syntax for the command is : "gain"
- mix, m
Change equalizer mix. Syntax for the command is : "mix"
29.88 extrastereo
Linearly increases the difference between left and right channels which adds some sort of "live" effect to playback.
The filter accepts the following options:
- m
Sets the difference coefficient (default: 2.5). 0.0 means mono sound (average of both channels), with 1.0 sound will be unchanged, with -1.0 left and right channels will be swapped.
- c
Enable clipping. By default is enabled.
29.88.1 Commands
This filter supports the all above options as commands.
29.89 firequalizer
Apply FIR Equalization using arbitrary frequency response.
The filter accepts the following option:
- gain
Set gain curve equation (in dB). The expression can contain variables:
- f
the evaluated frequency
- sr
sample rate
- ch
channel number, set to 0 when multichannels evaluation is disabled
- chid
channel id, see libavutil/channel_layout.h, set to the first channel id when multichannels evaluation is disabled
- chs
number of channels
- chlayout
channel_layout, see libavutil/channel_layout.h
and functions:
- gain_interpolate(f)
interpolate gain on frequency f based on gain_entry
- cubic_interpolate(f)
same as gain_interpolate, but smoother
This option is also available as command. Default is
gain_interpolate(f)
.- gain_entry
Set gain entry for gain_interpolate function. The expression can contain functions:
- entry(f, g)
store gain entry at frequency f with value g
This option is also available as command.
- delay
Set filter delay in seconds. Higher value means more accurate. Default is
0.01
.- accuracy
Set filter accuracy in Hz. Lower value means more accurate. Default is
5
.- wfunc
Set window function. Acceptable values are:
- rectangular
rectangular window, useful when gain curve is already smooth
- hann
hann window (default)
- hamming
hamming window
- blackman
blackman window
- nuttall3
3-terms continuous 1st derivative nuttall window
- mnuttall3
minimum 3-terms discontinuous nuttall window
- nuttall
4-terms continuous 1st derivative nuttall window
- bnuttall
minimum 4-terms discontinuous nuttall (blackman-nuttall) window
- bharris
blackman-harris window
- tukey
tukey window
- fixed
If enabled, use fixed number of audio samples. This improves speed when filtering with large delay. Default is disabled.
- multi
Enable multichannels evaluation on gain. Default is disabled.
- zero_phase
Enable zero phase mode by subtracting timestamp to compensate delay. Default is disabled.
- scale
Set scale used by gain. Acceptable values are:
- linlin
linear frequency, linear gain
- linlog
linear frequency, logarithmic (in dB) gain (default)
- loglin
logarithmic (in octave scale where 20 Hz is 0) frequency, linear gain
- loglog
logarithmic frequency, logarithmic gain
- dumpfile
Set file for dumping, suitable for gnuplot.
- dumpscale
Set scale for dumpfile. Acceptable values are same with scale option. Default is linlog.
- fft2
Enable 2-channel convolution using complex FFT. This improves speed significantly. Default is disabled.
- min_phase
Enable minimum phase impulse response. Default is disabled.
29.89.1 Examples
- lowpass at 1000 Hz:
firequalizer=gain='if(lt(f,1000), 0, -INF)'
- lowpass at 1000 Hz with gain_entry:
firequalizer=gain_entry='entry(1000,0); entry(1001, -INF)'
- custom equalization:
firequalizer=gain_entry='entry(100,0); entry(400, -4); entry(1000, -6); entry(2000, 0)'
- higher delay with zero phase to compensate delay:
firequalizer=delay=0.1:fixed=on:zero_phase=on
- lowpass on left channel, highpass on right channel:
firequalizer=gain='if(eq(chid,1), gain_interpolate(f), if(eq(chid,2), gain_interpolate(1e6+f), 0))' :gain_entry='entry(1000, 0); entry(1001,-INF); entry(1e6+1000,0)':multi=on
29.90 flanger
Apply a flanging effect to the audio.
The filter accepts the following options:
- delay
Set base delay in milliseconds. Range from 0 to 30. Default value is 0.
- depth
Set added sweep delay in milliseconds. Range from 0 to 10. Default value is 2.
- regen
Set percentage regeneration (delayed signal feedback). Range from -95 to 95. Default value is 0.
- width
Set percentage of delayed signal mixed with original. Range from 0 to 100. Default value is 71.
- speed
Set sweeps per second (Hz). Range from 0.1 to 10. Default value is 0.5.
- shape
Set swept wave shape, can be triangular or sinusoidal. Default value is sinusoidal.
- phase
Set swept wave percentage-shift for multi channel. Range from 0 to 100. Default value is 25.
- interp
Set delay-line interpolation, linear or quadratic. Default is linear.
29.91 haas
Apply Haas effect to audio.
Note that this makes most sense to apply on mono signals. With this filter applied to mono signals it give some directionality and stretches its stereo image.
The filter accepts the following options:
- level_in
Set input level. By default is 1, or 0dB
- level_out
Set output level. By default is 1, or 0dB.
- side_gain
Set gain applied to side part of signal. By default is 1.
- middle_source
Set kind of middle source. Can be one of the following:
- ‘left’
Pick left channel.
- ‘right’
Pick right channel.
- ‘mid’
Pick middle part signal of stereo image.
- ‘side’
Pick side part signal of stereo image.
- middle_phase
Change middle phase. By default is disabled.
- left_delay
Set left channel delay. By default is 2.05 milliseconds.
- left_balance
Set left channel balance. By default is -1.
- left_gain
Set left channel gain. By default is 1.
- left_phase
Change left phase. By default is disabled.
- right_delay
Set right channel delay. By defaults is 2.12 milliseconds.
- right_balance
Set right channel balance. By default is 1.
- right_gain
Set right channel gain. By default is 1.
- right_phase
Change right phase. By default is enabled.
29.92 hdcd
Decodes High Definition Compatible Digital (HDCD) data. A 16-bit PCM stream with embedded HDCD codes is expanded into a 20-bit PCM stream.
The filter supports the Peak Extend and Low-level Gain Adjustment features of HDCD, and detects the Transient Filter flag.
ffmpeg -i HDCD16.flac -af hdcd OUT24.flac
When using the filter with wav, note the default encoding for wav is 16-bit,
so the resulting 20-bit stream will be truncated back to 16-bit. Use something
like -acodec pcm_s24le
after the filter to get 24-bit PCM output.
ffmpeg -i HDCD16.wav -af hdcd OUT16.wav ffmpeg -i HDCD16.wav -af hdcd -c:a pcm_s24le OUT24.wav
The filter accepts the following options:
- disable_autoconvert
Disable any automatic format conversion or resampling in the filter graph.
- process_stereo
Process the stereo channels together. If target_gain does not match between channels, consider it invalid and use the last valid target_gain.
- cdt_ms
Set the code detect timer period in ms.
- force_pe
Always extend peaks above -3dBFS even if PE isn’t signaled.
- analyze_mode
Replace audio with a solid tone and adjust the amplitude to signal some specific aspect of the decoding process. The output file can be loaded in an audio editor alongside the original to aid analysis.
analyze_mode=pe:force_pe=true
can be used to see all samples above the PE level.Modes are:
- ‘0, off’
Disabled
- ‘1, lle’
Gain adjustment level at each sample
- ‘2, pe’
Samples where peak extend occurs
- ‘3, cdt’
Samples where the code detect timer is active
- ‘4, tgm’
Samples where the target gain does not match between channels
29.93 headphone
Apply head-related transfer functions (HRTFs) to create virtual loudspeakers around the user for binaural listening via headphones. The HRIRs are provided via additional streams, for each channel one stereo input stream is needed.
The filter accepts the following options:
- map
Set mapping of input streams for convolution. The argument is a ’|’-separated list of channel names in order as they are given as additional stream inputs for filter. This also specify number of input streams. Number of input streams must be not less than number of channels in first stream plus one.
- gain
Set gain applied to audio. Value is in dB. Default is 0.
- type
Set processing type. Can be time or freq. time is processing audio in time domain which is slow. freq is processing audio in frequency domain which is fast. Default is freq.
- lfe
Set custom gain for LFE channels. Value is in dB. Default is 0.
- size
Set size of frame in number of samples which will be processed at once. Default value is 1024. Allowed range is from 1024 to 96000.
- hrir
Set format of hrir stream. Default value is stereo. Alternative value is multich. If value is set to stereo, number of additional streams should be greater or equal to number of input channels in first input stream. Also each additional stream should have stereo number of channels. If value is set to multich, number of additional streams should be exactly one. Also number of input channels of additional stream should be equal or greater than twice number of channels of first input stream.
29.93.1 Examples
- Full example using wav files as coefficients with amovie filters for 7.1 downmix,
each amovie filter use stereo file with IR coefficients as input.
The files give coefficients for each position of virtual loudspeaker:
ffmpeg -i input.wav -filter_complex "amovie=azi_270_ele_0_DFC.wav[sr];amovie=azi_90_ele_0_DFC.wav[sl];amovie=azi_225_ele_0_DFC.wav[br];amovie=azi_135_ele_0_DFC.wav[bl];amovie=azi_0_ele_0_DFC.wav,asplit[fc][lfe];amovie=azi_35_ele_0_DFC.wav[fl];amovie=azi_325_ele_0_DFC.wav[fr];[0:a][fl][fr][fc][lfe][bl][br][sl][sr]headphone=FL|FR|FC|LFE|BL|BR|SL|SR" output.wav
- Full example using wav files as coefficients with amovie filters for 7.1 downmix,
but now in multich hrir format.
ffmpeg -i input.wav -filter_complex "amovie=minp.wav[hrirs];[0:a][hrirs]headphone=map=FL|FR|FC|LFE|BL|BR|SL|SR:hrir=multich" output.wav
29.94 highpass
Apply a high-pass filter with 3dB point frequency. The filter can be either single-pole, or double-pole (the default). The filter roll off at 6dB per pole per octave (20dB per pole per decade).
The filter accepts the following options:
- frequency, f
Set frequency in Hz. Default is 3000.
- poles, p
Set number of poles. Default is 2.
- width_type, t
Set method to specify band-width of filter.
- h
Hz
- q
Q-Factor
- o
octave
- s
slope
- k
kHz
- width, w
Specify the band-width of a filter in width_type units. Applies only to double-pole filter. The default is 0.707q and gives a Butterworth response.
- mix, m
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- channels, c
Specify which channels to filter, by default all available are filtered.
- normalize, n
Normalize biquad coefficients, by default is disabled. Enabling it will normalize magnitude response at DC to 0dB.
- transform, a
Set transform type of IIR filter.
- di
- dii
- tdi
- tdii
- latt
- svf
- zdf
- precision, r
Set precision of filtering.
- auto
Pick automatic sample format depending on surround filters.
- s16
Always use signed 16-bit.
- s32
Always use signed 32-bit.
- f32
Always use float 32-bit.
- f64
Always use float 64-bit.
- block_size, b
Set block size used for reverse IIR processing. If this value is set to high enough value (higher than impulse response length truncated when reaches near zero values) filtering will become linear phase otherwise if not big enough it will just produce nasty artifacts.
Note that filter delay will be exactly this many samples when set to non-zero value.
29.94.1 Commands
This filter supports the following commands:
- frequency, f
Change highpass frequency. Syntax for the command is : "frequency"
- width_type, t
Change highpass width_type. Syntax for the command is : "width_type"
- width, w
Change highpass width. Syntax for the command is : "width"
- mix, m
Change highpass mix. Syntax for the command is : "mix"
29.95 join
Join multiple input streams into one multi-channel stream.
It accepts the following parameters:
- inputs
The number of input streams. It defaults to 2.
- channel_layout
The desired output channel layout. It defaults to stereo.
- map
Map channels from inputs to output. The argument is a ’|’-separated list of mappings, each in the
input_idx.in_channel-out_channel
form. input_idx is the 0-based index of the input stream. in_channel can be either the name of the input channel (e.g. FL for front left) or its index in the specified input stream. out_channel is the name of the output channel.
The filter will attempt to guess the mappings when they are not specified explicitly. It does so by first trying to find an unused matching input channel and if that fails it picks the first unused input channel.
Join 3 inputs (with properly set channel layouts):
ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
Build a 5.1 output from 6 single-channel streams:
ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex 'join=inputs=6:channel_layout=5.1:map=0.0-FL|1.0-FR|2.0-FC|3.0-SL|4.0-SR|5.0-LFE' out
29.96 ladspa
Load a LADSPA (Linux Audio Developer’s Simple Plugin API) plugin.
To enable compilation of this filter you need to configure FFmpeg with
--enable-ladspa
.
- file, f
Specifies the name of LADSPA plugin library to load. If the environment variable
LADSPA_PATH
is defined, the LADSPA plugin is searched in each one of the directories specified by the colon separated list inLADSPA_PATH
, otherwise in the standard LADSPA paths, which are in this order: HOME/.ladspa/lib/, /usr/local/lib/ladspa/, /usr/lib/ladspa/.- plugin, p
Specifies the plugin within the library. Some libraries contain only one plugin, but others contain many of them. If this is not set filter will list all available plugins within the specified library.
- controls, c
Set the ’|’ separated list of controls which are zero or more floating point values that determine the behavior of the loaded plugin (for example delay, threshold or gain). Controls need to be defined using the following syntax: c0=value0|c1=value1|c2=value2|..., where valuei is the value set on the i-th control. Alternatively they can be also defined using the following syntax: value0|value1|value2|..., where valuei is the value set on the i-th control. If controls is set to
help
, all available controls and their valid ranges are printed.- sample_rate, s
Specify the sample rate, default to 44100. Only used if plugin have zero inputs.
- nb_samples, n
Set the number of samples per channel per each output frame, default is 1024. Only used if plugin have zero inputs.
- duration, d
Set the minimum duration of the sourced audio. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. Note that the resulting duration may be greater than the specified duration, as the generated audio is always cut at the end of a complete frame. If not specified, or the expressed duration is negative, the audio is supposed to be generated forever. Only used if plugin have zero inputs.
- latency, l
Enable latency compensation, by default is disabled. Only used if plugin have inputs.
29.96.1 Examples
- List all available plugins within amp (LADSPA example plugin) library:
ladspa=file=amp
- List all available controls and their valid ranges for
vcf_notch
plugin fromVCF
library:ladspa=f=vcf:p=vcf_notch:c=help
- Simulate low quality audio equipment using
Computer Music Toolkit
(CMT) plugin library:ladspa=file=cmt:plugin=lofi:controls=c0=22|c1=12|c2=12
- Add reverberation to the audio using TAP-plugins
(Tom’s Audio Processing plugins):
ladspa=file=tap_reverb:tap_reverb
- Generate white noise, with 0.2 amplitude:
ladspa=file=cmt:noise_source_white:c=c0=.2
- Generate 20 bpm clicks using plugin
C* Click - Metronome
from theC* Audio Plugin Suite
(CAPS) library:ladspa=file=caps:Click:c=c1=20'
- Apply
C* Eq10X2 - Stereo 10-band equaliser
effect:ladspa=caps:Eq10X2:c=c0=-48|c9=-24|c3=12|c4=2
- Increase volume by 20dB using fast lookahead limiter from Steve Harris
SWH Plugins
collection:ladspa=fast_lookahead_limiter_1913:fastLookaheadLimiter:20|0|2
- Attenuate low frequencies using Multiband EQ from Steve Harris
SWH Plugins
collection:ladspa=mbeq_1197:mbeq:-24|-24|-24|0|0|0|0|0|0|0|0|0|0|0|0
- Reduce stereo image using
Narrower
from theC* Audio Plugin Suite
(CAPS) library:ladspa=caps:Narrower
- Another white noise, now using
C* Audio Plugin Suite
(CAPS) library:ladspa=caps:White:.2
- Some fractal noise, using
C* Audio Plugin Suite
(CAPS) library:ladspa=caps:Fractal:c=c1=1
- Dynamic volume normalization using
VLevel
plugin:ladspa=vlevel-ladspa:vlevel_mono
29.96.2 Commands
This filter supports the following commands:
- cN
Modify the N-th control value.
If the specified value is not valid, it is ignored and prior one is kept.
29.97 loudnorm
EBU R128 loudness normalization. Includes both dynamic and linear normalization modes.
Support for both single pass (livestreams, files) and double pass (files) modes.
This algorithm can target IL, LRA, and maximum true peak. In dynamic mode, to accurately
detect true peaks, the audio stream will be upsampled to 192 kHz.
Use the -ar
option or aresample
filter to explicitly set an output sample rate.
The filter accepts the following options:
- I, i
Set integrated loudness target. Range is -70.0 - -5.0. Default value is -24.0.
- LRA, lra
Set loudness range target. Range is 1.0 - 50.0. Default value is 7.0.
- TP, tp
Set maximum true peak. Range is -9.0 - +0.0. Default value is -2.0.
- measured_I, measured_i
Measured IL of input file. Range is -99.0 - +0.0.
- measured_LRA, measured_lra
Measured LRA of input file. Range is 0.0 - 99.0.
- measured_TP, measured_tp
Measured true peak of input file. Range is -99.0 - +99.0.
- measured_thresh
Measured threshold of input file. Range is -99.0 - +0.0.
- offset
Set offset gain. Gain is applied before the true-peak limiter. Range is -99.0 - +99.0. Default is +0.0.
- linear
Normalize by linearly scaling the source audio.
measured_I
,measured_LRA
,measured_TP
, andmeasured_thresh
must all be specified. Target LRA shouldn’t be lower than source LRA and the change in integrated loudness shouldn’t result in a true peak which exceeds the target TP. If any of these conditions aren’t met, normalization mode will revert to dynamic. Options aretrue
orfalse
. Default istrue
.- dual_mono
Treat mono input files as "dual-mono". If a mono file is intended for playback on a stereo system, its EBU R128 measurement will be perceptually incorrect. If set to
true
, this option will compensate for this effect. Multi-channel input files are not affected by this option. Options are true or false. Default is false.- print_format
Set print format for stats. Options are summary, json, or none. Default value is none.
29.98 lowpass
Apply a low-pass filter with 3dB point frequency. The filter can be either single-pole or double-pole (the default). The filter roll off at 6dB per pole per octave (20dB per pole per decade).
The filter accepts the following options:
- frequency, f
Set frequency in Hz. Default is 500.
- poles, p
Set number of poles. Default is 2.
- width_type, t
Set method to specify band-width of filter.
- h
Hz
- q
Q-Factor
- o
octave
- s
slope
- k
kHz
- width, w
Specify the band-width of a filter in width_type units. Applies only to double-pole filter. The default is 0.707q and gives a Butterworth response.
- mix, m
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- channels, c
Specify which channels to filter, by default all available are filtered.
- normalize, n
Normalize biquad coefficients, by default is disabled. Enabling it will normalize magnitude response at DC to 0dB.
- transform, a
Set transform type of IIR filter.
- di
- dii
- tdi
- tdii
- latt
- svf
- zdf
- precision, r
Set precision of filtering.
- auto
Pick automatic sample format depending on surround filters.
- s16
Always use signed 16-bit.
- s32
Always use signed 32-bit.
- f32
Always use float 32-bit.
- f64
Always use float 64-bit.
- block_size, b
Set block size used for reverse IIR processing. If this value is set to high enough value (higher than impulse response length truncated when reaches near zero values) filtering will become linear phase otherwise if not big enough it will just produce nasty artifacts.
Note that filter delay will be exactly this many samples when set to non-zero value.
29.98.1 Examples
- Lowpass only LFE channel, it LFE is not present it does nothing:
lowpass=c=LFE
29.98.2 Commands
This filter supports the following commands:
- frequency, f
Change lowpass frequency. Syntax for the command is : "frequency"
- width_type, t
Change lowpass width_type. Syntax for the command is : "width_type"
- width, w
Change lowpass width. Syntax for the command is : "width"
- mix, m
Change lowpass mix. Syntax for the command is : "mix"
29.99 lv2
Load a LV2 (LADSPA Version 2) plugin.
To enable compilation of this filter you need to configure FFmpeg with
--enable-lv2
.
- plugin, p
Specifies the plugin URI. You may need to escape ’:’.
- controls, c
Set the ’|’ separated list of controls which are zero or more floating point values that determine the behavior of the loaded plugin (for example delay, threshold or gain). If controls is set to
help
, all available controls and their valid ranges are printed.- sample_rate, s
Specify the sample rate, default to 44100. Only used if plugin have zero inputs.
- nb_samples, n
Set the number of samples per channel per each output frame, default is 1024. Only used if plugin have zero inputs.
- duration, d
Set the minimum duration of the sourced audio. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. Note that the resulting duration may be greater than the specified duration, as the generated audio is always cut at the end of a complete frame. If not specified, or the expressed duration is negative, the audio is supposed to be generated forever. Only used if plugin have zero inputs.
29.99.1 Examples
- Apply bass enhancer plugin from Calf:
lv2=p=http\\\\://calf.sourceforge.net/plugins/BassEnhancer:c=amount=2
- Apply vinyl plugin from Calf:
lv2=p=http\\\\://calf.sourceforge.net/plugins/Vinyl:c=drone=0.2|aging=0.5
- Apply bit crusher plugin from ArtyFX:
lv2=p=http\\\\://www.openavproductions.com/artyfx#bitta:c=crush=0.3
29.99.2 Commands
This filter supports all options that are exported by plugin as commands.
29.100 mcompand
Multiband Compress or expand the audio’s dynamic range.
The input audio is divided into bands using 4th order Linkwitz-Riley IIRs. This is akin to the crossover of a loudspeaker, and results in flat frequency response when absent compander action.
It accepts the following parameters:
- args
This option syntax is: attack,decay,[attack,decay..] soft-knee points crossover_frequency [delay [initial_volume [gain]]] | attack,decay ... For explanation of each item refer to compand filter documentation.
29.101 pan
Mix channels with specific gain levels. The filter accepts the output channel layout followed by a set of channels definitions.
This filter is also designed to efficiently remap the channels of an audio stream.
The filter accepts parameters of the form: "l|outdef|outdef|..."
