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  int ret;
52  AVCodec *dec;
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 */
65  ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &dec, 0);
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 */
73  dec_ctx = avcodec_alloc_context3(dec);
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;
99  AVRational time_base = fmt_ctx->streams[audio_stream_index]->time_base;
100 
101  filter_graph = avfilter_graph_alloc();
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,
113  av_get_sample_fmt_name(dec_ctx->sample_fmt), dec_ctx->channel_layout);
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",
123  NULL, NULL, filter_graph);
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 
181  if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
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:
194  avfilter_inout_free(&inputs);
195  avfilter_inout_free(&outputs);
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) {
248  ret = avcodec_receive_frame(dec_ctx, frame);
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 */
258  if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0) {
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) {
265  ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
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  }
273  av_frame_unref(frame);
274  }
275  }
276  }
277  av_packet_unref(&packet);
278  }
279 end:
280  avfilter_graph_free(&filter_graph);
281  avcodec_free_context(&dec_ctx);
282  avformat_close_input(&fmt_ctx);
283  av_frame_free(&frame);
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 }
#define NULL
Definition: coverity.c:32
AVFilterContext * buffersink_ctx
This structure describes decoded (raw) audio or video data.
Definition: frame.h:268
AVFilterGraph * avfilter_graph_alloc(void)
Allocate a filter graph.
Definition: avfiltergraph.c:83
Memory buffer source API.
AVFilterGraph * filter_graph
int avfilter_graph_config(AVFilterGraph *graphctx, void *log_ctx)
Check validity and configure all the links and formats in the graph.
void avfilter_inout_free(AVFilterInOut **inout)
Free the supplied list of AVFilterInOut and set *inout to NULL.
Definition: graphparser.c:203
struct AVFilterInOut * next
next input/input in the list, NULL if this is the last
Definition: avfilter.h:1014
#define av_opt_set_int_list(obj, name, val, term, flags)
Set a binary option to an integer list.
Definition: opt.h:708
int num
Numerator.
Definition: rational.h:59
void avfilter_graph_free(AVFilterGraph **graph)
Free a graph, destroy its links, and set *graph to NULL.
int avformat_open_input(AVFormatContext **ps, const char *url, ff_const59 AVInputFormat *fmt, AVDictionary **options)
Open an input stream and read the header.
Definition: utils.c:537
AVCodec.
Definition: avcodec.h:3477
static int audio_stream_index
int av_get_channel_layout_nb_channels(uint64_t channel_layout)
Return the number of channels in the channel layout.
Format I/O context.
Definition: avformat.h:1358
memory buffer sink API for audio and video
AVFilterLink ** inputs
array of pointers to input links
Definition: avfilter.h:346
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:2229
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:189
AVOptions.
static av_cold int end(AVCodecContext *avctx)
Definition: avrndec.c:90
static int init_filters(const char *filters_descr)
static const char * filter_descr
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1426
int avcodec_parameters_to_context(AVCodecContext *codec, const AVCodecParameters *par)
Fill the codec context based on the values from the supplied codec parameters.
Definition: utils.c:2088
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.
#define AVERROR_EOF
End of file.
Definition: error.h:55
#define av_log(a,...)
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
int av_find_best_stream(AVFormatContext *ic, enum AVMediaType type, int wanted_stream_nb, int related_stream, AVCodec **decoder_ret, int flags)
Find the "best" stream in the file.
Definition: utils.c:4183
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
int main(int argc, char **argv)
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:202
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder.
Definition: decode.c:740
AVFilterContext * buffersrc_ctx
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
uint64_t channel_layout
Audio channel layout.
Definition: avcodec.h:2272
uint64_t channel_layout
Channel layout of the audio data.
Definition: frame.h:445
const AVFilter * avfilter_get_by_name(const char *name)
Get a filter definition matching the given name.
Definition: allfilters.c:484
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Definition: options.c:156
#define AV_OPT_SEARCH_CHILDREN
Search in possible children of the given object first.
Definition: opt.h:556
#define av_err2str(errnum)
Convenience macro, the return value should be used only directly in function arguments but never stan...
Definition: error.h:119
static int open_input_file(const char *filename)
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
int n
Definition: avisynth_c.h:760
static const char * player
AVFilterContext * filter_ctx
filter context associated to this input/output
Definition: avfilter.h:1008
static const AVFilterPad outputs[]
Definition: af_acontrast.c:203
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.
A linked-list of the inputs/outputs of the filter chain.
Definition: avfilter.h:1003
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
Definition: decode.c:677
#define AV_LOG_INFO
Standard information.
Definition: log.h:187
char * av_strdup(const char *s)
Duplicate a string.
Definition: mem.c:251
Libavcodec external API header.
AVSampleFormat
Audio sample formats.
Definition: samplefmt.h:58
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:171
int sample_rate
samples per second
Definition: avcodec.h:2221
main external API structure.
Definition: avcodec.h:1565
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:599
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
Filter definition.
Definition: avfilter.h:144
int pad_idx
index of the filt_ctx pad to use for linking
Definition: avfilter.h:1011
Rational number (pair of numerator and denominator).
Definition: rational.h:58
static void print_frame(const AVFrame *frame)
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
Definition: utils.c:542
#define snprintf
Definition: snprintf.h:34
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
Return the next frame of a stream.
Definition: utils.c:1768
char * name
unique name for this input/output in the list
Definition: avfilter.h:1005
void av_frame_unref(AVFrame *frame)
Unreference all the buffers referenced by frame and reset the frame fields.
Definition: frame.c:553
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:282
static AVFormatContext * fmt_ctx
Main libavformat public API header.
AVFilterInOut * avfilter_inout_alloc(void)
Allocate a single AVFilterInOut entry.
Definition: graphparser.c:198
int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
Read packets of a media file to get stream information.
Definition: utils.c:3564
signed 16 bits
Definition: samplefmt.h:61
static AVCodecContext * dec_ctx
int den
Denominator.
Definition: rational.h:60
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:158
void avformat_close_input(AVFormatContext **s)
Close an opened input AVFormatContext.
Definition: utils.c:4427
int channels
number of audio channels
Definition: avcodec.h:2222
Keep a reference to the frame.
Definition: buffersrc.h:53
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:538
An instance of a filter.
Definition: avfilter.h:338
int64_t av_get_default_channel_layout(int nb_channels)
Return default channel layout for a given number of channels.
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1028
int stream_index
Definition: avcodec.h:1479
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented...
Definition: avformat.h:910
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
#define AV_CH_LAYOUT_MONO
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:67
This structure stores compressed data.
Definition: avcodec.h:1454
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:334