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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/avcodec.h>
37 #include <libavfilter/buffersink.h>
38 #include <libavfilter/buffersrc.h>
39 #include <libavutil/opt.h>
40 
41 static const char *filter_descr = "aresample=8000,aformat=sample_fmts=s16:channel_layouts=mono";
42 static const char *player = "ffplay -f s16le -ar 8000 -ac 1 -";
43 
49 static int audio_stream_index = -1;
50 
51 static int open_input_file(const char *filename)
52 {
53  int ret;
54  AVCodec *dec;
55 
56  if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
57  av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
58  return ret;
59  }
60 
61  if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
62  av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
63  return ret;
64  }
65 
66  /* select the audio stream */
67  ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &dec, 0);
68  if (ret < 0) {
69  av_log(NULL, AV_LOG_ERROR, "Cannot find a audio stream in the input file\n");
70  return ret;
71  }
73  dec_ctx = fmt_ctx->streams[audio_stream_index]->codec;
74  av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);
75 
76  /* init the audio decoder */
77  if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
78  av_log(NULL, AV_LOG_ERROR, "Cannot open audio decoder\n");
79  return ret;
80  }
81 
82  return 0;
83 }
84 
85 static int init_filters(const char *filters_descr)
86 {
87  char args[512];
88  int ret = 0;
89  AVFilter *abuffersrc = avfilter_get_by_name("abuffer");
90  AVFilter *abuffersink = avfilter_get_by_name("abuffersink");
93  static const enum AVSampleFormat out_sample_fmts[] = { AV_SAMPLE_FMT_S16, -1 };
94  static const int64_t out_channel_layouts[] = { AV_CH_LAYOUT_MONO, -1 };
95  static const int out_sample_rates[] = { 8000, -1 };
96  const AVFilterLink *outlink;
97  AVRational time_base = fmt_ctx->streams[audio_stream_index]->time_base;
98 
99  filter_graph = avfilter_graph_alloc();
100  if (!outputs || !inputs || !filter_graph) {
101  ret = AVERROR(ENOMEM);
102  goto end;
103  }
104 
105  /* buffer audio source: the decoded frames from the decoder will be inserted here. */
106  if (!dec_ctx->channel_layout)
108  snprintf(args, sizeof(args),
109  "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
110  time_base.num, time_base.den, dec_ctx->sample_rate,
111  av_get_sample_fmt_name(dec_ctx->sample_fmt), dec_ctx->channel_layout);
112  ret = avfilter_graph_create_filter(&buffersrc_ctx, abuffersrc, "in",
113  args, NULL, filter_graph);
114  if (ret < 0) {
115  av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
116  goto end;
117  }
118 
119  /* buffer audio sink: to terminate the filter chain. */
120  ret = avfilter_graph_create_filter(&buffersink_ctx, abuffersink, "out",
121  NULL, NULL, filter_graph);
122  if (ret < 0) {
123  av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
124  goto end;
125  }
126 
127  ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
129  if (ret < 0) {
130  av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
131  goto end;
132  }
133 
134  ret = av_opt_set_int_list(buffersink_ctx, "channel_layouts", out_channel_layouts, -1,
136  if (ret < 0) {
137  av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
138  goto end;
139  }
140 
141  ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
143  if (ret < 0) {
144  av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
145  goto end;
146  }
147 
148  /* Endpoints for the filter graph. */
149  outputs->name = av_strdup("in");
150  outputs->filter_ctx = buffersrc_ctx;
151  outputs->pad_idx = 0;
152  outputs->next = NULL;
153 
154  inputs->name = av_strdup("out");
155  inputs->filter_ctx = buffersink_ctx;
156  inputs->pad_idx = 0;
157  inputs->next = NULL;
158 
159  if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
160  &inputs, &outputs, NULL)) < 0)
161  goto end;
162 
163  if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
164  goto end;
165 
166  /* Print summary of the sink buffer
167  * Note: args buffer is reused to store channel layout string */
168  outlink = buffersink_ctx->inputs[0];
169  av_get_channel_layout_string(args, sizeof(args), -1, outlink->channel_layout);
170  av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
171  (int)outlink->sample_rate,
172  (char *)av_x_if_null(av_get_sample_fmt_name(outlink->format), "?"),
173  args);
174 
175 end:
176  avfilter_inout_free(&inputs);
177  avfilter_inout_free(&outputs);
178 
179  return ret;
180 }
181 
182 static void print_frame(const AVFrame *frame)
183 {
185  const uint16_t *p = (uint16_t*)frame->data[0];
186  const uint16_t *p_end = p + n;
187 
188  while (p < p_end) {
189  fputc(*p & 0xff, stdout);
190  fputc(*p>>8 & 0xff, stdout);
191  p++;
192  }
193  fflush(stdout);
194 }
195 
196 int main(int argc, char **argv)
197 {
198  int ret;
199  AVPacket packet0, packet;
201  AVFrame *filt_frame = av_frame_alloc();
202  int got_frame;
203 
204  if (!frame || !filt_frame) {
205  perror("Could not allocate frame");
206  exit(1);
207  }
208  if (argc != 2) {
209  fprintf(stderr, "Usage: %s file | %s\n", argv[0], player);
210  exit(1);
211  }
212 
213  av_register_all();
215 
216  if ((ret = open_input_file(argv[1])) < 0)
217  goto end;
218  if ((ret = init_filters(filter_descr)) < 0)
219  goto end;
220 
221  /* read all packets */
222  packet0.data = NULL;
223  packet.data = NULL;
224  while (1) {
225  if (!packet0.data) {
226  if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
227  break;
228  packet0 = packet;
229  }
230 
231  if (packet.stream_index == audio_stream_index) {
232  got_frame = 0;
233  ret = avcodec_decode_audio4(dec_ctx, frame, &got_frame, &packet);
234  if (ret < 0) {
235  av_log(NULL, AV_LOG_ERROR, "Error decoding audio\n");
236  continue;
237  }
238  packet.size -= ret;
239  packet.data += ret;
240 
241  if (got_frame) {
242  /* push the audio data from decoded frame into the filtergraph */
243  if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, 0) < 0) {
244  av_log(NULL, AV_LOG_ERROR, "Error while feeding the audio filtergraph\n");
245  break;
246  }
247 
248  /* pull filtered audio from the filtergraph */
249  while (1) {
250  ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
251  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
252  break;
253  if (ret < 0)
254  goto end;
255  print_frame(filt_frame);
256  av_frame_unref(filt_frame);
257  }
258  }
259 
260  if (packet.size <= 0)
261  av_free_packet(&packet0);
262  } else {
263  /* discard non-wanted packets */
264  av_free_packet(&packet0);
265  }
266  }
267 end:
268  avfilter_graph_free(&filter_graph);
269  avcodec_close(dec_ctx);
270  avformat_close_input(&fmt_ctx);
271  av_frame_free(&frame);
272  av_frame_free(&filt_frame);
273 
274  if (ret < 0 && ret != AVERROR_EOF) {
275  fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
276  exit(1);
277  }
278 
279  exit(0);
280 }