- l
output channel layout or number of channels
- outdef
output channel specification, of the form: "out_name=[gain*]in_name[(+-)[gain*]in_name...]"
- out_name
output channel to define, either a channel name (FL, FR, etc.) or a channel number (c0, c1, etc.)
- gain
multiplicative coefficient for the channel, 1 leaving the volume unchanged
- in_name
input channel to use, see out_name for details; it is not possible to mix named and numbered input channels
If the ‘=’ in a channel specification is replaced by ‘<’, then the gains for that specification will be renormalized so that the total is 1, thus avoiding clipping noise.
29.101.1 Mixing examples
For example, if you want to down-mix from stereo to mono, but with a bigger factor for the left channel:
pan=1c|c0=0.9*c0+0.1*c1
A customized down-mix to stereo that works automatically for 3-, 4-, 5- and 7-channels surround:
pan=stereo| FL < FL + 0.5*FC + 0.6*BL + 0.6*SL | FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
Note that ffmpeg
integrates a default down-mix (and up-mix) system
that should be preferred (see "-ac" option) unless you have very specific
needs.
29.101.2 Remapping examples
The channel remapping will be effective if, and only if:
- gain coefficients are zeroes or ones,
- only one input per channel output,
If all these conditions are satisfied, the filter will notify the user ("Pure channel mapping detected"), and use an optimized and lossless method to do the remapping.
For example, if you have a 5.1 source and want a stereo audio stream by dropping the extra channels:
pan="stereo| c0=FL | c1=FR"
Given the same source, you can also switch front left and front right channels and keep the input channel layout:
pan="5.1| c0=c1 | c1=c0 | c2=c2 | c3=c3 | c4=c4 | c5=c5"
If the input is a stereo audio stream, you can mute the front left channel (and still keep the stereo channel layout) with:
pan="stereo|c1=c1"
Still with a stereo audio stream input, you can copy the right channel in both front left and right:
pan="stereo| c0=FR | c1=FR"
29.102 replaygain
ReplayGain scanner filter. This filter takes an audio stream as an input and
outputs it unchanged.
At end of filtering it displays track_gain
and track_peak
.
The filter accepts the following exported read-only options:
- track_gain
Exported track gain in dB at end of stream.
- track_peak
Exported track peak at end of stream.
29.103 resample
Convert the audio sample format, sample rate and channel layout. It is not meant to be used directly.
29.104 rubberband
Apply time-stretching and pitch-shifting with librubberband.
To enable compilation of this filter, you need to configure FFmpeg with
--enable-librubberband
.
The filter accepts the following options:
- tempo
Set tempo scale factor.
- pitch
Set pitch scale factor.
- transients
Set transients detector. Possible values are:
- crisp
- mixed
- smooth
- detector
Set detector. Possible values are:
- compound
- percussive
- soft
- phase
Set phase. Possible values are:
- laminar
- independent
- window
Set processing window size. Possible values are:
- standard
- short
- long
- smoothing
Set smoothing. Possible values are:
- off
- on
- formant
Enable formant preservation when shift pitching. Possible values are:
- shifted
- preserved
- pitchq
Set pitch quality. Possible values are:
- quality
- speed
- consistency
- channels
Set channels. Possible values are:
- apart
- together
29.104.1 Commands
This filter supports the following commands:
- tempo
Change filter tempo scale factor. Syntax for the command is : "tempo"
- pitch
Change filter pitch scale factor. Syntax for the command is : "pitch"
29.105 sidechaincompress
This filter acts like normal compressor but has the ability to compress detected signal using second input signal. It needs two input streams and returns one output stream. First input stream will be processed depending on second stream signal. The filtered signal then can be filtered with other filters in later stages of processing. See pan and amerge filter.
The filter accepts the following options:
- level_in
Set input gain. Default is 1. Range is between 0.015625 and 64.
- mode
Set mode of compressor operation. Can be
upward
ordownward
. Default isdownward
.- threshold
If a signal of second stream raises above this level it will affect the gain reduction of first stream. By default is 0.125. Range is between 0.00097563 and 1.
- ratio
Set a ratio about which the signal is reduced. 1:2 means that if the level raised 4dB above the threshold, it will be only 2dB above after the reduction. Default is 2. Range is between 1 and 20.
- attack
Amount of milliseconds the signal has to rise above the threshold before gain reduction starts. Default is 20. Range is between 0.01 and 2000.
- release
Amount of milliseconds the signal has to fall below the threshold before reduction is decreased again. Default is 250. Range is between 0.01 and 9000.
- makeup
Set the amount by how much signal will be amplified after processing. Default is 1. Range is from 1 to 64.
- knee
Curve the sharp knee around the threshold to enter gain reduction more softly. Default is 2.82843. Range is between 1 and 8.
- link
Choose if the
average
level between all channels of side-chain stream or the louder(maximum
) channel of side-chain stream affects the reduction. Default isaverage
.- detection
Should the exact signal be taken in case of
peak
or an RMS one in case ofrms
. Default isrms
which is mainly smoother.- level_sc
Set sidechain gain. Default is 1. Range is between 0.015625 and 64.
- mix
How much to use compressed signal in output. Default is 1. Range is between 0 and 1.
29.105.1 Commands
This filter supports the all above options as commands.
29.105.2 Examples
- Full ffmpeg example taking 2 audio inputs, 1st input to be compressed
depending on the signal of 2nd input and later compressed signal to be
merged with 2nd input:
ffmpeg -i main.flac -i sidechain.flac -filter_complex "[1:a]asplit=2[sc][mix];[0:a][sc]sidechaincompress[compr];[compr][mix]amerge"
29.106 sidechaingate
A sidechain gate acts like a normal (wideband) gate but has the ability to filter the detected signal before sending it to the gain reduction stage. Normally a gate uses the full range signal to detect a level above the threshold. For example: If you cut all lower frequencies from your sidechain signal the gate will decrease the volume of your track only if not enough highs appear. With this technique you are able to reduce the resonation of a natural drum or remove "rumbling" of muted strokes from a heavily distorted guitar. It needs two input streams and returns one output stream. First input stream will be processed depending on second stream signal.
The filter accepts the following options:
- level_in
Set input level before filtering. Default is 1. Allowed range is from 0.015625 to 64.
- mode
Set the mode of operation. Can be
upward
ordownward
. Default isdownward
. If set toupward
mode, higher parts of signal will be amplified, expanding dynamic range in upward direction. Otherwise, in case ofdownward
lower parts of signal will be reduced.- range
Set the level of gain reduction when the signal is below the threshold. Default is 0.06125. Allowed range is from 0 to 1. Setting this to 0 disables reduction and then filter behaves like expander.
- threshold
If a signal rises above this level the gain reduction is released. Default is 0.125. Allowed range is from 0 to 1.
- ratio
Set a ratio about which the signal is reduced. Default is 2. Allowed range is from 1 to 9000.
- attack
Amount of milliseconds the signal has to rise above the threshold before gain reduction stops. Default is 20 milliseconds. Allowed range is from 0.01 to 9000.
- release
Amount of milliseconds the signal has to fall below the threshold before the reduction is increased again. Default is 250 milliseconds. Allowed range is from 0.01 to 9000.
- makeup
Set amount of amplification of signal after processing. Default is 1. Allowed range is from 1 to 64.
- knee
Curve the sharp knee around the threshold to enter gain reduction more softly. Default is 2.828427125. Allowed range is from 1 to 8.
- detection
Choose if exact signal should be taken for detection or an RMS like one. Default is rms. Can be peak or rms.
- link
Choose if the average level between all channels or the louder channel affects the reduction. Default is average. Can be average or maximum.
- level_sc
Set sidechain gain. Default is 1. Range is from 0.015625 to 64.
29.106.1 Commands
This filter supports the all above options as commands.
29.107 silencedetect
Detect silence in an audio stream.
This filter logs a message when it detects that the input audio volume is less or equal to a noise tolerance value for a duration greater or equal to the minimum detected noise duration.
The printed times and duration are expressed in seconds. The
lavfi.silence_start
or lavfi.silence_start.X
metadata key
is set on the first frame whose timestamp equals or exceeds the detection
duration and it contains the timestamp of the first frame of the silence.
The lavfi.silence_duration
or lavfi.silence_duration.X
and lavfi.silence_end
or lavfi.silence_end.X
metadata
keys are set on the first frame after the silence. If mono is
enabled, and each channel is evaluated separately, the .X
suffixed keys are used, and X
corresponds to the channel number.
The filter accepts the following options:
- noise, n
Set noise tolerance. Can be specified in dB (in case "dB" is appended to the specified value) or amplitude ratio. Default is -60dB, or 0.001.
- duration, d
Set silence duration until notification (default is 2 seconds). See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax.
- mono, m
Process each channel separately, instead of combined. By default is disabled.
29.107.1 Examples
- Detect 5 seconds of silence with -50dB noise tolerance:
silencedetect=n=-50dB:d=5
- Complete example with
ffmpeg
to detect silence with 0.0001 noise tolerance in silence.mp3:ffmpeg -i silence.mp3 -af silencedetect=noise=0.0001 -f null -
29.108 silenceremove
Remove silence from the beginning, middle or end of the audio.
The filter accepts the following options:
- start_periods
This value is used to indicate if audio should be trimmed at beginning of the audio. A value of zero indicates no silence should be trimmed from the beginning. When specifying a non-zero value, it trims audio up until it finds non-silence. Normally, when trimming silence from beginning of audio the start_periods will be
1
but it can be increased to higher values to trim all audio up to specific count of non-silence periods. Default value is0
.- start_duration
Specify the amount of time that non-silence must be detected before it stops trimming audio. By increasing the duration, bursts of noises can be treated as silence and trimmed off. Default value is
0
.- start_threshold
This indicates what sample value should be treated as silence. For digital audio, a value of
0
may be fine but for audio recorded from analog, you may wish to increase the value to account for background noise. Can be specified in dB (in case "dB" is appended to the specified value) or amplitude ratio. Default value is0
.- start_silence
Specify max duration of silence at beginning that will be kept after trimming. Default is 0, which is equal to trimming all samples detected as silence.
- start_mode
Specify mode of detection of silence end at start of multi-channel audio. Can be any or all. Default is any. With any, any sample from any channel that is detected as non-silence will trigger end of silence trimming at start of audio stream. With all, only if every sample from every channel is detected as non-silence will trigger end of silence trimming at start of audio stream, limited usage.
- stop_periods
Set the count for trimming silence from the end of audio. When specifying a positive value, it trims audio after it finds specified silence period. To remove silence from the middle of a file, specify a stop_periods that is negative. This value is then treated as a positive value and is used to indicate the effect should restart processing as specified by stop_periods, making it suitable for removing periods of silence in the middle of the audio. Default value is
0
.- stop_duration
Specify a duration of silence that must exist before audio is not copied any more. By specifying a higher duration, silence that is wanted can be left in the audio. Default value is
0
.- stop_threshold
This is the same as start_threshold but for trimming silence from the end of audio. Can be specified in dB (in case "dB" is appended to the specified value) or amplitude ratio. Default value is
0
.- stop_silence
Specify max duration of silence at end that will be kept after trimming. Default is 0, which is equal to trimming all samples detected as silence.
- stop_mode
Specify mode of detection of silence start after start of multi-channel audio. Can be any or all. Default is all. With any, any sample from any channel that is detected as silence will trigger start of silence trimming after start of audio stream, limited usage. With all, only if every sample from every channel is detected as silence will trigger start of silence trimming after start of audio stream.
- detection
Set how is silence detected.
- avg
Mean of absolute values of samples in moving window.
- rms
Root squared mean of absolute values of samples in moving window.
- peak
Maximum of absolute values of samples in moving window.
- median
Median of absolute values of samples in moving window.
- ptp
Absolute of max peak to min peak difference of samples in moving window.
- dev
Standard deviation of values of samples in moving window.
Default value is
rms
.- window
Set duration in number of seconds used to calculate size of window in number of samples for detecting silence. Using
0
will effectively disable any windowing and use only single sample per channel for silence detection. In that case it may be needed to also set start_silence and/or stop_silence to nonzero values with also start_duration and/or stop_duration to nonzero values. Default value is0.02
. Allowed range is from0
to10
.- timestamp
Set processing mode of every audio frame output timestamp.
- write
Full timestamps rewrite, keep only the start time for the first output frame.
- copy
Non-dropped frames are left with same timestamp as input audio frame.
Defaults value is
write
.
29.108.1 Examples
- The following example shows how this filter can be used to start a recording
that does not contain the delay at the start which usually occurs between
pressing the record button and the start of the performance:
silenceremove=start_periods=1:start_duration=5:start_threshold=0.02
- Trim all silence encountered from beginning to end where there is more than 1
second of silence in audio:
silenceremove=stop_periods=-1:stop_duration=1:stop_threshold=-90dB
- Trim all digital silence samples, using peak detection, from beginning to end
where there is more than 0 samples of digital silence in audio and digital
silence is detected in all channels at same positions in stream:
silenceremove=window=0:detection=peak:stop_mode=all:start_mode=all:stop_periods=-1:stop_threshold=0
- Trim every 2nd encountered silence period from beginning to end where there is
more than 1 second of silence per silence period in audio:
silenceremove=stop_periods=-2:stop_duration=1:stop_threshold=-90dB
- Similar as above, but keep maximum of 0.5 seconds of silence from each trimmed period:
silenceremove=stop_periods=-2:stop_duration=1:stop_threshold=-90dB:stop_silence=0.5
- Similar as above, but keep maximum of 1.5 seconds of silence from start of audio:
silenceremove=stop_periods=-2:stop_duration=1:stop_threshold=-90dB:stop_silence=0.5:start_periods=1:start_duration=1:start_silence=1.5:stop_threshold=-90dB
29.108.2 Commands
This filter supports some above options as commands.
29.109 sofalizer
SOFAlizer uses head-related transfer functions (HRTFs) to create virtual loudspeakers around the user for binaural listening via headphones (audio formats up to 9 channels supported). The HRTFs are stored in SOFA files (see http://www.sofacoustics.org/ for a database). SOFAlizer is developed at the Acoustics Research Institute (ARI) of the Austrian Academy of Sciences.
To enable compilation of this filter you need to configure FFmpeg with
--enable-libmysofa
.
The filter accepts the following options:
- sofa
Set the SOFA file used for rendering.
- gain
Set gain applied to audio. Value is in dB. Default is 0.
- rotation
Set rotation of virtual loudspeakers in deg. Default is 0.
- elevation
Set elevation of virtual speakers in deg. Default is 0.
- radius
Set distance in meters between loudspeakers and the listener with near-field HRTFs. Default is 1.
- type
Set processing type. Can be time or freq. time is processing audio in time domain which is slow. freq is processing audio in frequency domain which is fast. Default is freq.
- speakers
Set custom positions of virtual loudspeakers. Syntax for this option is: <CH> <AZIM> <ELEV>[|<CH> <AZIM> <ELEV>|...]. Each virtual loudspeaker is described with short channel name following with azimuth and elevation in degrees. Each virtual loudspeaker description is separated by ’|’. For example to override front left and front right channel positions use: ’speakers=FL 45 15|FR 345 15’. Descriptions with unrecognised channel names are ignored.
- lfegain
Set custom gain for LFE channels. Value is in dB. Default is 0.
- framesize
Set custom frame size in number of samples. Default is 1024. Allowed range is from 1024 to 96000. Only used if option ‘type’ is set to freq.
- normalize
Should all IRs be normalized upon importing SOFA file. By default is enabled.
- interpolate
Should nearest IRs be interpolated with neighbor IRs if exact position does not match. By default is disabled.
- minphase
Minphase all IRs upon loading of SOFA file. By default is disabled.
- anglestep
Set neighbor search angle step. Only used if option interpolate is enabled.
- radstep
Set neighbor search radius step. Only used if option interpolate is enabled.
29.109.1 Examples
- Using ClubFritz6 sofa file:
sofalizer=sofa=/path/to/ClubFritz6.sofa:type=freq:radius=1
- Using ClubFritz12 sofa file and bigger radius with small rotation:
sofalizer=sofa=/path/to/ClubFritz12.sofa:type=freq:radius=2:rotation=5
- Similar as above but with custom speaker positions for front left, front right, back left and back right
and also with custom gain:
"sofalizer=sofa=/path/to/ClubFritz6.sofa:type=freq:radius=2:speakers=FL 45|FR 315|BL 135|BR 225:gain=28"
29.110 speechnorm
Speech Normalizer.
This filter expands or compresses each half-cycle of audio samples (local set of samples all above or all below zero and between two nearest zero crossings) depending on threshold value, so audio reaches target peak value under conditions controlled by below options.
The filter accepts the following options:
- peak, p
Set the expansion target peak value. This specifies the highest allowed absolute amplitude level for the normalized audio input. Default value is 0.95. Allowed range is from 0.0 to 1.0.
- expansion, e
Set the maximum expansion factor. Allowed range is from 1.0 to 50.0. Default value is 2.0. This option controls maximum local half-cycle of samples expansion. The maximum expansion would be such that local peak value reaches target peak value but never to surpass it and that ratio between new and previous peak value does not surpass this option value.
- compression, c
Set the maximum compression factor. Allowed range is from 1.0 to 50.0. Default value is 2.0. This option controls maximum local half-cycle of samples compression. This option is used only if threshold option is set to value greater than 0.0, then in such cases when local peak is lower or same as value set by threshold all samples belonging to that peak’s half-cycle will be compressed by current compression factor.
- threshold, t
Set the threshold value. Default value is 0.0. Allowed range is from 0.0 to 1.0. This option specifies which half-cycles of samples will be compressed and which will be expanded. Any half-cycle samples with their local peak value below or same as this option value will be compressed by current compression factor, otherwise, if greater than threshold value they will be expanded with expansion factor so that it could reach peak target value but never surpass it.
- raise, r
Set the expansion raising amount per each half-cycle of samples. Default value is 0.001. Allowed range is from 0.0 to 1.0. This controls how fast expansion factor is raised per each new half-cycle until it reaches expansion value. Setting this options too high may lead to distortions.
- fall, f
Set the compression raising amount per each half-cycle of samples. Default value is 0.001. Allowed range is from 0.0 to 1.0. This controls how fast compression factor is raised per each new half-cycle until it reaches compression value.
- channels, h
Specify which channels to filter, by default all available channels are filtered.
- invert, i
Enable inverted filtering, by default is disabled. This inverts interpretation of threshold option. When enabled any half-cycle of samples with their local peak value below or same as threshold option will be expanded otherwise it will be compressed.
- link, l
Link channels when calculating gain applied to each filtered channel sample, by default is disabled. When disabled each filtered channel gain calculation is independent, otherwise when this option is enabled the minimum of all possible gains for each filtered channel is used.
- rms, m
Set the expansion target RMS value. This specifies the highest allowed RMS level for the normalized audio input. Default value is 0.0, thus disabled. Allowed range is from 0.0 to 1.0.
29.110.1 Commands
This filter supports the all above options as commands.
29.110.2 Examples
- Weak and slow amplification:
speechnorm=e=3:r=0.00001:l=1
- Moderate and slow amplification:
speechnorm=e=6.25:r=0.00001:l=1
- Strong and fast amplification:
speechnorm=e=12.5:r=0.0001:l=1
- Very strong and fast amplification:
speechnorm=e=25:r=0.0001:l=1
- Extreme and fast amplification:
speechnorm=e=50:r=0.0001:l=1
29.111 stereotools
This filter has some handy utilities to manage stereo signals, for converting M/S stereo recordings to L/R signal while having control over the parameters or spreading the stereo image of master track.
The filter accepts the following options:
- level_in
Set input level before filtering for both channels. Defaults is 1. Allowed range is from 0.015625 to 64.
- level_out
Set output level after filtering for both channels. Defaults is 1. Allowed range is from 0.015625 to 64.
- balance_in
Set input balance between both channels. Default is 0. Allowed range is from -1 to 1.
- balance_out
Set output balance between both channels. Default is 0. Allowed range is from -1 to 1.
- softclip
Enable softclipping. Results in analog distortion instead of harsh digital 0dB clipping. Disabled by default.
- mutel
Mute the left channel. Disabled by default.
- muter
Mute the right channel. Disabled by default.
- phasel
Change the phase of the left channel. Disabled by default.
- phaser
Change the phase of the right channel. Disabled by default.
- mode
Set stereo mode. Available values are:
- ‘lr>lr’
Left/Right to Left/Right, this is default.
- ‘lr>ms’
Left/Right to Mid/Side.
- ‘ms>lr’
Mid/Side to Left/Right.
- ‘lr>ll’
Left/Right to Left/Left.
- ‘lr>rr’
Left/Right to Right/Right.
- ‘lr>l+r’
Left/Right to Left + Right.
- ‘lr>rl’
Left/Right to Right/Left.
- ‘ms>ll’
Mid/Side to Left/Left.
- ‘ms>rr’
Mid/Side to Right/Right.
- ‘ms>rl’
Mid/Side to Right/Left.
- ‘lr>l-r’
Left/Right to Left - Right.
- slev
Set level of side signal. Default is 1. Allowed range is from 0.015625 to 64.
- sbal
Set balance of side signal. Default is 0. Allowed range is from -1 to 1.
- mlev
Set level of the middle signal. Default is 1. Allowed range is from 0.015625 to 64.
- mpan
Set middle signal pan. Default is 0. Allowed range is from -1 to 1.
- base
Set stereo base between mono and inversed channels. Default is 0. Allowed range is from -1 to 1.
- delay
Set delay in milliseconds how much to delay left from right channel and vice versa. Default is 0. Allowed range is from -20 to 20.
- sclevel
Set S/C level. Default is 1. Allowed range is from 1 to 100.
- phase
Set the stereo phase in degrees. Default is 0. Allowed range is from 0 to 360.
- bmode_in, bmode_out
Set balance mode for balance_in/balance_out option.
Can be one of the following:
- ‘balance’
Classic balance mode. Attenuate one channel at time. Gain is raised up to 1.
