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 doc/examples/filtering_audio.c
33 #include <libavcodec/avcodec.h>
34 #include <libavformat/avformat.h>
35 #include <libavfilter/avfiltergraph.h>
36 #include <libavfilter/avcodec.h>
37 #include <libavfilter/buffersink.h>
38 #include <libavfilter/buffersrc.h>
39 #include <libavutil/opt.h>
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 -";
44 static AVFormatContext *fmt_ctx;
45 static AVCodecContext *dec_ctx;
46 AVFilterContext *buffersink_ctx;
47 AVFilterContext *buffersrc_ctx;
48 AVFilterGraph *filter_graph;
49 static int audio_stream_index = -1;
51 static int open_input_file(const char *filename)
56 if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
57 av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
61 if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
62 av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
66 /* select the audio stream */
67 ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &dec, 0);
69 av_log(NULL, AV_LOG_ERROR, "Cannot find a audio stream in the input file\n");
72 audio_stream_index = ret;
73 dec_ctx = fmt_ctx->streams[audio_stream_index]->codec;
74 av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);
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");
85 static int init_filters(const char *filters_descr)
89 AVFilter *abuffersrc = avfilter_get_by_name("abuffer");
90 AVFilter *abuffersink = avfilter_get_by_name("abuffersink");
91 AVFilterInOut *outputs = avfilter_inout_alloc();
92 AVFilterInOut *inputs = avfilter_inout_alloc();
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;
99 filter_graph = avfilter_graph_alloc();
101 /* buffer audio source: the decoded frames from the decoder will be inserted here. */
102 if (!dec_ctx->channel_layout)
103 dec_ctx->channel_layout = av_get_default_channel_layout(dec_ctx->channels);
104 snprintf(args, sizeof(args),
105 "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
106 time_base.num, time_base.den, dec_ctx->sample_rate,
107 av_get_sample_fmt_name(dec_ctx->sample_fmt), dec_ctx->channel_layout);
108 ret = avfilter_graph_create_filter(&buffersrc_ctx, abuffersrc, "in",
109 args, NULL, filter_graph);
111 av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
115 /* buffer audio sink: to terminate the filter chain. */
116 ret = avfilter_graph_create_filter(&buffersink_ctx, abuffersink, "out",
117 NULL, NULL, filter_graph);
119 av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
123 ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
124 AV_OPT_SEARCH_CHILDREN);
126 av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
130 ret = av_opt_set_int_list(buffersink_ctx, "channel_layouts", out_channel_layouts, -1,
131 AV_OPT_SEARCH_CHILDREN);
133 av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
137 ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
138 AV_OPT_SEARCH_CHILDREN);
140 av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
144 /* Endpoints for the filter graph. */
145 outputs->name = av_strdup("in");
146 outputs->filter_ctx = buffersrc_ctx;
147 outputs->pad_idx = 0;
148 outputs->next = NULL;
150 inputs->name = av_strdup("out");
151 inputs->filter_ctx = buffersink_ctx;
155 if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
156 &inputs, &outputs, NULL)) < 0)
159 if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
162 /* Print summary of the sink buffer
163 * Note: args buffer is reused to store channel layout string */
164 outlink = buffersink_ctx->inputs[0];
165 av_get_channel_layout_string(args, sizeof(args), -1, outlink->channel_layout);
166 av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
167 (int)outlink->sample_rate,
168 (char *)av_x_if_null(av_get_sample_fmt_name(outlink->format), "?"),
174 static void print_frame(const AVFrame *frame)
176 const int n = frame->nb_samples * av_get_channel_layout_nb_channels(av_frame_get_channel_layout(frame));
177 const uint16_t *p = (uint16_t*)frame->data[0];
178 const uint16_t *p_end = p + n;
181 fputc(*p & 0xff, stdout);
182 fputc(*p>>8 & 0xff, stdout);
188 int main(int argc, char **argv)
192 AVFrame *frame = av_frame_alloc();
193 AVFrame *filt_frame = av_frame_alloc();
196 if (!frame || !filt_frame) {
197 perror("Could not allocate frame");
201 fprintf(stderr, "Usage: %s file | %s\n", argv[0], player);
205 avcodec_register_all();
207 avfilter_register_all();
209 if ((ret = open_input_file(argv[1])) < 0)
211 if ((ret = init_filters(filter_descr)) < 0)
214 /* read all packets */
216 if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
219 if (packet.stream_index == audio_stream_index) {
220 avcodec_get_frame_defaults(frame);
222 ret = avcodec_decode_audio4(dec_ctx, frame, &got_frame, &packet);
224 av_log(NULL, AV_LOG_ERROR, "Error decoding audio\n");
229 /* push the audio data from decoded frame into the filtergraph */
230 if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, 0) < 0) {
231 av_log(NULL, AV_LOG_ERROR, "Error while feeding the audio filtergraph\n");
235 /* pull filtered audio from the filtergraph */
237 ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
238 if(ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
242 print_frame(filt_frame);
243 av_frame_unref(filt_frame);
247 av_free_packet(&packet);
250 avfilter_graph_free(&filter_graph);
252 avcodec_close(dec_ctx);
253 avformat_close_input(&fmt_ctx);
254 av_frame_free(&frame);
255 av_frame_free(&filt_frame);
257 if (ret < 0 && ret != AVERROR_EOF) {
259 av_strerror(ret, buf, sizeof(buf));
260 fprintf(stderr, "Error occurred: %s\n", buf);