FFmpeg
decode_filter_audio.c
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1 /*
2  * Copyright (c) 2010 Nicolas George
3  * Copyright (c) 2011 Stefano Sabatini
4  * Copyright (c) 2012 Clément Bœsch
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining a copy
7  * of this software and associated documentation files (the "Software"), to deal
8  * in the Software without restriction, including without limitation the rights
9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10  * copies of the Software, and to permit persons to whom the Software is
11  * furnished to do so, subject to the following conditions:
12  *
13  * The above copyright notice and this permission notice shall be included in
14  * all copies or substantial portions of the Software.
15  *
16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22  * THE SOFTWARE.
23  */
24 
25 /**
26  * @file audio decoding and filtering usage example
27  * @example decode_filter_audio.c
28  *
29  * Demux, decode and filter audio input file, generate a raw audio
30  * file to be played with ffplay.
31  */
32 
33 #include <unistd.h>
34 
35 #include <libavcodec/avcodec.h>
36 #include <libavformat/avformat.h>
37 #include <libavfilter/buffersink.h>
38 #include <libavfilter/buffersrc.h>
40 #include <libavutil/mem.h>
41 #include <libavutil/opt.h>
42 
43 static const char *filter_descr = "aresample=8000,aformat=sample_fmts=s16:channel_layouts=mono";
44 static const char *player = "ffplay -f s16le -ar 8000 -ac 1 -";
45 
51 static int audio_stream_index = -1;
52 
53 static int open_input_file(const char *filename)
54 {
55  const AVCodec *dec;
56  int ret;
57 
58  if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
59  av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
60  return ret;
61  }
62 
63  if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
64  av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
65  return ret;
66  }
67 
68  /* select the audio stream */
70  if (ret < 0) {
71  av_log(NULL, AV_LOG_ERROR, "Cannot find an audio stream in the input file\n");
72  return ret;
73  }
75 
76  /* create decoding context */
78  if (!dec_ctx)
79  return AVERROR(ENOMEM);
81 
82  /* init the audio decoder */
83  if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
84  av_log(NULL, AV_LOG_ERROR, "Cannot open audio decoder\n");
85  return ret;
86  }
87 
88  return 0;
89 }
90 
91 static int init_filters(const char *filters_descr)
92 {
93  char args[512];
94  int ret = 0;
95  const AVFilter *abuffersrc = avfilter_get_by_name("abuffer");
96  const AVFilter *abuffersink = avfilter_get_by_name("abuffersink");
99  static const int out_sample_rate = 8000;
100  const AVFilterLink *outlink;
102 
104  if (!outputs || !inputs || !filter_graph) {
105  ret = AVERROR(ENOMEM);
106  goto end;
107  }
108 
109  /* buffer audio source: the decoded frames from the decoder will be inserted here. */
112  ret = snprintf(args, sizeof(args),
113  "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=",
114  time_base.num, time_base.den, dec_ctx->sample_rate,
116  av_channel_layout_describe(&dec_ctx->ch_layout, args + ret, sizeof(args) - ret);
117  ret = avfilter_graph_create_filter(&buffersrc_ctx, abuffersrc, "in",
118  args, NULL, filter_graph);
119  if (ret < 0) {
120  av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
121  goto end;
122  }
123 
124  /* buffer audio sink: to terminate the filter chain. */
126  if (!buffersink_ctx) {
127  av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
128  ret = AVERROR(ENOMEM);
129  goto end;
130  }
131 
132  ret = av_opt_set(buffersink_ctx, "sample_formats", "s16",
134  if (ret < 0) {
135  av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
136  goto end;
137  }
138 
139  ret = av_opt_set(buffersink_ctx, "channel_layouts", "mono",
141  if (ret < 0) {
142  av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
143  goto end;
144  }
145 
147  0, 1, AV_OPT_TYPE_INT, &out_sample_rate);
148  if (ret < 0) {
149  av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
150  goto end;
151  }
152 
154  if (ret < 0) {
155  av_log(NULL, AV_LOG_ERROR, "Cannot initialize audio buffer sink\n");
156  goto end;
157  }
158 
159  /*
160  * Set the endpoints for the filter graph. The filter_graph will
161  * be linked to the graph described by filters_descr.
162  */
163 
164  /*
165  * The buffer source output must be connected to the input pad of
166  * the first filter described by filters_descr; since the first
167  * filter input label is not specified, it is set to "in" by
168  * default.
169  */
170  outputs->name = av_strdup("in");
171  outputs->filter_ctx = buffersrc_ctx;
172  outputs->pad_idx = 0;
173  outputs->next = NULL;
174 
175  /*
176  * The buffer sink input must be connected to the output pad of
177  * the last filter described by filters_descr; since the last
178  * filter output label is not specified, it is set to "out" by
179  * default.