- ‘amplitude’
Similar as classic mode above but gain is raised up to 2.
- ‘power’
Equal power distribution, from -6dB to +6dB range.
29.111.1 Commands
This filter supports the all above options as commands.
29.111.2 Examples
- Apply karaoke like effect:
stereotools=mlev=0.015625
- Convert M/S signal to L/R:
"stereotools=mode=ms>lr"
29.112 stereowiden
This filter enhance the stereo effect by suppressing signal common to both channels and by delaying the signal of left into right and vice versa, thereby widening the stereo effect.
The filter accepts the following options:
- delay
Time in milliseconds of the delay of left signal into right and vice versa. Default is 20 milliseconds.
- feedback
Amount of gain in delayed signal into right and vice versa. Gives a delay effect of left signal in right output and vice versa which gives widening effect. Default is 0.3.
- crossfeed
Cross feed of left into right with inverted phase. This helps in suppressing the mono. If the value is 1 it will cancel all the signal common to both channels. Default is 0.3.
- drymix
Set level of input signal of original channel. Default is 0.8.
29.112.1 Commands
This filter supports the all above options except delay
as commands.
29.113 superequalizer
Apply 18 band equalizer.
The filter accepts the following options:
- 1b
Set 65Hz band gain.
- 2b
Set 92Hz band gain.
- 3b
Set 131Hz band gain.
- 4b
Set 185Hz band gain.
- 5b
Set 262Hz band gain.
- 6b
Set 370Hz band gain.
- 7b
Set 523Hz band gain.
- 8b
Set 740Hz band gain.
- 9b
Set 1047Hz band gain.
- 10b
Set 1480Hz band gain.
- 11b
Set 2093Hz band gain.
- 12b
Set 2960Hz band gain.
- 13b
Set 4186Hz band gain.
- 14b
Set 5920Hz band gain.
- 15b
Set 8372Hz band gain.
- 16b
Set 11840Hz band gain.
- 17b
Set 16744Hz band gain.
- 18b
Set 20000Hz band gain.
29.114 surround
Apply audio surround upmix filter.
This filter allows to produce multichannel output from audio stream.
The filter accepts the following options:
- chl_out
Set output channel layout. By default, this is 5.1.
See (ffmpeg-utils)the Channel Layout section in the ffmpeg-utils(1) manual for the required syntax.
- chl_in
Set input channel layout. By default, this is stereo.
See (ffmpeg-utils)the Channel Layout section in the ffmpeg-utils(1) manual for the required syntax.
- level_in
Set input volume level. By default, this is 1.
- level_out
Set output volume level. By default, this is 1.
- lfe
Enable LFE channel output if output channel layout has it. By default, this is enabled.
- lfe_low
Set LFE low cut off frequency. By default, this is 128 Hz.
- lfe_high
Set LFE high cut off frequency. By default, this is 256 Hz.
- lfe_mode
Set LFE mode, can be add or sub. Default is add. In add mode, LFE channel is created from input audio and added to output. In sub mode, LFE channel is created from input audio and added to output but also all non-LFE output channels are subtracted with output LFE channel.
- smooth
Set temporal smoothness strength, used to gradually change factors when transforming stereo sound in time. Allowed range is from 0.0 to 1.0. Useful to improve output quality with focus option values greater than 0.0. Default is 0.0. Only values inside this range and without edges are effective.
- angle
Set angle of stereo surround transform, Allowed range is from 0 to 360. Default is 90.
- focus
Set focus of stereo surround transform, Allowed range is from -1 to 1. Default is 0.
- fc_in
Set front center input volume. By default, this is 1.
- fc_out
Set front center output volume. By default, this is 1.
- fl_in
Set front left input volume. By default, this is 1.
- fl_out
Set front left output volume. By default, this is 1.
- fr_in
Set front right input volume. By default, this is 1.
- fr_out
Set front right output volume. By default, this is 1.
- sl_in
Set side left input volume. By default, this is 1.
- sl_out
Set side left output volume. By default, this is 1.
- sr_in
Set side right input volume. By default, this is 1.
- sr_out
Set side right output volume. By default, this is 1.
- bl_in
Set back left input volume. By default, this is 1.
- bl_out
Set back left output volume. By default, this is 1.
- br_in
Set back right input volume. By default, this is 1.
- br_out
Set back right output volume. By default, this is 1.
- bc_in
Set back center input volume. By default, this is 1.
- bc_out
Set back center output volume. By default, this is 1.
- lfe_in
Set LFE input volume. By default, this is 1.
- lfe_out
Set LFE output volume. By default, this is 1.
- allx
Set spread usage of stereo image across X axis for all channels. Allowed range is from -1 to 15. By default this value is negative -1, and thus unused.
- ally
Set spread usage of stereo image across Y axis for all channels. Allowed range is from -1 to 15. By default this value is negative -1, and thus unused.
- fcx, flx, frx, blx, brx, slx, srx, bcx
Set spread usage of stereo image across X axis for each channel. Allowed range is from 0.06 to 15. By default this value is 0.5.
- fcy, fly, fry, bly, bry, sly, sry, bcy
Set spread usage of stereo image across Y axis for each channel. Allowed range is from 0.06 to 15. By default this value is 0.5.
- win_size
Set window size. Allowed range is from 1024 to 65536. Default size is 4096.
- win_func
Set window function.
It accepts the following values:
- ‘rect’
- ‘bartlett’
- ‘hann, hanning’
- ‘hamming’
- ‘blackman’
- ‘welch’
- ‘flattop’
- ‘bharris’
- ‘bnuttall’
- ‘bhann’
- ‘sine’
- ‘nuttall’
- ‘lanczos’
- ‘gauss’
- ‘tukey’
- ‘dolph’
- ‘cauchy’
- ‘parzen’
- ‘poisson’
- ‘bohman’
- ‘kaiser’
Default is
hann
.- overlap
Set window overlap. If set to 1, the recommended overlap for selected window function will be picked. Default is
0.5
.
29.115 tiltshelf
Boost or cut the lower frequencies and cut or boost higher frequencies of the audio using a two-pole shelving filter with a response similar to that of a standard hi-fi’s tone-controls. This is also known as shelving equalisation (EQ).
The filter accepts the following options:
- gain, g
Give the gain at 0 Hz. Its useful range is about -20 (for a large cut) to +20 (for a large boost). Beware of clipping when using a positive gain.
- frequency, f
Set the filter’s central frequency and so can be used to extend or reduce the frequency range to be boosted or cut. The default value is
3000
Hz.- width_type, t
Set method to specify band-width of filter.
- h
Hz
- q
Q-Factor
- o
octave
- s
slope
- k
kHz
- width, w
Determine how steep is the filter’s shelf transition.
- poles, p
Set number of poles. Default is 2.
- mix, m
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- channels, c
Specify which channels to filter, by default all available are filtered.
- normalize, n
Normalize biquad coefficients, by default is disabled. Enabling it will normalize magnitude response at DC to 0dB.
- transform, a
Set transform type of IIR filter.
- di
- dii
- tdi
- tdii
- latt
- svf
- zdf
- precision, r
Set precision of filtering.
- auto
Pick automatic sample format depending on surround filters.
- s16
Always use signed 16-bit.
- s32
Always use signed 32-bit.
- f32
Always use float 32-bit.
- f64
Always use float 64-bit.
- block_size, b
Set block size used for reverse IIR processing. If this value is set to high enough value (higher than impulse response length truncated when reaches near zero values) filtering will become linear phase otherwise if not big enough it will just produce nasty artifacts.
Note that filter delay will be exactly this many samples when set to non-zero value.
29.115.1 Commands
This filter supports some options as commands.
29.116 treble, highshelf
Boost or cut treble (upper) frequencies of the audio using a two-pole shelving filter with a response similar to that of a standard hi-fi’s tone-controls. This is also known as shelving equalisation (EQ).
The filter accepts the following options:
- gain, g
Give the gain at whichever is the lower of ~22 kHz and the Nyquist frequency. Its useful range is about -20 (for a large cut) to +20 (for a large boost). Beware of clipping when using a positive gain.
- frequency, f
Set the filter’s central frequency and so can be used to extend or reduce the frequency range to be boosted or cut. The default value is
3000
Hz.- width_type, t
Set method to specify band-width of filter.
- h
Hz
- q
Q-Factor
- o
octave
- s
slope
- k
kHz
- width, w
Determine how steep is the filter’s shelf transition.
- poles, p
Set number of poles. Default is 2.
- mix, m
How much to use filtered signal in output. Default is 1. Range is between 0 and 1.
- channels, c
Specify which channels to filter, by default all available are filtered.
- normalize, n
Normalize biquad coefficients, by default is disabled. Enabling it will normalize magnitude response at DC to 0dB.
- transform, a
Set transform type of IIR filter.
- di
- dii
- tdi
- tdii
- latt
- svf
- zdf
- precision, r
Set precision of filtering.
- auto
Pick automatic sample format depending on surround filters.
- s16
Always use signed 16-bit.
- s32
Always use signed 32-bit.
- f32
Always use float 32-bit.
- f64
Always use float 64-bit.
- block_size, b
Set block size used for reverse IIR processing. If this value is set to high enough value (higher than impulse response length truncated when reaches near zero values) filtering will become linear phase otherwise if not big enough it will just produce nasty artifacts.
Note that filter delay will be exactly this many samples when set to non-zero value.
29.116.1 Commands
This filter supports the following commands:
- frequency, f
Change treble frequency. Syntax for the command is : "frequency"
- width_type, t
Change treble width_type. Syntax for the command is : "width_type"
- width, w
Change treble width. Syntax for the command is : "width"
- gain, g
Change treble gain. Syntax for the command is : "gain"
- mix, m
Change treble mix. Syntax for the command is : "mix"
29.117 tremolo
Sinusoidal amplitude modulation.
The filter accepts the following options:
- f
Modulation frequency in Hertz. Modulation frequencies in the subharmonic range (20 Hz or lower) will result in a tremolo effect. This filter may also be used as a ring modulator by specifying a modulation frequency higher than 20 Hz. Range is 0.1 - 20000.0. Default value is 5.0 Hz.
- d
Depth of modulation as a percentage. Range is 0.0 - 1.0. Default value is 0.5.
29.118 vibrato
Sinusoidal phase modulation.
The filter accepts the following options:
- f
Modulation frequency in Hertz. Range is 0.1 - 20000.0. Default value is 5.0 Hz.
- d
Depth of modulation as a percentage. Range is 0.0 - 1.0. Default value is 0.5.
29.119 virtualbass
Apply audio Virtual Bass filter.
This filter accepts stereo input and produce stereo with LFE (2.1) channels output. The newly produced LFE channel have enhanced virtual bass originally obtained from both stereo channels. This filter outputs front left and front right channels unchanged as available in stereo input.
The filter accepts the following options:
- cutoff
Set the virtual bass cutoff frequency. Default value is 250 Hz. Allowed range is from 100 to 500 Hz.
- strength
Set the virtual bass strength. Allowed range is from 0.5 to 3. Default value is 3.
29.120 volume
Adjust the input audio volume.
It accepts the following parameters:
- volume
Set audio volume expression.
Output values are clipped to the maximum value.
The output audio volume is given by the relation:
output_volume = volume * input_volume
The default value for volume is "1.0".
- precision
This parameter represents the mathematical precision.
It determines which input sample formats will be allowed, which affects the precision of the volume scaling.
- fixed
8-bit fixed-point; this limits input sample format to U8, S16, and S32.
- float
32-bit floating-point; this limits input sample format to FLT. (default)
- double
64-bit floating-point; this limits input sample format to DBL.
- replaygain
Choose the behaviour on encountering ReplayGain side data in input frames.
- drop
Remove ReplayGain side data, ignoring its contents (the default).
- ignore
Ignore ReplayGain side data, but leave it in the frame.
- track
Prefer the track gain, if present.
- album
Prefer the album gain, if present.
- replaygain_preamp
Pre-amplification gain in dB to apply to the selected replaygain gain.
Default value for replaygain_preamp is 0.0.
- replaygain_noclip
Prevent clipping by limiting the gain applied.
Default value for replaygain_noclip is 1.
- eval
Set when the volume expression is evaluated.
It accepts the following values:
- ‘once’
only evaluate expression once during the filter initialization, or when the ‘volume’ command is sent
- ‘frame’
evaluate expression for each incoming frame
Default value is ‘once’.
The volume expression can contain the following parameters.
- n
frame number (starting at zero)
- nb_channels
number of channels
- nb_consumed_samples
number of samples consumed by the filter
- nb_samples
number of samples in the current frame
- pos
original frame position in the file; deprecated, do not use
- pts
frame PTS
- sample_rate
sample rate
- startpts
PTS at start of stream
- startt
time at start of stream
- t
frame time
- tb
timestamp timebase
- volume
last set volume value
Note that when eval is set to ‘once’ only the sample_rate and tb variables are available, all other variables will evaluate to NAN.
29.120.1 Commands
This filter supports the following commands:
- volume
Modify the volume expression. The command accepts the same syntax of the corresponding option.
If the specified expression is not valid, it is kept at its current value.
29.120.2 Examples
- Halve the input audio volume:
volume=volume=0.5 volume=volume=1/2 volume=volume=-6.0206dB
In all the above example the named key for volume can be omitted, for example like in:
volume=0.5
- Increase input audio power by 6 decibels using fixed-point precision:
volume=volume=6dB:precision=fixed
- Fade volume after time 10 with an annihilation period of 5 seconds:
volume='if(lt(t,10),1,max(1-(t-10)/5,0))':eval=frame
29.121 volumedetect
Detect the volume of the input video.
The filter has no parameters. It supports only 16-bit signed integer samples, so the input will be converted when needed. Statistics about the volume will be printed in the log when the input stream end is reached.
In particular it will show the mean volume (root mean square), maximum volume (on a per-sample basis), and the beginning of a histogram of the registered volume values (from the maximum value to a cumulated 1/1000 of the samples).
All volumes are in decibels relative to the maximum PCM value.
29.121.1 Examples
Here is an excerpt of the output:
[Parsed_volumedetect_0 0xa23120] mean_volume: -27 dB [Parsed_volumedetect_0 0xa23120] max_volume: -4 dB [Parsed_volumedetect_0 0xa23120] histogram_4db: 6 [Parsed_volumedetect_0 0xa23120] histogram_5db: 62 [Parsed_volumedetect_0 0xa23120] histogram_6db: 286 [Parsed_volumedetect_0 0xa23120] histogram_7db: 1042 [Parsed_volumedetect_0 0xa23120] histogram_8db: 2551 [Parsed_volumedetect_0 0xa23120] histogram_9db: 4609 [Parsed_volumedetect_0 0xa23120] histogram_10db: 8409
It means that:
- The mean square energy is approximately -27 dB, or 10^-2.7.
- The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
- There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.
In other words, raising the volume by +4 dB does not cause any clipping, raising it by +5 dB causes clipping for 6 samples, etc.
30 Audio Sources
Below is a description of the currently available audio sources.
30.1 abuffer
Buffer audio frames, and make them available to the filter chain.
This source is mainly intended for a programmatic use, in particular through the interface defined in libavfilter/buffersrc.h.
It accepts the following parameters:
- time_base
The timebase which will be used for timestamps of submitted frames. It must be either a floating-point number or in numerator/denominator form.
- sample_rate
The sample rate of the incoming audio buffers.
- sample_fmt
The sample format of the incoming audio buffers. Either a sample format name or its corresponding integer representation from the enum AVSampleFormat in libavutil/samplefmt.h
- channel_layout
The channel layout of the incoming audio buffers. Either a channel layout name from channel_layout_map in libavutil/channel_layout.c or its corresponding integer representation from the AV_CH_LAYOUT_* macros in libavutil/channel_layout.h
- channels
The number of channels of the incoming audio buffers. If both channels and channel_layout are specified, then they must be consistent.
30.1.1 Examples
abuffer=sample_rate=44100:sample_fmt=s16p:channel_layout=stereo
will instruct the source to accept planar 16bit signed stereo at 44100Hz. Since the sample format with name "s16p" corresponds to the number 6 and the "stereo" channel layout corresponds to the value 0x3, this is equivalent to:
abuffer=sample_rate=44100:sample_fmt=6:channel_layout=0x3
30.2 aevalsrc
Generate an audio signal specified by an expression.
This source accepts in input one or more expressions (one for each channel), which are evaluated and used to generate a corresponding audio signal.
This source accepts the following options:
- exprs
Set the ’|’-separated expressions list for each separate channel. In case the channel_layout option is not specified, the selected channel layout depends on the number of provided expressions. Otherwise the last specified expression is applied to the remaining output channels.
- channel_layout, c
Set the channel layout. The number of channels in the specified layout must be equal to the number of specified expressions.
- duration, d
Set the minimum duration of the sourced audio. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax. Note that the resulting duration may be greater than the specified duration, as the generated audio is always cut at the end of a complete frame.
If not specified, or the expressed duration is negative, the audio is supposed to be generated forever.
- nb_samples, n
Set the number of samples per channel per each output frame, default to 1024.
- sample_rate, s
Specify the sample rate, default to 44100.
Each expression in exprs can contain the following constants:
- n
number of the evaluated sample, starting from 0
- t
time of the evaluated sample expressed in seconds, starting from 0
- s
sample rate
30.2.1 Examples
- Generate silence:
aevalsrc=0
- Generate a sin signal with frequency of 440 Hz, set sample rate to
8000 Hz:
aevalsrc="sin(440*2*PI*t):s=8000"
- Generate a two channels signal, specify the channel layout (Front
Center + Back Center) explicitly:
aevalsrc="sin(420*2*PI*t)|cos(430*2*PI*t):c=FC|BC"
- Generate white noise:
aevalsrc="-2+random(0)"
- Generate an amplitude modulated signal:
aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
- Generate 2.5 Hz binaural beats on a 360 Hz carrier:
aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) | 0.1*sin(2*PI*(360+2.5/2)*t)"
30.3 afdelaysrc
Generate a fractional delay FIR coefficients.
The resulting stream can be used with afir filter for filtering the audio signal.
The filter accepts the following options:
- delay, d
Set the fractional delay. Default is 0.
- sample_rate, r
Set the sample rate, default is 44100.
- nb_samples, n
Set the number of samples per each frame. Default is 1024.
- taps, t
Set the number of filter coefficients in output audio stream. Default value is 0.
- channel_layout, c
Specifies the channel layout, and can be a string representing a channel layout. The default value of channel_layout is "stereo".
30.4 afireqsrc
Generate a FIR equalizer coefficients.
The resulting stream can be used with afir filter for filtering the audio signal.
The filter accepts the following options:
- preset, p
Set equalizer preset. Default preset is
flat
.Available presets are:
- ‘custom’
- ‘flat’
- ‘acoustic’
- ‘bass’
- ‘beats’
- ‘classic’
- ‘clear’
- ‘deep bass’
- ‘dubstep’
- ‘electronic’
- ‘hard-style’
- ‘hip-hop’
- ‘jazz’
- ‘metal’
- ‘movie’
- ‘pop’
- ‘r&b’
- ‘rock’
- ‘vocal booster’
- gains, g
Set custom gains for each band. Only used if the preset option is set to
custom
. Gains are separated by white spaces and each gain is set in dBFS. Default is0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
.- bands, b
Set the custom bands from where custon equalizer gains are set. This must be in strictly increasing order. Only used if the preset option is set to
custom
. Bands are separated by white spaces and each band represent frequency in Hz. Default is25 40 63 100 160 250 400 630 1000 1600 2500 4000 6300 10000 16000 24000
.- taps, t
Set number of filter coefficients in output audio stream. Default value is
4096
.- sample_rate, r
Set sample rate of output audio stream, default is
44100
.- nb_samples, n
Set number of samples per each frame in output audio stream. Default is
1024
.- interp, i
Set interpolation method for FIR equalizer coefficients. Can be
linear
orcubic
.- phase, h
Set phase type of FIR filter. Can be
linear
ormin
: minimum-phase. Default is minimum-phase filter.
30.5 afirsrc
Generate a FIR coefficients using frequency sampling method.
The resulting stream can be used with afir filter for filtering the audio signal.
The filter accepts the following options:
- taps, t
Set number of filter coefficients in output audio stream. Default value is 1025.
- frequency, f
Set frequency points from where magnitude and phase are set. This must be in non decreasing order, and first element must be 0, while last element must be 1. Elements are separated by white spaces.
- magnitude, m
Set magnitude value for every frequency point set by frequency. Number of values must be same as number of frequency points. Values are separated by white spaces.
- phase, p
Set phase value for every frequency point set by frequency. Number of values must be same as number of frequency points. Values are separated by white spaces.
- sample_rate, r
Set sample rate, default is 44100.
- nb_samples, n
Set number of samples per each frame. Default is 1024.
- win_func, w
Set window function. Default is blackman.
30.6 anullsrc
The null audio source, return unprocessed audio frames. It is mainly useful as a template and to be employed in analysis / debugging tools, or as the source for filters which ignore the input data (for example the sox synth filter).
This source accepts the following options:
- channel_layout, cl
-
Specifies the channel layout, and can be either an integer or a string representing a channel layout. The default value of channel_layout is "stereo".
Check the channel_layout_map definition in libavutil/channel_layout.c for the mapping between strings and channel layout values.
- sample_rate, r
Specifies the sample rate, and defaults to 44100.
- nb_samples, n
Set the number of samples per requested frames.
- duration, d
Set the duration of the sourced audio. See (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual for the accepted syntax.
If not specified, or the expressed duration is negative, the audio is supposed to be generated forever.
30.6.1 Examples
- Set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
anullsrc=r=48000:cl=4
- Do the same operation with a more obvious syntax:
anullsrc=r=48000:cl=mono
All the parameters need to be explicitly defined.
30.7 flite
Synthesize a voice utterance using the libflite library.
To enable compilation of this filter you need to configure FFmpeg with
--enable-libflite
.
Note that versions of the flite library prior to 2.0 are not thread-safe.
The filter accepts the following options:
- list_voices
If set to 1, list the names of the available voices and exit immediately. Default value is 0.
