FFmpeg Codecs Documentation

Table of Contents

1 Description

This document describes the codecs (decoders and encoders) provided by the libavcodec library.

2 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 unsensical 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.

gmc

Use gmc.

mv0

Always try a mb with mv=<0,0>.

input_preserved
pass1

Use internal 2pass ratecontrol in first pass mode.

pass2

Use internal 2pass ratecontrol in second pass mode.

gray

Only decode/encode grayscale.

emu_edge

Do not draw edges.

psnr

Set error[?] variables during encoding.

truncated
naq

Normalize adaptive quantization.

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 reproducable and match between platforms. Its primary use is for regression testing.

aic

Apply H263 advanced intra coding / mpeg4 ac prediction.

cbp

Deprecated, use mpegvideo private options instead.

qprd

Deprecated, use mpegvideo private options instead.

ilme

Apply interlaced motion estimation.

cgop

Use closed gop.

me_method integer (encoding,video)

Set motion estimation method.

Possible values:

zero

zero motion estimation (fastest)

full

full motion estimation (slowest)

epzs

EPZS motion estimation (default)

esa

esa motion estimation (alias for full)

tesa

tesa motion estimation

dia

dia motion estimation (alias for epzs)

log

log motion estimation

phods

phods motion estimation

x1

X1 motion estimation

hex

hex motion estimation

umh

umh motion estimation

iter

iter motion estimation

extradata_size integer

Set extradata size.

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 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.

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.

rc_strategy integer (encoding,video)

Set ratecontrol method.

b_strategy integer (encoding,video)

Set strategy to choose between I/P/B-frames.

ps integer (encoding,video)

Set RTP payload size in bytes.

mv_bits integer
header_bits integer
i_tex_bits integer
p_tex_bits integer
i_count integer
p_count integer
skip_count integer
misc_bits integer
frame_bits integer
codec_tag integer
bug flags (decoding,video)

Workaround not auto detected encoder bugs.

Possible values:

autodetect
old_msmpeg4

some old lavc generated msmpeg4v3 files (no autodetection)

xvid_ilace

Xvid interlacing bug (autodetected if fourcc==XVIX)

ump4

(autodetected if fourcc==UMP4)

no_padding

padding bug (autodetected)

amv
ac_vlc

illegal vlc bug (autodetected per fourcc)

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

lelim integer (encoding,video)

Set single coefficient elimination threshold for luminance (negative values also consider DC coefficient).

celim integer (encoding,video)

Set single coefficient elimination threshold for chrominance (negative values also consider dc coefficient)

strict integer (decoding/encoding,audio,video)

Specify how strictly to follow the standards.

Possible values:

very

strictly conform to a 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
mpeg_quant integer (encoding,video)

Use MPEG quantizers instead of H.263.

qsquish float (encoding,video)

How to keep quantizer between qmin and qmax (0 = clip, 1 = use differentiable function).

rc_qmod_amp float (encoding,video)

Set experimental quantizer modulation.

rc_qmod_freq integer (encoding,video)

Set experimental quantizer modulation.

rc_override_count integer
rc_eq string (encoding,video)

Set rate control equation. When computing the expression, besides the standard functions defined in the section ’Expression Evaluation’, the following functions are available: bits2qp(bits), qp2bits(qp). Also the following constants are available: iTex pTex tex mv fCode iCount mcVar var isI isP isB avgQP qComp avgIITex avgPITex avgPPTex avgBPTex avgTex.

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).

rc_buf_aggressivity float (encoding,video)

Currently useless.

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.

rc_init_cplx float (encoding,video)

Set initial complexity for 1-pass encoding.

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
simplealpha
ipp
xvidmmx
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
pred integer (encoding,video)

Set prediction method.

Possible values:

left
plane
median
aspect rational number (encoding,video)

Set sample aspect ratio.

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)

mv

motion vector

dct_coeff
skip
startcode
pts
er

error recognition

mmco

memory management control operations (H.264)

bugs
vis_qp

visualize quantization parameter (QP), lower QP are tinted greener

vis_mb_type

visualize block types

buffers

picture buffer allocations

thread_ops

threading operations

vismv integer (decoding,video)

Visualize motion vectors (MVs).

This option is deprecated, see the codecview filter instead.

Possible values:

pf

forward predicted MVs of P-frames

bf

forward predicted MVs of B-frames

bb

backward predicted MVs of B-frames

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.

last_pred integer (encoding,video)

Set amount of motion predictors from the previous frame.

preme integer (encoding,video)

Set pre motion estimation.

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.

dtg_active_format integer
me_range integer (encoding,video)

Set limit motion vectors range (1023 for DivX player).

ibias integer (encoding,video)

Set intra quant bias.

pbias integer (encoding,video)

Set inter quant bias.

color_table_id integer
global_quality integer (encoding,audio,video)
coder integer (encoding,video)

Possible values:

vlc

variable length coder / huffman coder

ac

arithmetic coder

raw

raw (no encoding)

rle

run-length coder

deflate

deflate-based coder

context integer (encoding,video)

Set context model.

slice_flags integer
xvmc_acceleration 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

stream_codec_tag integer
sc_threshold integer (encoding,video)

Set scene change threshold.

lmin integer (encoding,video)

Set min lagrange factor (VBR).

lmax integer (encoding,video)

Set max lagrange factor (VBR).

nr integer (encoding,video)

Set noise reduction.

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)

Possible values:

fast

Allow non spec compliant speedup tricks.

sgop

Deprecated, use mpegvideo private options instead.

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.

skiprd

Deprecated, use mpegvideo private options instead.

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.

error integer (encoding,video)
qns integer (encoding,video)

Deprecated, use mpegvideo private options instead.

threads integer (decoding/encoding,video)

Possible values:

auto

detect a good number of threads

me_threshold integer (encoding,video)

Set motion estimation threshold.

mb_threshold integer (encoding,video)

Set macroblock threshold.

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)

Possible values:

unknown
aac_main
aac_low
aac_ssr
aac_ltp
aac_he
aac_he_v2
aac_ld
aac_eld
mpeg2_aac_low
mpeg2_aac_he
dts
dts_es
dts_96_24
dts_hd_hra
dts_hd_ma
level integer (encoding,audio,video)

Possible values:

unknown
lowres integer (decoding,audio,video)

Decode at 1= 1/2, 2=1/4, 3=1/8 resolutions.

skip_threshold integer (encoding,video)

Set frame skip threshold.

skip_factor integer (encoding,video)

Set frame skip factor.

skip_exp integer (encoding,video)

Set frame skip exponent. Negative values behave identical to the corresponding positive ones, except that the score is normalized. Positive values exist primarily for compatibility reasons and are not so useful.

skipcmp integer (encoding,video)

Set frame skip 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
border_mask float (encoding,video)

Increase the quantizer for macroblocks close to borders.

mblmin integer (encoding,video)

Set min macroblock lagrange factor (VBR).

mblmax integer (encoding,video)

Set max macroblock lagrange factor (VBR).

mepc integer (encoding,video)

Set motion estimation bitrate penalty compensation (1.0 = 256).

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.

all

Discard all frames.

