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
26 * @file audio decoding and filtering usage example
27 * @example decode_filter_audio.c
29 * Demux, decode and filter audio input file, generate a raw audio
30 * file to be played with ffplay.
35 #include <libavcodec/avcodec.h>
36 #include <libavformat/avformat.h>
37 #include <libavfilter/buffersink.h>
38 #include <libavfilter/buffersrc.h>
39 #include <libavutil/channel_layout.h>
40 #include <libavutil/opt.h>
42 static const char *filter_descr = "aresample=8000,aformat=sample_fmts=s16:channel_layouts=mono";
43 static const char *player = "ffplay -f s16le -ar 8000 -ac 1 -";
45 static AVFormatContext *fmt_ctx;
46 static AVCodecContext *dec_ctx;
47 AVFilterContext *buffersink_ctx;
48 AVFilterContext *buffersrc_ctx;
49 AVFilterGraph *filter_graph;
50 static int audio_stream_index = -1;
52 static int open_input_file(const char *filename)
57 if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
58 av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
62 if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
63 av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
67 /* select the audio stream */
68 ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &dec, 0);
70 av_log(NULL, AV_LOG_ERROR, "Cannot find an audio stream in the input file\n");
73 audio_stream_index = ret;
75 /* create decoding context */
76 dec_ctx = avcodec_alloc_context3(dec);
78 return AVERROR(ENOMEM);
79 avcodec_parameters_to_context(dec_ctx, fmt_ctx->streams[audio_stream_index]->codecpar);
81 /* init the audio decoder */
82 if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
83 av_log(NULL, AV_LOG_ERROR, "Cannot open audio decoder\n");
90 static int init_filters(const char *filters_descr)
94 const AVFilter *abuffersrc = avfilter_get_by_name("abuffer");
95 const AVFilter *abuffersink = avfilter_get_by_name("abuffersink");
96 AVFilterInOut *outputs = avfilter_inout_alloc();
97 AVFilterInOut *inputs = avfilter_inout_alloc();
98 static const enum AVSampleFormat out_sample_fmts[] = { AV_SAMPLE_FMT_S16, -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->ch_layout.order == AV_CHANNEL_ORDER_UNSPEC)
111 av_channel_layout_default(&dec_ctx->ch_layout, dec_ctx->ch_layout.nb_channels);
112 ret = snprintf(args, sizeof(args),
113 "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=",
114 time_base.num, time_base.den, dec_ctx->sample_rate,
115 av_get_sample_fmt_name(dec_ctx->sample_fmt));
116 av_channel_layout_describe(&dec_ctx->ch_layout, args + ret, sizeof(args) - ret);
117 ret = avfilter_graph_create_filter(&buffersrc_ctx, abuffersrc, "in",
118 args, NULL, filter_graph);
120 av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
124 /* buffer audio sink: to terminate the filter chain. */
125 ret = avfilter_graph_create_filter(&buffersink_ctx, abuffersink, "out",
126 NULL, NULL, filter_graph);
128 av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
132 ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
133 AV_OPT_SEARCH_CHILDREN);
135 av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
139 ret = av_opt_set(buffersink_ctx, "ch_layouts", "mono",
140 AV_OPT_SEARCH_CHILDREN);
142 av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
146 ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
147 AV_OPT_SEARCH_CHILDREN);
149 av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
154 * Set the endpoints for the filter graph. The filter_graph will
155 * be linked to the graph described by filters_descr.
159 * The buffer source output must be connected to the input pad of
160 * the first filter described by filters_descr; since the first
161 * filter input label is not specified, it is set to "in" by
164 outputs->name = av_strdup("in");
165 outputs->filter_ctx = buffersrc_ctx;
166 outputs->pad_idx = 0;
167 outputs->next = NULL;
170 * The buffer sink input must be connected to the output pad of
171 * the last filter described by filters_descr; since the last
172 * filter output label is not specified, it is set to "out" by
175 inputs->name = av_strdup("out");
176 inputs->filter_ctx = buffersink_ctx;
180 if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
181 &inputs, &outputs, NULL)) < 0)
184 if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
187 /* Print summary of the sink buffer
188 * Note: args buffer is reused to store channel layout string */
189 outlink = buffersink_ctx->inputs[0];
190 av_channel_layout_describe(&outlink->ch_layout, args, sizeof(args));
191 av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
192 (int)outlink->sample_rate,
193 (char *)av_x_if_null(av_get_sample_fmt_name(outlink->format), "?"),
197 avfilter_inout_free(&inputs);
198 avfilter_inout_free(&outputs);
203 static void print_frame(const AVFrame *frame)
205 const int n = frame->nb_samples * frame->ch_layout.nb_channels;
206 const uint16_t *p = (uint16_t*)frame->data[0];
207 const uint16_t *p_end = p + n;
210 fputc(*p & 0xff, stdout);
211 fputc(*p>>8 & 0xff, stdout);
217 int main(int argc, char **argv)
220 AVPacket *packet = av_packet_alloc();
221 AVFrame *frame = av_frame_alloc();
222 AVFrame *filt_frame = av_frame_alloc();
224 if (!packet || !frame || !filt_frame) {
225 fprintf(stderr, "Could not allocate frame or packet\n");
229 fprintf(stderr, "Usage: %s file | %s\n", argv[0], player);
233 if ((ret = open_input_file(argv[1])) < 0)
235 if ((ret = init_filters(filter_descr)) < 0)
238 /* read all packets */
240 if ((ret = av_read_frame(fmt_ctx, packet)) < 0)
243 if (packet->stream_index == audio_stream_index) {
244 ret = avcodec_send_packet(dec_ctx, packet);
246 av_log(NULL, AV_LOG_ERROR, "Error while sending a packet to the decoder\n");
251 ret = avcodec_receive_frame(dec_ctx, frame);
252 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
254 } else if (ret < 0) {
255 av_log(NULL, AV_LOG_ERROR, "Error while receiving a frame from the decoder\n");
260 /* push the audio data from decoded frame into the filtergraph */
261 if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0) {
262 av_log(NULL, AV_LOG_ERROR, "Error while feeding the audio filtergraph\n");
266 /* pull filtered audio from the filtergraph */
268 ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
269 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
273 print_frame(filt_frame);
274 av_frame_unref(filt_frame);
276 av_frame_unref(frame);
280 av_packet_unref(packet);
283 avfilter_graph_free(&filter_graph);
284 avcodec_free_context(&dec_ctx);
285 avformat_close_input(&fmt_ctx);
286 av_packet_free(&packet);
287 av_frame_free(&frame);
288 av_frame_free(&filt_frame);
290 if (ret < 0 && ret != AVERROR_EOF) {
291 fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));