- nb_samples, n
Set the maximum number of samples per frame. Default value is 512.
- textfile
Set the filename containing the text to speak.
- text
Set the text to speak.
- voice, v
Set the voice to use for the speech synthesis. Default value is
kal
. See also the list_voices option.
30.7.1 Examples
- Read from file speech.txt, and synthesize the text using the
standard flite voice:
flite=textfile=speech.txt
- Read the specified text selecting the
slt
voice:flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
- Input text to ffmpeg:
ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
- Make ffplay speak the specified text, using
flite
and thelavfi
device:ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'
For more information about libflite, check: http://www.festvox.org/flite/
30.8 anoisesrc
Generate a noise audio signal.
The filter accepts the following options:
- sample_rate, r
Specify the sample rate. Default value is 48000 Hz.
- amplitude, a
Specify the amplitude (0.0 - 1.0) of the generated audio stream. Default value is 1.0.
- duration, d
Specify the duration of the generated audio stream. Not specifying this option results in noise with an infinite length.
- color, colour, c
Specify the color of noise. Available noise colors are white, pink, brown, blue, violet and velvet. Default color is white.
- seed, s
Specify a value used to seed the PRNG.
- nb_samples, n
Set the number of samples per each output frame, default is 1024.
- density
Set the density (0.0 - 1.0) for the velvet noise generator, default is 0.05.
30.8.1 Examples
- Generate 60 seconds of pink noise, with a 44.1 kHz sampling rate and an amplitude of 0.5:
anoisesrc=d=60:c=pink:r=44100:a=0.5
30.9 hilbert
Generate odd-tap Hilbert transform FIR coefficients.
The resulting stream can be used with afir filter for phase-shifting the signal by 90 degrees.
This is used in many matrix coding schemes and for analytic signal generation. The process is often written as a multiplication by i (or j), the imaginary unit.
The filter accepts the following options:
- sample_rate, s
Set sample rate, default is 44100.
- taps, t
Set length of FIR filter, default is 22051.
- nb_samples, n
Set number of samples per each frame.
- win_func, w
Set window function to be used when generating FIR coefficients.
30.10 sinc
Generate a sinc kaiser-windowed low-pass, high-pass, band-pass, or band-reject FIR coefficients.
The resulting stream can be used with afir filter for filtering the audio signal.
The filter accepts the following options:
- sample_rate, r
Set sample rate, default is 44100.
- nb_samples, n
Set number of samples per each frame. Default is 1024.
- hp
Set high-pass frequency. Default is 0.
- lp
Set low-pass frequency. Default is 0. If high-pass frequency is lower than low-pass frequency and low-pass frequency is higher than 0 then filter will create band-pass filter coefficients, otherwise band-reject filter coefficients.
- phase
Set filter phase response. Default is 50. Allowed range is from 0 to 100.
- beta
Set Kaiser window beta.
- att
Set stop-band attenuation. Default is 120dB, allowed range is from 40 to 180 dB.
- round
Enable rounding, by default is disabled.
- hptaps
Set number of taps for high-pass filter.
- lptaps
Set number of taps for low-pass filter.
30.11 sine
Generate an audio signal made of a sine wave with amplitude 1/8.
The audio signal is bit-exact.
The filter accepts the following options:
- frequency, f
Set the carrier frequency. Default is 440 Hz.
- beep_factor, b
Enable a periodic beep every second with frequency beep_factor times the carrier frequency. Default is 0, meaning the beep is disabled.
- sample_rate, r
Specify the sample rate, default is 44100.
- duration, d
Specify the duration of the generated audio stream.
- samples_per_frame
Set the number of samples per output frame.
The expression can contain the following constants:
- n
The (sequential) number of the output audio frame, starting from 0.
- pts
The PTS (Presentation TimeStamp) of the output audio frame, expressed in TB units.
- t
The PTS of the output audio frame, expressed in seconds.
- TB
The timebase of the output audio frames.
Default is
1024
.
30.11.1 Examples
- Generate a simple 440 Hz sine wave:
sine
- Generate a 220 Hz sine wave with a 880 Hz beep each second, for 5 seconds:
sine=220:4:d=5 sine=f=220:b=4:d=5 sine=frequency=220:beep_factor=4:duration=5
- Generate a 1 kHz sine wave following
1602,1601,1602,1601,1602
NTSC pattern:sine=1000:samples_per_frame='st(0,mod(n,5)); 1602-not(not(eq(ld(0),1)+eq(ld(0),3)))'
31 Audio Sinks
Below is a description of the currently available audio sinks.
31.1 abuffersink
Buffer audio frames, and make them available to the end of filter chain.
This sink is mainly intended for programmatic use, in particular through the interface defined in libavfilter/buffersink.h or the options system.
It accepts a pointer to an AVABufferSinkContext structure, which
defines the incoming buffers’ formats, to be passed as the opaque
parameter to avfilter_init_filter
for initialization.
31.2 anullsink
Null audio sink; do absolutely nothing with the input audio. It is mainly useful as a template and for use in analysis / debugging tools.
32 Video Filters
When you configure your FFmpeg build, you can disable any of the
existing filters using --disable-filters
.
The configure output will show the video filters included in your
build.
Below is a description of the currently available video filters.
32.1 addroi
Mark a region of interest in a video frame.
The frame data is passed through unchanged, but metadata is attached to the frame indicating regions of interest which can affect the behaviour of later encoding. Multiple regions can be marked by applying the filter multiple times.
- x
Region distance in pixels from the left edge of the frame.
- y
Region distance in pixels from the top edge of the frame.
- w
Region width in pixels.
- h
Region height in pixels.
The parameters x, y, w and h are expressions, and may contain the following variables:
- iw
Width of the input frame.
- ih
Height of the input frame.
- qoffset
Quantisation offset to apply within the region.
This must be a real value in the range -1 to +1. A value of zero indicates no quality change. A negative value asks for better quality (less quantisation), while a positive value asks for worse quality (greater quantisation).
The range is calibrated so that the extreme values indicate the largest possible offset - if the rest of the frame is encoded with the worst possible quality, an offset of -1 indicates that this region should be encoded with the best possible quality anyway. Intermediate values are then interpolated in some codec-dependent way.
For example, in 10-bit H.264 the quantisation parameter varies between -12 and 51. A typical qoffset value of -1/10 therefore indicates that this region should be encoded with a QP around one-tenth of the full range better than the rest of the frame. So, if most of the frame were to be encoded with a QP of around 30, this region would get a QP of around 24 (an offset of approximately -1/10 * (51 - -12) = -6.3). An extreme value of -1 would indicate that this region should be encoded with the best possible quality regardless of the treatment of the rest of the frame - that is, should be encoded at a QP of -12.
- clear
If set to true, remove any existing regions of interest marked on the frame before adding the new one.
32.1.1 Examples
- Mark the centre quarter of the frame as interesting.
addroi=iw/4:ih/4:iw/2:ih/2:-1/10
- Mark the 100-pixel-wide region on the left edge of the frame as very
uninteresting (to be encoded at much lower quality than the rest of
the frame).
addroi=0:0:100:ih:+1/5
32.2 alphaextract
Extract the alpha component from the input as a grayscale video. This is especially useful with the alphamerge filter.
32.3 alphamerge
Add or replace the alpha component of the primary input with the grayscale value of a second input. This is intended for use with alphaextract to allow the transmission or storage of frame sequences that have alpha in a format that doesn’t support an alpha channel.
For example, to reconstruct full frames from a normal YUV-encoded video and a separate video created with alphaextract, you might use:
movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
32.4 amplify
Amplify differences between current pixel and pixels of adjacent frames in same pixel location.
This filter accepts the following options:
- radius
Set frame radius. Default is 2. Allowed range is from 1 to 63. For example radius of 3 will instruct filter to calculate average of 7 frames.
- factor
Set factor to amplify difference. Default is 2. Allowed range is from 0 to 65535.
- threshold
Set threshold for difference amplification. Any difference greater or equal to this value will not alter source pixel. Default is 10. Allowed range is from 0 to 65535.
- tolerance
Set tolerance for difference amplification. Any difference lower to this value will not alter source pixel. Default is 0. Allowed range is from 0 to 65535.
- low
Set lower limit for changing source pixel. Default is 65535. Allowed range is from 0 to 65535. This option controls maximum possible value that will decrease source pixel value.
- high
Set high limit for changing source pixel. Default is 65535. Allowed range is from 0 to 65535. This option controls maximum possible value that will increase source pixel value.
- planes
Set which planes to filter. Default is all. Allowed range is from 0 to 15.
32.4.1 Commands
This filter supports the following commands that corresponds to option of same name:
- factor
- threshold
- tolerance
- low
- high
- planes
32.5 ass
Same as the subtitles filter, except that it doesn’t require libavcodec and libavformat to work. On the other hand, it is limited to ASS (Advanced Substation Alpha) subtitles files.
This filter accepts the following option in addition to the common options from the subtitles filter:
- shaping
Set the shaping engine
Available values are:
- ‘auto’
The default libass shaping engine, which is the best available.
- ‘simple’
Fast, font-agnostic shaper that can do only substitutions
- ‘complex’
Slower shaper using OpenType for substitutions and positioning
The default is
auto
.
32.6 atadenoise
Apply an Adaptive Temporal Averaging Denoiser to the video input.
The filter accepts the following options:
- 0a
Set threshold A for 1st plane. Default is 0.02. Valid range is 0 to 0.3.
- 0b
Set threshold B for 1st plane. Default is 0.04. Valid range is 0 to 5.
- 1a
Set threshold A for 2nd plane. Default is 0.02. Valid range is 0 to 0.3.
- 1b
Set threshold B for 2nd plane. Default is 0.04. Valid range is 0 to 5.
- 2a
Set threshold A for 3rd plane. Default is 0.02. Valid range is 0 to 0.3.
- 2b
Set threshold B for 3rd plane. Default is 0.04. Valid range is 0 to 5.
Threshold A is designed to react on abrupt changes in the input signal and threshold B is designed to react on continuous changes in the input signal.
- s
Set number of frames filter will use for averaging. Default is 9. Must be odd number in range [5, 129].
- p
Set what planes of frame filter will use for averaging. Default is all.
- a
Set what variant of algorithm filter will use for averaging. Default is
p
parallel. Alternatively can be set tos
serial.Parallel can be faster then serial, while other way around is never true. Parallel will abort early on first change being greater then thresholds, while serial will continue processing other side of frames if they are equal or below thresholds.
- 0s
- 1s
- 2s
Set sigma for 1st plane, 2nd plane or 3rd plane. Default is 32767. Valid range is from 0 to 32767. This options controls weight for each pixel in radius defined by size. Default value means every pixel have same weight. Setting this option to 0 effectively disables filtering.
32.6.1 Commands
This filter supports same commands as options except option s
.
The command accepts the same syntax of the corresponding option.
32.7 avgblur
Apply average blur filter.
The filter accepts the following options:
- sizeX
Set horizontal radius size.
- planes
Set which planes to filter. By default all planes are filtered.
- sizeY
Set vertical radius size, if zero it will be same as
sizeX
. Default is0
.
32.7.1 Commands
This filter supports same commands as options. The command accepts the same syntax of the corresponding option.
If the specified expression is not valid, it is kept at its current value.
32.8 backgroundkey
Turns a static background into transparency.
The filter accepts the following option:
- threshold
Threshold for scene change detection.
- similarity
Similarity percentage with the background.
- blend
Set the blend amount for pixels that are not similar.
32.8.1 Commands
This filter supports the all above options as commands.
32.9 bbox
Compute the bounding box for the non-black pixels in the input frame luma plane.
This filter computes the bounding box containing all the pixels with a luma value greater than the minimum allowed value. The parameters describing the bounding box are printed on the filter log.
The filter accepts the following option:
- min_val
Set the minimal luma value. Default is
16
.
32.9.1 Commands
This filter supports the all above options as commands.
32.10 bilateral
Apply bilateral filter, spatial smoothing while preserving edges.
The filter accepts the following options:
- sigmaS
Set sigma of gaussian function to calculate spatial weight. Allowed range is 0 to 512. Default is 0.1.
- sigmaR
Set sigma of gaussian function to calculate range weight. Allowed range is 0 to 1. Default is 0.1.
- planes
Set planes to filter. Default is first only.
32.10.1 Commands
This filter supports the all above options as commands.
32.11 bilateral_cuda
CUDA accelerated bilateral filter, an edge preserving filter. This filter is mathematically accurate thanks to the use of GPU acceleration. For best output quality, use one to one chroma subsampling, i.e. yuv444p format.
The filter accepts the following options:
- sigmaS
Set sigma of gaussian function to calculate spatial weight, also called sigma space. Allowed range is 0.1 to 512. Default is 0.1.
- sigmaR
Set sigma of gaussian function to calculate color range weight, also called sigma color. Allowed range is 0.1 to 512. Default is 0.1.
- window_size
Set window size of the bilateral function to determine the number of neighbours to loop on. If the number entered is even, one will be added automatically. Allowed range is 1 to 255. Default is 1.
32.11.1 Examples
- Apply the bilateral filter on a video.
./ffmpeg -v verbose \ -hwaccel cuda -hwaccel_output_format cuda -i input.mp4 \ -init_hw_device cuda \ -filter_complex \ " \ [0:v]scale_cuda=format=yuv444p[scaled_video]; [scaled_video]bilateral_cuda=window_size=9:sigmaS=3.0:sigmaR=50.0" \ -an -sn -c:v h264_nvenc -cq 20 out.mp4
32.12 bitplanenoise
Show and measure bit plane noise.
The filter accepts the following options:
- bitplane
Set which plane to analyze. Default is
1
.- filter
Filter out noisy pixels from
bitplane
set above. Default is disabled.
32.13 blackdetect
Detect video intervals that are (almost) completely black. Can be useful to detect chapter transitions, commercials, or invalid recordings.
The filter outputs its detection analysis to both the log as well as
frame metadata. If a black segment of at least the specified minimum
duration is found, a line with the start and end timestamps as well
as duration is printed to the log with level info
. In addition,
a log line with level debug
is printed per frame showing the
black amount detected for that frame.
The filter also attaches metadata to the first frame of a black
segment with key lavfi.black_start
and to the first frame
after the black segment ends with key lavfi.black_end
. The
value is the frame’s timestamp. This metadata is added regardless
of the minimum duration specified.
The filter accepts the following options:
- black_min_duration, d
Set the minimum detected black duration expressed in seconds. It must be a non-negative floating point number.
Default value is 2.0.
- picture_black_ratio_th, pic_th
Set the threshold for considering a picture "black". Express the minimum value for the ratio:
nb_black_pixels / nb_pixels
for which a picture is considered black. Default value is 0.98.
- pixel_black_th, pix_th
Set the threshold for considering a pixel "black".
The threshold expresses the maximum pixel luma value for which a pixel is considered "black". The provided value is scaled according to the following equation:
absolute_threshold = luma_minimum_value + pixel_black_th * luma_range_size
luma_range_size and luma_minimum_value depend on the input video format, the range is [0-255] for YUV full-range formats and [16-235] for YUV non full-range formats.
Default value is 0.10.
The following example sets the maximum pixel threshold to the minimum value, and detects only black intervals of 2 or more seconds:
blackdetect=d=2:pix_th=0.00
32.14 blackframe
Detect frames that are (almost) completely black. Can be useful to detect chapter transitions or commercials. Output lines consist of the frame number of the detected frame, the percentage of blackness, the position in the file if known or -1 and the timestamp in seconds.
In order to display the output lines, you need to set the loglevel at least to the AV_LOG_INFO value.
This filter exports frame metadata lavfi.blackframe.pblack
.
The value represents the percentage of pixels in the picture that
are below the threshold value.
It accepts the following parameters:
- amount
The percentage of the pixels that have to be below the threshold; it defaults to
98
.- threshold, thresh
The threshold below which a pixel value is considered black; it defaults to
32
.
32.15 blend
Blend two video frames into each other.
The blend
filter takes two input streams and outputs one
stream, the first input is the "top" layer and second input is
"bottom" layer. By default, the output terminates when the longest input terminates.
The tblend
(time blend) filter takes two consecutive frames
from one single stream, and outputs the result obtained by blending
the new frame on top of the old frame.
A description of the accepted options follows.
- c0_mode
- c1_mode
- c2_mode
- c3_mode
- all_mode
Set blend mode for specific pixel component or all pixel components in case of all_mode. Default value is
normal
.Available values for component modes are:
- ‘addition’
- ‘and’
- ‘average’
- ‘bleach’
- ‘burn’
- ‘darken’
- ‘difference’
- ‘divide’
- ‘dodge’
- ‘exclusion’
- ‘extremity’
- ‘freeze’
- ‘geometric’
- ‘glow’
- ‘grainextract’
- ‘grainmerge’
- ‘hardlight’
- ‘hardmix’
- ‘hardoverlay’
- ‘harmonic’
- ‘heat’
- ‘interpolate’
- ‘lighten’
- ‘linearlight’
- ‘multiply’
- ‘multiply128’
- ‘negation’
- ‘normal’
- ‘or’
- ‘overlay’
- ‘phoenix’
- ‘pinlight’
- ‘reflect’
- ‘screen’
- ‘softdifference’
- ‘softlight’
- ‘stain’
- ‘subtract’
- ‘vividlight’
- ‘xor’
- c0_opacity
- c1_opacity
- c2_opacity
- c3_opacity
- all_opacity
Set blend opacity for specific pixel component or all pixel components in case of all_opacity. Only used in combination with pixel component blend modes.
- c0_expr
- c1_expr
- c2_expr
- c3_expr
- all_expr
Set blend expression for specific pixel component or all pixel components in case of all_expr. Note that related mode options will be ignored if those are set.
The expressions can use the following variables:
- N
The sequential number of the filtered frame, starting from
0
.- X
- Y
the coordinates of the current sample
- W
- H
the width and height of currently filtered plane
- SW
- SH
Width and height scale for the plane being filtered. It is the ratio between the dimensions of the current plane to the luma plane, e.g. for a
yuv420p
frame, the values are1,1
for the luma plane and0.5,0.5
for the chroma planes.- T
Time of the current frame, expressed in seconds.
- TOP, A
Value of pixel component at current location for first video frame (top layer).
- BOTTOM, B
Value of pixel component at current location for second video frame (bottom layer).
The blend
filter also supports the framesync options.
32.15.1 Examples
- Apply transition from bottom layer to top layer in first 10 seconds:
blend=all_expr='A*(if(gte(T,10),1,T/10))+B*(1-(if(gte(T,10),1,T/10)))'
- Apply linear horizontal transition from top layer to bottom layer:
blend=all_expr='A*(X/W)+B*(1-X/W)'
- Apply 1x1 checkerboard effect:
blend=all_expr='if(eq(mod(X,2),mod(Y,2)),A,B)'
- Apply uncover left effect:
blend=all_expr='if(gte(N*SW+X,W),A,B)'
- Apply uncover down effect:
blend=all_expr='if(gte(Y-N*SH,0),A,B)'
- Apply uncover up-left effect:
blend=all_expr='if(gte(T*SH*40+Y,H)*gte((T*40*SW+X)*W/H,W),A,B)'
- Split diagonally video and shows top and bottom layer on each side:
blend=all_expr='if(gt(X,Y*(W/H)),A,B)'
- Display differences between the current and the previous frame:
tblend=all_mode=grainextract
32.15.2 Commands
This filter supports same commands as options.
32.16 blockdetect
Determines blockiness of frames without altering the input frames.
Based on Remco Muijs and Ihor Kirenko: "A no-reference blocking artifact measure for adaptive video processing." 2005 13th European signal processing conference.
The filter accepts the following options:
- period_min
- period_max
Set minimum and maximum values for determining pixel grids (periods). Default values are [3,24].
- planes
Set planes to filter. Default is first only.
32.16.1 Examples
- Determine blockiness for the first plane and search for periods within [8,32]:
blockdetect=period_min=8:period_max=32:planes=1
32.17 blurdetect
Determines blurriness of frames without altering the input frames.
Based on Marziliano, Pina, et al. "A no-reference perceptual blur metric." Allows for a block-based abbreviation.
The filter accepts the following options:
- low
- high
Set low and high threshold values used by the Canny thresholding algorithm.
The high threshold selects the "strong" edge pixels, which are then connected through 8-connectivity with the "weak" edge pixels selected by the low threshold.
low and high threshold values must be chosen in the range [0,1], and low should be lesser or equal to high.
Default value for low is
20/255
, and default value for high is50/255
.- radius
Define the radius to search around an edge pixel for local maxima.
- block_pct
Determine blurriness only for the most significant blocks, given in percentage.
- block_width
Determine blurriness for blocks of width block_width. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of block_height.
- block_height
Determine blurriness for blocks of height block_height. If set to any value smaller 1, no blocks are used and the whole image is processed as one no matter of block_width.
- planes
Set planes to filter. Default is first only.
32.17.1 Examples
- Determine blur for 80% of most significant 32x32 blocks:
blurdetect=block_width=32:block_height=32:block_pct=80
32.18 bm3d
Denoise frames using Block-Matching 3D algorithm.
The filter accepts the following options.
- sigma
Set denoising strength. Default value is 1. Allowed range is from 0 to 999.9. The denoising algorithm is very sensitive to sigma, so adjust it according to the source.
- block
Set local patch size. This sets dimensions in 2D.
- bstep
Set sliding step for processing blocks. Default value is 4. Allowed range is from 1 to 64. Smaller values allows processing more reference blocks and is slower.
- group
Set maximal number of similar blocks for 3rd dimension. Default value is 1. When set to 1, no block matching is done. Larger values allows more blocks in single group. Allowed range is from 1 to 256.
- range
Set radius for search block matching. Default is 9. Allowed range is from 1 to INT32_MAX.
- mstep
Set step between two search locations for block matching. Default is 1. Allowed range is from 1 to 64. Smaller is slower.
- thmse
Set threshold of mean square error for block matching. Valid range is 0 to INT32_MAX.