Default value is ‘default’.

bidir_refine integer (encoding,video)

Refine the two motion vectors used in bidirectional macroblocks.

brd_scale integer (encoding,video)

Downscale frames for dynamic B-frame decision.

keyint_min integer (encoding,video)

Set minimum interval between IDR-frames.

refs integer (encoding,video)

Set reference frames to consider for motion compensation.

chromaoffset integer (encoding,video)

Set chroma qp offset from luma.

trellis integer (encoding,audio,video)

Set rate-distortion optimal quantization.

sc_factor integer (encoding,video)

Set value multiplied by qscale for each frame and added to scene_change_score.

mv0_threshold integer (encoding,video)
b_sensitivity integer (encoding,video)

Adjust sensitivity of b_frame_strategy 1.

compression_level integer (encoding,audio,video)
min_prediction_order integer (encoding,audio)
max_prediction_order integer (encoding,audio)
timecode_frame_start integer (encoding,video)

Set GOP timecode frame start number, in non drop frame format.

request_channels integer (decoding,audio)

Set desired number of audio channels.

bits_per_raw_sample integer
channel_layout integer (decoding/encoding,audio)

Possible values:

request_channel_layout integer (decoding,audio)

Possible values:

rc_max_vbv_use float (encoding,video)
rc_min_vbv_use float (encoding,video)
ticks_per_frame integer (decoding/encoding,audio,video)
color_primaries integer (decoding/encoding,video)
color_trc integer (decoding/encoding,video)
colorspace integer (decoding/encoding,video)
color_range integer (decoding/encoding,video)
chroma_sample_location integer (decoding/encoding,video)
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 integer (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 indention:

ffprobe -dump_separator "
                          "  -i ~/videos/matrixbench_mpeg2.mpg

3 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.

4 Video Decoders

A description of some of the currently available video decoders follows.

4.1 rawvideo

Raw video decoder.

This decoder decodes rawvideo streams.

4.1.1 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

5 Audio Decoders

A description of some of the currently available audio decoders follows.

5.1 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).

5.1.1 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. 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.

5.2 ffwavesynth

Internal wave synthetizer.

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.

5.3 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.

5.4 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.

5.5 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.

5.5.1 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).

5.6 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.

5.7 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.

5.8 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.

6 Subtitles Decoders

6.1 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.

6.1.1 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 comas, 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 is 0.

6.2 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.

6.2.1 Options

txt_page

List of teletext page numbers to decode. You may use the special * string to match all pages. Pages that do not match the specified list are dropped. Default value is *.

txt_chop_top

Discards the top teletext line. Default value is 1.

txt_format

Specifies the format of the decoded subtitles. The teletext decoder is capable of decoding the teletext pages to bitmaps or to simple text, you should use "bitmap" for teletext pages, because certain graphics and colors cannot be expressed in simple text. You might use "text" for teletext based subtitles if your application can handle simple text based subtitles. Default value is bitmap.

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 charactes. Default value is 1.

txt_duration

Sets the display duration of the decoded teletext pages or subtitles in miliseconds. Default value is 30000 which is 30 seconds.

txt_transparent

Force transparent background of the generated teletext bitmaps. Default value is 0 which means an opaque (black) background.

7 Encoders

Encoders are configured elements in FFmpeg which allow the encoding of multimedia streams.

When you configure your FFmpeg build, all the supported native encoders are enabled by default. Encoders requiring an external library must be enabled manually via the corresponding --enable-lib option. You can list all available encoders using the configure option --list-encoders.

You can disable all the encoders with the configure option --disable-encoders and selectively enable / disable single encoders with the options --enable-encoder=ENCODER / --disable-encoder=ENCODER.

The option -encoders of the ff* tools will display the list of enabled encoders.

8 Audio Encoders

A description of some of the currently available audio encoders follows.

8.1 aac

Advanced Audio Coding (AAC) encoder.

This encoder is an experimental FFmpeg-native AAC encoder. Currently only the low complexity (AAC-LC) profile is supported. To use this encoder, you must set strict option to ‘experimental’ or lower.

As this encoder is experimental, unexpected behavior may exist from time to time. For a more stable AAC encoder, see libvo-aacenc. However, be warned that it has a worse quality reported by some users.

See also libfdk_aac and libfaac.

8.1.1 Options

b

Set bit rate in bits/s. Setting this automatically activates constant bit rate (CBR) mode.

q

Set quality for variable bit rate (VBR) mode. This option is valid only using the ffmpeg command-line tool. For library interface users, use global_quality.

stereo_mode

Set stereo encoding mode. Possible values:

auto

Automatically selected by the encoder.

ms_off

Disable middle/side encoding. This is the default.

ms_force

Force middle/side encoding.

aac_coder

Set AAC encoder coding method. Possible values:

faac

FAAC-inspired method.

This method is a simplified reimplementation of the method used in FAAC, which sets thresholds proportional to the band energies, and then decreases all the thresholds with quantizer steps to find the appropriate quantization with distortion below threshold band by band.

The quality of this method is comparable to the two loop searching method described below, but somewhat a little better and slower.

anmr

Average noise to mask ratio (ANMR) trellis-based solution.

This has a theoretic best quality out of all the coding methods, but at the cost of the slowest speed.

twoloop

Two loop searching (TLS) method.

This method first sets quantizers depending on band thresholds and then tries to find an optimal combination by adding or subtracting a specific value from all quantizers and adjusting some individual quantizer a little.

This method produces similar quality with the FAAC method and is the default.

fast

Constant quantizer method.

This method sets a constant quantizer for all bands. This is the fastest of all the methods, yet produces the worst quality.

8.2 ac3 and ac3_fixed

AC-3 audio encoders.

These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as the undocumented RealAudio 3 (a.k.a. dnet).

The ac3 encoder uses floating-point math, while the ac3_fixed encoder only uses fixed-point integer math. This does not mean that one is always faster, just that one or the other may be better suited to a particular system. The floating-point encoder will generally produce better quality audio for a given bitrate. The ac3_fixed encoder is not the default codec for any of the output formats, so it must be specified explicitly using the option -acodec ac3_fixed in order to use it.

8.2.1 AC-3 Metadata

The AC-3 metadata options are used to set parameters that describe the audio, but in most cases do not affect the audio encoding itself. Some of the options do directly affect or influence the decoding and playback of the resulting bitstream, while others are just for informational purposes. A few of the options will add bits to the output stream that could otherwise be used for audio data, and will thus affect the quality of the output. Those will be indicated accordingly with a note in the option list below.

These parameters are described in detail in several publicly-available documents.

8.2.1.1 Metadata Control Options

-per_frame_metadata boolean

Allow Per-Frame Metadata. Specifies if the encoder should check for changing metadata for each frame.

0

The metadata values set at initialization will be used for every frame in the stream. (default)

1

Metadata values can be changed before encoding each frame.

8.2.1.2 Downmix Levels

-center_mixlev level

Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo. This field will only be written to the bitstream if a center channel is present. The value is specified as a scale factor. There are 3 valid values:

0.707

Apply -3dB gain

0.595

Apply -4.5dB gain (default)

0.500

Apply -6dB gain

-surround_mixlev level

Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo. This field will only be written to the bitstream if one or more surround channels are present. The value is specified as a scale factor. There are 3 valid values:

0.707

Apply -3dB gain

0.500

Apply -6dB gain (default)

0.000

Silence Surround Channel(s)

8.2.1.3 Audio Production Information

Audio Production Information is optional information describing the mixing environment. Either none or both of the fields are written to the bitstream.

-mixing_level number

Mixing Level. Specifies peak sound pressure level (SPL) in the production environment when the mix was mastered. Valid values are 80 to 111, or -1 for unknown or not indicated. The default value is -1, but that value cannot be used if the Audio Production Information is written to the bitstream. Therefore, if the room_type option is not the default value, the mixing_level option must not be -1.

