FFmpeg
filtering_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
27  * API example for audio decoding and filtering
28  * @example filtering_audio.c
29  */
30 
31 #include <unistd.h>
32 
33 #include <libavcodec/avcodec.h>
34 #include <libavformat/avformat.h>
35 #include <libavfilter/buffersink.h>
36 #include <libavfilter/buffersrc.h>
37 #include <libavutil/opt.h>
38 
39 static const char *filter_descr = "aresample=8000,aformat=sample_fmts=s16:channel_layouts=mono";
40 static const char *player = "ffplay -f s16le -ar 8000 -ac 1 -";
41 
47 static int audio_stream_index = -1;
48 
49 static int open_input_file(const char *filename)
50 {
51  const AVCodec *dec;
52  int ret;
53 
54  if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
55  av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
56  return ret;
57  }
58 
59  if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
60  av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
61  return ret;
62  }
63 
64  /* select the audio stream */
66  if (ret < 0) {
67  av_log(NULL, AV_LOG_ERROR, "Cannot find an audio stream in the input file\n");
68  return ret;
69  }
71 
72  /* create decoding context */
74  if (!dec_ctx)
75  return AVERROR(ENOMEM);
77 
78  /* init the audio decoder */
79  if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
80  av_log(NULL, AV_LOG_ERROR, "Cannot open audio decoder\n");
81  return ret;
82  }
83 
84  return 0;
85 }
86 
87 static int init_filters(const char *filters_descr)
88 {
89  char args[512];
90  int ret = 0;
91  const AVFilter *abuffersrc = avfilter_get_by_name("abuffer");
92  const AVFilter *abuffersink = avfilter_get_by_name("abuffersink");
95  static const enum AVSampleFormat out_sample_fmts[] = { AV_SAMPLE_FMT_S16, -1 };
96  static const int64_t out_channel_layouts[] = { AV_CH_LAYOUT_MONO, -1 };
97  static const int out_sample_rates[] = { 8000, -1 };
98  const AVFilterLink *outlink;
100 
102  if (!outputs || !inputs || !filter_graph) {
103  ret = AVERROR(ENOMEM);
104  goto end;
105  }
106 
107  /* buffer audio source: the decoded frames from the decoder will be inserted here. */
108  if (!dec_ctx->channel_layout)
110  snprintf(args, sizeof(args),
111  "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
112  time_base.num, time_base.den, dec_ctx->sample_rate,
114  ret = avfilter_graph_create_filter(&buffersrc_ctx, abuffersrc, "in",
115  args, NULL, filter_graph);
116  if (ret < 0) {
117  av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
118  goto end;
119  }
120 
121  /* buffer audio sink: to terminate the filter chain. */
122  ret = avfilter_graph_create_filter(&buffersink_ctx, abuffersink, "out",
124  if (ret < 0) {
125  av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
126  goto end;
127  }
128 
129  ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
131  if (ret < 0) {
132  av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
133  goto end;
134  }
135 
136  ret = av_opt_set_int_list(buffersink_ctx, "channel_layouts", out_channel_layouts, -1,
138  if (ret < 0) {
139  av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
140  goto end;
141  }
142 
143  ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
145  if (ret < 0) {
146  av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
147  goto end;
148  }
149 
150  /*
151  * Set the endpoints for the filter graph. The filter_graph will
152  * be linked to the graph described by filters_descr.
153  */
154 
155  /*
156  * The buffer source output must be connected to the input pad of
157  * the first filter described by filters_descr; since the first
158  * filter input label is not specified, it is set to "in" by
159  * default.
160  */
161  outputs->name = av_strdup("in");
162  outputs->filter_ctx = buffersrc_ctx;
163  outputs->pad_idx = 0;
164  outputs->next = NULL;
165 
166  /*
167  * The buffer sink input must be connected to the output pad of
168  * the last filter described by filters_descr; since the last
169  * filter output label is not specified, it is set to "out" by
170  * default.