- hdthr
Set thresholding parameter for hard thresholding in 3D transformed domain. Larger values results in stronger hard-thresholding filtering in frequency domain.
- estim
Set filtering estimation mode. Can be
basic
orfinal
. Default isbasic
.- ref
If enabled, filter will use 2nd stream for block matching. Default is disabled for
basic
value of estim option, and always enabled if value of estim isfinal
.- planes
Set planes to filter. Default is all available except alpha.
32.18.1 Examples
- Basic filtering with bm3d:
bm3d=sigma=3:block=4:bstep=2:group=1:estim=basic
- Same as above, but filtering only luma:
bm3d=sigma=3:block=4:bstep=2:group=1:estim=basic:planes=1
- Same as above, but with both estimation modes:
split[a][b],[a]bm3d=sigma=3:block=4:bstep=2:group=1:estim=basic[a],[b][a]bm3d=sigma=3:block=4:bstep=2:group=16:estim=final:ref=1
- Same as above, but prefilter with nlmeans filter instead:
split[a][b],[a]nlmeans=s=3:r=7:p=3[a],[b][a]bm3d=sigma=3:block=4:bstep=2:group=16:estim=final:ref=1
32.19 boxblur
Apply a boxblur algorithm to the input video.
It accepts the following parameters:
- luma_radius, lr
- luma_power, lp
- chroma_radius, cr
- chroma_power, cp
- alpha_radius, ar
- alpha_power, ap
A description of the accepted options follows.
- luma_radius, lr
- chroma_radius, cr
- alpha_radius, ar
Set an expression for the box radius in pixels used for blurring the corresponding input plane.
The radius value must be a non-negative number, and must not be greater than the value of the expression
min(w,h)/2
for the luma and alpha planes, and ofmin(cw,ch)/2
for the chroma planes.Default value for luma_radius is "2". If not specified, chroma_radius and alpha_radius default to the corresponding value set for luma_radius.
The expressions can contain the following constants:
- w
- h
The input width and height in pixels.
- cw
- ch
The input chroma image width and height in pixels.
- hsub
- vsub
The horizontal and vertical chroma subsample values. For example, for the pixel format "yuv422p", hsub is 2 and vsub is 1.
- luma_power, lp
- chroma_power, cp
- alpha_power, ap
Specify how many times the boxblur filter is applied to the corresponding plane.
Default value for luma_power is 2. If not specified, chroma_power and alpha_power default to the corresponding value set for luma_power.
A value of 0 will disable the effect.
32.19.1 Examples
- Apply a boxblur filter with the luma, chroma, and alpha radii
set to 2:
boxblur=luma_radius=2:luma_power=1 boxblur=2:1
- Set the luma radius to 2, and alpha and chroma radius to 0:
boxblur=2:1:cr=0:ar=0
- Set the luma and chroma radii to a fraction of the video dimension:
boxblur=luma_radius=min(h\,w)/10:luma_power=1:chroma_radius=min(cw\,ch)/10:chroma_power=1
32.20 bwdif
Deinterlace the input video ("bwdif" stands for "Bob Weaver Deinterlacing Filter").
Motion adaptive deinterlacing based on yadif with the use of w3fdif and cubic interpolation algorithms. It accepts the following parameters:
- mode
The interlacing mode to adopt. It accepts one of the following values:
- 0, send_frame
Output one frame for each frame.
- 1, send_field
Output one frame for each field.
The default value is
send_field
.- parity
The picture field parity assumed for the input interlaced video. It accepts one of the following values:
- 0, tff
Assume the top field is first.
- 1, bff
Assume the bottom field is first.
- -1, auto
Enable automatic detection of field parity.
The default value is
auto
. If the interlacing is unknown or the decoder does not export this information, top field first will be assumed.- deint
Specify which frames to deinterlace. Accepts one of the following values:
- 0, all
Deinterlace all frames.
- 1, interlaced
Only deinterlace frames marked as interlaced.
The default value is
all
.
32.21 bwdif_cuda
Deinterlace the input video using the bwdif algorithm, but implemented in CUDA so that it can work as part of a GPU accelerated pipeline with nvdec and/or nvenc.
It accepts the following parameters:
- mode
The interlacing mode to adopt. It accepts one of the following values:
- 0, send_frame
Output one frame for each frame.
- 1, send_field
Output one frame for each field.
The default value is
send_field
.- parity
The picture field parity assumed for the input interlaced video. It accepts one of the following values:
- 0, tff
Assume the top field is first.
- 1, bff
Assume the bottom field is first.
- -1, auto
Enable automatic detection of field parity.
The default value is
auto
. If the interlacing is unknown or the decoder does not export this information, top field first will be assumed.- deint
Specify which frames to deinterlace. Accepts one of the following values:
- 0, all
Deinterlace all frames.
- 1, interlaced
Only deinterlace frames marked as interlaced.
The default value is
all
.
32.22 ccrepack
Repack CEA-708 closed captioning side data
This filter fixes various issues seen with commerical encoders related to upstream malformed CEA-708 payloads, specifically incorrect number of tuples (wrong cc_count for the target FPS), and incorrect ordering of tuples (i.e. the CEA-608 tuples are not at the first entries in the payload).
32.23 cas
Apply Contrast Adaptive Sharpen filter to video stream.
The filter accepts the following options:
- strength
Set the sharpening strength. Default value is 0.
- planes
Set planes to filter. Default value is to filter all planes except alpha plane.
32.23.1 Commands
This filter supports same commands as options.
32.24 chromahold
Remove all color information for all colors except for certain one.
The filter accepts the following options:
- color
The color which will not be replaced with neutral chroma.
- similarity
Similarity percentage with the above color. 0.01 matches only the exact key color, while 1.0 matches everything.
- blend
Blend percentage. 0.0 makes pixels either fully gray, or not gray at all. Higher values result in more preserved color.
- yuv
Signals that the color passed is already in YUV instead of RGB.
Literal colors like "green" or "red" don’t make sense with this enabled anymore. This can be used to pass exact YUV values as hexadecimal numbers.
32.24.1 Commands
This filter supports same commands as options. The command accepts the same syntax of the corresponding option.
If the specified expression is not valid, it is kept at its current value.
32.25 chromakey
YUV colorspace color/chroma keying.
The filter accepts the following options:
- color
The color which will be replaced with transparency.
- similarity
Similarity percentage with the key color.
0.01 matches only the exact key color, while 1.0 matches everything.
- blend
Blend percentage.
0.0 makes pixels either fully transparent, or not transparent at all.
Higher values result in semi-transparent pixels, with a higher transparency the more similar the pixels color is to the key color.
- yuv
Signals that the color passed is already in YUV instead of RGB.
Literal colors like "green" or "red" don’t make sense with this enabled anymore. This can be used to pass exact YUV values as hexadecimal numbers.
32.25.1 Commands
This filter supports same commands as options. The command accepts the same syntax of the corresponding option.
If the specified expression is not valid, it is kept at its current value.
32.25.2 Examples
- Make every green pixel in the input image transparent:
ffmpeg -i input.png -vf chromakey=green out.png
- Overlay a greenscreen-video on top of a static black background.
ffmpeg -f lavfi -i color=c=black:s=1280x720 -i video.mp4 -shortest -filter_complex "[1:v]chromakey=0x70de77:0.1:0.2[ckout];[0:v][ckout]overlay[out]" -map "[out]" output.mkv
32.26 chromakey_cuda
CUDA accelerated YUV colorspace color/chroma keying.
This filter works like normal chromakey filter but operates on CUDA frames. for more details and parameters see chromakey.
32.26.1 Examples
- Make all the green pixels in the input video transparent and use it as an overlay for another video:
./ffmpeg \ -hwaccel cuda -hwaccel_output_format cuda -i input_green.mp4 \ -hwaccel cuda -hwaccel_output_format cuda -i base_video.mp4 \ -init_hw_device cuda \ -filter_complex \ " \ [0:v]chromakey_cuda=0x25302D:0.1:0.12:1[overlay_video]; \ [1:v]scale_cuda=format=yuv420p[base]; \ [base][overlay_video]overlay_cuda" \ -an -sn -c:v h264_nvenc -cq 20 output.mp4
- Process two software sources, explicitly uploading the frames:
./ffmpeg -init_hw_device cuda=cuda -filter_hw_device cuda \ -f lavfi -i color=size=800x600:color=white,format=yuv420p \ -f lavfi -i yuvtestsrc=size=200x200,format=yuv420p \ -filter_complex \ " \ [0]hwupload[under]; \ [1]hwupload,chromakey_cuda=green:0.1:0.12[over]; \ [under][over]overlay_cuda" \ -c:v hevc_nvenc -cq 18 -preset slow output.mp4
32.27 chromanr
Reduce chrominance noise.
The filter accepts the following options:
- thres
Set threshold for averaging chrominance values. Sum of absolute difference of Y, U and V pixel components of current pixel and neighbour pixels lower than this threshold will be used in averaging. Luma component is left unchanged and is copied to output. Default value is 30. Allowed range is from 1 to 200.
- sizew
Set horizontal radius of rectangle used for averaging. Allowed range is from 1 to 100. Default value is 5.
- sizeh
Set vertical radius of rectangle used for averaging. Allowed range is from 1 to 100. Default value is 5.
- stepw
Set horizontal step when averaging. Default value is 1. Allowed range is from 1 to 50. Mostly useful to speed-up filtering.
- steph
Set vertical step when averaging. Default value is 1. Allowed range is from 1 to 50. Mostly useful to speed-up filtering.
- threy
Set Y threshold for averaging chrominance values. Set finer control for max allowed difference between Y components of current pixel and neigbour pixels. Default value is 200. Allowed range is from 1 to 200.
- threu
Set U threshold for averaging chrominance values. Set finer control for max allowed difference between U components of current pixel and neigbour pixels. Default value is 200. Allowed range is from 1 to 200.
- threv
Set V threshold for averaging chrominance values. Set finer control for max allowed difference between V components of current pixel and neigbour pixels. Default value is 200. Allowed range is from 1 to 200.
- distance
Set distance type used in calculations.
- ‘manhattan’
Absolute difference.
- ‘euclidean’
Difference squared.
Default distance type is manhattan.
32.27.1 Commands
This filter supports same commands as options. The command accepts the same syntax of the corresponding option.
32.28 chromashift
Shift chroma pixels horizontally and/or vertically.
The filter accepts the following options:
- cbh
Set amount to shift chroma-blue horizontally.
- cbv
Set amount to shift chroma-blue vertically.
- crh
Set amount to shift chroma-red horizontally.
- crv
Set amount to shift chroma-red vertically.
- edge
Set edge mode, can be smear, default, or warp.
32.28.1 Commands
This filter supports the all above options as commands.
32.29 ciescope
Display CIE color diagram with pixels overlaid onto it.
The filter accepts the following options:
- system
Set color system.
- ‘ntsc, 470m’
- ‘ebu, 470bg’
- ‘smpte’
- ‘240m’
- ‘apple’
- ‘widergb’
- ‘cie1931’
- ‘rec709, hdtv’
- ‘uhdtv, rec2020’
- ‘dcip3’
- cie
Set CIE system.
- ‘xyy’
- ‘ucs’
- ‘luv’
- gamuts
Set what gamuts to draw.
See
system
option for available values.- size, s
Set ciescope size, by default set to 512.
- intensity, i
Set intensity used to map input pixel values to CIE diagram.
- contrast
Set contrast used to draw tongue colors that are out of active color system gamut.
- corrgamma
Correct gamma displayed on scope, by default enabled.
- showwhite
Show white point on CIE diagram, by default disabled.
- gamma
Set input gamma. Used only with XYZ input color space.
- fill
Fill with CIE colors. By default is enabled.
32.30 codecview
Visualize information exported by some codecs.
Some codecs can export information through frames using side-data or other means. For example, some MPEG based codecs export motion vectors through the export_mvs flag in the codec flags2 option.
The filter accepts the following option:
- block
Display block partition structure using the luma plane.
- mv
Set motion vectors to visualize.
Available flags for mv are:
- ‘pf’
forward predicted MVs of P-frames
- ‘bf’
forward predicted MVs of B-frames
- ‘bb’
backward predicted MVs of B-frames
- qp
Display quantization parameters using the chroma planes.
- mv_type, mvt
Set motion vectors type to visualize. Includes MVs from all frames unless specified by frame_type option.
Available flags for mv_type are:
- ‘fp’
forward predicted MVs
- ‘bp’
backward predicted MVs
- frame_type, ft
Set frame type to visualize motion vectors of.
Available flags for frame_type are:
- ‘if’
intra-coded frames (I-frames)
- ‘pf’
predicted frames (P-frames)
- ‘bf’
bi-directionally predicted frames (B-frames)
32.30.1 Examples
- Visualize forward predicted MVs of all frames using
ffplay
:ffplay -flags2 +export_mvs input.mp4 -vf codecview=mv_type=fp
- Visualize multi-directionals MVs of P and B-Frames using
ffplay
:ffplay -flags2 +export_mvs input.mp4 -vf codecview=mv=pf+bf+bb
32.31 colorbalance
Modify intensity of primary colors (red, green and blue) of input frames.
The filter allows an input frame to be adjusted in the shadows, midtones or highlights regions for the red-cyan, green-magenta or blue-yellow balance.
A positive adjustment value shifts the balance towards the primary color, a negative value towards the complementary color.
The filter accepts the following options:
- rs
- gs
- bs
Adjust red, green and blue shadows (darkest pixels).
- rm
- gm
- bm
Adjust red, green and blue midtones (medium pixels).
- rh
- gh
- bh
Adjust red, green and blue highlights (brightest pixels).
Allowed ranges for options are
[-1.0, 1.0]
. Defaults are0
.- pl
Preserve lightness when changing color balance. Default is disabled.
32.31.1 Examples
- Add red color cast to shadows:
colorbalance=rs=.3
32.31.2 Commands
This filter supports the all above options as commands.
32.32 colorcontrast
Adjust color contrast between RGB components.
The filter accepts the following options:
- rc
Set the red-cyan contrast. Defaults is 0.0. Allowed range is from -1.0 to 1.0.
- gm
Set the green-magenta contrast. Defaults is 0.0. Allowed range is from -1.0 to 1.0.
- by
Set the blue-yellow contrast. Defaults is 0.0. Allowed range is from -1.0 to 1.0.
- rcw
- gmw
- byw
Set the weight of each
rc
,gm
,by
option value. Default value is 0.0. Allowed range is from 0.0 to 1.0. If all weights are 0.0 filtering is disabled.- pl
Set the amount of preserving lightness. Default value is 0.0. Allowed range is from 0.0 to 1.0.
32.32.1 Commands
This filter supports the all above options as commands.
32.33 colorcorrect
Adjust color white balance selectively for blacks and whites. This filter operates in YUV colorspace.
The filter accepts the following options:
- rl
Set the red shadow spot. Allowed range is from -1.0 to 1.0. Default value is 0.
- bl
Set the blue shadow spot. Allowed range is from -1.0 to 1.0. Default value is 0.
- rh
Set the red highlight spot. Allowed range is from -1.0 to 1.0. Default value is 0.
- bh
Set the blue highlight spot. Allowed range is from -1.0 to 1.0. Default value is 0.
- saturation
Set the amount of saturation. Allowed range is from -3.0 to 3.0. Default value is 1.
- analyze
If set to anything other than
manual
it will analyze every frame and use derived parameters for filtering output frame.Possible values are:
- ‘manual’
- ‘average’
- ‘minmax’
- ‘median’
Default value is
manual
.
32.33.1 Commands
This filter supports the all above options as commands.
32.34 colorchannelmixer
Adjust video input frames by re-mixing color channels.
This filter modifies a color channel by adding the values associated to the other channels of the same pixels. For example if the value to modify is red, the output value will be:
red=red*rr + blue*rb + green*rg + alpha*ra
The filter accepts the following options:
- rr
- rg
- rb
- ra
Adjust contribution of input red, green, blue and alpha channels for output red channel. Default is
1
for rr, and0
for rg, rb and ra.- gr
- gg
- gb
- ga
Adjust contribution of input red, green, blue and alpha channels for output green channel. Default is
1
for gg, and0
for gr, gb and ga.- br
- bg
- bb
- ba
Adjust contribution of input red, green, blue and alpha channels for output blue channel. Default is
1
for bb, and0
for br, bg and ba.- ar
- ag
- ab
- aa
Adjust contribution of input red, green, blue and alpha channels for output alpha channel. Default is
1
for aa, and0
for ar, ag and ab.Allowed ranges for options are
[-2.0, 2.0]
.- pc
Set preserve color mode. The accepted values are:
- ‘none’
Disable color preserving, this is default.
- ‘lum’
Preserve luminance.
- ‘max’
Preserve max value of RGB triplet.
- ‘avg’
Preserve average value of RGB triplet.
- ‘sum’
Preserve sum value of RGB triplet.
- ‘nrm’
Preserve normalized value of RGB triplet.
- ‘pwr’
Preserve power value of RGB triplet.
- pa
Set the preserve color amount when changing colors. Allowed range is from
[0.0, 1.0]
. Default is0.0
, thus disabled.
32.34.1 Examples
- Convert source to grayscale:
colorchannelmixer=.3:.4:.3:0:.3:.4:.3:0:.3:.4:.3
- Simulate sepia tones:
colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131
32.34.2 Commands
This filter supports the all above options as commands.
32.35 colorize
Overlay a solid color on the video stream.
The filter accepts the following options:
- hue
Set the color hue. Allowed range is from 0 to 360. Default value is 0.
- saturation
Set the color saturation. Allowed range is from 0 to 1. Default value is 0.5.
- lightness
Set the color lightness. Allowed range is from 0 to 1. Default value is 0.5.
- mix
Set the mix of source lightness. By default is set to 1.0. Allowed range is from 0.0 to 1.0.
32.35.1 Commands
This filter supports the all above options as commands.
32.36 colorkey
RGB colorspace color keying. This filter operates on 8-bit RGB format frames by setting the alpha component of each pixel which falls within the similarity radius of the key color to 0. The alpha value for pixels outside the similarity radius depends on the value of the blend option.
The filter accepts the following options:
- color
Set the color for which alpha will be set to 0 (full transparency). See (ffmpeg-utils)"Color" section in the ffmpeg-utils manual. Default is
black
.- similarity
Set the radius from the key color within which other colors also have full transparency. The computed distance is related to the unit fractional distance in 3D space between the RGB values of the key color and the pixel’s color. Range is 0.01 to 1.0. 0.01 matches within a very small radius around the exact key color, while 1.0 matches everything. Default is
0.01
.- blend
Set how the alpha value for pixels that fall outside the similarity radius is computed. 0.0 makes pixels either fully transparent or fully opaque. Higher values result in semi-transparent pixels, with greater transparency the more similar the pixel color is to the key color. Range is 0.0 to 1.0. Default is
0.0
.
32.36.1 Examples
- Make every green pixel in the input image transparent:
ffmpeg -i input.png -vf colorkey=green out.png
- Overlay a greenscreen-video on top of a static background image.
ffmpeg -i background.png -i video.mp4 -filter_complex "[1:v]colorkey=0x3BBD1E:0.3:0.2[ckout];[0:v][ckout]overlay[out]" -map "[out]" output.flv
32.36.2 Commands
This filter supports same commands as options. The command accepts the same syntax of the corresponding option.
If the specified expression is not valid, it is kept at its current value.
32.37 colorhold
Remove all color information for all RGB colors except for certain one.
The filter accepts the following options:
- color
The color which will not be replaced with neutral gray.
- similarity
Similarity percentage with the above color. 0.01 matches only the exact key color, while 1.0 matches everything.
- blend
Blend percentage. 0.0 makes pixels fully gray. Higher values result in more preserved color.
32.37.1 Commands
This filter supports same commands as options. The command accepts the same syntax of the corresponding option.
If the specified expression is not valid, it is kept at its current value.
32.38 colorlevels
Adjust video input frames using levels.
The filter accepts the following options:
- rimin
- gimin
- bimin
- aimin
Adjust red, green, blue and alpha input black point. Allowed ranges for options are
[-1.0, 1.0]
. Defaults are0
.- rimax
- gimax
- bimax
- aimax
Adjust red, green, blue and alpha input white point. Allowed ranges for options are
[-1.0, 1.0]
. Defaults are1
.Input levels are used to lighten highlights (bright tones), darken shadows (dark tones), change the balance of bright and dark tones.
- romin
- gomin
- bomin
- aomin
Adjust red, green, blue and alpha output black point. Allowed ranges for options are
[0, 1.0]
. Defaults are0
.- romax
- gomax
- bomax
- aomax
Adjust red, green, blue and alpha output white point. Allowed ranges for options are
[0, 1.0]
. Defaults are1
.Output levels allows manual selection of a constrained output level range.
- preserve
Set preserve color mode. The accepted values are:
- ‘none’
Disable color preserving, this is default.
- ‘lum’
Preserve luminance.
- ‘max’
Preserve max value of RGB triplet.
- ‘avg’
Preserve average value of RGB triplet.
- ‘sum’
Preserve sum value of RGB triplet.
- ‘nrm’
Preserve normalized value of RGB triplet.
- ‘pwr’
Preserve power value of RGB triplet.
32.38.1 Examples
- Make video output darker:
colorlevels=rimin=0.058:gimin=0.058:bimin=0.058
- Increase contrast:
colorlevels=rimin=0.039:gimin=0.039:bimin=0.039:rimax=0.96:gimax=0.96:bimax=0.96
- Make video output lighter:
colorlevels=rimax=0.902:gimax=0.902:bimax=0.902
- Increase brightness:
colorlevels=romin=0.5:gomin=0.5:bomin=0.5
32.38.2 Commands
This filter supports the all above options as commands.
32.39 colormap
Apply custom color maps to video stream.
This filter needs three input video streams. First stream is video stream that is going to be filtered out. Second and third video stream specify color patches for source color to target color mapping.
The filter accepts the following options:
- patch_size
Set the source and target video stream patch size in pixels.