-room_type type

Room Type. Describes the equalization used during the final mixing session at the studio or on the dubbing stage. A large room is a dubbing stage with the industry standard X-curve equalization; a small room has flat equalization. This field will not be written to the bitstream if both the mixing_level option and the room_type option have the default values.

0
notindicated

Not Indicated (default)

1
large

Large Room

2
small

Small Room

8.2.1.4 Other Metadata Options

-copyright boolean

Copyright Indicator. Specifies whether a copyright exists for this audio.

0
off

No Copyright Exists (default)

1
on

Copyright Exists

-dialnorm value

Dialogue Normalization. Indicates how far the average dialogue level of the program is below digital 100% full scale (0 dBFS). This parameter determines a level shift during audio reproduction that sets the average volume of the dialogue to a preset level. The goal is to match volume level between program sources. A value of -31dB will result in no volume level change, relative to the source volume, during audio reproduction. Valid values are whole numbers in the range -31 to -1, with -31 being the default.

-dsur_mode mode

Dolby Surround Mode. Specifies whether the stereo signal uses Dolby Surround (Pro Logic). This field will only be written to the bitstream if the audio stream is stereo. Using this option does NOT mean the encoder will actually apply Dolby Surround processing.

0
notindicated

Not Indicated (default)

1
off

Not Dolby Surround Encoded

2
on

Dolby Surround Encoded

-original boolean

Original Bit Stream Indicator. Specifies whether this audio is from the original source and not a copy.

0
off

Not Original Source

1
on

Original Source (default)

8.2.2 Extended Bitstream Information

The extended bitstream options are part of the Alternate Bit Stream Syntax as specified in Annex D of the A/52:2010 standard. It is grouped into 2 parts. If any one parameter in a group is specified, all values in that group will be written to the bitstream. Default values are used for those that are written but have not been specified. If the mixing levels are written, the decoder will use these values instead of the ones specified in the center_mixlev and surround_mixlev options if it supports the Alternate Bit Stream Syntax.

8.2.2.1 Extended Bitstream Information - Part 1

-dmix_mode mode

Preferred Stereo Downmix Mode. Allows the user to select either Lt/Rt (Dolby Surround) or Lo/Ro (normal stereo) as the preferred stereo downmix mode.

0
notindicated

Not Indicated (default)

1
ltrt

Lt/Rt Downmix Preferred

2
loro

Lo/Ro Downmix Preferred

-ltrt_cmixlev level

Lt/Rt Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo in Lt/Rt mode.

1.414

Apply +3dB gain

1.189

Apply +1.5dB gain

1.000

Apply 0dB gain

0.841

Apply -1.5dB gain

0.707

Apply -3.0dB gain

0.595

Apply -4.5dB gain (default)

0.500

Apply -6.0dB gain

0.000

Silence Center Channel

-ltrt_surmixlev level

Lt/Rt Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo in Lt/Rt mode.

0.841

Apply -1.5dB gain

0.707

Apply -3.0dB gain

0.595

Apply -4.5dB gain

0.500

Apply -6.0dB gain (default)

0.000

Silence Surround Channel(s)

-loro_cmixlev level

Lo/Ro Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo in Lo/Ro mode.

1.414

Apply +3dB gain

1.189

Apply +1.5dB gain

1.000

Apply 0dB gain

0.841

Apply -1.5dB gain

0.707

Apply -3.0dB gain

0.595

Apply -4.5dB gain (default)

0.500

Apply -6.0dB gain

0.000

Silence Center Channel

-loro_surmixlev level

Lo/Ro Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo in Lo/Ro mode.

0.841

Apply -1.5dB gain

0.707

Apply -3.0dB gain

0.595

Apply -4.5dB gain

0.500

Apply -6.0dB gain (default)

0.000

Silence Surround Channel(s)

8.2.2.2 Extended Bitstream Information - Part 2

-dsurex_mode mode

Dolby Surround EX Mode. Indicates whether the stream uses Dolby Surround EX (7.1 matrixed to 5.1). Using this option does NOT mean the encoder will actually apply Dolby Surround EX processing.

0
notindicated

Not Indicated (default)

1
on

Dolby Surround EX Off

2
off

Dolby Surround EX On

-dheadphone_mode mode

Dolby Headphone Mode. Indicates whether the stream uses Dolby Headphone encoding (multi-channel matrixed to 2.0 for use with headphones). Using this option does NOT mean the encoder will actually apply Dolby Headphone processing.

0
notindicated

Not Indicated (default)

1
on

Dolby Headphone Off

2
off

Dolby Headphone On

-ad_conv_type type

A/D Converter Type. Indicates whether the audio has passed through HDCD A/D conversion.

0
standard

Standard A/D Converter (default)

1
hdcd

HDCD A/D Converter

8.2.3 Other AC-3 Encoding Options

-stereo_rematrixing boolean

Stereo Rematrixing. Enables/Disables use of rematrixing for stereo input. This is an optional AC-3 feature that increases quality by selectively encoding the left/right channels as mid/side. This option is enabled by default, and it is highly recommended that it be left as enabled except for testing purposes.

8.2.4 Floating-Point-Only AC-3 Encoding Options

These options are only valid for the floating-point encoder and do not exist for the fixed-point encoder due to the corresponding features not being implemented in fixed-point.

-channel_coupling boolean

Enables/Disables use of channel coupling, which is an optional AC-3 feature that increases quality by combining high frequency information from multiple channels into a single channel. The per-channel high frequency information is sent with less accuracy in both the frequency and time domains. This allows more bits to be used for lower frequencies while preserving enough information to reconstruct the high frequencies. This option is enabled by default for the floating-point encoder and should generally be left as enabled except for testing purposes or to increase encoding speed.

-1
auto

Selected by Encoder (default)

0
off

Disable Channel Coupling

1
on

Enable Channel Coupling

-cpl_start_band number

Coupling Start Band. Sets the channel coupling start band, from 1 to 15. If a value higher than the bandwidth is used, it will be reduced to 1 less than the coupling end band. If auto is used, the start band will be determined by the encoder based on the bit rate, sample rate, and channel layout. This option has no effect if channel coupling is disabled.

-1
auto

Selected by Encoder (default)

8.3 libfaac

libfaac AAC (Advanced Audio Coding) encoder wrapper.

Requires the presence of the libfaac headers and library during configuration. You need to explicitly configure the build with --enable-libfaac --enable-nonfree.

This encoder is considered to be of higher quality with respect to the the native experimental FFmpeg AAC encoder.

For more information see the libfaac project at http://www.audiocoding.com/faac.html/.

8.3.1 Options

The following shared FFmpeg codec options are recognized.

The following options are supported by the libfaac wrapper. The faac-equivalent of the options are listed in parentheses.

b (-b)

Set bit rate in bits/s for ABR (Average Bit Rate) mode. If the bit rate is not explicitly specified, it is automatically set to a suitable value depending on the selected profile. faac bitrate is expressed in kilobits/s.

Note that libfaac does not support CBR (Constant Bit Rate) but only ABR (Average Bit Rate).

If VBR mode is enabled this option is ignored.

ar (-R)

Set audio sampling rate (in Hz).

ac (-c)

Set the number of audio channels.

cutoff (-C)

Set cutoff frequency. If not specified (or explicitly set to 0) it will use a value automatically computed by the library. Default value is 0.

profile

Set audio profile.

The following profiles are recognized:

aac_main

Main AAC (Main)

aac_low

Low Complexity AAC (LC)

aac_ssr

Scalable Sample Rate (SSR)

aac_ltp

Long Term Prediction (LTP)

If not specified it is set to ‘aac_low’.

flags +qscale

Set constant quality VBR (Variable Bit Rate) mode.

global_quality

Set quality in VBR mode as an integer number of lambda units.