171  */
172  inputs->name = av_strdup("out");
173  inputs->filter_ctx = buffersink_ctx;
174  inputs->pad_idx = 0;
175  inputs->next = NULL;
176 
177  if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
178  &inputs, &outputs, NULL)) < 0)
179  goto end;
180 
182  goto end;
183 
184  /* Print summary of the sink buffer
185  * Note: args buffer is reused to store channel layout string */
186  outlink = buffersink_ctx->inputs[0];
187  av_get_channel_layout_string(args, sizeof(args), -1, outlink->channel_layout);
188  av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
189  (int)outlink->sample_rate,
190  (char *)av_x_if_null(av_get_sample_fmt_name(outlink->format), "?"),
191  args);
192 
193 end:
196 
197  return ret;
198 }
199 
200 static void print_frame(const AVFrame *frame)
201 {
202  const int n = frame->nb_samples * av_get_channel_layout_nb_channels(frame->channel_layout);
203  const uint16_t *p = (uint16_t*)frame->data[0];
204  const uint16_t *p_end = p + n;
205 
206  while (p < p_end) {
207  fputc(*p & 0xff, stdout);
208  fputc(*p>>8 & 0xff, stdout);
209  p++;
210  }
211  fflush(stdout);
212 }
213 
214 int main(int argc, char **argv)
215 {
216  int ret;
217  AVPacket packet;
219  AVFrame *filt_frame = av_frame_alloc();
220 
221  if (!frame || !filt_frame) {
222  perror("Could not allocate frame");
223  exit(1);
224  }
225  if (argc != 2) {
226  fprintf(stderr, "Usage: %s file | %s\n", argv[0], player);
227  exit(1);
228  }
229 
230  if ((ret = open_input_file(argv[1])) < 0)
231  goto end;
232  if ((ret = init_filters(filter_descr)) < 0)
233  goto end;
234 
235  /* read all packets */
236  while (1) {
237  if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
238  break;
239 
240  if (packet.stream_index == audio_stream_index) {
241  ret = avcodec_send_packet(dec_ctx, &packet);
242  if (ret < 0) {
243  av_log(NULL, AV_LOG_ERROR, "Error while sending a packet to the decoder\n");
244  break;
245  }
246 
247  while (ret >= 0) {
249  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
250  break;
251  } else if (ret < 0) {
252  av_log(NULL, AV_LOG_ERROR, "Error while receiving a frame from the decoder\n");
253  goto end;
254  }
255 
256  if (ret >= 0) {
257  /* push the audio data from decoded frame into the filtergraph */
259  av_log(NULL, AV_LOG_ERROR, "Error while feeding the audio filtergraph\n");
260  break;
261  }
262 
263  /* pull filtered audio from the filtergraph */
264  while (1) {
266  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
267  break;
268  if (ret < 0)
269  goto end;
270  print_frame(filt_frame);
271  av_frame_unref(filt_frame);
272  }
274  }
275  }
276  }
277  av_packet_unref(&packet);
278  }
279 end:
284  av_frame_free(&filt_frame);
285 
286  if (ret < 0 && ret != AVERROR_EOF) {
287  fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
288  exit(1);
289  }
290 
291  exit(0);
292 }
av_packet_unref
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:403
AVCodec
AVCodec.
Definition: codec.h:197
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
AVCodecContext::channel_layout
uint64_t channel_layout
Audio channel layout.
Definition: avcodec.h:1149
AVCodecContext::sample_rate
int sample_rate
samples per second
Definition: avcodec.h:1098
AVERROR_EOF
#define AVERROR_EOF
End of file.
Definition: error.h:55
buffersink_ctx
AVFilterContext * buffersink_ctx
Definition: filtering_audio.c:44
AV_CH_LAYOUT_MONO
#define AV_CH_LAYOUT_MONO
Definition: channel_layout.h:90
av_opt_set_int_list
#define av_opt_set_int_list(obj, name, val, term, flags)
Set a binary option to an integer list.
Definition: opt.h:714
av_frame_free
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:111
av_get_channel_layout_string
void av_get_channel_layout_string(char *buf, int buf_size, int nb_channels, uint64_t channel_layout)
Return a description of a channel layout.
Definition: channel_layout.c:217
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:303
AVFormatContext::streams
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1197
av_read_frame
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
Return the next frame of a stream.
Definition: utils.c:1660
avfilter_graph_free
void avfilter_graph_free(AVFilterGraph **graph)
Free a graph, destroy its links, and set *graph to NULL.
Definition: avfiltergraph.c:120
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)
Find the "best" stream in the file.
Definition: utils.c:4112
avformat_close_input
void avformat_close_input(AVFormatContext **s)
Close an opened input AVFormatContext.
Definition: utils.c:4340
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)
Create and add a filter instance into an existing graph.
Definition: avfiltergraph.c:139
filter_graph
AVFilterGraph * filter_graph
Definition: filtering_audio.c:46
avfilter_graph_alloc
AVFilterGraph * avfilter_graph_alloc(void)
Allocate a filter graph.
Definition: avfiltergraph.c:83
AVRational::num
int num
Numerator.
