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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>
36 #include <libavfilter/buffersink.h>
37 #include <libavfilter/buffersrc.h>
38 #include <libavutil/opt.h>
39 
40 static const char *filter_descr = "aresample=8000,aformat=sample_fmts=s16:channel_layouts=mono";
41 static const char *player = "ffplay -f s16le -ar 8000 -ac 1 -";
42 
48 static int audio_stream_index = -1;
49 
50 static int open_input_file(const char *filename)
51 {
52  int ret;
53  AVCodec *dec;
54 
55  if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
56  av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
57  return ret;
58  }
59 
60  if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
61  av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
62  return ret;
63  }
64 
65  /* select the audio stream */
66  ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &dec, 0);
67  if (ret < 0) {
68  av_log(NULL, AV_LOG_ERROR, "Cannot find an audio stream in the input file\n");
69  return ret;
70  }
71  audio_stream_index = ret;
72 
73  /* create decoding context */
74  dec_ctx = avcodec_alloc_context3(dec);
75  if (!dec_ctx)
76  return AVERROR(ENOMEM);
78  av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);
79 
80  /* init the audio decoder */
81  if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
82  av_log(NULL, AV_LOG_ERROR, "Cannot open audio decoder\n");
83  return ret;
84  }
85 
86  return 0;
87 }
88 
89 static int init_filters(const char *filters_descr)
90 {
91  char args[512];
92  int ret = 0;
93  AVFilter *abuffersrc = avfilter_get_by_name("abuffer");
94  AVFilter *abuffersink = avfilter_get_by_name("abuffersink");
97  static const enum AVSampleFormat out_sample_fmts[] = { AV_SAMPLE_FMT_S16, -1 };
98  static const int64_t out_channel_layouts[] = { AV_CH_LAYOUT_MONO, -1 };
99  static const int out_sample_rates[] = { 8000, -1 };
100  const AVFilterLink *outlink;
101  AVRational time_base = fmt_ctx->streams[audio_stream_index]->time_base;
102 
103  filter_graph = avfilter_graph_alloc();
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. */
110  if (!dec_ctx->channel_layout)
112  snprintf(args, sizeof(args),
113  "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
114  time_base.num, time_base.den, dec_ctx->sample_rate,
115  av_get_sample_fmt_name(dec_ctx->sample_fmt), dec_ctx->channel_layout);
116  ret = avfilter_graph_create_filter(&buffersrc_ctx, abuffersrc, "in",
117  args, NULL, filter_graph);
118  if (ret < 0) {
119  av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
120  goto end;
121  }
122 
123  /* buffer audio sink: to terminate the filter chain. */
124  ret = avfilter_graph_create_filter(&buffersink_ctx, abuffersink, "out",
125  NULL, NULL, filter_graph);
126  if (ret < 0) {
127  av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
128  goto end;
129  }
130 
131  ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
133  if (ret < 0) {
134  av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
135  goto end;
136  }
137 
138  ret = av_opt_set_int_list(buffersink_ctx, "channel_layouts", out_channel_layouts, -1,
140  if (ret < 0) {
141  av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
142  goto end;
143  }
144 
145  ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
147  if (ret < 0) {
148  av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
149  goto end;
150  }
151 
152  /*
153  * Set the endpoints for the filter graph. The filter_graph will
154  * be linked to the graph described by filters_descr.
155  */
156 
157  /*
158  * The buffer source output must be connected to the input pad of
159  * the first filter described by filters_descr; since the first
160  * filter input label is not specified, it is set to "in" by
161  * default.
162  */
163  outputs->name = av_strdup("in");
164  outputs->filter_ctx = buffersrc_ctx;
165  outputs->pad_idx = 0;
166  outputs->next = NULL;
167 
168  /*
169  * The buffer sink input must be connected to the output pad of
170  * the last filter described by filters_descr; since the last
171  * filter output label is not specified, it is set to "out" by
172  * default.
173  */
174  inputs->name = av_strdup("out");
175  inputs->filter_ctx = buffersink_ctx;
176  inputs->pad_idx = 0;
177  inputs->next = NULL;
178 
179  if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
180  &inputs, &outputs, NULL)) < 0)
181  goto end;
182 
183  if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
184  goto end;
185 
186  /* Print summary of the sink buffer
187  * Note: args buffer is reused to store channel layout string */
188  outlink = buffersink_ctx->inputs[0];
189  av_get_channel_layout_string(args, sizeof(args), -1, outlink->channel_layout);
190  av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
191  (int)outlink->sample_rate,
192  (char *)av_x_if_null(av_get_sample_fmt_name(outlink->format), "?"),
193  args);
194 
195 end:
196  avfilter_inout_free(&inputs);
197  avfilter_inout_free(&outputs);
198 
199  return ret;
200 }
201 
202 static void print_frame(const AVFrame *frame)
203 {
204  const int n = frame->nb_samples * av_get_channel_layout_nb_channels(frame->channel_layout);
205  const uint16_t *p = (uint16_t*)frame->data[0];
206  const uint16_t *p_end = p + n;
207 
208  while (p < p_end) {
209  fputc(*p & 0xff, stdout);
210  fputc(*p>>8 & 0xff, stdout);
211  p++;
212  }
213  fflush(stdout);
214 }
215 
216 int main(int argc, char **argv)
217 {
218  int ret;
219  AVPacket packet;
221  AVFrame *filt_frame = av_frame_alloc();
222 
223  if (!frame || !filt_frame) {
224  perror("Could not allocate frame");
225  exit(1);
226  }
227  if (argc != 2) {
228  fprintf(stderr, "Usage: %s file | %s\n", argv[0], player);
229  exit(1);
230  }
231 
232  av_register_all();
234 
235  if ((ret = open_input_file(argv[1])) < 0)
236  goto end;
237  if ((ret = init_filters(filter_descr)) < 0)
238  goto end;
239 
240  /* read all packets */
241  while (1) {
242  if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
243  break;
244 
245  if (packet.stream_index == audio_stream_index) {
246  ret = avcodec_send_packet(dec_ctx, &packet);
247  if (ret < 0) {
248  av_log(NULL, AV_LOG_ERROR, "Error while sending a packet to the decoder\n");
249  break;
250  }
251 
252  while (ret >= 0) {
