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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  dec_ctx = fmt_ctx->streams[audio_stream_index]->codec;
73  av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);
74 
75  /* init the audio decoder */
76  if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
77  av_log(NULL, AV_LOG_ERROR, "Cannot open audio decoder\n");
78  return ret;
79  }
80 
81  return 0;
82 }
83 
84 static int init_filters(const char *filters_descr)
85 {
86  char args[512];
87  int ret = 0;
88  AVFilter *abuffersrc = avfilter_get_by_name("abuffer");
89  AVFilter *abuffersink = avfilter_get_by_name("abuffersink");
92  static const enum AVSampleFormat out_sample_fmts[] = { AV_SAMPLE_FMT_S16, -1 };
93  static const int64_t out_channel_layouts[] = { AV_CH_LAYOUT_MONO, -1 };
94  static const int out_sample_rates[] = { 8000, -1 };
95  const AVFilterLink *outlink;
96  AVRational time_base = fmt_ctx->streams[audio_stream_index]->time_base;
97 
98  filter_graph = avfilter_graph_alloc();
99  if (!outputs || !inputs || !filter_graph) {
100  ret = AVERROR(ENOMEM);
101  goto end;
102  }
103 
104  /* buffer audio source: the decoded frames from the decoder will be inserted here. */
105  if (!dec_ctx->channel_layout)
107  snprintf(args, sizeof(args),
108  "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
109  time_base.num, time_base.den, dec_ctx->sample_rate,
110  av_get_sample_fmt_name(dec_ctx->sample_fmt), dec_ctx->channel_layout);
111  ret = avfilter_graph_create_filter(&buffersrc_ctx, abuffersrc, "in",
112  args, NULL, filter_graph);
113  if (ret < 0) {
114  av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
115  goto end;
116  }
117 
118  /* buffer audio sink: to terminate the filter chain. */
119  ret = avfilter_graph_create_filter(&buffersink_ctx, abuffersink, "out",
120  NULL, NULL, filter_graph);
121  if (ret < 0) {
122  av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
123  goto end;
124  }
125 
126  ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
128  if (ret < 0) {
129  av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
130  goto end;
131  }
132 
133  ret = av_opt_set_int_list(buffersink_ctx, "channel_layouts", out_channel_layouts, -1,
135  if (ret < 0) {
136  av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
137  goto end;
138  }
139 
140  ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
142  if (ret < 0) {
143  av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
144  goto end;
145  }
146 
147  /*
148  * Set the endpoints for the filter graph. The filter_graph will
149  * be linked to the graph described by filters_descr.
150  */
151 
152  /*
153  * The buffer source output must be connected to the input pad of
154  * the first filter described by filters_descr; since the first
155  * filter input label is not specified, it is set to "in" by
156  * default.
157  */
158  outputs->name = av_strdup("in");
159  outputs->filter_ctx = buffersrc_ctx;
160  outputs->pad_idx = 0;
161  outputs->next = NULL;
162 
163  /*
164  * The buffer sink input must be connected to the output pad of
165  * the last filter described by filters_descr; since the last
166  * filter output label is not specified, it is set to "out" by
167  * default.
168  */
169  inputs->name = av_strdup("out");
170  inputs->filter_ctx = buffersink_ctx;
171  inputs->pad_idx = 0;
172  inputs->next = NULL;
173 
174  if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
175  &inputs, &outputs, NULL)) < 0)
176  goto end;
177 
178  if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
179  goto end;
180 
181  /* Print summary of the sink buffer
182  * Note: args buffer is reused to store channel layout string */
183  outlink = buffersink_ctx->inputs[0];
184  av_get_channel_layout_string(args, sizeof(args), -1, outlink->channel_layout);
185  av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
186  (int)outlink->sample_rate,
187  (char *)av_x_if_null(av_get_sample_fmt_name(outlink->format), "?"),
188  args);
189 
190 end:
191  avfilter_inout_free(&inputs);
192  avfilter_inout_free(&outputs);
193 
194  return ret;
195 }
196 
197 static void print_frame(const AVFrame *frame)
198 {
200  const uint16_t *p = (uint16_t*)frame->data[0];
201  const uint16_t *p_end = p + n;
202 
203  while (p < p_end) {
204  fputc(*p & 0xff, stdout);
205  fputc(*p>>8 & 0xff, stdout);
206  p++;
207  }
208  fflush(stdout);
209 }
210 
211 int main(int argc, char **argv)
212 {
213  int ret;
214  AVPacket packet0, packet;
216  AVFrame *filt_frame = av_frame_alloc();
217  int got_frame;
218 
219  if (!frame || !filt_frame) {
220  perror("Could not allocate frame");
221  exit(1);
222  }
223  if (argc != 2) {
224  fprintf(stderr, "Usage: %s file | %s\n", argv[0], player);
225  exit(1);
226  }
227 
228  av_register_all();
230 
231  if ((ret = open_input_file(argv[1])) < 0)
232  goto end;
233  if ((ret = init_filters(filter_descr)) < 0)
234  goto end;
235 
236  /* read all packets */
237  packet0.data = NULL;
238  packet.data = NULL;
239  while (1) {
240  if (!packet0.data) {
241  if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
242  break;
243  packet0 = packet;
244  }
245 
246  if (packet.stream_index == audio_stream_index) {
247  got_frame = 0;
248  ret = avcodec_decode_audio4(dec_ctx, frame, &got_frame, &packet);
249  if (ret < 0) {
250  av_log(NULL, AV_LOG_ERROR, "Error decoding audio\n");
251  continue;
252  }
253  packet.size -= ret;
254  packet.data += ret;
255 
256  if (got_frame) {
257  /* push the audio data from decoded frame into the filtergraph */
258  if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, 0) < 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  }
274 
275  if (packet.size <= 0)
276  av_packet_unref(&packet0);
277  } else {
278  /* discard non-wanted packets */
279  av_packet_unref(&packet0);
280  }
281  }
282 end:
283  avfilter_graph_free(&filter_graph);
284  avcodec_close(dec_ctx);
285  avformat_close_input(&fmt_ctx);
286  av_frame_free(&frame);
287  av_frame_free(&filt_frame);
288 
289  if (ret < 0 && ret != AVERROR_EOF) {
290  fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
291  exit(1);
292  }
293 
294  exit(0);
295 }
#define NULL
Definition: coverity.c:32
AVFilterContext * buffersink_ctx
This structure describes decoded (raw) audio or video data.
