2 * Copyright (c) 2001 Fabrice Bellard
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5 * of this software and associated documentation files (the "Software"), to deal
6 * in the Software without restriction, including without limitation the rights
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8 * copies of the Software, and to permit persons to whom the Software is
9 * furnished to do so, subject to the following conditions:
11 * The above copyright notice and this permission notice shall be included in
12 * all copies or substantial portions of the Software.
14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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19 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
25 * audio encoding with libavcodec API example.
27 * @example encode_audio.c
34 #include <libavcodec/avcodec.h>
36 #include <libavutil/channel_layout.h>
37 #include <libavutil/common.h>
38 #include <libavutil/frame.h>
39 #include <libavutil/samplefmt.h>
41 /* check that a given sample format is supported by the encoder */
42 static int check_sample_fmt(const AVCodec *codec, enum AVSampleFormat sample_fmt)
44 const enum AVSampleFormat *p = codec->sample_fmts;
46 while (*p != AV_SAMPLE_FMT_NONE) {
54 /* just pick the highest supported samplerate */
55 static int select_sample_rate(const AVCodec *codec)
58 int best_samplerate = 0;
60 if (!codec->supported_samplerates)
63 p = codec->supported_samplerates;
65 if (!best_samplerate || abs(44100 - *p) < abs(44100 - best_samplerate))
69 return best_samplerate;
72 /* select layout with the highest channel count */
73 static int select_channel_layout(const AVCodec *codec)
76 uint64_t best_ch_layout = 0;
77 int best_nb_channels = 0;
79 if (!codec->channel_layouts)
80 return AV_CH_LAYOUT_STEREO;
82 p = codec->channel_layouts;
84 int nb_channels = av_get_channel_layout_nb_channels(*p);
86 if (nb_channels > best_nb_channels) {
88 best_nb_channels = nb_channels;
92 return best_ch_layout;
95 static void encode(AVCodecContext *ctx, AVFrame *frame, AVPacket *pkt,
100 /* send the frame for encoding */
101 ret = avcodec_send_frame(ctx, frame);
103 fprintf(stderr, "Error sending the frame to the encoder\n");
107 /* read all the available output packets (in general there may be any
110 ret = avcodec_receive_packet(ctx, pkt);
111 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
114 fprintf(stderr, "Error encoding audio frame\n");
118 fwrite(pkt->data, 1, pkt->size, output);
119 av_packet_unref(pkt);
123 int main(int argc, char **argv)
125 const char *filename;
126 const AVCodec *codec;
127 AVCodecContext *c= NULL;
136 fprintf(stderr, "Usage: %s <output file>\n", argv[0]);
141 /* register all the codecs */
142 avcodec_register_all();
144 /* find the MP2 encoder */
145 codec = avcodec_find_encoder(AV_CODEC_ID_MP2);
147 fprintf(stderr, "Codec not found\n");
151 c = avcodec_alloc_context3(codec);
153 fprintf(stderr, "Could not allocate audio codec context\n");
157 /* put sample parameters */
160 /* check that the encoder supports s16 pcm input */
161 c->sample_fmt = AV_SAMPLE_FMT_S16;
162 if (!check_sample_fmt(codec, c->sample_fmt)) {
163 fprintf(stderr, "Encoder does not support sample format %s",
164 av_get_sample_fmt_name(c->sample_fmt));
168 /* select other audio parameters supported by the encoder */
169 c->sample_rate = select_sample_rate(codec);
170 c->channel_layout = select_channel_layout(codec);
171 c->channels = av_get_channel_layout_nb_channels(c->channel_layout);
174 if (avcodec_open2(c, codec, NULL) < 0) {
175 fprintf(stderr, "Could not open codec\n");
179 f = fopen(filename, "wb");
181 fprintf(stderr, "Could not open %s\n", filename);
185 /* packet for holding encoded output */
186 pkt = av_packet_alloc();
188 fprintf(stderr, "could not allocate the packet\n");
192 /* frame containing input raw audio */
193 frame = av_frame_alloc();
195 fprintf(stderr, "Could not allocate audio frame\n");
199 frame->nb_samples = c->frame_size;
200 frame->format = c->sample_fmt;
201 frame->channel_layout = c->channel_layout;
203 /* allocate the data buffers */
204 ret = av_frame_get_buffer(frame, 0);
206 fprintf(stderr, "Could not allocate audio data buffers\n");
210 /* encode a single tone sound */
212 tincr = 2 * M_PI * 440.0 / c->sample_rate;
213 for (i = 0; i < 200; i++) {
214 /* make sure the frame is writable -- makes a copy if the encoder
215 * kept a reference internally */
216 ret = av_frame_make_writable(frame);
219 samples = (uint16_t*)frame->data[0];
221 for (j = 0; j < c->frame_size; j++) {
222 samples[2*j] = (int)(sin(t) * 10000);
224 for (k = 1; k < c->channels; k++)
225 samples[2*j + k] = samples[2*j];
228 encode(c, frame, pkt, f);
231 /* flush the encoder */
232 encode(c, NULL, pkt, f);
236 av_frame_free(&frame);
237 av_packet_free(&pkt);
238 avcodec_free_context(&c);