Only relevant when VBR mode is enabled with flags +qscale. The value is converted to QP units by dividing it by FF_QP2LAMBDA, and used to set the quality value used by libfaac. A reasonable range for the option value in QP units is [10-500], the higher the value the higher the quality.

q (-q)

Enable VBR mode when set to a non-negative value, and set constant quality value as a double floating point value in QP units.

The value sets the quality value used by libfaac. A reasonable range for the option value is [10-500], the higher the value the higher the quality.

This option is valid only using the ffmpeg command-line tool. For library interface users, use global_quality.

8.3.2 Examples

  • Use ffmpeg to convert an audio file to ABR 128 kbps AAC in an M4A (MP4) container:
    ffmpeg -i input.wav -codec:a libfaac -b:a 128k -output.m4a
    
  • Use ffmpeg to convert an audio file to VBR AAC, using the LTP AAC profile:
    ffmpeg -i input.wav -c:a libfaac -profile:a aac_ltp -q:a 100 output.m4a
    

8.4 libfdk_aac

libfdk-aac AAC (Advanced Audio Coding) encoder wrapper.

The libfdk-aac library is based on the Fraunhofer FDK AAC code from the Android project.

Requires the presence of the libfdk-aac headers and library during configuration. You need to explicitly configure the build with --enable-libfdk-aac. The library is also incompatible with GPL, so if you allow the use of GPL, you should configure with --enable-gpl --enable-nonfree --enable-libfdk-aac.

This encoder is considered to be of higher quality with respect to both the native experimental FFmpeg AAC encoder and libfaac.

VBR encoding, enabled through the vbr or flags +qscale options, is experimental and only works with some combinations of parameters.

Support for encoding 7.1 audio is only available with libfdk-aac 0.1.3 or higher.

For more information see the fdk-aac project at http://sourceforge.net/p/opencore-amr/fdk-aac/.

8.4.1 Options

The following options are mapped on the shared FFmpeg codec options.

b

Set bit rate in bits/s. If the bitrate is not explicitly specified, it is automatically set to a suitable value depending on the selected profile.

In case VBR mode is enabled the option is ignored.

ar

Set audio sampling rate (in Hz).

channels

Set the number of audio channels.

flags +qscale

Enable fixed quality, VBR (Variable Bit Rate) mode. Note that VBR is implicitly enabled when the vbr value is positive.

cutoff

Set cutoff frequency. If not specified (or explicitly set to 0) it will use a value automatically computed by the library. Default value is 0.

profile

Set audio profile.

The following profiles are recognized:

aac_low

Low Complexity AAC (LC)

aac_he

High Efficiency AAC (HE-AAC)

aac_he_v2

High Efficiency AAC version 2 (HE-AACv2)

aac_ld

Low Delay AAC (LD)

aac_eld

Enhanced Low Delay AAC (ELD)

If not specified it is set to ‘aac_low’.

The following are private options of the libfdk_aac encoder.

afterburner

Enable afterburner feature if set to 1, disabled if set to 0. This improves the quality but also the required processing power.

Default value is 1.

eld_sbr

Enable SBR (Spectral Band Replication) for ELD if set to 1, disabled if set to 0.

Default value is 0.

signaling

Set SBR/PS signaling style.

It can assume one of the following values:

default

choose signaling implicitly (explicit hierarchical by default, implicit if global header is disabled)

implicit

implicit backwards compatible signaling

explicit_sbr

explicit SBR, implicit PS signaling

explicit_hierarchical

explicit hierarchical signaling

Default value is ‘default’.

latm

Output LATM/LOAS encapsulated data if set to 1, disabled if set to 0.

Default value is 0.

header_period

Set StreamMuxConfig and PCE repetition period (in frames) for sending in-band configuration buffers within LATM/LOAS transport layer.

Must be a 16-bits non-negative integer.

Default value is 0.

vbr

Set VBR mode, from 1 to 5. 1 is lowest quality (though still pretty good) and 5 is highest quality. A value of 0 will disable VBR, and CBR (Constant Bit Rate) is enabled.

Currently only the ‘aac_low’ profile supports VBR encoding.

VBR modes 1-5 correspond to roughly the following average bit rates:

1

32 kbps/channel

2

40 kbps/channel

3

48-56 kbps/channel

4

64 kbps/channel

5

about 80-96 kbps/channel

Default value is 0.

8.4.2 Examples

  • Use ffmpeg to convert an audio file to VBR AAC in an M4A (MP4) container:
    ffmpeg -i input.wav -codec:a libfdk_aac -vbr 3 output.m4a
    
  • Use ffmpeg to convert an audio file to CBR 64k kbps AAC, using the High-Efficiency AAC profile:
    ffmpeg -i input.wav -c:a libfdk_aac -profile:a aac_he -b:a 64k output.m4a
    

8.5 libmp3lame

LAME (Lame Ain’t an MP3 Encoder) MP3 encoder wrapper.

Requires the presence of the libmp3lame headers and library during configuration. You need to explicitly configure the build with --enable-libmp3lame.

See libshine for a fixed-point MP3 encoder, although with a lower quality.

8.5.1 Options

The following options are supported by the libmp3lame wrapper. The lame-equivalent of the options are listed in parentheses.

b (-b)

Set bitrate expressed in bits/s for CBR or ABR. LAME bitrate is expressed in kilobits/s.

q (-V)

Set constant quality setting for VBR. This option is valid only using the ffmpeg command-line tool. For library interface users, use global_quality.

compression_level (-q)

Set algorithm quality. Valid arguments are integers in the 0-9 range, with 0 meaning highest quality but slowest, and 9 meaning fastest while producing the worst quality.

reservoir

Enable use of bit reservoir when set to 1. Default value is 1. LAME has this enabled by default, but can be overridden by use --nores option.

joint_stereo (-m j)

Enable the encoder to use (on a frame by frame basis) either L/R stereo or mid/side stereo. Default value is 1.

abr (--abr)

Enable the encoder to use ABR when set to 1. The lame --abr sets the target bitrate, while this options only tells FFmpeg to use ABR still relies on b to set bitrate.

8.6 libopencore-amrnb

OpenCORE Adaptive Multi-Rate Narrowband encoder.

Requires the presence of the libopencore-amrnb headers and library during configuration. You need to explicitly configure the build with --enable-libopencore-amrnb --enable-version3.

This is a mono-only encoder. Officially it only supports 8000Hz sample rate, but you can override it by setting strict to ‘unofficial’ or lower.

8.6.1 Options

b

Set bitrate in bits per second. Only the following bitrates are supported, otherwise libavcodec will round to the nearest valid bitrate.

4750
5150
5900
6700
7400
7950
10200
12200
dtx

Allow discontinuous transmission (generate comfort noise) when set to 1. The default value is 0 (disabled).

8.7 libshine

Shine Fixed-Point MP3 encoder wrapper.

Shine is a fixed-point MP3 encoder. It has a far better performance on platforms without an FPU, e.g. armel CPUs, and some phones and tablets. However, as it is more targeted on performance than quality, it is not on par with LAME and other production-grade encoders quality-wise. Also, according to the project’s homepage, this encoder may not be free of bugs as the code was written a long time ago and the project was dead for at least 5 years.

This encoder only supports stereo and mono input. This is also CBR-only.

The original project (last updated in early 2007) is at http://sourceforge.net/projects/libshine-fxp/. We only support the updated fork by the Savonet/Liquidsoap project at https://github.com/savonet/shine.

