2 * Copyright (c) 2010 Nicolas George
3 * Copyright (c) 2011 Stefano Sabatini
4 * Copyright (c) 2012 Clément Bœsch
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:
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
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
27 * API example for audio decoding and filtering
28 * @example filtering_audio.c
33 #include <libavcodec/avcodec.h>
34 #include <libavformat/avformat.h>
35 #include <libavfilter/avfiltergraph.h>
36 #include <libavfilter/buffersink.h>
37 #include <libavfilter/buffersrc.h>
38 #include <libavutil/opt.h>
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 -";
43 static AVFormatContext *fmt_ctx;
44 static AVCodecContext *dec_ctx;
45 AVFilterContext *buffersink_ctx;
46 AVFilterContext *buffersrc_ctx;
47 AVFilterGraph *filter_graph;
48 static int audio_stream_index = -1;
50 static int open_input_file(const char *filename)
55 if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
56 av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
60 if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
61 av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
65 /* select the audio stream */
66 ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &dec, 0);
68 av_log(NULL, AV_LOG_ERROR, "Cannot find an audio stream in the input file\n");
71 audio_stream_index = ret;
73 /* create decoding context */
74 dec_ctx = avcodec_alloc_context3(dec);
76 return AVERROR(ENOMEM);
77 avcodec_parameters_to_context(dec_ctx, fmt_ctx->streams[audio_stream_index]->codecpar);
78 av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);
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");
89 static int init_filters(const char *filters_descr)
93 AVFilter *abuffersrc = avfilter_get_by_name("abuffer");
94 AVFilter *abuffersink = avfilter_get_by_name("abuffersink");
95 AVFilterInOut *outputs = avfilter_inout_alloc();
96 AVFilterInOut *inputs = avfilter_inout_alloc();
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;
103 filter_graph = avfilter_graph_alloc();
104 if (!outputs || !inputs || !filter_graph) {
105 ret = AVERROR(ENOMEM);
109 /* buffer audio source: the decoded frames from the decoder will be inserted here. */
110 if (!dec_ctx->channel_layout)
111 dec_ctx->channel_layout = av_get_default_channel_layout(dec_ctx->channels);
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);
119 av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
123 /* buffer audio sink: to terminate the filter chain. */
124 ret = avfilter_graph_create_filter(&buffersink_ctx, abuffersink, "out",
125 NULL, NULL, filter_graph);
127 av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
131 ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
132 AV_OPT_SEARCH_CHILDREN);
134 av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
138 ret = av_opt_set_int_list(buffersink_ctx, "channel_layouts", out_channel_layouts, -1,
139 AV_OPT_SEARCH_CHILDREN);
141 av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
145 ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
146 AV_OPT_SEARCH_CHILDREN);
148 av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
153 * Set the endpoints for the filter graph. The filter_graph will
154 * be linked to the graph described by filters_descr.
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
163 outputs->name = av_strdup("in");
164 outputs->filter_ctx = buffersrc_ctx;
165 outputs->pad_idx = 0;
166 outputs->next = NULL;
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
174 inputs->name = av_strdup("out");
175 inputs->filter_ctx = buffersink_ctx;
179 if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
180 &inputs, &outputs, NULL)) < 0)
183 if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
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), "?"),
196 avfilter_inout_free(&inputs);
197 avfilter_inout_free(&outputs);
202 static void print_frame(const AVFrame *frame)
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;
209 fputc(*p & 0xff, stdout);
210 fputc(*p>>8 & 0xff, stdout);
216 int main(int argc, char **argv)
220 AVFrame *frame = av_frame_alloc();
221 AVFrame *filt_frame = av_frame_alloc();
223 if (!frame || !filt_frame) {
224 perror("Could not allocate frame");
228 fprintf(stderr, "Usage: %s file | %s\n", argv[0], player);
233 avfilter_register_all();
235 if ((ret = open_input_file(argv[1])) < 0)
237 if ((ret = init_filters(filter_descr)) < 0)
240 /* read all packets */
242 if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
245 if (packet.stream_index == audio_stream_index) {
246 ret = avcodec_send_packet(dec_ctx, &packet);
248 av_log(NULL, AV_LOG_ERROR, "Error while sending a packet to the decoder\n");
253 ret = avcodec_receive_frame(dec_ctx, frame);
254 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
256 } else if (ret < 0) {
257 av_log(NULL, AV_LOG_ERROR, "Error while receiving a frame from the decoder\n");
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");
268 /* pull filtered audio from the filtergraph */
270 ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
271 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
275 print_frame(filt_frame);
276 av_frame_unref(filt_frame);
278 av_frame_unref(frame);
282 av_packet_unref(&packet);
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);
291 if (ret < 0 && ret != AVERROR_EOF) {
292 fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));