180  */
181  inputs->name = av_strdup("out");
182  inputs->filter_ctx = buffersink_ctx;
183  inputs->pad_idx = 0;
184  inputs->next = NULL;
185 
186  if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
187  &inputs, &outputs, NULL)) < 0)
188  goto end;
189 
191  goto end;
192 
193  /* Print summary of the sink buffer
194  * Note: args buffer is reused to store channel layout string */
195  outlink = buffersink_ctx->inputs[0];
196  av_channel_layout_describe(&outlink->ch_layout, args, sizeof(args));
197  av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
198  (int)outlink->sample_rate,
199  (char *)av_x_if_null(av_get_sample_fmt_name(outlink->format), "?"),
200  args);
201 
202 end:
205 
206  return ret;
207 }
208 
209 static void print_frame(const AVFrame *frame)
210 {
211  const int n = frame->nb_samples * frame->ch_layout.nb_channels;
212  const uint16_t *p = (uint16_t*)frame->data[0];
213  const uint16_t *p_end = p + n;
214 
215  while (p < p_end) {
216  fputc(*p & 0xff, stdout);
217  fputc(*p>>8 & 0xff, stdout);
218  p++;
219  }
220  fflush(stdout);
221 }
222 
223 int main(int argc, char **argv)
224 {
225  int ret;
226  AVPacket *packet = av_packet_alloc();
228  AVFrame *filt_frame = av_frame_alloc();
229 
230  if (!packet || !frame || !filt_frame) {
231  fprintf(stderr, "Could not allocate frame or packet\n");
232  exit(1);
233  }
234  if (argc != 2) {
235  fprintf(stderr, "Usage: %s file | %s\n", argv[0], player);
236  exit(1);
237  }
238 
239  if ((ret = open_input_file(argv[1])) < 0)
240  goto end;
241  if ((ret = init_filters(filter_descr)) < 0)
242  goto end;
243 
244  /* read all packets */
245  while (1) {
246  if ((ret = av_read_frame(fmt_ctx, packet)) < 0)
247  break;
248 
249  if (packet->stream_index == audio_stream_index) {
250  ret = avcodec_send_packet(dec_ctx, packet);
251  if (ret < 0) {
252  av_log(NULL, AV_LOG_ERROR, "Error while sending a packet to the decoder\n");
253  break;
254  }
255 
256  while (ret >= 0) {
258  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
259  break;
260  } else if (ret < 0) {
261  av_log(NULL, AV_LOG_ERROR, "Error while receiving a frame from the decoder\n");
262  goto end;
263  }
264 
265  if (ret >= 0) {
266  /* push the audio data from decoded frame into the filtergraph */
268  av_log(NULL, AV_LOG_ERROR, "Error while feeding the audio filtergraph\n");
269  break;
270  }
271 
272  /* pull filtered audio from the filtergraph */
273  while (1) {
275  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
276  break;
277  if (ret < 0)
278  goto end;
279  print_frame(filt_frame);
280  av_frame_unref(filt_frame);
281  }
283  }
284  }
285  }
286  av_packet_unref(packet);
287  }
288  if (ret == AVERROR_EOF) {
289  /* signal EOF to the filtergraph */
291  av_log(NULL, AV_LOG_ERROR, "Error while closing the filtergraph\n");
292  goto end;
293  }
294 
295  /* pull remaining frames from the filtergraph */
296  while (1) {
298  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
299  break;
300  if (ret < 0)
301  goto end;
302  print_frame(filt_frame);
303  av_frame_unref(filt_frame);
304  }
305  }
306 
307 end:
311  av_packet_free(&packet);
313  av_frame_free(&filt_frame);
314 
315  if (ret < 0 && ret != AVERROR_EOF) {
316  fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
317  exit(1);
318  }
319 
320  exit(0);
321 }
AV_OPT_SEARCH_CHILDREN
#define AV_OPT_SEARCH_CHILDREN
Search in possible children of the given object first.
Definition: opt.h:605
av_packet_unref
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: packet.c:429
AVCodec
AVCodec.
Definition: codec.h:187
main
int main(int argc, char **argv)
Definition: decode_filter_audio.c:223
dec_ctx
static AVCodecContext * dec_ctx
Definition: decode_filter_audio.c:47
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
opt.h
av_find_best_stream
int av_find_best_stream(AVFormatContext *ic, enum AVMediaType type, int wanted_stream_nb, int related_stream, const AVCodec **decoder_ret, int flags)
Definition: avformat.c:450
AVCodecContext::sample_rate
int sample_rate
samples per second
Definition: avcodec.h:1056
AVERROR_EOF
#define AVERROR_EOF
End of file.
Definition: error.h:57
av_frame_free
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:162
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:389
AVFormatContext::streams
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1368
AVChannelLayout::order
enum AVChannelOrder order
Channel order used in this layout.