Requires the presence of the libshine headers and library during configuration. You need to explicitly configure the build with --enable-libshine.

See also libmp3lame.

8.7.1 Options

The following options are supported by the libshine wrapper. The shineenc-equivalent of the options are listed in parentheses.

b (-b)

Set bitrate expressed in bits/s for CBR. shineenc -b option is expressed in kilobits/s.

8.8 libtwolame

TwoLAME MP2 encoder wrapper.

Requires the presence of the libtwolame headers and library during configuration. You need to explicitly configure the build with --enable-libtwolame.

8.8.1 Options

The following options are supported by the libtwolame wrapper. The twolame-equivalent options follow the FFmpeg ones and are in parentheses.

b (-b)

Set bitrate expressed in bits/s for CBR. twolame b option is expressed in kilobits/s. Default value is 128k.

q (-V)

Set quality for experimental VBR support. Maximum value range is from -50 to 50, useful range is from -10 to 10. The higher the value, the better the quality. This option is valid only using the ffmpeg command-line tool. For library interface users, use global_quality.

mode (--mode)

Set the mode of the resulting audio. Possible values:

auto

Choose mode automatically based on the input. This is the default.

stereo

Stereo

joint_stereo

Joint stereo

dual_channel

Dual channel

mono

Mono

psymodel (--psyc-mode)

Set psychoacoustic model to use in encoding. The argument must be an integer between -1 and 4, inclusive. The higher the value, the better the quality. The default value is 3.

energy_levels (--energy)

Enable energy levels extensions when set to 1. The default value is 0 (disabled).

error_protection (--protect)

Enable CRC error protection when set to 1. The default value is 0 (disabled).

copyright (--copyright)

Set MPEG audio copyright flag when set to 1. The default value is 0 (disabled).

original (--original)

Set MPEG audio original flag when set to 1. The default value is 0 (disabled).

8.9 libvo-aacenc

VisualOn AAC encoder.

Requires the presence of the libvo-aacenc headers and library during configuration. You need to explicitly configure the build with --enable-libvo-aacenc --enable-version3.

This encoder is considered to be worse than the native experimental FFmpeg AAC encoder, according to multiple sources.

8.9.1 Options

The VisualOn AAC encoder only support encoding AAC-LC and up to 2 channels. It is also CBR-only.

b

Set bit rate in bits/s.

8.10 libvo-amrwbenc

VisualOn Adaptive Multi-Rate Wideband encoder.

Requires the presence of the libvo-amrwbenc headers and library during configuration. You need to explicitly configure the build with --enable-libvo-amrwbenc --enable-version3.

This is a mono-only encoder. Officially it only supports 16000Hz sample rate, but you can override it by setting strict to ‘unofficial’ or lower.

8.10.1 Options

b

Set bitrate in bits/s. Only the following bitrates are supported, otherwise libavcodec will round to the nearest valid bitrate.

6600
8850
12650
14250
15850
18250
19850
23050
23850
dtx

Allow discontinuous transmission (generate comfort noise) when set to 1. The default value is 0 (disabled).

8.11 libopus

libopus Opus Interactive Audio Codec encoder wrapper.

Requires the presence of the libopus headers and library during configuration. You need to explicitly configure the build with --enable-libopus.

8.11.1 Option Mapping

Most libopus options are modelled after the opusenc utility from opus-tools. The following is an option mapping chart describing options supported by the libopus wrapper, and their opusenc-equivalent in parentheses.

b (bitrate)

Set the bit rate in bits/s. FFmpeg’s b option is expressed in bits/s, while opusenc’s bitrate in kilobits/s.

vbr (vbr, hard-cbr, and cvbr)

Set VBR mode. The FFmpeg vbr option has the following valid arguments, with the their opusenc equivalent options in parentheses:

off (hard-cbr)

Use constant bit rate encoding.

on (vbr)

Use variable bit rate encoding (the default).

constrained (cvbr)

Use constrained variable bit rate encoding.

compression_level (comp)

Set encoding algorithm complexity. Valid options are integers in the 0-10 range. 0 gives the fastest encodes but lower quality, while 10 gives the highest quality but slowest encoding. The default is 10.

frame_duration (framesize)

Set maximum frame size, or duration of a frame in milliseconds. The argument must be exactly the following: 2.5, 5, 10, 20, 40, 60. Smaller frame sizes achieve lower latency but less quality at a given bitrate. Sizes greater than 20ms are only interesting at fairly low bitrates. The default is 20ms.

packet_loss (expect-loss)

Set expected packet loss percentage. The default is 0.

application (N.A.)

Set intended application type. Valid options are listed below:

voip

Favor improved speech intelligibility.

audio

Favor faithfulness to the input (the default).

lowdelay

Restrict to only the lowest delay modes.

cutoff (N.A.)

Set cutoff bandwidth in Hz. The argument must be exactly one of the following: 4000, 6000, 8000, 12000, or 20000, corresponding to narrowband, mediumband, wideband, super wideband, and fullband respectively. The default is 0 (cutoff disabled).

8.12 libvorbis

libvorbis encoder wrapper.

Requires the presence of the libvorbisenc headers and library during configuration. You need to explicitly configure the build with --enable-libvorbis.

8.12.1 Options

The following options are supported by the libvorbis wrapper. The oggenc-equivalent of the options are listed in parentheses.

To get a more accurate and extensive documentation of the libvorbis options, consult the libvorbisenc’s and oggenc’s documentations. See http://xiph.org/vorbis/, http://wiki.xiph.org/Vorbis-tools, and oggenc(1).

b (-b)

Set bitrate expressed in bits/s for ABR. oggenc -b is expressed in kilobits/s.

q (-q)

Set constant quality setting for VBR. The value should be a float number in the range of -1.0 to 10.0. The higher the value, the better the quality. The default value is ‘3.0’.

This option is valid only using the ffmpeg command-line tool. For library interface users, use global_quality.

cutoff (--advanced-encode-option lowpass_frequency=N)

Set cutoff bandwidth in Hz, a value of 0 disables cutoff. oggenc’s related option is expressed in kHz. The default value is ‘0’ (cutoff disabled).

minrate (-m)

Set minimum bitrate expressed in bits/s. oggenc -m is expressed in kilobits/s.

maxrate (-M)

Set maximum bitrate expressed in bits/s. oggenc -M is expressed in kilobits/s. This only has effect on ABR mode.

iblock (--advanced-encode-option impulse_noisetune=N)

Set noise floor bias for impulse blocks. The value is a float number from -15.0 to 0.0. A negative bias instructs the encoder to pay special attention to the crispness of transients in the encoded audio. The tradeoff for better transient response is a higher bitrate.

8.13 libwavpack

A wrapper providing WavPack encoding through libwavpack.

Only lossless mode using 32-bit integer samples is supported currently.

Requires the presence of the libwavpack headers and library during configuration. You need to explicitly configure the build with --enable-libwavpack.

Note that a libavcodec-native encoder for the WavPack codec exists so users can encode audios with this codec without using this encoder. See wavpackenc.

8.13.1 Options

wavpack command line utility’s corresponding options are listed in parentheses, if any.

frame_size (--blocksize)

Default is 32768.

compression_level

Set speed vs. compression tradeoff. Acceptable arguments are listed below:

0 (-f)

Fast mode.

1

Normal (default) settings.

2 (-h)

High quality.

3 (-hh)

Very high quality.

4-8 (-hh -xEXTRAPROC)

Same as ‘3’, but with extra processing enabled.