- nb_patches
Set the max number of used patches from source and target video stream. Default value is number of patches available in additional video streams. Max allowed number of patches is
64
.- type
Set the adjustments used for target colors. Can be
relative
orabsolute
. Defaults isabsolute
.- kernel
Set the kernel used to measure color differences between mapped colors.
The accepted values are:
- ‘euclidean’
- ‘weuclidean’
Default is
euclidean
.
32.40 colormatrix
Convert color matrix.
The filter accepts the following options:
- src
- dst
Specify the source and destination color matrix. Both values must be specified.
The accepted values are:
- ‘bt709’
BT.709
- ‘fcc’
FCC
- ‘bt601’
BT.601
- ‘bt470’
BT.470
- ‘bt470bg’
BT.470BG
- ‘smpte170m’
SMPTE-170M
- ‘smpte240m’
SMPTE-240M
- ‘bt2020’
BT.2020
For example to convert from BT.601 to SMPTE-240M, use the command:
colormatrix=bt601:smpte240m
32.41 colorspace
Convert colorspace, transfer characteristics or color primaries. Input video needs to have an even size.
The filter accepts the following options:
- all
Specify all color properties at once.
The accepted values are:
- ‘bt470m’
BT.470M
- ‘bt470bg’
BT.470BG
- ‘bt601-6-525’
BT.601-6 525
- ‘bt601-6-625’
BT.601-6 625
- ‘bt709’
BT.709
- ‘smpte170m’
SMPTE-170M
- ‘smpte240m’
SMPTE-240M
- ‘bt2020’
BT.2020
- space
Specify output colorspace.
The accepted values are:
- ‘bt709’
BT.709
- ‘fcc’
FCC
- ‘bt470bg’
BT.470BG or BT.601-6 625
- ‘smpte170m’
SMPTE-170M or BT.601-6 525
- ‘smpte240m’
SMPTE-240M
- ‘ycgco’
YCgCo
- ‘bt2020ncl’
BT.2020 with non-constant luminance
- trc
Specify output transfer characteristics.
The accepted values are:
- ‘bt709’
BT.709
- ‘bt470m’
BT.470M
- ‘bt470bg’
BT.470BG
- ‘gamma22’
Constant gamma of 2.2
- ‘gamma28’
Constant gamma of 2.8
- ‘smpte170m’
SMPTE-170M, BT.601-6 625 or BT.601-6 525
- ‘smpte240m’
SMPTE-240M
- ‘srgb’
SRGB
- ‘iec61966-2-1’
iec61966-2-1
- ‘iec61966-2-4’
iec61966-2-4
- ‘xvycc’
xvycc
- ‘bt2020-10’
BT.2020 for 10-bits content
- ‘bt2020-12’
BT.2020 for 12-bits content
- primaries
Specify output color primaries.
The accepted values are:
- ‘bt709’
BT.709
- ‘bt470m’
BT.470M
- ‘bt470bg’
BT.470BG or BT.601-6 625
- ‘smpte170m’
SMPTE-170M or BT.601-6 525
- ‘smpte240m’
SMPTE-240M
- ‘film’
film
- ‘smpte431’
SMPTE-431
- ‘smpte432’
SMPTE-432
- ‘bt2020’
BT.2020
- ‘jedec-p22’
JEDEC P22 phosphors
- range
Specify output color range.
The accepted values are:
- ‘tv’
TV (restricted) range
- ‘mpeg’
MPEG (restricted) range
- ‘pc’
PC (full) range
- ‘jpeg’
JPEG (full) range
- format
Specify output color format.
The accepted values are:
- ‘yuv420p’
YUV 4:2:0 planar 8-bits
- ‘yuv420p10’
YUV 4:2:0 planar 10-bits
- ‘yuv420p12’
YUV 4:2:0 planar 12-bits
- ‘yuv422p’
YUV 4:2:2 planar 8-bits
- ‘yuv422p10’
YUV 4:2:2 planar 10-bits
- ‘yuv422p12’
YUV 4:2:2 planar 12-bits
- ‘yuv444p’
YUV 4:4:4 planar 8-bits
- ‘yuv444p10’
YUV 4:4:4 planar 10-bits
- ‘yuv444p12’
YUV 4:4:4 planar 12-bits
- fast
Do a fast conversion, which skips gamma/primary correction. This will take significantly less CPU, but will be mathematically incorrect. To get output compatible with that produced by the colormatrix filter, use fast=1.
- dither
Specify dithering mode.
The accepted values are:
- ‘none’
No dithering
- ‘fsb’
Floyd-Steinberg dithering
- wpadapt
Whitepoint adaptation mode.
The accepted values are:
- ‘bradford’
Bradford whitepoint adaptation
- ‘vonkries’
von Kries whitepoint adaptation
- ‘identity’
identity whitepoint adaptation (i.e. no whitepoint adaptation)
- iall
Override all input properties at once. Same accepted values as all.
- ispace
Override input colorspace. Same accepted values as space.
- iprimaries
Override input color primaries. Same accepted values as primaries.
- itrc
Override input transfer characteristics. Same accepted values as trc.
- irange
Override input color range. Same accepted values as range.
The filter converts the transfer characteristics, color space and color primaries to the specified user values. The output value, if not specified, is set to a default value based on the "all" property. If that property is also not specified, the filter will log an error. The output color range and format default to the same value as the input color range and format. The input transfer characteristics, color space, color primaries and color range should be set on the input data. If any of these are missing, the filter will log an error and no conversion will take place.
For example to convert the input to SMPTE-240M, use the command:
colorspace=smpte240m
32.42 colorspace_cuda
CUDA accelerated implementation of the colorspace filter.
It is by no means feature complete compared to the software colorspace filter, and at the current time only supports color range conversion between jpeg/full and mpeg/limited range.
The filter accepts the following options:
- range
Specify output color range.
The accepted values are:
- ‘tv’
TV (restricted) range
- ‘mpeg’
MPEG (restricted) range
- ‘pc’
PC (full) range
- ‘jpeg’
JPEG (full) range
32.43 colortemperature
Adjust color temperature in video to simulate variations in ambient color temperature.
The filter accepts the following options:
- temperature
Set the temperature in Kelvin. Allowed range is from 1000 to 40000. Default value is 6500 K.
- mix
Set mixing with filtered output. Allowed range is from 0 to 1. Default value is 1.
- pl
Set the amount of preserving lightness. Allowed range is from 0 to 1. Default value is 0.
32.43.1 Commands
This filter supports same commands as options.
32.44 convolution
Apply convolution of 3x3, 5x5, 7x7 or horizontal/vertical up to 49 elements.
The filter accepts the following options:
- 0m
- 1m
- 2m
- 3m
Set matrix for each plane. Matrix is sequence of 9, 25 or 49 signed integers in square mode, and from 1 to 49 odd number of signed integers in row mode.
- 0rdiv
- 1rdiv
- 2rdiv
- 3rdiv
Set multiplier for calculated value for each plane. If unset or 0, it will be 1/sum of all matrix elements.
- 0bias
- 1bias
- 2bias
- 3bias
Set bias for each plane. This value is added to the result of the multiplication. Useful for making the overall image brighter or darker. Default is 0.0.
- 0mode
- 1mode
- 2mode
- 3mode
Set matrix mode for each plane. Can be square, row or column. Default is square.
32.44.1 Commands
This filter supports the all above options as commands.
32.44.2 Examples
- Apply sharpen:
convolution="0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0"
- Apply blur:
convolution="1 1 1 1 1 1 1 1 1:1 1 1 1 1 1 1 1 1:1 1 1 1 1 1 1 1 1:1 1 1 1 1 1 1 1 1:1/9:1/9:1/9:1/9"
- Apply edge enhance:
convolution="0 0 0 -1 1 0 0 0 0:0 0 0 -1 1 0 0 0 0:0 0 0 -1 1 0 0 0 0:0 0 0 -1 1 0 0 0 0:5:1:1:1:0:128:128:128"
- Apply edge detect:
convolution="0 1 0 1 -4 1 0 1 0:0 1 0 1 -4 1 0 1 0:0 1 0 1 -4 1 0 1 0:0 1 0 1 -4 1 0 1 0:5:5:5:1:0:128:128:128"
- Apply laplacian edge detector which includes diagonals:
convolution="1 1 1 1 -8 1 1 1 1:1 1 1 1 -8 1 1 1 1:1 1 1 1 -8 1 1 1 1:1 1 1 1 -8 1 1 1 1:5:5:5:1:0:128:128:0"
- Apply emboss:
convolution="-2 -1 0 -1 1 1 0 1 2:-2 -1 0 -1 1 1 0 1 2:-2 -1 0 -1 1 1 0 1 2:-2 -1 0 -1 1 1 0 1 2"
32.45 convolve
Apply 2D convolution of video stream in frequency domain using second stream as impulse.
The filter accepts the following options:
- planes
Set which planes to process.
- impulse
Set which impulse video frames will be processed, can be first or all. Default is all.
The convolve
filter also supports the framesync options.
32.46 copy
Copy the input video source unchanged to the output. This is mainly useful for testing purposes.
32.47 coreimage
Video filtering on GPU using Apple’s CoreImage API on OSX.
Hardware acceleration is based on an OpenGL context. Usually, this means it is processed by video hardware. However, software-based OpenGL implementations exist which means there is no guarantee for hardware processing. It depends on the respective OSX.
There are many filters and image generators provided by Apple that come with a large variety of options. The filter has to be referenced by its name along with its options.
The coreimage filter accepts the following options:
- list_filters
List all available filters and generators along with all their respective options as well as possible minimum and maximum values along with the default values.
list_filters=true
- filter
Specify all filters by their respective name and options. Use list_filters to determine all valid filter names and options. Numerical options are specified by a float value and are automatically clamped to their respective value range. Vector and color options have to be specified by a list of space separated float values. Character escaping has to be done. A special option name
default
is available to use default options for a filter.It is required to specify either
default
or at least one of the filter options. All omitted options are used with their default values. The syntax of the filter string is as follows:filter=<NAME>@<OPTION>=<VALUE>[@<OPTION>=<VALUE>][@...][#<NAME>@<OPTION>=<VALUE>[@<OPTION>=<VALUE>][@...]][#...]
- output_rect
Specify a rectangle where the output of the filter chain is copied into the input image. It is given by a list of space separated float values:
output_rect=x\ y\ width\ height
If not given, the output rectangle equals the dimensions of the input image. The output rectangle is automatically cropped at the borders of the input image. Negative values are valid for each component.
output_rect=25\ 25\ 100\ 100
Several filters can be chained for successive processing without GPU-HOST transfers allowing for fast processing of complex filter chains. Currently, only filters with zero (generators) or exactly one (filters) input image and one output image are supported. Also, transition filters are not yet usable as intended.
Some filters generate output images with additional padding depending on the respective filter kernel. The padding is automatically removed to ensure the filter output has the same size as the input image.
For image generators, the size of the output image is determined by the previous output image of the filter chain or the input image of the whole filterchain, respectively. The generators do not use the pixel information of this image to generate their output. However, the generated output is blended onto this image, resulting in partial or complete coverage of the output image.
The coreimagesrc video source can be used for generating input images which are directly fed into the filter chain. By using it, providing input images by another video source or an input video is not required.
32.47.1 Examples
- List all filters available:
coreimage=list_filters=true
- Use the CIBoxBlur filter with default options to blur an image:
coreimage=filter=CIBoxBlur@default
- Use a filter chain with CISepiaTone at default values and CIVignetteEffect with
its center at 100x100 and a radius of 50 pixels:
coreimage=filter=CIBoxBlur@default#CIVignetteEffect@inputCenter=100\ 100@inputRadius=50
- Use nullsrc and CIQRCodeGenerator to create a QR code for the FFmpeg homepage,
given as complete and escaped command-line for Apple’s standard bash shell:
ffmpeg -f lavfi -i nullsrc=s=100x100,coreimage=filter=CIQRCodeGenerator@inputMessage=https\\\\\://FFmpeg.org/@inputCorrectionLevel=H -frames:v 1 QRCode.png
32.48 corr
Obtain the correlation between two input videos.
This filter takes two input videos.
Both input videos must have the same resolution and pixel format for this filter to work correctly. Also it assumes that both inputs have the same number of frames, which are compared one by one.
The obtained per component, average, min and max correlation is printed through the logging system.
The filter stores the calculated correlation of each frame in frame metadata.
This filter also supports the framesync options.
In the below example the input file main.mpg being processed is compared with the reference file ref.mpg.
ffmpeg -i main.mpg -i ref.mpg -lavfi corr -f null -
32.49 cover_rect
Cover a rectangular object
It accepts the following options:
- cover
Filepath of the optional cover image, needs to be in yuv420.
- mode
Set covering mode.
It accepts the following values:
- ‘cover’
cover it by the supplied image
- ‘blur’
cover it by interpolating the surrounding pixels
Default value is blur.
32.49.1 Examples
- Cover a rectangular object by the supplied image of a given video using
ffmpeg
:ffmpeg -i file.ts -vf find_rect=newref.pgm,cover_rect=cover.jpg:mode=cover new.mkv
32.50 crop
Crop the input video to given dimensions.
It accepts the following parameters:
- w, out_w
The width of the output video. It defaults to
iw
. This expression is evaluated only once during the filter configuration, or when the ‘w’ or ‘out_w’ command is sent.- h, out_h
The height of the output video. It defaults to
ih
. This expression is evaluated only once during the filter configuration, or when the ‘h’ or ‘out_h’ command is sent.- x
The horizontal position, in the input video, of the left edge of the output video. It defaults to
(in_w-out_w)/2
. This expression is evaluated per-frame.- y
The vertical position, in the input video, of the top edge of the output video. It defaults to
(in_h-out_h)/2
. This expression is evaluated per-frame.- keep_aspect
If set to 1 will force the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio. It defaults to 0.
- exact
Enable exact cropping. If enabled, subsampled videos will be cropped at exact width/height/x/y as specified and will not be rounded to nearest smaller value. It defaults to 0.
The out_w, out_h, x, y parameters are expressions containing the following constants:
- x
- y
The computed values for x and y. They are evaluated for each new frame.
- in_w
- in_h
The input width and height.
- iw
- ih
These are the same as in_w and in_h.
- out_w
- out_h
The output (cropped) width and height.
- ow
- oh
These are the same as out_w and out_h.
- a
same as iw / ih
- sar
input sample aspect ratio
- dar
input display aspect ratio, it is the same as (iw / ih) * sar
- hsub
- vsub
horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.
- n
The number of the input frame, starting from 0.
- pos
the position in the file of the input frame, NAN if unknown; deprecated, do not use
- t
The timestamp expressed in seconds. It’s NAN if the input timestamp is unknown.
The expression for out_w may depend on the value of out_h, and the expression for out_h may depend on out_w, but they cannot depend on x and y, as x and y are evaluated after out_w and out_h.
The x and y parameters specify the expressions for the position of the top-left corner of the output (non-cropped) area. They are evaluated for each frame. If the evaluated value is not valid, it is approximated to the nearest valid value.
The expression for x may depend on y, and the expression for y may depend on x.
32.50.1 Examples
- Crop area with size 100x100 at position (12,34).
crop=100:100:12:34
Using named options, the example above becomes:
crop=w=100:h=100:x=12:y=34
- Crop the central input area with size 100x100:
crop=100:100
- Crop the central input area with size 2/3 of the input video:
crop=2/3*in_w:2/3*in_h
- Crop the input video central square:
crop=out_w=in_h crop=in_h
- Delimit the rectangle with the top-left corner placed at position
100:100 and the right-bottom corner corresponding to the right-bottom
corner of the input image.
crop=in_w-100:in_h-100:100:100
- Crop 10 pixels from the left and right borders, and 20 pixels from
the top and bottom borders
crop=in_w-2*10:in_h-2*20
- Keep only the bottom right quarter of the input image:
crop=in_w/2:in_h/2:in_w/2:in_h/2
- Crop height for getting Greek harmony:
crop=in_w:1/PHI*in_w
- Apply trembling effect:
crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)
- Apply erratic camera effect depending on timestamp:
crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)
- Set x depending on the value of y:
crop=in_w/2:in_h/2:y:10+10*sin(n/10)
32.50.2 Commands
This filter supports the following commands:
- w, out_w
- h, out_h
- x
- y
Set width/height of the output video and the horizontal/vertical position in the input video. The command accepts the same syntax of the corresponding option.
If the specified expression is not valid, it is kept at its current value.
32.51 cropdetect
Auto-detect the crop size.
It calculates the necessary cropping parameters and prints the recommended parameters via the logging system. The detected dimensions correspond to the non-black or video area of the input video according to mode.
It accepts the following parameters:
- mode
Depending on mode crop detection is based on either the mere black value of surrounding pixels or a combination of motion vectors and edge pixels.
- ‘black’
Detect black pixels surrounding the playing video. For fine control use option limit.
- ‘mvedges’
Detect the playing video by the motion vectors inside the video and scanning for edge pixels typically forming the border of a playing video.
- limit
Set higher black value threshold, which can be optionally specified from nothing (0) to everything (255 for 8-bit based formats). An intensity value greater to the set value is considered non-black. It defaults to 24. You can also specify a value between 0.0 and 1.0 which will be scaled depending on the bitdepth of the pixel format.
- round
The value which the width/height should be divisible by. It defaults to 16. The offset is automatically adjusted to center the video. Use 2 to get only even dimensions (needed for 4:2:2 video). 16 is best when encoding to most video codecs.
- skip
Set the number of initial frames for which evaluation is skipped. Default is 2. Range is 0 to INT_MAX.
- reset_count, reset
Set the counter that determines after how many frames cropdetect will reset the previously detected largest video area and start over to detect the current optimal crop area. Default value is 0.
This can be useful when channel logos distort the video area. 0 indicates ’never reset’, and returns the largest area encountered during playback.
- mv_threshold
Set motion in pixel units as threshold for motion detection. It defaults to 8.
- low
- high
Set low and high threshold values used by the Canny thresholding algorithm.
The high threshold selects the "strong" edge pixels, which are then connected through 8-connectivity with the "weak" edge pixels selected by the low threshold.
low and high threshold values must be chosen in the range [0,1], and low should be lesser or equal to high.
Default value for low is
5/255
, and default value for high is15/255
.
32.51.1 Examples
- Find video area surrounded by black borders:
ffmpeg -i file.mp4 -vf cropdetect,metadata=mode=print -f null -
- Find an embedded video area, generate motion vectors beforehand:
ffmpeg -i file.mp4 -vf mestimate,cropdetect=mode=mvedges,metadata=mode=print -f null -
- Find an embedded video area, use motion vectors from decoder:
ffmpeg -flags2 +export_mvs -i file.mp4 -vf cropdetect=mode=mvedges,metadata=mode=print -f null -
32.51.2 Commands
This filter supports the following commands:
- limit
The command accepts the same syntax of the corresponding option. If the specified expression is not valid, it is kept at its current value.
32.52 cue
Delay video filtering until a given wallclock timestamp. The filter first passes on preroll amount of frames, then it buffers at most buffer amount of frames and waits for the cue. After reaching the cue it forwards the buffered frames and also any subsequent frames coming in its input.
The filter can be used synchronize the output of multiple ffmpeg processes for realtime output devices like decklink. By putting the delay in the filtering chain and pre-buffering frames the process can pass on data to output almost immediately after the target wallclock timestamp is reached.
Perfect frame accuracy cannot be guaranteed, but the result is good enough for some use cases.
- cue
The cue timestamp expressed in a UNIX timestamp in microseconds. Default is 0.
- preroll
The duration of content to pass on as preroll expressed in seconds. Default is 0.
- buffer
The maximum duration of content to buffer before waiting for the cue expressed in seconds. Default is 0.
32.53 curves
Apply color adjustments using curves.
This filter is similar to the Adobe Photoshop and GIMP curves tools. Each component (red, green and blue) has its values defined by N key points tied from each other using a smooth curve. The x-axis represents the pixel values from the input frame, and the y-axis the new pixel values to be set for the output frame.
By default, a component curve is defined by the two points (0;0) and (1;1). This creates a straight line where each original pixel value is "adjusted" to its own value, which means no change to the image.
The filter allows you to redefine these two points and add some more. A new
curve will be defined to pass smoothly through all these new coordinates. The
new defined points need to be strictly increasing over the x-axis, and their
x and y values must be in the [0;1] interval. The curve is
formed by using a natural or monotonic cubic spline interpolation, depending
on the interp option (default: natural
). The natural
spline produces a smoother curve in general while the monotonic (pchip
)
spline guarantees the transitions between the specified points to be
monotonic. If the computed curves happened to go outside the vector spaces,
the values will be clipped accordingly.
The filter accepts the following options:
- preset
Select one of the available color presets. This option can be used in addition to the r, g, b parameters; in this case, the later options takes priority on the preset values. Available presets are:
- ‘none’
- ‘color_negative’
- ‘cross_process’
- ‘darker’
- ‘increase_contrast’
- ‘lighter’
- ‘linear_contrast’
- ‘medium_contrast’
- ‘negative’
- ‘strong_contrast’
- ‘vintage’
Default is
none
.- master, m
Set the master key points. These points will define a second pass mapping. It is sometimes called a "luminance" or "value" mapping. It can be used with r, g, b or all since it acts like a post-processing LUT.
- red, r
Set the key points for the red component.
- green, g
Set the key points for the green component.
- blue, b
Set the key points for the blue component.
- all
Set the key points for all components (not including master). Can be used in addition to the other key points component options. In this case, the unset component(s) will fallback on this all setting.
- psfile
Specify a Photoshop curves file (
.acv
) to import the settings from.- plot
Save Gnuplot script of the curves in specified file.
- interp
Specify the kind of interpolation. Available algorithms are:
- ‘natural’
Natural cubic spline using a piece-wise cubic polynomial that is twice continuously differentiable.
- ‘pchip’
Monotonic cubic spline using a piecewise cubic Hermite interpolating polynomial (PCHIP).