Definition: channel_layout.h:316
av_read_frame
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
Return the next frame of a stream.
Definition: demux.c:1538
AVChannelLayout::nb_channels
int nb_channels
Number of channels in this layout.
Definition: channel_layout.h:321
av_packet_free
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
Definition: packet.c:74
avfilter_graph_free
void avfilter_graph_free(AVFilterGraph **graph)
Free a graph, destroy its links, and set *graph to NULL.
Definition: avfiltergraph.c:117
avformat_close_input
void avformat_close_input(AVFormatContext **s)
Close an opened input AVFormatContext.
Definition: demux.c:363
print_frame
static void print_frame(const AVFrame *frame)
Definition: decode_filter_audio.c:209
avfilter_graph_create_filter
int avfilter_graph_create_filter(AVFilterContext **filt_ctx, const AVFilter *filt, const char *name, const char *args, void *opaque, AVFilterGraph *graph_ctx)
A convenience wrapper that allocates and initializes a filter in a single step.
Definition: avfiltergraph.c:138
avfilter_graph_alloc_filter
AVFilterContext * avfilter_graph_alloc_filter(AVFilterGraph *graph, const AVFilter *filter, const char *name)
Create a new filter instance in a filter graph.
Definition: avfiltergraph.c:165
AVCodecContext::ch_layout
AVChannelLayout ch_layout
Audio channel layout.
Definition: avcodec.h:1071
avfilter_graph_alloc
AVFilterGraph * avfilter_graph_alloc(void)
Allocate a filter graph.
Definition: avfiltergraph.c:83
av_opt_set
int av_opt_set(void *obj, const char *name, const char *val, int search_flags)
Definition: opt.c:827
open_input_file
static int open_input_file(const char *filename)
Definition: decode_filter_audio.c:53
AVRational::num
int num
Numerator.
Definition: rational.h:59
av_frame_alloc
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:150
avfilter_inout_free
void avfilter_inout_free(AVFilterInOut **inout)
Free the supplied list of AVFilterInOut and set *inout to NULL.
Definition: graphparser.c:76
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:209
avformat_open_input
int avformat_open_input(AVFormatContext **ps, const char *url, const AVInputFormat *fmt, AVDictionary **options)
Open an input stream and read the header.
Definition: demux.c:215
av_channel_layout_describe
int av_channel_layout_describe(const AVChannelLayout *channel_layout, char *buf, size_t buf_size)
Get a human-readable string describing the channel layout properties.
Definition: channel_layout.c:648
avcodec_alloc_context3
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Definition: options.c:149
AVMEDIA_TYPE_AUDIO
@ AVMEDIA_TYPE_AUDIO
Definition: avutil.h:202
AV_CHANNEL_ORDER_UNSPEC
@ AV_CHANNEL_ORDER_UNSPEC
Only the channel count is specified, without any further information about the channel order.
Definition: channel_layout.h:116
av_buffersink_get_frame
int attribute_align_arg av_buffersink_get_frame(AVFilterContext *ctx, AVFrame *frame)
Get a frame with filtered data from sink and put it in frame.
Definition: buffersink.c:89
avcodec_receive_frame
int attribute_align_arg avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder or encoder (when the AV_CODEC_FLAG_RECON_FRAME flag is used...
Definition: avcodec.c:704
av_opt_set_array
int av_opt_set_array(void *obj, const char *name, int search_flags, unsigned int start_elem, unsigned int nb_elems, enum AVOptionType val_type, const void *val)
Add, replace, or remove elements for an array option.
Definition: opt.c:2273
av_get_sample_fmt_name
const char * av_get_sample_fmt_name(enum AVSampleFormat sample_fmt)
Return the name of sample_fmt, or NULL if sample_fmt is not recognized.
Definition: samplefmt.c:51
audio_stream_index
static int audio_stream_index
Definition: decode_filter_audio.c:51
AVFormatContext
Format I/O context.
Definition: avformat.h:1300
avfilter_get_by_name
const AVFilter * avfilter_get_by_name(const char *name)
Get a filter definition matching the given name.
Definition: allfilters.c:634
AVStream::codecpar
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:771
avcodec_parameters_to_context
int avcodec_parameters_to_context(AVCodecContext *codec, const struct AVCodecParameters *par)
Fill the codec context based on the values from the supplied codec parameters.
avfilter_graph_config
int avfilter_graph_config(AVFilterGraph *graphctx, void *log_ctx)
Check validity and configure all the links and formats in the graph.
Definition: avfiltergraph.c:1294
AVStream::time_base
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented.
Definition: avformat.h:787
NULL
#define NULL
Definition: coverity.c:32
avcodec_free_context
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer.
Definition: options.c:164
AVRational
Rational number (pair of numerator and denominator).