4’ is the same as -x2 and ‘8’ is the same as -x6.

8.14 wavpack

WavPack lossless audio encoder.

This is a libavcodec-native WavPack encoder. There is also an encoder based on libwavpack, but there is virtually no reason to use that encoder.

See also libwavpack.

8.14.1 Options

The equivalent options for wavpack command line utility are listed in parentheses.

8.14.1.1 Shared options

The following shared options are effective for this encoder. Only special notes about this particular encoder will be documented here. For the general meaning of the options, see the Codec Options chapter.

frame_size (--blocksize)

For this encoder, the range for this option is between 128 and 131072. Default is automatically decided based on sample rate and number of channel.

For the complete formula of calculating default, see libavcodec/wavpackenc.c.

compression_level (-f, -h, -hh, and -x)

This option’s syntax is consistent with libwavpack’s.

8.14.1.2 Private options

joint_stereo (-j)

Set whether to enable joint stereo. Valid values are:

on (1)

Force mid/side audio encoding.

off (0)

Force left/right audio encoding.

auto

Let the encoder decide automatically.

optimize_mono

Set whether to enable optimization for mono. This option is only effective for non-mono streams. Available values:

on

enabled

off

disabled

9 Video Encoders

A description of some of the currently available video encoders follows.

9.1 libtheora

libtheora Theora encoder wrapper.

Requires the presence of the libtheora headers and library during configuration. You need to explicitly configure the build with --enable-libtheora.

For more information about the libtheora project see http://www.theora.org/.

9.1.1 Options

The following global options are mapped to internal libtheora options which affect the quality and the bitrate of the encoded stream.

b

Set the video bitrate in bit/s for CBR (Constant Bit Rate) mode. In case VBR (Variable Bit Rate) mode is enabled this option is ignored.

flags

Used to enable constant quality mode (VBR) encoding through the qscale flag, and to enable the pass1 and pass2 modes.

g

Set the GOP size.

global_quality

Set the global quality as an integer in lambda units.

Only relevant when VBR mode is enabled with flags +qscale. The value is converted to QP units by dividing it by FF_QP2LAMBDA, clipped in the [0 - 10] range, and then multiplied by 6.3 to get a value in the native libtheora range [0-63]. A higher value corresponds to a higher quality.

q

Enable VBR mode when set to a non-negative value, and set constant quality value as a double floating point value in QP units.

The value is clipped in the [0-10] range, and then multiplied by 6.3 to get a value in the native libtheora range [0-63].

This option is valid only using the ffmpeg command-line tool. For library interface users, use global_quality.

9.1.2 Examples

  • Set maximum constant quality (VBR) encoding with ffmpeg:
    ffmpeg -i INPUT -codec:v libtheora -q:v 10 OUTPUT.ogg
    
  • Use ffmpeg to convert a CBR 1000 kbps Theora video stream:
    ffmpeg -i INPUT -codec:v libtheora -b:v 1000k OUTPUT.ogg
    

9.2 libvpx

VP8/VP9 format supported through libvpx.

Requires the presence of the libvpx headers and library during configuration. You need to explicitly configure the build with --enable-libvpx.

9.2.1 Options

Mapping from FFmpeg to libvpx options with conversion notes in parentheses.

threads

g_threads

profile

g_profile

vb

rc_target_bitrate

g

kf_max_dist

keyint_min

kf_min_dist

qmin

rc_min_quantizer

qmax

rc_max_quantizer

bufsize, vb

rc_buf_sz (bufsize * 1000 / vb)

rc_buf_optimal_sz (bufsize * 1000 / vb * 5 / 6)

rc_init_occupancy, vb

rc_buf_initial_sz (rc_init_occupancy * 1000 / vb)

rc_buffer_aggressivity

rc_undershoot_pct

skip_threshold

rc_dropframe_thresh

qcomp

rc_2pass_vbr_bias_pct

maxrate, vb

rc_2pass_vbr_maxsection_pct (maxrate * 100 / vb)

minrate, vb

rc_2pass_vbr_minsection_pct (minrate * 100 / vb)

minrate, maxrate, vb

VPX_CBR (minrate == maxrate == vb)

crf

VPX_CQ, VP8E_SET_CQ_LEVEL

quality
best

VPX_DL_BEST_QUALITY

good

VPX_DL_GOOD_QUALITY

realtime

VPX_DL_REALTIME

speed

VP8E_SET_CPUUSED

nr

VP8E_SET_NOISE_SENSITIVITY

mb_threshold

VP8E_SET_STATIC_THRESHOLD

slices

VP8E_SET_TOKEN_PARTITIONS

max-intra-rate

VP8E_SET_MAX_INTRA_BITRATE_PCT

force_key_frames

VPX_EFLAG_FORCE_KF

Alternate reference frame related
vp8flags altref

VP8E_SET_ENABLEAUTOALTREF

arnr_max_frames

VP8E_SET_ARNR_MAXFRAMES

arnr_type

VP8E_SET_ARNR_TYPE

arnr_strength

VP8E_SET_ARNR_STRENGTH

rc_lookahead

g_lag_in_frames

vp8flags error_resilient

g_error_resilient

aq_mode

VP9E_SET_AQ_MODE

For more information about libvpx see: http://www.webmproject.org/

9.3 libwebp

libwebp WebP Image encoder wrapper

libwebp is Google’s official encoder for WebP images. It can encode in either lossy or lossless mode. Lossy images are essentially a wrapper around a VP8 frame. Lossless images are a separate codec developed by Google.

9.3.1 Pixel Format

Currently, libwebp only supports YUV420 for lossy and RGB for lossless due to limitations of the format and libwebp. Alpha is supported for either mode. Because of API limitations, if RGB is passed in when encoding lossy or YUV is passed in for encoding lossless, the pixel format will automatically be converted using functions from libwebp. This is not ideal and is done only for convenience.

9.3.2 Options

-lossless boolean

Enables/Disables use of lossless mode. Default is 0.

-compression_level integer

For lossy, this is a quality/speed tradeoff. Higher values give better quality for a given size at the cost of increased encoding time. For lossless, this is a size/speed tradeoff. Higher values give smaller size at the cost of increased encoding time. More specifically, it controls the number of extra algorithms and compression tools used, and varies the combination of these tools. This maps to the method option in libwebp. The valid range is 0 to 6. Default is 4.

-qscale float

For lossy encoding, this controls image quality, 0 to 100. For lossless encoding, this controls the effort and time spent at compressing more. The default value is 75. Note that for usage via libavcodec, this option is called global_quality and must be multiplied by FF_QP2LAMBDA.

-preset type

Configuration preset. This does some automatic settings based on the general type of the image.

none

Do not use a preset.

default

Use the encoder default.

picture

Digital picture, like portrait, inner shot

photo

Outdoor photograph, with natural lighting

drawing

Hand or line drawing, with high-contrast details

icon

Small-sized colorful images

text

Text-like

9.4 libx264, libx264rgb

x264 H.264/MPEG-4 AVC encoder wrapper.

This encoder requires the presence of the libx264 headers and library during configuration. You need to explicitly configure the build with --enable-libx264.

libx264 supports an impressive number of features, including 8x8 and 4x4 adaptive spatial transform, adaptive B-frame placement, CAVLC/CABAC entropy coding, interlacing (MBAFF), lossless mode, psy optimizations for detail retention (adaptive quantization, psy-RD, psy-trellis).

Many libx264 encoder options are mapped to FFmpeg global codec options, while unique encoder options are provided through private options. Additionally the x264opts and x264-params private options allows one to pass a list of key=value tuples as accepted by the libx264 x264_param_parse function.