To avoid some filtergraph syntax conflicts, each key points list need to be
defined using the following syntax: x0/y0 x1/y1 x2/y2 ...
.
32.53.1 Commands
This filter supports same commands as options.
32.53.2 Examples
- Increase slightly the middle level of blue:
curves=blue='0/0 0.5/0.58 1/1'
- Vintage effect:
curves=r='0/0.11 .42/.51 1/0.95':g='0/0 0.50/0.48 1/1':b='0/0.22 .49/.44 1/0.8'
Here we obtain the following coordinates for each components:
- red
(0;0.11) (0.42;0.51) (1;0.95)
- green
(0;0) (0.50;0.48) (1;1)
- blue
(0;0.22) (0.49;0.44) (1;0.80)
- The previous example can also be achieved with the associated built-in preset:
curves=preset=vintage
- Or simply:
curves=vintage
- Use a Photoshop preset and redefine the points of the green component:
curves=psfile='MyCurvesPresets/purple.acv':green='0/0 0.45/0.53 1/1'
- Check out the curves of the
cross_process
profile usingffmpeg
andgnuplot
:ffmpeg -f lavfi -i color -vf curves=cross_process:plot=/tmp/curves.plt -frames:v 1 -f null - gnuplot -p /tmp/curves.plt
32.54 datascope
Video data analysis filter.
This filter shows hexadecimal pixel values of part of video.
The filter accepts the following options:
- size, s
Set output video size.
- x
Set x offset from where to pick pixels.
- y
Set y offset from where to pick pixels.
- mode
Set scope mode, can be one of the following:
- ‘mono’
Draw hexadecimal pixel values with white color on black background.
- ‘color’
Draw hexadecimal pixel values with input video pixel color on black background.
- ‘color2’
Draw hexadecimal pixel values on color background picked from input video, the text color is picked in such way so its always visible.
- axis
Draw rows and columns numbers on left and top of video.
- opacity
Set background opacity.
- format
Set display number format. Can be
hex
, ordec
. Default ishex
.- components
Set pixel components to display. By default all pixel components are displayed.
32.54.1 Commands
This filter supports same commands as options excluding size
option.
32.55 dblur
Apply Directional blur filter.
The filter accepts the following options:
- angle
Set angle of directional blur. Default is
45
.- radius
Set radius of directional blur. Default is
5
.- planes
Set which planes to filter. By default all planes are filtered.
32.55.1 Commands
This filter supports same commands as options. The command accepts the same syntax of the corresponding option.
If the specified expression is not valid, it is kept at its current value.
32.56 dctdnoiz
Denoise frames using 2D DCT (frequency domain filtering).
This filter is not designed for real time.
The filter accepts the following options:
- sigma, s
Set the noise sigma constant.
This sigma defines a hard threshold of
3 * sigma
; every DCT coefficient (absolute value) below this threshold with be dropped.If you need a more advanced filtering, see expr.
Default is
0
.- overlap
Set number overlapping pixels for each block. Since the filter can be slow, you may want to reduce this value, at the cost of a less effective filter and the risk of various artefacts.
If the overlapping value doesn’t permit processing the whole input width or height, a warning will be displayed and according borders won’t be denoised.
Default value is blocksize-1, which is the best possible setting.
- expr, e
Set the coefficient factor expression.
For each coefficient of a DCT block, this expression will be evaluated as a multiplier value for the coefficient.
If this is option is set, the sigma option will be ignored.
The absolute value of the coefficient can be accessed through the c variable.
- n
Set the blocksize using the number of bits.
1<<n
defines the blocksize, which is the width and height of the processed blocks.The default value is 3 (8x8) and can be raised to 4 for a blocksize of 16x16. Note that changing this setting has huge consequences on the speed processing. Also, a larger block size does not necessarily means a better de-noising.
32.56.1 Examples
Apply a denoise with a sigma of 4.5
:
dctdnoiz=4.5
The same operation can be achieved using the expression system:
dctdnoiz=e='gte(c, 4.5*3)'
Violent denoise using a block size of 16x16
:
dctdnoiz=15:n=4
32.57 deband
Remove banding artifacts from input video. It works by replacing banded pixels with average value of referenced pixels.
The filter accepts the following options:
- 1thr
- 2thr
- 3thr
- 4thr
Set banding detection threshold for each plane. Default is 0.02. Valid range is 0.00003 to 0.5. If difference between current pixel and reference pixel is less than threshold, it will be considered as banded.
- range, r
Banding detection range in pixels. Default is 16. If positive, random number in range 0 to set value will be used. If negative, exact absolute value will be used. The range defines square of four pixels around current pixel.
- direction, d
Set direction in radians from which four pixel will be compared. If positive, random direction from 0 to set direction will be picked. If negative, exact of absolute value will be picked. For example direction 0, -PI or -2*PI radians will pick only pixels on same row and -PI/2 will pick only pixels on same column.
- blur, b
If enabled, current pixel is compared with average value of all four surrounding pixels. The default is enabled. If disabled current pixel is compared with all four surrounding pixels. The pixel is considered banded if only all four differences with surrounding pixels are less than threshold.
- coupling, c
If enabled, current pixel is changed if and only if all pixel components are banded, e.g. banding detection threshold is triggered for all color components. The default is disabled.
32.57.1 Commands
This filter supports the all above options as commands.
32.58 deblock
Remove blocking artifacts from input video.
The filter accepts the following options:
- filter
Set filter type, can be weak or strong. Default is strong. This controls what kind of deblocking is applied.
- block
Set size of block, allowed range is from 4 to 512. Default is 8.
- alpha
- beta
- gamma
- delta
Set blocking detection thresholds. Allowed range is 0 to 1. Defaults are: 0.098 for alpha and 0.05 for the rest. Using higher threshold gives more deblocking strength. Setting alpha controls threshold detection at exact edge of block. Remaining options controls threshold detection near the edge. Each one for below/above or left/right. Setting any of those to 0 disables deblocking.
- planes
Set planes to filter. Default is to filter all available planes.
32.58.1 Examples
- Deblock using weak filter and block size of 4 pixels.
deblock=filter=weak:block=4
- Deblock using strong filter, block size of 4 pixels and custom thresholds for
deblocking more edges.
deblock=filter=strong:block=4:alpha=0.12:beta=0.07:gamma=0.06:delta=0.05
- Similar as above, but filter only first plane.
deblock=filter=strong:block=4:alpha=0.12:beta=0.07:gamma=0.06:delta=0.05:planes=1
- Similar as above, but filter only second and third plane.
deblock=filter=strong:block=4:alpha=0.12:beta=0.07:gamma=0.06:delta=0.05:planes=6
32.58.2 Commands
This filter supports the all above options as commands.
32.59 decimate
Drop duplicated frames at regular intervals.
The filter accepts the following options:
- cycle
Set the number of frames from which one will be dropped. Setting this to N means one frame in every batch of N frames will be dropped. Default is
5
.- dupthresh
Set the threshold for duplicate detection. If the difference metric for a frame is less than or equal to this value, then it is declared as duplicate. Default is
1.1
- scthresh
Set scene change threshold. Default is
15
.- blockx
- blocky
Set the size of the x and y-axis blocks used during metric calculations. Larger blocks give better noise suppression, but also give worse detection of small movements. Must be a power of two. Default is
32
.- ppsrc
Mark main input as a pre-processed input and activate clean source input stream. This allows the input to be pre-processed with various filters to help the metrics calculation while keeping the frame selection lossless. When set to
1
, the first stream is for the pre-processed input, and the second stream is the clean source from where the kept frames are chosen. Default is0
.- chroma
Set whether or not chroma is considered in the metric calculations. Default is
1
.- mixed
Set whether or not the input only partially contains content to be decimated. Default is
false
. If enabled video output stream will be in variable frame rate.
32.60 deconvolve
Apply 2D deconvolution of video stream in frequency domain using second stream as impulse.
The filter accepts the following options:
- planes
Set which planes to process.
- impulse
Set which impulse video frames will be processed, can be first or all. Default is all.
- noise
Set noise when doing divisions. Default is 0.0000001. Useful when width and height are not same and not power of 2 or if stream prior to convolving had noise.
The deconvolve
filter also supports the framesync options.
32.61 dedot
Reduce cross-luminance (dot-crawl) and cross-color (rainbows) from video.
It accepts the following options:
- m
Set mode of operation. Can be combination of dotcrawl for cross-luminance reduction and/or rainbows for cross-color reduction.
- lt
Set spatial luma threshold. Lower values increases reduction of cross-luminance.
- tl
Set tolerance for temporal luma. Higher values increases reduction of cross-luminance.
- tc
Set tolerance for chroma temporal variation. Higher values increases reduction of cross-color.
- ct
Set temporal chroma threshold. Lower values increases reduction of cross-color.
32.62 deflate
Apply deflate effect to the video.
This filter replaces the pixel by the local(3x3) average by taking into account only values lower than the pixel.
It accepts the following options:
- threshold0
- threshold1
- threshold2
- threshold3
Limit the maximum change for each plane, default is 65535. If 0, plane will remain unchanged.
32.62.1 Commands
This filter supports the all above options as commands.
32.63 deflicker
Remove temporal frame luminance variations.
It accepts the following options:
- size, s
Set moving-average filter size in frames. Default is 5. Allowed range is 2 - 129.
- mode, m
Set averaging mode to smooth temporal luminance variations.
Available values are:
- ‘am’
Arithmetic mean
- ‘gm’
Geometric mean
- ‘hm’
Harmonic mean
- ‘qm’
Quadratic mean
- ‘cm’
Cubic mean
- ‘pm’
Power mean
- ‘median’
Median
- bypass
Do not actually modify frame. Useful when one only wants metadata.
32.64 dejudder
Remove judder produced by partially interlaced telecined content.
Judder can be introduced, for instance, by pullup filter. If the original
source was partially telecined content then the output of pullup,dejudder
will have a variable frame rate. May change the recorded frame rate of the
container. Aside from that change, this filter will not affect constant frame
rate video.
The option available in this filter is:
- cycle
Specify the length of the window over which the judder repeats.
Accepts any integer greater than 1. Useful values are:
- ‘4’
If the original was telecined from 24 to 30 fps (Film to NTSC).
- ‘5’
If the original was telecined from 25 to 30 fps (PAL to NTSC).
- ‘20’
If a mixture of the two.
The default is ‘4’.
32.65 delogo
Suppress a TV station logo by a simple interpolation of the surrounding pixels. Just set a rectangle covering the logo and watch it disappear (and sometimes something even uglier appear - your mileage may vary).
It accepts the following parameters:
- x
- y
Specify the top left corner coordinates of the logo. They must be specified.
- w
- h
Specify the width and height of the logo to clear. They must be specified.
- show
When set to 1, a green rectangle is drawn on the screen to simplify finding the right x, y, w, and h parameters. The default value is 0.
The rectangle is drawn on the outermost pixels which will be (partly) replaced with interpolated values. The values of the next pixels immediately outside this rectangle in each direction will be used to compute the interpolated pixel values inside the rectangle.
32.65.1 Examples
- Set a rectangle covering the area with top left corner coordinates 0,0
and size 100x77:
delogo=x=0:y=0:w=100:h=77
32.66 derain
Remove the rain in the input image/video by applying the derain methods based on convolutional neural networks. Supported models:
- Recurrent Squeeze-and-Excitation Context Aggregation Net (RESCAN). See http://openaccess.thecvf.com/content_ECCV_2018/papers/Xia_Li_Recurrent_Squeeze-and-Excitation_Context_ECCV_2018_paper.pdf.
Training as well as model generation scripts are provided in the repository at https://github.com/XueweiMeng/derain_filter.git.
The filter accepts the following options:
- filter_type
Specify which filter to use. This option accepts the following values:
- ‘derain’
Derain filter. To conduct derain filter, you need to use a derain model.
- ‘dehaze’
Dehaze filter. To conduct dehaze filter, you need to use a dehaze model.
Default value is ‘derain’.
- dnn_backend
Specify which DNN backend to use for model loading and execution. This option accepts the following values:
- ‘tensorflow’
TensorFlow backend. To enable this backend you need to install the TensorFlow for C library (see https://www.tensorflow.org/install/lang_c) and configure FFmpeg with
--enable-libtensorflow
- model
Set path to model file specifying network architecture and its parameters. Note that different backends use different file formats. TensorFlow can load files for only its format.
To get full functionality (such as async execution), please use the dnn_processing filter.
32.67 deshake
Attempt to fix small changes in horizontal and/or vertical shift. This filter helps remove camera shake from hand-holding a camera, bumping a tripod, moving on a vehicle, etc.
The filter accepts the following options:
- x
- y
- w
- h
Specify a rectangular area where to limit the search for motion vectors. If desired the search for motion vectors can be limited to a rectangular area of the frame defined by its top left corner, width and height. These parameters have the same meaning as the drawbox filter which can be used to visualise the position of the bounding box.
This is useful when simultaneous movement of subjects within the frame might be confused for camera motion by the motion vector search.
If any or all of x, y, w and h are set to -1 then the full frame is used. This allows later options to be set without specifying the bounding box for the motion vector search.
Default - search the whole frame.
- rx
- ry
Specify the maximum extent of movement in x and y directions in the range 0-64 pixels. Default 16.
- edge
Specify how to generate pixels to fill blanks at the edge of the frame. Available values are:
- ‘blank, 0’
Fill zeroes at blank locations
- ‘original, 1’
Original image at blank locations
- ‘clamp, 2’
Extruded edge value at blank locations
- ‘mirror, 3’
Mirrored edge at blank locations
Default value is ‘mirror’.
- blocksize
Specify the blocksize to use for motion search. Range 4-128 pixels, default 8.
- contrast
Specify the contrast threshold for blocks. Only blocks with more than the specified contrast (difference between darkest and lightest pixels) will be considered. Range 1-255, default 125.
- search
Specify the search strategy. Available values are:
- ‘exhaustive, 0’
Set exhaustive search
- ‘less, 1’
Set less exhaustive search.
Default value is ‘exhaustive’.
- filename
If set then a detailed log of the motion search is written to the specified file.
32.68 despill
Remove unwanted contamination of foreground colors, caused by reflected color of greenscreen or bluescreen.
This filter accepts the following options:
- type
Set what type of despill to use.
- mix
Set how spillmap will be generated.
- expand
Set how much to get rid of still remaining spill.
- red
Controls amount of red in spill area.
- green
Controls amount of green in spill area. Should be -1 for greenscreen.
- blue
Controls amount of blue in spill area. Should be -1 for bluescreen.
- brightness
Controls brightness of spill area, preserving colors.
- alpha
Modify alpha from generated spillmap.
32.68.1 Commands
This filter supports the all above options as commands.
32.69 detelecine
Apply an exact inverse of the telecine operation. It requires a predefined pattern specified using the pattern option which must be the same as that passed to the telecine filter.
This filter accepts the following options:
- first_field
- ‘top, t’
top field first
- ‘bottom, b’
bottom field first The default value is
top
.
- pattern
A string of numbers representing the pulldown pattern you wish to apply. The default value is
23
.- start_frame
A number representing position of the first frame with respect to the telecine pattern. This is to be used if the stream is cut. The default value is
0
.
32.70 dilation
Apply dilation effect to the video.
This filter replaces the pixel by the local(3x3) maximum.
It accepts the following options:
- threshold0
- threshold1
- threshold2
- threshold3
Limit the maximum change for each plane, default is 65535. If 0, plane will remain unchanged.
- coordinates
Flag which specifies the pixel to refer to. Default is 255 i.e. all eight pixels are used.
Flags to local 3x3 coordinates maps like this:
1 2 3 4 5 6 7 8
32.70.1 Commands
This filter supports the all above options as commands.
32.71 displace
Displace pixels as indicated by second and third input stream.
It takes three input streams and outputs one stream, the first input is the source, and second and third input are displacement maps.
The second input specifies how much to displace pixels along the x-axis, while the third input specifies how much to displace pixels along the y-axis. If one of displacement map streams terminates, last frame from that displacement map will be used.
Note that once generated, displacements maps can be reused over and over again.
A description of the accepted options follows.
- edge
Set displace behavior for pixels that are out of range.
Available values are:
- ‘blank’
Missing pixels are replaced by black pixels.
- ‘smear’
Adjacent pixels will spread out to replace missing pixels.
- ‘wrap’
Out of range pixels are wrapped so they point to pixels of other side.
- ‘mirror’
Out of range pixels will be replaced with mirrored pixels.
Default is ‘smear’.
32.71.1 Examples
- Add ripple effect to rgb input of video size hd720:
ffmpeg -i INPUT -f lavfi -i nullsrc=s=hd720,lutrgb=128:128:128 -f lavfi -i nullsrc=s=hd720,geq='r=128+30*sin(2*PI*X/400+T):g=128+30*sin(2*PI*X/400+T):b=128+30*sin(2*PI*X/400+T)' -lavfi '[0][1][2]displace' OUTPUT
- Add wave effect to rgb input of video size hd720:
ffmpeg -i INPUT -f lavfi -i nullsrc=hd720,geq='r=128+80*(sin(sqrt((X-W/2)*(X-W/2)+(Y-H/2)*(Y-H/2))/220*2*PI+T)):g=128+80*(sin(sqrt((X-W/2)*(X-W/2)+(Y-H/2)*(Y-H/2))/220*2*PI+T)):b=128+80*(sin(sqrt((X-W/2)*(X-W/2)+(Y-H/2)*(Y-H/2))/220*2*PI+T))' -lavfi '[1]split[x][y],[0][x][y]displace' OUTPUT
32.72 dnn_classify
Do classification with deep neural networks based on bounding boxes.
The filter accepts the following options:
- dnn_backend
Specify which DNN backend to use for model loading and execution. This option accepts only openvino now, tensorflow backends will be added.
- model
Set path to model file specifying network architecture and its parameters. Note that different backends use different file formats.
- input
Set the input name of the dnn network.
- output
Set the output name of the dnn network.
- confidence
Set the confidence threshold (default: 0.5).
- labels
Set path to label file specifying the mapping between label id and name. Each label name is written in one line, tailing spaces and empty lines are skipped. The first line is the name of label id 0, and the second line is the name of label id 1, etc. The label id is considered as name if the label file is not provided.
- backend_configs
Set the configs to be passed into backend
For tensorflow backend, you can set its configs with sess_config options, please use tools/python/tf_sess_config.py to get the configs for your system.
32.73 dnn_detect
Do object detection with deep neural networks.
The filter accepts the following options:
- dnn_backend
Specify which DNN backend to use for model loading and execution. This option accepts only openvino now, tensorflow backends will be added.
- model
Set path to model file specifying network architecture and its parameters. Note that different backends use different file formats.
- input
Set the input name of the dnn network.
- output
Set the output name of the dnn network.
- confidence
Set the confidence threshold (default: 0.5).
- labels
Set path to label file specifying the mapping between label id and name. Each label name is written in one line, tailing spaces and empty lines are skipped. The first line is the name of label id 0 (usually it is ’background’), and the second line is the name of label id 1, etc. The label id is considered as name if the label file is not provided.
- backend_configs
Set the configs to be passed into backend. To use async execution, set async (default: set). Roll back to sync execution if the backend does not support async.
32.74 dnn_processing
Do image processing with deep neural networks. It works together with another filter which converts the pixel format of the Frame to what the dnn network requires.
The filter accepts the following options:
- dnn_backend
Specify which DNN backend to use for model loading and execution. This option accepts the following values:
- ‘tensorflow’
TensorFlow backend. To enable this backend you need to install the TensorFlow for C library (see https://www.tensorflow.org/install/lang_c) and configure FFmpeg with
--enable-libtensorflow
- ‘openvino’
OpenVINO backend. To enable this backend you need to build and install the OpenVINO for C library (see https://github.com/openvinotoolkit/openvino/blob/master/build-instruction.md) and configure FFmpeg with
--enable-libopenvino
(–extra-cflags=-I... –extra-ldflags=-L... might be needed if the header files and libraries are not installed into system path)- ‘torch’
Libtorch backend. To enable this backend you need to build and install Libtroch for C++ library. Please download cxx11 ABI version (see https://pytorch.org/get-started/locally) and configure FFmpeg with
--enable-libtorch --extra-cflags=-I/libtorch_root/libtorch/include --extra-cflags=-I/libtorch_root/libtorch/include/torch/csrc/api/include --extra-ldflags=-L/libtorch_root/libtorch/lib/
- model
Set path to model file specifying network architecture and its parameters. Note that different backends use different file formats. TensorFlow, OpenVINO and Libtorch backend can load files for only its format.
- input
Set the input name of the dnn network.
- output
Set the output name of the dnn network.
- backend_configs
Set the configs to be passed into backend. To use async execution, set async (default: set). Roll back to sync execution if the backend does not support async.
For tensorflow backend, you can set its configs with sess_config options, please use tools/python/tf_sess_config.py to get the configs of TensorFlow backend for your system.
32.74.1 Examples
- Remove rain in rgb24 frame with can.pb (see derain filter):
./ffmpeg -i rain.jpg -vf format=rgb24,dnn_processing=dnn_backend=tensorflow:model=can.pb:input=x:output=y derain.jpg
- Handle the Y channel with srcnn.pb (see sr filter) for frame with yuv420p (planar YUV formats supported):
./ffmpeg -i 480p.jpg -vf format=yuv420p,scale=w=iw*2:h=ih*2,dnn_processing=dnn_backend=tensorflow:model=srcnn.pb:input=x:output=y -y srcnn.jpg
- Handle the Y channel with espcn.pb (see sr filter), which changes frame size, for format yuv420p (planar YUV formats supported),
please use tools/python/tf_sess_config.py to get the configs of TensorFlow backend for your system.
./ffmpeg -i 480p.jpg -vf format=yuv420p,dnn_processing=dnn_backend=tensorflow:model=espcn.pb:input=x:output=y:backend_configs=sess_config=0x10022805320e09cdccccccccccec3f20012a01303801 -y tmp.espcn.jpg
32.75 drawbox
Draw a colored box on the input image.