Definition: rational.h:58
AVFilterContext::inputs
AVFilterLink ** inputs
array of pointers to input links
Definition: avfilter.h:465
avfilter_inout_alloc
AVFilterInOut * avfilter_inout_alloc(void)
Allocate a single AVFilterInOut entry.
Definition: graphparser.c:71
avcodec_open2
int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
Definition: avcodec.c:143
AVFilterGraph
Definition: avfilter.h:781
inputs
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several inputs
Definition: filter_design.txt:243
filter_descr
static const char * filter_descr
Definition: decode_filter_audio.c:43
avformat_find_stream_info
int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
Read packets of a media file to get stream information.
Definition: demux.c:2516
fmt_ctx
static AVFormatContext * fmt_ctx
Definition: decode_filter_audio.c:46
init_filters
static int init_filters(const char *filters_descr)
Definition: decode_filter_audio.c:91
av_err2str
#define av_err2str(errnum)
Convenience macro, the return value should be used only directly in function arguments but never stan...
Definition: error.h:122
AVCodecContext::sample_fmt
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:1063
av_packet_alloc
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
Definition: packet.c:63
AV_LOG_INFO
#define AV_LOG_INFO
Standard information.
Definition: log.h:220
buffersink.h
buffersink_ctx
AVFilterContext * buffersink_ctx
Definition: decode_filter_audio.c:48
av_channel_layout_default
void av_channel_layout_default(AVChannelLayout *ch_layout, int nb_channels)
Get the default channel layout for a given number of channels.
Definition: channel_layout.c:834
avcodec_send_packet
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
Definition: decode.c:727
player
static const char * player
Definition: decode_filter_audio.c:44
avfilter_graph_parse_ptr
int avfilter_graph_parse_ptr(AVFilterGraph *graph, const char *filters, AVFilterInOut **inputs, AVFilterInOut **outputs, void *log_ctx)
Add a graph described by a string to a graph.
Definition: graphparser.c:920
av_buffersrc_add_frame_flags
int attribute_align_arg av_buffersrc_add_frame_flags(AVFilterContext *ctx, AVFrame *frame, int flags)
Add a frame to the buffer source.
Definition: buffersrc.c:192
av_frame_unref
void av_frame_unref(AVFrame *frame)
Unreference all the buffers referenced by frame and reset the frame fields.
Definition: frame.c:610
AVFilterPad::name
const char * name
Pad name.
Definition: filters.h:44
outputs
static const AVFilterPad outputs[]
Definition: af_aap.c:310
avcodec.h
AVFilter
Filter definition.
Definition: avfilter.h:201
ret
ret
Definition: filter_design.txt:187
frame
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several the filter must be ready for frames arriving randomly on any input any filter with several inputs will most likely require some kind of queuing mechanism It is perfectly acceptable to have a limited queue and to drop frames when the inputs are too unbalanced request_frame For filters that do not use the this method is called when a frame is wanted on an output For a it should directly call filter_frame on the corresponding output For a if there are queued frames already one of these frames should be pushed If the filter should request a frame on one of its repeatedly until at least one frame has been pushed Return or at least make progress towards producing a frame
Definition: filter_design.txt:264
avformat.h
AVCodecContext
main external API structure.
Definition: avcodec.h:451
channel_layout.h
avfilter_init_dict
int avfilter_init_dict(AVFilterContext *ctx, AVDictionary **options)
Initialize a filter with the supplied dictionary of options.
Definition: avfilter.c:914
AVRational::den
int den
Denominator.
Definition: rational.h:60
AV_OPT_TYPE_INT
@ AV_OPT_TYPE_INT
Underlying C type is int.
Definition: opt.h:259
AV_BUFFERSRC_FLAG_KEEP_REF
@ AV_BUFFERSRC_FLAG_KEEP_REF
Keep a reference to the frame.
Definition: buffersrc.h:53
AVPacket::stream_index
int stream_index
Definition: packet.h:541
AVFilterContext
An instance of a filter.
Definition: avfilter.h:457
av_strdup
char * av_strdup(const char *s)
Duplicate a string.
Definition: mem.c:272
mem.h
AVPacket
This structure stores compressed data.
Definition: packet.h:516
filter_graph
AVFilterGraph * filter_graph
Definition: decode_filter_audio.c:50
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:27
AVFilterInOut
A linked-list of the inputs/outputs of the filter chain.
Definition: avfilter.h:930
snprintf
#define snprintf
Definition: snprintf.h:34
buffersrc.h
av_x_if_null
static void * av_x_if_null(const void *p, const void *x)
Return x default pointer in case p is NULL.
Definition: avutil.h:312
buffersrc_ctx
AVFilterContext * buffersrc_ctx
Definition: decode_filter_audio.c:49