The x264 project website is at http://www.videolan.org/developers/x264.html.

The libx264rgb encoder is the same as libx264, except it accepts packed RGB pixel formats as input instead of YUV.

9.4.1 Supported Pixel Formats

x264 supports 8- to 10-bit color spaces. The exact bit depth is controlled at x264’s configure time. FFmpeg only supports one bit depth in one particular build. In other words, it is not possible to build one FFmpeg with multiple versions of x264 with different bit depths.

9.4.2 Options

The following options are supported by the libx264 wrapper. The x264-equivalent options or values are listed in parentheses for easy migration.

To reduce the duplication of documentation, only the private options and some others requiring special attention are documented here. For the documentation of the undocumented generic options, see the Codec Options chapter.

To get a more accurate and extensive documentation of the libx264 options, invoke the command x264 --full-help or consult the libx264 documentation.

b (bitrate)

Set bitrate in bits/s. Note that FFmpeg’s b option is expressed in bits/s, while x264’s bitrate is in kilobits/s.

bf (bframes)
g (keyint)
qmin (qpmin)

Minimum quantizer scale.

qmax (qpmax)

Maximum quantizer scale.

qdiff (qpstep)

Maximum difference between quantizer scales.

qblur (qblur)

Quantizer curve blur

qcomp (qcomp)

Quantizer curve compression factor

refs (ref)

Number of reference frames each P-frame can use. The range is from 0-16.

sc_threshold (scenecut)

Sets the threshold for the scene change detection.

trellis (trellis)

Performs Trellis quantization to increase efficiency. Enabled by default.

nr (nr)
me_range (merange)

Maximum range of the motion search in pixels.

me_method (me)

Set motion estimation method. Possible values in the decreasing order of speed:

dia (dia)
epzs (dia)

Diamond search with radius 1 (fastest). ‘epzs’ is an alias for ‘dia’.

hex (hex)

Hexagonal search with radius 2.

umh (umh)

Uneven multi-hexagon search.

esa (esa)

Exhaustive search.

tesa (tesa)

Hadamard exhaustive search (slowest).

subq (subme)

Sub-pixel motion estimation method.

b_strategy (b-adapt)

Adaptive B-frame placement decision algorithm. Use only on first-pass.

keyint_min (min-keyint)

Minimum GOP size.

coder

Set entropy encoder. Possible values:

ac

Enable CABAC.

vlc

Enable CAVLC and disable CABAC. It generates the same effect as x264’s --no-cabac option.

cmp

Set full pixel motion estimation comparation algorithm. Possible values:

chroma

Enable chroma in motion estimation.

sad

Ignore chroma in motion estimation. It generates the same effect as x264’s --no-chroma-me option.

threads (threads)

Number of encoding threads.

thread_type

Set multithreading technique. Possible values:

slice

Slice-based multithreading. It generates the same effect as x264’s --sliced-threads option.

frame

Frame-based multithreading.

flags

Set encoding flags. It can be used to disable closed GOP and enable open GOP by setting it to -cgop. The result is similar to the behavior of x264’s --open-gop option.

rc_init_occupancy (vbv-init)
preset (preset)

Set the encoding preset.

tune (tune)

Set tuning of the encoding params.

profile (profile)

Set profile restrictions.

fastfirstpass

Enable fast settings when encoding first pass, when set to 1. When set to 0, it has the same effect of x264’s --slow-firstpass option.

crf (crf)

Set the quality for constant quality mode.

crf_max (crf-max)

In CRF mode, prevents VBV from lowering quality beyond this point.

qp (qp)

Set constant quantization rate control method parameter.

aq-mode (aq-mode)

Set AQ method. Possible values:

none (0)

Disabled.

variance (1)

Variance AQ (complexity mask).

autovariance (2)

Auto-variance AQ (experimental).

aq-strength (aq-strength)

Set AQ strength, reduce blocking and blurring in flat and textured areas.

psy

Use psychovisual optimizations when set to 1. When set to 0, it has the same effect as x264’s --no-psy option.

psy-rd (psy-rd)

Set strength of psychovisual optimization, in psy-rd:psy-trellis format.

rc-lookahead (rc-lookahead)

Set number of frames to look ahead for frametype and ratecontrol.

weightb

Enable weighted prediction for B-frames when set to 1. When set to 0, it has the same effect as x264’s --no-weightb option.

weightp (weightp)

Set weighted prediction method for P-frames. Possible values:

none (0)

Disabled

simple (1)

Enable only weighted refs

smart (2)

Enable both weighted refs and duplicates

ssim (ssim)

Enable calculation and printing SSIM stats after the encoding.

intra-refresh (intra-refresh)

Enable the use of Periodic Intra Refresh instead of IDR frames when set to 1.

avcintra-class (class)

Configure the encoder to generate AVC-Intra. Valid values are 50,100 and 200

bluray-compat (bluray-compat)

Configure the encoder to be compatible with the bluray standard. It is a shorthand for setting "bluray-compat=1 force-cfr=1".

b-bias (b-bias)

Set the influence on how often B-frames are used.

b-pyramid (b-pyramid)

Set method for keeping of some B-frames as references. Possible values:

none (none)

Disabled.

strict (strict)

Strictly hierarchical pyramid.

normal (normal)

Non-strict (not Blu-ray compatible).

mixed-refs

Enable the use of one reference per partition, as opposed to one reference per macroblock when set to 1. When set to 0, it has the same effect as x264’s --no-mixed-refs option.

8x8dct

Enable adaptive spatial transform (high profile 8x8 transform) when set to 1. When set to 0, it has the same effect as x264’s --no-8x8dct option.

fast-pskip

Enable early SKIP detection on P-frames when set to 1. When set to 0, it has the same effect as x264’s --no-fast-pskip option.

aud (aud)

Enable use of access unit delimiters when set to 1.

mbtree

Enable use macroblock tree ratecontrol when set to 1. When set to 0, it has the same effect as x264’s --no-mbtree option.

deblock (deblock)

Set loop filter parameters, in alpha:beta form.

cplxblur (cplxblur)

Set fluctuations reduction in QP (before curve compression).

partitions (partitions)

Set partitions to consider as a comma-separated list of. Possible values in the list:

p8x8

8x8 P-frame partition.

p4x4

4x4 P-frame partition.

b8x8

4x4 B-frame partition.

i8x8

8x8 I-frame partition.

i4x4

4x4 I-frame partition. (Enabling ‘p4x4’ requires ‘p8x8’ to be enabled. Enabling ‘i8x8’ requires adaptive spatial transform (8x8dct option) to be enabled.)

none (none)

Do not consider any partitions.

all (all)

Consider every partition.

direct-pred (direct)

Set direct MV prediction mode. Possible values:

none (none)

Disable MV prediction.

spatial (spatial)

Enable spatial predicting.

temporal (temporal)

Enable temporal predicting.

auto (auto)

Automatically decided.

slice-max-size (slice-max-size)

Set the limit of the size of each slice in bytes. If not specified but RTP payload size (ps) is specified, that is used.

stats (stats)

Set the file name for multi-pass stats.

nal-hrd (nal-hrd)

Set signal HRD information (requires vbv-bufsize to be set). Possible values:

none (none)

Disable HRD information signaling.

vbr (vbr)

Variable bit rate.

cbr (cbr)

Constant bit rate (not allowed in MP4 container).

x264opts (N.A.)

Set any x264 option, see x264 --fullhelp for a list.