Definition: frame.h:184
AVFilterGraph * avfilter_graph_alloc(void)
Allocate a filter graph.
Definition: avfiltergraph.c:76
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:963
#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:44
int size
Definition: avcodec.h:1589
void avfilter_graph_free(AVFilterGraph **graph)
Free a graph, destroy its links, and set *graph to NULL.
attribute_deprecated int avcodec_decode_audio4(AVCodecContext *avctx, AVFrame *frame, int *got_frame_ptr, const AVPacket *avpkt)
Decode the audio frame of size avpkt->size from avpkt->data into frame.
Definition: utils.c:2281
AVCodec.
Definition: avcodec.h:3559
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:1325
memory buffer sink API for audio and video
AVFilterLink ** inputs
array of pointers to input links
Definition: avfilter.h:313
enum AVSampleFormat sample_fmt
audio sample format
Definition: avcodec.h:2426
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:140
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:1393
void avfilter_register_all(void)
Initialize the filter system.
Definition: allfilters.c:40
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.
uint8_t * data
Definition: avcodec.h:1588
#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:300
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:3872
int avcodec_close(AVCodecContext *avctx)
Close a given AVCodecContext and free all the data associated with it (but not the AVCodecContext its...
Definition: utils.c:2959
#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:153
int av_opt_set_int(void *obj, const char *name, int64_t val, int search_flags)
Definition: opt.c:539
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:47
uint64_t channel_layout
Audio channel layout.
Definition: avcodec.h:2469
const AVFilter * avfilter_get_by_name(const char *name)
Get a filter definition matching the given name.
Definition: avfilter.c:519
#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:547
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:957
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:952
#define AV_LOG_INFO
Standard information.
Definition: log.h:187
static const AVFilterPad inputs[]
Definition: af_afftfilt.c:376
Libavcodec external API header.
AVSampleFormat
Audio sample formats.
Definition: samplefmt.h:58
char * av_strdup(const char *s)
Duplicate the string s.
Definition: mem.c:267
int sample_rate
samples per second
Definition: avcodec.h:2418
main external API structure.
Definition: avcodec.h:1657
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:563
Filter definition.
Definition: avfilter.h:142
int pad_idx
index of the filt_ctx pad to use for linking
Definition: avfilter.h:960
rational number numerator/denominator
Definition: rational.h:43
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:1208
#define snprintf
Definition: snprintf.h:34
int av_read_frame(AVFormatContext *s, AVPacket *pkt)
Return the next frame of a stream.
Definition: utils.c:1640
int64_t av_frame_get_channel_layout(const AVFrame *frame)
char * name
unique name for this input/output in the list
Definition: avfilter.h:954
void av_frame_unref(AVFrame *frame)
Unreference all the buffers referenced by frame and reset the frame fields.
Definition: frame.c:484
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:198
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:3277
signed 16 bits
Definition: samplefmt.h:61
static AVCodecContext * dec_ctx
int den
denominator
Definition: rational.h:45
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:4103
int channels
number of audio channels
Definition: avcodec.h:2419
int avformat_open_input(AVFormatContext **ps, const char *url, AVInputFormat *fmt, AVDictionary **options)
Open an input stream and read the header.
Definition: utils.c:471
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:305
int64_t av_get_default_channel_layout(int nb_channels)
Return default channel layout for a given number of channels.
int stream_index
Definition: avcodec.h:1590
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented...
Definition: avformat.h:913
#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:123
This structure stores compressed data.
Definition: avcodec.h:1565
void av_register_all(void)
Initialize libavformat and register all the muxers, demuxers and protocols.
Definition: allformats.c:44
int nb_samples
number of audio samples (per channel) described by this frame
Definition: frame.h:241