Definition: rational.h:59
main
int main(int argc, char **argv)
Definition: filtering_audio.c:214
av_frame_alloc
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:98
avfilter_inout_free
void avfilter_inout_free(AVFilterInOut **inout)
Free the supplied list of AVFilterInOut and set *inout to NULL.
Definition: graphparser.c:212
player
static const char * player
Definition: filtering_audio.c:40
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:181
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
open_input_file
static int open_input_file(const char *filename)
Definition: filtering_audio.c:49
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: utils.c:476
avcodec_alloc_context3
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Definition: options.c:141
AVMEDIA_TYPE_AUDIO
@ AVMEDIA_TYPE_AUDIO
Definition: avutil.h:202
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:88
avcodec_receive_frame
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder.
Definition: decode.c:628
outputs
static const AVFilterPad outputs[]
Definition: af_acontrast.c:203
init_filters
static int init_filters(const char *filters_descr)
Definition: filtering_audio.c:87
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:49
buffersrc_ctx
AVFilterContext * buffersrc_ctx
Definition: filtering_audio.c:45
AVFormatContext
Format I/O context.
Definition: avformat.h:1129
avfilter_get_by_name
const AVFilter * avfilter_get_by_name(const char *name)
Get a filter definition matching the given name.
Definition: allfilters.c:546
AVStream::codecpar
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:979
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:1215
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:855
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:156
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:341
avfilter_inout_alloc
AVFilterInOut * avfilter_inout_alloc(void)
Allocate a single AVFilterInOut entry.
Definition: graphparser.c:207
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:135
AVFilterGraph
Definition: avfilter.h:798
av_get_channel_layout_nb_channels
int av_get_channel_layout_nb_channels(uint64_t channel_layout)
Return the number of channels in the channel layout.
Definition: channel_layout.c:226
avformat_find_stream_info
int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
Read packets of a media file to get stream information.
Definition: utils.c:3538
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:119
AVCodecContext::sample_fmt
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:1106
AV_OPT_SEARCH_CHILDREN
#define AV_OPT_SEARCH_CHILDREN
Search in possible children of the given object first.
Definition: opt.h:560
filter_descr
static const char * filter_descr
Definition: filtering_audio.c:39
AV_LOG_INFO
#define AV_LOG_INFO
Standard information.
Definition: log.h:192
AVCodecContext::channels
int channels
number of audio channels
Definition: avcodec.h:1099
buffersink.h
avcodec_send_packet
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
Definition: decode.c:565
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:549
avcodec_parameters_to_context
int avcodec_parameters_to_context(AVCodecContext *codec, const AVCodecParameters *par)
Fill the codec context based on the values from the supplied codec parameters.
Definition: codec_par.c:147
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:166
AVSampleFormat
AVSampleFormat
Audio sample formats.
Definition: samplefmt.h:58
print_frame
static void print_frame(const AVFrame *frame)
Definition: filtering_audio.c:200
AV_BUFFERSRC_FLAG_KEEP_REF
@ AV_BUFFERSRC_FLAG_KEEP_REF
Keep a reference to the frame.
Definition: buffersrc.h:53
av_frame_unref
void av_frame_unref(AVFrame *frame)
Unreference all the buffers referenced by frame and reset the frame fields.
Definition: frame.c:436
AV_SAMPLE_FMT_S16
@ AV_SAMPLE_FMT_S16
signed 16 bits
Definition: samplefmt.h:61
fmt_ctx
static AVFormatContext * fmt_ctx
Definition: filtering_audio.c:42
AVFilterPad::name
const char * name
Pad name.
Definition: internal.h:60
avcodec.h
AVFilter
Filter definition.
Definition: avfilter.h:145
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:501
AVRational::den
int den
Denominator.
Definition: rational.h:60
AVPacket::stream_index
int stream_index
Definition: packet.h:367
AVFilterContext
An instance of a filter.
Definition: avfilter.h:333
av_strdup
char * av_strdup(const char *s)
Duplicate a string.
Definition: mem.c:259
av_get_default_channel_layout
int64_t av_get_default_channel_layout(int nb_channels)
Return default channel layout for a given number of channels.
Definition: channel_layout.c:231
AVPacket
This structure stores compressed data.
Definition: packet.h:342
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:28
AVFilterInOut
A linked-list of the inputs/outputs of the filter chain.
Definition: avfilter.h:958
snprintf
#define snprintf
Definition: snprintf.h:34
buffersrc.h
audio_stream_index
static int audio_stream_index
Definition: filtering_audio.c:47
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:308
dec_ctx
static AVCodecContext * dec_ctx
Definition: filtering_audio.c:43