Argument is a list of key=value couples separated by ":". In filter and psy-rd options that use ":" as a separator themselves, use "," instead. They accept it as well since long ago but this is kept undocumented for some reason.

For example to specify libx264 encoding options with ffmpeg:

ffmpeg -i foo.mpg -vcodec libx264 -x264opts keyint=123:min-keyint=20 -an out.mkv
x264-params (N.A.)

Override the x264 configuration using a :-separated list of key=value parameters.

This option is functionally the same as the x264opts, but is duplicated for compatibility with the Libav fork.

For example to specify libx264 encoding options with ffmpeg:

ffmpeg -i INPUT -c:v libx264 -x264-params level=30:bframes=0:weightp=0:\
cabac=0:ref=1:vbv-maxrate=768:vbv-bufsize=2000:analyse=all:me=umh:\
no-fast-pskip=1:subq=6:8x8dct=0:trellis=0 OUTPUT

Encoding ffpresets for common usages are provided so they can be used with the general presets system (e.g. passing the pre option).

9.5 libx265

x265 H.265/HEVC encoder wrapper.

This encoder requires the presence of the libx265 headers and library during configuration. You need to explicitly configure the build with --enable-libx265.

9.5.1 Options

preset

Set the x265 preset.

tune

Set the x265 tune parameter.

x265-params

Set x265 options using a list of key=value couples separated by ":". See x265 --help for a list of options.

For example to specify libx265 encoding options with -x265-params:

ffmpeg -i input -c:v libx265 -x265-params crf=26:psy-rd=1 output.mp4

9.6 libxvid

Xvid MPEG-4 Part 2 encoder wrapper.

This encoder requires the presence of the libxvidcore headers and library during configuration. You need to explicitly configure the build with --enable-libxvid --enable-gpl.

The native mpeg4 encoder supports the MPEG-4 Part 2 format, so users can encode to this format without this library.

9.6.1 Options

The following options are supported by the libxvid wrapper. Some of the following options are listed but are not documented, and correspond to shared codec options. See the Codec Options chapter for their documentation. The other shared options which are not listed have no effect for the libxvid encoder.

b
g
qmin
qmax
mpeg_quant
threads
bf
b_qfactor
b_qoffset
flags

Set specific encoding flags. Possible values:

mv4

Use four motion vector by macroblock.

aic

Enable high quality AC prediction.

gray

Only encode grayscale.

gmc

Enable the use of global motion compensation (GMC).

qpel

Enable quarter-pixel motion compensation.

cgop

Enable closed GOP.

global_header

Place global headers in extradata instead of every keyframe.

trellis
me_method

Set motion estimation method. Possible values in decreasing order of speed and increasing order of quality:

zero

Use no motion estimation (default).

phods
x1
log

Enable advanced diamond zonal search for 16x16 blocks and half-pixel refinement for 16x16 blocks. ‘x1’ and ‘log’ are aliases for ‘phods’.

epzs

Enable all of the things described above, plus advanced diamond zonal search for 8x8 blocks, half-pixel refinement for 8x8 blocks, and motion estimation on chroma planes.

full

Enable all of the things described above, plus extended 16x16 and 8x8 blocks search.

mbd

Set macroblock decision algorithm. Possible values in the increasing order of quality:

simple

Use macroblock comparing function algorithm (default).

bits

Enable rate distortion-based half pixel and quarter pixel refinement for 16x16 blocks.

rd

Enable all of the things described above, plus rate distortion-based half pixel and quarter pixel refinement for 8x8 blocks, and rate distortion-based search using square pattern.

lumi_aq

Enable lumi masking adaptive quantization when set to 1. Default is 0 (disabled).

variance_aq

Enable variance adaptive quantization when set to 1. Default is 0 (disabled).

When combined with lumi_aq, the resulting quality will not be better than any of the two specified individually. In other words, the resulting quality will be the worse one of the two effects.

ssim

Set structural similarity (SSIM) displaying method. Possible values:

off

Disable displaying of SSIM information.

avg

Output average SSIM at the end of encoding to stdout. The format of showing the average SSIM is:

Average SSIM: %f

For users who are not familiar with C, %f means a float number, or a decimal (e.g. 0.939232).

frame

Output both per-frame SSIM data during encoding and average SSIM at the end of encoding to stdout. The format of per-frame information is:

       SSIM: avg: %1.3f min: %1.3f max: %1.3f

For users who are not familiar with C, %1.3f means a float number rounded to 3 digits after the dot (e.g. 0.932).

ssim_acc

Set SSIM accuracy. Valid options are integers within the range of 0-4, while 0 gives the most accurate result and 4 computes the fastest.

9.7 mpeg2

MPEG-2 video encoder.

9.7.1 Options

seq_disp_ext integer

Specifies if the encoder should write a sequence_display_extension to the output.

-1
auto

Decide automatically to write it or not (this is the default) by checking if the data to be written is different from the default or unspecified values.

0
never

Never write it.

1
always

Always write it.

9.8 png

PNG image encoder.

9.8.1 Private options

dpi integer

Set physical density of pixels, in dots per inch, unset by default

dpm integer

Set physical density of pixels, in dots per meter, unset by default

9.9 ProRes

Apple ProRes encoder.

FFmpeg contains 2 ProRes encoders, the prores-aw and prores-ks encoder. The used encoder can be chosen with the -vcodec option.

9.9.1 Private Options for prores-ks

profile integer

Select the ProRes profile to encode

proxy
lt
standard
hq
4444
quant_mat integer

Select quantization matrix.

auto
default
proxy
lt
standard
hq

If set to auto, the matrix matching the profile will be picked. If not set, the matrix providing the highest quality, default, will be picked.

bits_per_mb integer

How many bits to allot for coding one macroblock. Different profiles use between 200 and 2400 bits per macroblock, the maximum is 8000.

mbs_per_slice integer

Number of macroblocks in each slice (1-8); the default value (8) should be good in almost all situations.

vendor string

Override the 4-byte vendor ID. A custom vendor ID like apl0 would claim the stream was produced by the Apple encoder.

alpha_bits integer

Specify number of bits for alpha component. Possible values are 0, 8 and 16. Use 0 to disable alpha plane coding.

9.9.2 Speed considerations

In the default mode of operation the encoder has to honor frame constraints (i.e. not produc frames with size bigger than requested) while still making output picture as good as possible. A frame containing a lot of small details is harder to compress and the encoder would spend more time searching for appropriate quantizers for each slice.

Setting a higher bits_per_mb limit will improve the speed.

For the fastest encoding speed set the qscale parameter (4 is the recommended value) and do not set a size constraint.

10 Subtitles Encoders

10.1 dvdsub

This codec encodes the bitmap subtitle format that is used in DVDs. Typically they are stored in VOBSUB file pairs (*.idx + *.sub), and they can also be used in Matroska files.

10.1.1 Options

even_rows_fix

When set to 1, enable a work-around that makes the number of pixel rows even in all subtitles. This fixes a problem with some players that cut off the bottom row if the number is odd. The work-around just adds a fully transparent row if needed. The overhead is low, typically one byte per subtitle on average.

By default, this work-around is disabled.

11 See Also

ffmpeg, ffplay, ffprobe, ffserver, libavcodec

12 Authors

The FFmpeg developers.

For details about the authorship, see the Git history of the project (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command git log in the FFmpeg source directory, or browsing the online repository at http://source.ffmpeg.org.

Maintainers for the specific components are listed in the file MAINTAINERS in the source code tree.

This document was generated on November 27, 2014 using makeinfo.