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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>
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  }
70  audio_stream_index = ret;
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:218
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.
AVCodec.
Definition: avcodec.h:3408
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:1351
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:2181
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:1419
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:2078
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.
Keep a reference to the frame.
Definition: buffersrc.h:53
#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:4184
#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:202
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder.
Definition: decode.c:709
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:2224
uint64_t channel_layout
Channel layout of the audio data.
Definition: frame.h:396
const AVFilter * avfilter_get_by_name(const char *name)
Get a filter definition matching the given name.
Definition: allfilters.c:439
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)
int n
Definition: avisynth_c.h:684
static const char * player
static const AVFilterPad inputs[]
Definition: af_acontrast.c:193
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:642
#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:2173
main external API structure.
Definition: avcodec.h:1518
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:592
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:538
#define snprintf
Definition: snprintf.h:34
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
Return the next frame of a stream.
Definition: utils.c:1767
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:551
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:232
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:3565
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:4428
int channels
number of audio channels
Definition: avcodec.h:2174
int avformat_open_input(AVFormatContext **ps, const char *url, AVInputFormat *fmt, AVDictionary **options)
Open an input stream and read the header.
Definition: utils.c:537
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:1021
int stream_index
Definition: avcodec.h:1432
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented...
Definition: avformat.h:903
#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:1407
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:284