253  ret = avcodec_receive_frame(dec_ctx, frame);
254  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
255  break;
256  } else if (ret < 0) {
257  av_log(NULL, AV_LOG_ERROR, "Error while receiving a frame from the decoder\n");
258  goto end;
259  }
260 
261  if (ret >= 0) {
262  /* push the audio data from decoded frame into the filtergraph */
263  if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0) {
264  av_log(NULL, AV_LOG_ERROR, "Error while feeding the audio filtergraph\n");
265  break;
266  }
267 
268  /* pull filtered audio from the filtergraph */
269  while (1) {
270  ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
271  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
272  break;
273  if (ret < 0)
274  goto end;
275  print_frame(filt_frame);
276  av_frame_unref(filt_frame);
277  }
278  av_frame_unref(frame);
279  }
280  }
281  }
282  av_packet_unref(&packet);
283  }
284 end:
285  avfilter_graph_free(&filter_graph);
286  avcodec_free_context(&dec_ctx);
287  avformat_close_input(&fmt_ctx);
288  av_frame_free(&frame);
289  av_frame_free(&filt_frame);
290 
291  if (ret < 0 && ret != AVERROR_EOF) {
292  fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
293  exit(1);
294  }
295 
296  exit(0);
297 }
#define NULL
Definition: coverity.c:32
AVFilterContext * buffersink_ctx
This structure describes decoded (raw) audio or video data.
Definition: frame.h:193
AVFilterGraph * avfilter_graph_alloc(void)
Allocate a filter graph.
Definition: avfiltergraph.c:80
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:187
struct AVFilterInOut * next
next input/input in the list, NULL if this is the last
Definition: avfilter.h:1028
#define av_opt_set_int_list(obj, name, val, term, flags)
Set a binary option to an integer list.
Definition: opt.h:709
int num
Numerator.
Definition: rational.h:59
void avfilter_graph_free(AVFilterGraph **graph)
Free a graph, destroy its links, and set *graph to NULL.
AVCodec.
Definition: avcodec.h:3681
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:1349
memory buffer sink API for audio and video
AVFilterLink ** inputs
array of pointers to input links
Definition: avfilter.h:331
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:2502
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:150
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:1417
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:2354
void avfilter_register_all(void)
Initialize the filter system.
Definition: allfilters.c:384
static AVFrame * frame
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:4095
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
int main(int argc, char **argv)
#define AVERROR(e)
Definition: error.h:43
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:163
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder.
Definition: decode.c:667
int av_opt_set_int(void *obj, const char *name, int64_t val, int search_flags)
Definition: opt.c:558
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:2545
uint64_t channel_layout
Channel layout of the audio data.
Definition: frame.h:362
const AVFilter * avfilter_get_by_name(const char *name)
Get a filter definition matching the given name.
Definition: avfilter.c:564
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Definition: options.c:157
#define AV_OPT_SEARCH_CHILDREN
Search in possible children of the given object first.
Definition: opt.h:557
#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)
int n
Definition: avisynth_c.h:684
static const char * player
static const AVFilterPad outputs[]
Definition: af_afftfilt.c:386
AVFilterContext * filter_ctx
filter context associated to this input/output
Definition: avfilter.h:1022
Keep a reference to the frame.
Definition: buffersrc.h:53
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:1017
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
Definition: decode.c:627
#define AV_LOG_INFO
Standard information.
Definition: log.h:187
static const AVFilterPad inputs[]
Definition: af_afftfilt.c:376
char * av_strdup(const char *s)
Duplicate a string.
Definition: mem.c:237
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:172
int sample_rate
samples per second
Definition: avcodec.h:2494
main external API structure.
Definition: avcodec.h:1732
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:576
Filter definition.
Definition: avfilter.h:144
int pad_idx
index of the filt_ctx pad to use for linking
Definition: avfilter.h:1025
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:627
#define snprintf
Definition: snprintf.h:34
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
Return the next frame of a stream.
Definition: utils.c:1710
char * name
unique name for this input/output in the list
Definition: avfilter.h:1019
void av_frame_unref(AVFrame *frame)
Unreference all the buffers referenced by frame and reset the frame fields.
Definition: frame.c:498
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:207
static AVFormatContext * fmt_ctx
Main libavformat public API header.
AVFilterInOut * avfilter_inout_alloc(void)
Allocate a single AVFilterInOut entry.
Definition: graphparser.c:182
int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
Read packets of a media file to get stream information.
Definition: utils.c:3494
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:152
void avformat_close_input(AVFormatContext **s)
Close an opened input AVFormatContext.
Definition: utils.c:4329
int channels
number of audio channels
Definition: avcodec.h:2495
int avformat_open_input(AVFormatContext **ps, const char *url, AVInputFormat *fmt, AVDictionary **options)
Open an input stream and read the header.
Definition: utils.c:510
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:522
An instance of a filter.
Definition: avfilter.h:323
int64_t av_get_default_channel_layout(int nb_channels)
Return default channel layout for a given number of channels.
AVCodecParameters * codecpar
Definition: avformat.h:1252
int stream_index
Definition: avcodec.h:1659
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented...
Definition: avformat.h:926
#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:1634
void av_register_all(void)
Initialize libavformat and register all the muxers, demuxers and protocols.
Definition: allformats.c:385
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:250