It accepts the following parameters:
- x
- y
The expressions which specify the top left corner coordinates of the box. It defaults to 0.
- width, w
- height, h
The expressions which specify the width and height of the box; if 0 they are interpreted as the input width and height. It defaults to 0.
- color, c
Specify the color of the box to write. For the general syntax of this option, check the (ffmpeg-utils)"Color" section in the ffmpeg-utils manual. If the special value
invert
is used, the box edge color is the same as the video with inverted luma.- thickness, t
The expression which sets the thickness of the box edge. A value of
fill
will create a filled box. Default value is3
.See below for the list of accepted constants.
- replace
Applicable if the input has alpha. With value
1
, the pixels of the painted box will overwrite the video’s color and alpha pixels. Default is0
, which composites the box onto the input, leaving the video’s alpha intact.
The parameters for x, y, w and h and t are expressions containing the following constants:
- dar
The input display aspect ratio, it is the same as (w / h) * sar.
- hsub
- vsub
horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.
- in_h, ih
- in_w, iw
The input width and height.
- sar
The input sample aspect ratio.
- x
- y
The x and y offset coordinates where the box is drawn.
- w
- h
The width and height of the drawn box.
- box_source
Box source can be set as side_data_detection_bboxes if you want to use box data in detection bboxes of side data.
If box_source is set, the x, y, width and height will be ignored and still use box data in detection bboxes of side data. So please do not use this parameter if you were not sure about the box source.
- t
The thickness of the drawn box.
These constants allow the x, y, w, h and t expressions to refer to each other, so you may for example specify
y=x/dar
orh=w/dar
.
32.75.1 Examples
- Draw a black box around the edge of the input image:
drawbox
- Draw a box with color red and an opacity of 50%:
drawbox=10:20:200:60:red@0.5
The previous example can be specified as:
drawbox=x=10:y=20:w=200:h=60:color=red@0.5
- Fill the box with pink color:
drawbox=x=10:y=10:w=100:h=100:color=pink@0.5:t=fill
- Draw a 2-pixel red 2.40:1 mask:
drawbox=x=-t:y=0.5*(ih-iw/2.4)-t:w=iw+t*2:h=iw/2.4+t*2:t=2:c=red
32.75.2 Commands
This filter supports same commands as options. The command accepts the same syntax of the corresponding option.
If the specified expression is not valid, it is kept at its current value.
32.76 drawgraph
Draw a graph using input video metadata.
It accepts the following parameters:
- m1
Set 1st frame metadata key from which metadata values will be used to draw a graph.
- fg1
Set 1st foreground color expression.
- m2
Set 2nd frame metadata key from which metadata values will be used to draw a graph.
- fg2
Set 2nd foreground color expression.
- m3
Set 3rd frame metadata key from which metadata values will be used to draw a graph.
- fg3
Set 3rd foreground color expression.
- m4
Set 4th frame metadata key from which metadata values will be used to draw a graph.
- fg4
Set 4th foreground color expression.
- min
Set minimal value of metadata value.
- max
Set maximal value of metadata value.
- bg
Set graph background color. Default is white.
- mode
Set graph mode.
Available values for mode is:
- ‘bar’
- ‘dot’
- ‘line’
Default is
line
.- slide
Set slide mode.
Available values for slide is:
- ‘frame’
Draw new frame when right border is reached.
- ‘replace’
Replace old columns with new ones.
- ‘scroll’
Scroll from right to left.
- ‘rscroll’
Scroll from left to right.
- ‘picture’
Draw single picture.
Default is
frame
.- size
Set size of graph video. For the syntax of this option, check the (ffmpeg-utils)"Video size" section in the ffmpeg-utils manual. The default value is
900x256
.- rate, r
Set the output frame rate. Default value is
25
.The foreground color expressions can use the following variables:
- MIN
Minimal value of metadata value.
- MAX
Maximal value of metadata value.
- VAL
Current metadata key value.
The color is defined as 0xAABBGGRR.
Example using metadata from signalstats filter:
signalstats,drawgraph=lavfi.signalstats.YAVG:min=0:max=255
Example using metadata from ebur128 filter:
ebur128=metadata=1,adrawgraph=lavfi.r128.M:min=-120:max=5
32.77 drawgrid
Draw a grid on the input image.
It accepts the following parameters:
- x
- y
The expressions which specify the coordinates of some point of grid intersection (meant to configure offset). Both default to 0.
- width, w
- height, h
The expressions which specify the width and height of the grid cell, if 0 they are interpreted as the input width and height, respectively, minus
thickness
, so image gets framed. Default to 0.- color, c
Specify the color of the grid. For the general syntax of this option, check the (ffmpeg-utils)"Color" section in the ffmpeg-utils manual. If the special value
invert
is used, the grid color is the same as the video with inverted luma.- thickness, t
The expression which sets the thickness of the grid line. Default value is
1
.See below for the list of accepted constants.
- replace
Applicable if the input has alpha. With
1
the pixels of the painted grid will overwrite the video’s color and alpha pixels. Default is0
, which composites the grid onto the input, leaving the video’s alpha intact.
The parameters for x, y, w and h and t are expressions containing the following constants:
- dar
The input display aspect ratio, it is the same as (w / h) * sar.
- hsub
- vsub
horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.
- in_h, ih
- in_w, iw
The input grid cell width and height.
- sar
The input sample aspect ratio.
- x
- y
The x and y coordinates of some point of grid intersection (meant to configure offset).
- w
- h
The width and height of the drawn cell.
- t
The thickness of the drawn cell.
These constants allow the x, y, w, h and t expressions to refer to each other, so you may for example specify
y=x/dar
orh=w/dar
.
32.77.1 Examples
- Draw a grid with cell 100x100 pixels, thickness 2 pixels, with color red and an opacity of 50%:
drawgrid=width=100:height=100:thickness=2:color=red@0.5
- Draw a white 3x3 grid with an opacity of 50%:
drawgrid=w=iw/3:h=ih/3:t=2:c=white@0.5
32.77.2 Commands
This filter supports same commands as options. The command accepts the same syntax of the corresponding option.
If the specified expression is not valid, it is kept at its current value.
32.78 drawtext
Draw a text string or text from a specified file on top of a video, using the libfreetype library.
To enable compilation of this filter, you need to configure FFmpeg with
--enable-libfreetype
and --enable-libharfbuzz
.
To enable default font fallback and the font option you need to
configure FFmpeg with --enable-libfontconfig
.
To enable the text_shaping option, you need to configure FFmpeg with
--enable-libfribidi
.
32.78.1 Syntax
It accepts the following parameters:
- box
Used to draw a box around text using the background color. The value must be either 1 (enable) or 0 (disable). The default value of box is 0.
- boxborderw
Set the width of the border to be drawn around the box using boxcolor. The value must be specified using one of the following formats:
-
boxborderw=10
set the width of all the borders to 10 -
boxborderw=10|20
set the width of the top and bottom borders to 10 and the width of the left and right borders to 20 -
boxborderw=10|20|30
set the width of the top border to 10, the width of the bottom border to 30 and the width of the left and right borders to 20 -
boxborderw=10|20|30|40
set the borders width to 10 (top), 20 (right), 30 (bottom), 40 (left)
The default value of boxborderw is "0".
-
- boxcolor
The color to be used for drawing box around text. For the syntax of this option, check the (ffmpeg-utils)"Color" section in the ffmpeg-utils manual.
The default value of boxcolor is "white".
- line_spacing
Set the line spacing in pixels. The default value of line_spacing is 0.
- text_align
Set the vertical and horizontal alignment of the text with respect to the box boundaries. The value is combination of flags, one for the vertical alignment (T=top, M=middle, B=bottom) and one for the horizontal alignment (L=left, C=center, R=right). Please note that tab characters are only supported with the left horizontal alignment.
- y_align
Specify what the y value is referred to. Possible values are:
-
text
the top of the highest glyph of the first text line is placed at y -
baseline
the baseline of the first text line is placed at y -
font
the baseline of the first text line is placed at y plus the ascent (in pixels) defined in the font metrics
The default value of y_align is "text" for backward compatibility.
-
- borderw
Set the width of the border to be drawn around the text using bordercolor. The default value of borderw is 0.
- bordercolor
Set the color to be used for drawing border around text. For the syntax of this option, check the (ffmpeg-utils)"Color" section in the ffmpeg-utils manual.
The default value of bordercolor is "black".
- expansion
Select how the text is expanded. Can be either
none
,strftime
(deprecated) ornormal
(default). See the Text expansion section below for details.- basetime
Set a start time for the count. Value is in microseconds. Only applied in the deprecated
strftime
expansion mode. To emulate in normal expansion mode use thepts
function, supplying the start time (in seconds) as the second argument.- fix_bounds
If true, check and fix text coords to avoid clipping.
- fontcolor
The color to be used for drawing fonts. For the syntax of this option, check the (ffmpeg-utils)"Color" section in the ffmpeg-utils manual.
The default value of fontcolor is "black".
- fontcolor_expr
String which is expanded the same way as text to obtain dynamic fontcolor value. By default this option has empty value and is not processed. When this option is set, it overrides fontcolor option.
- font
The font family to be used for drawing text. By default Sans.
- fontfile
The font file to be used for drawing text. The path must be included. This parameter is mandatory if the fontconfig support is disabled.
- alpha
Draw the text applying alpha blending. The value can be a number between 0.0 and 1.0. The expression accepts the same variables x, y as well. The default value is 1. Please see fontcolor_expr.
- fontsize
The font size to be used for drawing text. The default value of fontsize is 16.
- text_shaping
If set to 1, attempt to shape the text (for example, reverse the order of right-to-left text and join Arabic characters) before drawing it. Otherwise, just draw the text exactly as given. By default 1 (if supported).
- ft_load_flags
The flags to be used for loading the fonts.
The flags map the corresponding flags supported by libfreetype, and are a combination of the following values:
- default
- no_scale
- no_hinting
- render
- no_bitmap
- vertical_layout
- force_autohint
- crop_bitmap
- pedantic
- ignore_global_advance_width
- no_recurse
- ignore_transform
- monochrome
- linear_design
- no_autohint
Default value is "default".
For more information consult the documentation for the FT_LOAD_* libfreetype flags.
- shadowcolor
The color to be used for drawing a shadow behind the drawn text. For the syntax of this option, check the (ffmpeg-utils)"Color" section in the ffmpeg-utils manual.
The default value of shadowcolor is "black".
- boxw
Set the width of the box to be drawn around text. The default value of boxw is computed automatically to match the text width
- boxh
Set the height of the box to be drawn around text. The default value of boxh is computed automatically to match the text height
- shadowx
- shadowy
The x and y offsets for the text shadow position with respect to the position of the text. They can be either positive or negative values. The default value for both is "0".
- start_number
The starting frame number for the n/frame_num variable. The default value is "0".
- tabsize
The size in number of spaces to use for rendering the tab. Default value is 4.
- timecode
Set the initial timecode representation in "hh:mm:ss[:;.]ff" format. It can be used with or without text parameter. timecode_rate option must be specified.
- timecode_rate, rate, r
Set the timecode frame rate (timecode only). Value will be rounded to nearest integer. Minimum value is "1". Drop-frame timecode is supported for frame rates 30 & 60.
- tc24hmax
If set to 1, the output of the timecode option will wrap around at 24 hours. Default is 0 (disabled).
- text
The text string to be drawn. The text must be a sequence of UTF-8 encoded characters. This parameter is mandatory if no file is specified with the parameter textfile.
- textfile
A text file containing text to be drawn. The text must be a sequence of UTF-8 encoded characters.
This parameter is mandatory if no text string is specified with the parameter text.
If both text and textfile are specified, an error is thrown.
- text_source
Text source should be set as side_data_detection_bboxes if you want to use text data in detection bboxes of side data.
If text source is set, text and textfile will be ignored and still use text data in detection bboxes of side data. So please do not use this parameter if you are not sure about the text source.
- reload
The textfile will be reloaded at specified frame interval. Be sure to update textfile atomically, or it may be read partially, or even fail. Range is 0 to INT_MAX. Default is 0.
- x
- y
The expressions which specify the offsets where text will be drawn within the video frame. They are relative to the top/left border of the output image.
The default value of x and y is "0".
See below for the list of accepted constants and functions.
The parameters for x and y are expressions containing the following constants and functions:
- dar
input display aspect ratio, it is the same as (w / h) * sar
- hsub
- vsub
horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.
- line_h, lh
the height of each text line
- main_h, h, H
the input height
- main_w, w, W
the input width
- max_glyph_a, ascent
the maximum distance from the baseline to the highest/upper grid coordinate used to place a glyph outline point, for all the rendered glyphs. It is a positive value, due to the grid’s orientation with the Y axis upwards.
- max_glyph_d, descent
the maximum distance from the baseline to the lowest grid coordinate used to place a glyph outline point, for all the rendered glyphs. This is a negative value, due to the grid’s orientation, with the Y axis upwards.
- max_glyph_h
maximum glyph height, that is the maximum height for all the glyphs contained in the rendered text, it is equivalent to ascent - descent.
- max_glyph_w
maximum glyph width, that is the maximum width for all the glyphs contained in the rendered text
- font_a
the ascent size defined in the font metrics
- font_d
the descent size defined in the font metrics
- top_a
the maximum ascender of the glyphs of the first text line
- bottom_d
the maximum descender of the glyphs of the last text line
- n
the number of input frame, starting from 0
- rand(min, max)
return a random number included between min and max
- sar
The input sample aspect ratio.
- t
timestamp expressed in seconds, NAN if the input timestamp is unknown
- text_h, th
the height of the rendered text
- text_w, tw
the width of the rendered text
- x
- y
the x and y offset coordinates where the text is drawn.
These parameters allow the x and y expressions to refer to each other, so you can for example specify
y=x/dar
.- pict_type
A one character description of the current frame’s picture type.
- pkt_pos
The current packet’s position in the input file or stream (in bytes, from the start of the input). A value of -1 indicates this info is not available.
- duration
The current packet’s duration, in seconds.
- pkt_size
The current packet’s size (in bytes).
32.78.2 Text expansion
If expansion is set to strftime
, the filter recognizes
sequences accepted by the strftime
C function in the provided
text and expands them accordingly. Check the documentation of
strftime
. This feature is deprecated in favor of normal
expansion with the gmtime
or localtime
expansion
functions.
If expansion is set to none
, the text is printed verbatim.
If expansion is set to normal
(which is the default),
the following expansion mechanism is used.
The backslash character ‘\’, followed by any character, always expands to the second character.
Sequences of the form %{...}
are expanded. The text between the
braces is a function name, possibly followed by arguments separated by ’:’.
If the arguments contain special characters or delimiters (’:’ or ’}’),
they should be escaped.
Note that they probably must also be escaped as the value for the text option in the filter argument string and as the filter argument in the filtergraph description, and possibly also for the shell, that makes up to four levels of escaping; using a text file with the textfile option avoids these problems.
The following functions are available:
expr, e
The expression evaluation result.
It must take one argument specifying the expression to be evaluated, which accepts the same constants and functions as the x and y values. Note that not all constants should be used, for example the text size is not known when evaluating the expression, so the constants text_w and text_h will have an undefined value.
expr_int_format, eif
Evaluate the expression’s value and output as formatted integer.
The first argument is the expression to be evaluated, just as for the expr function. The second argument specifies the output format. Allowed values are ‘x’, ‘X’, ‘d’ and ‘u’. They are treated exactly as in the
printf
function. The third parameter is optional and sets the number of positions taken by the output. It can be used to add padding with zeros from the left.gmtime
The time at which the filter is running, expressed in UTC. It can accept an argument: a
strftime
C function format string. The format string is extended to support the variable %[1-6]N which prints fractions of the second with optionally specified number of digits.localtime
The time at which the filter is running, expressed in the local time zone. It can accept an argument: a
strftime
C function format string. The format string is extended to support the variable %[1-6]N which prints fractions of the second with optionally specified number of digits.metadata
Frame metadata. Takes one or two arguments.
The first argument is mandatory and specifies the metadata key.
The second argument is optional and specifies a default value, used when the metadata key is not found or empty.
Available metadata can be identified by inspecting entries starting with TAG included within each frame section printed by running
ffprobe -show_frames
.String metadata generated in filters leading to the drawtext filter are also available.
n, frame_num
The frame number, starting from 0.
pict_type
A one character description of the current picture type.
pts
The timestamp of the current frame. It can take up to three arguments.
The first argument is the format of the timestamp; it defaults to
flt
for seconds as a decimal number with microsecond accuracy;hms
stands for a formatted [-]HH:MM:SS.mmm timestamp with millisecond accuracy.gmtime
stands for the timestamp of the frame formatted as UTC time;localtime
stands for the timestamp of the frame formatted as local time zone time.The second argument is an offset added to the timestamp.
If the format is set to
hms
, a third argument24HH
may be supplied to present the hour part of the formatted timestamp in 24h format (00-23).If the format is set to
localtime
orgmtime
, a third argument may be supplied: astrftime
C function format string. By default, YYYY-MM-DD HH:MM:SS format will be used.
32.78.3 Commands
This filter supports altering parameters via commands:
- reinit
Alter existing filter parameters.
Syntax for the argument is the same as for filter invocation, e.g.
fontsize=56:fontcolor=green:text='Hello World'
Full filter invocation with sendcmd would look like this:
sendcmd=c='56.0 drawtext reinit fontsize=56\:fontcolor=green\:text=Hello\\ World'
If the entire argument can’t be parsed or applied as valid values then the filter will continue with its existing parameters.
The following options are also supported as commands:
- x
- y
- alpha
- fontsize
- fontcolor
- boxcolor
- bordercolor
- shadowcolor
- box
- boxw
- boxh
- boxborderw
- line_spacing
- text_align
- shadowx
- shadowy
- borderw
32.78.4 Examples
- Draw "Test Text" with font FreeSerif, using the default values for the
optional parameters.
drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
- Draw ’Test Text’ with font FreeSerif of size 24 at position x=100
and y=50 (counting from the top-left corner of the screen), text is
yellow with a red box around it. Both the text and the box have an
opacity of 20%.
drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\ x=100: y=50: fontsize=24: fontcolor=yellow@0.2: box=1: boxcolor=red@0.2"
Note that the double quotes are not necessary if spaces are not used within the parameter list.
- Show the text at the center of the video frame:
drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h)/2"
- Show the text at a random position, switching to a new position every 30 seconds:
drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=if(eq(mod(t\,30)\,0)\,rand(0\,(w-text_w))\,x):y=if(eq(mod(t\,30)\,0)\,rand(0\,(h-text_h))\,y)"
- Show a text line sliding from right to left in the last row of the video
frame. The file LONG_LINE is assumed to contain a single line
with no newlines.
drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
- Show the content of file CREDITS off the bottom of the frame and scroll up.
drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
- Draw a single green letter "g", at the center of the input video.
The glyph baseline is placed at half screen height.
drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
- Show text for 1 second every 3 seconds:
drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:enable=lt(mod(t\,3)\,1):text='blink'"
- Use fontconfig to set the font. Note that the colons need to be escaped.
drawtext='fontfile=Linux Libertine O-40\\:style=Semibold:text=FFmpeg'
- Draw "Test Text" with font size dependent on height of the video.
drawtext="text='Test Text': fontsize=h/30: x=(w-text_w)/2: y=(h-text_h*2)"
- Print the date of a real-time encoding (see documentation for the
strftime
C function):drawtext='fontfile=FreeSans.ttf:text=%{localtime\:%a %b %d %Y}'
- Show text fading in and out (appearing/disappearing):
#!/bin/sh DS=1.0 # display start DE=10.0 # display end FID=1.5 # fade in duration FOD=5 # fade out duration ffplay -f lavfi "color,drawtext=text=TEST:fontsize=50:fontfile=FreeSerif.ttf:fontcolor_expr=ff0000%{eif\\\\: clip(255*(1*between(t\\, $DS + $FID\\, $DE - $FOD) + ((t - $DS)/$FID)*between(t\\, $DS\\, $DS + $FID) + (-(t - $DE)/$FOD)*between(t\\, $DE - $FOD\\, $DE) )\\, 0\\, 255) \\\\: x\\\\: 2 }"
- Horizontally align multiple separate texts. Note that max_glyph_a
and the fontsize value are included in the y offset.
drawtext=fontfile=FreeSans.ttf:text=DOG:fontsize=24:x=10:y=20+24-max_glyph_a, drawtext=fontfile=FreeSans.ttf:text=cow:fontsize=24:x=80:y=20+24-max_glyph_a
- Plot special lavf.image2dec.source_basename metadata onto each frame if
such metadata exists. Otherwise, plot the string "NA". Note that image2 demuxer
must have option -export_path_metadata 1 for the special metadata fields
to be available for filters.
drawtext="fontsize=20:fontcolor=white:fontfile=FreeSans.ttf:text='%{metadata\:lavf.image2dec.source_basename\:NA}':x=10:y=10"
For more information about libfreetype, check: http://www.freetype.org/.
For more information about fontconfig, check: http://freedesktop.org/software/fontconfig/fontconfig-user.html.
For more information about libfribidi, check: http://fribidi.org/.
For more information about libharfbuzz, check: https://github.com/harfbuzz/harfbuzz.
32.79 edgedetect
Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
The filter accepts the following options:
- low
- high
Set low and high threshold values used by the Canny thresholding algorithm.
The high threshold selects the "strong" edge pixels, which are then connected through 8-connectivity with the "weak" edge pixels selected by the low threshold.
low and high threshold values must be chosen in the range [0,1], and low should be lesser or equal to high.
Default value for low is
20/255
, and default value for high is50/255
.- mode
Define the drawing mode.
- ‘wires’
Draw white/gray wires on black background.
- ‘colormix’
Mix the colors to create a paint/cartoon effect.
- ‘canny’
Apply Canny edge detector on all selected planes.
Default value is wires.
- planes
Select planes for filtering. By default all available planes are filtered.
32.79.1 Examples
- Standard edge detection with custom values for the hysteresis thresholding: