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25 * libavformat API example.
27 * Output a media file in any supported libavformat format.
28 * The default codecs are used.
29 * @example doc/examples/muxing.c
37 #include <libavutil/mathematics.h>
38 #include <libavformat/avformat.h>
39 #include <libswscale/swscale.h>
41 /* 5 seconds stream duration */
42 #define STREAM_DURATION 200.0
43 #define STREAM_FRAME_RATE 25 /* 25 images/s */
44 #define STREAM_NB_FRAMES ((int)(STREAM_DURATION * STREAM_FRAME_RATE))
45 #define STREAM_PIX_FMT AV_PIX_FMT_YUV420P /* default pix_fmt */
47 static int sws_flags = SWS_BICUBIC;
49 /**************************************************************/
52 static float t, tincr, tincr2;
53 static int16_t *samples;
54 static int audio_input_frame_size;
56 /* Add an output stream. */
57 static AVStream *add_stream(AVFormatContext *oc, AVCodec **codec,
58 enum AVCodecID codec_id)
63 /* find the encoder */
64 *codec = avcodec_find_encoder(codec_id);
66 fprintf(stderr, "Could not find encoder for '%s'\n",
67 avcodec_get_name(codec_id));
71 st = avformat_new_stream(oc, *codec);
73 fprintf(stderr, "Could not allocate stream\n");
76 st->id = oc->nb_streams-1;
79 switch ((*codec)->type) {
80 case AVMEDIA_TYPE_AUDIO:
82 c->sample_fmt = AV_SAMPLE_FMT_S16;
84 c->sample_rate = 44100;
88 case AVMEDIA_TYPE_VIDEO:
89 avcodec_get_context_defaults3(c, *codec);
90 c->codec_id = codec_id;
93 /* Resolution must be a multiple of two. */
96 /* timebase: This is the fundamental unit of time (in seconds) in terms
97 * of which frame timestamps are represented. For fixed-fps content,
98 * timebase should be 1/framerate and timestamp increments should be
100 c->time_base.den = STREAM_FRAME_RATE;
101 c->time_base.num = 1;
102 c->gop_size = 12; /* emit one intra frame every twelve frames at most */
103 c->pix_fmt = STREAM_PIX_FMT;
104 if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
105 /* just for testing, we also add B frames */
108 if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
109 /* Needed to avoid using macroblocks in which some coeffs overflow.
110 * This does not happen with normal video, it just happens here as
111 * the motion of the chroma plane does not match the luma plane. */
120 /* Some formats want stream headers to be separate. */
121 if (oc->oformat->flags & AVFMT_GLOBALHEADER)
122 c->flags |= CODEC_FLAG_GLOBAL_HEADER;
127 /**************************************************************/
130 static float t, tincr, tincr2;
131 static int16_t *samples;
132 static int audio_input_frame_size;
134 static void open_audio(AVFormatContext *oc, AVCodec *codec, AVStream *st)
142 ret = avcodec_open2(c, codec, NULL);
144 fprintf(stderr, "Could not open audio codec: %s\n", av_err2str(ret));
148 /* init signal generator */
150 tincr = 2 * M_PI * 110.0 / c->sample_rate;
151 /* increment frequency by 110 Hz per second */
152 tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
154 if (c->codec->capabilities & CODEC_CAP_VARIABLE_FRAME_SIZE)
155 audio_input_frame_size = 10000;
157 audio_input_frame_size = c->frame_size;
158 samples = av_malloc(audio_input_frame_size *
159 av_get_bytes_per_sample(c->sample_fmt) *
162 fprintf(stderr, "Could not allocate audio samples buffer\n");
167 /* Prepare a 16 bit dummy audio frame of 'frame_size' samples and
168 * 'nb_channels' channels. */
169 static void get_audio_frame(int16_t *samples, int frame_size, int nb_channels)
175 for (j = 0; j < frame_size; j++) {
176 v = (int)(sin(t) * 10000);
177 for (i = 0; i < nb_channels; i++)
184 static void write_audio_frame(AVFormatContext *oc, AVStream *st)
187 AVPacket pkt = { 0 }; // data and size must be 0;
188 AVFrame *frame = avcodec_alloc_frame();
191 av_init_packet(&pkt);
194 get_audio_frame(samples, audio_input_frame_size, c->channels);
195 frame->nb_samples = audio_input_frame_size;
196 avcodec_fill_audio_frame(frame, c->channels, c->sample_fmt,
198 audio_input_frame_size *
199 av_get_bytes_per_sample(c->sample_fmt) *
202 ret = avcodec_encode_audio2(c, &pkt, frame, &got_packet);
204 fprintf(stderr, "Error encoding audio frame: %s\n", av_err2str(ret));
211 pkt.stream_index = st->index;
213 /* Write the compressed frame to the media file. */
214 ret = av_interleaved_write_frame(oc, &pkt);
216 fprintf(stderr, "Error while writing audio frame: %s\n",
220 avcodec_free_frame(&frame);
223 static void close_audio(AVFormatContext *oc, AVStream *st)
225 avcodec_close(st->codec);
230 /**************************************************************/
233 static AVFrame *frame;
234 static AVPicture src_picture, dst_picture;
235 static int frame_count;
237 static void open_video(AVFormatContext *oc, AVCodec *codec, AVStream *st)
240 AVCodecContext *c = st->codec;
243 ret = avcodec_open2(c, codec, NULL);
245 fprintf(stderr, "Could not open video codec: %s\n", av_err2str(ret));
249 /* allocate and init a re-usable frame */
250 frame = avcodec_alloc_frame();
252 fprintf(stderr, "Could not allocate video frame\n");
256 /* Allocate the encoded raw picture. */
257 ret = avpicture_alloc(&dst_picture, c->pix_fmt, c->width, c->height);
259 fprintf(stderr, "Could not allocate picture: %s\n", av_err2str(ret));
263 /* If the output format is not YUV420P, then a temporary YUV420P
264 * picture is needed too. It is then converted to the required
266 if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
267 ret = avpicture_alloc(&src_picture, AV_PIX_FMT_YUV420P, c->width, c->height);
269 fprintf(stderr, "Could not allocate temporary picture: %s\n",
275 /* copy data and linesize picture pointers to frame */
276 *((AVPicture *)frame) = dst_picture;
279 /* Prepare a dummy image. */
280 static void fill_yuv_image(AVPicture *pict, int frame_index,
281 int width, int height)
288 for (y = 0; y < height; y++)
289 for (x = 0; x < width; x++)
290 pict->data[0][y * pict->linesize[0] + x] = x + y + i * 3;
293 for (y = 0; y < height / 2; y++) {
294 for (x = 0; x < width / 2; x++) {
295 pict->data[1][y * pict->linesize[1] + x] = 128 + y + i * 2;
296 pict->data[2][y * pict->linesize[2] + x] = 64 + x + i * 5;
301 static void write_video_frame(AVFormatContext *oc, AVStream *st)
304 static struct SwsContext *sws_ctx;
305 AVCodecContext *c = st->codec;
307 if (frame_count >= STREAM_NB_FRAMES) {
308 /* No more frames to compress. The codec has a latency of a few
309 * frames if using B-frames, so we get the last frames by
310 * passing the same picture again. */
312 if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
313 /* as we only generate a YUV420P picture, we must convert it
314 * to the codec pixel format if needed */
316 sws_ctx = sws_getContext(c->width, c->height, AV_PIX_FMT_YUV420P,
317 c->width, c->height, c->pix_fmt,
318 sws_flags, NULL, NULL, NULL);
321 "Could not initialize the conversion context\n");
325 fill_yuv_image(&src_picture, frame_count, c->width, c->height);
327 (const uint8_t * const *)src_picture.data, src_picture.linesize,
328 0, c->height, dst_picture.data, dst_picture.linesize);
330 fill_yuv_image(&dst_picture, frame_count, c->width, c->height);
334 if (oc->oformat->flags & AVFMT_RAWPICTURE) {
335 /* Raw video case - directly store the picture in the packet */
337 av_init_packet(&pkt);
339 pkt.flags |= AV_PKT_FLAG_KEY;
340 pkt.stream_index = st->index;
341 pkt.data = dst_picture.data[0];
342 pkt.size = sizeof(AVPicture);
344 ret = av_interleaved_write_frame(oc, &pkt);
346 /* encode the image */
350 av_init_packet(&pkt);
351 pkt.data = NULL; // packet data will be allocated by the encoder
354 ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
356 fprintf(stderr, "Error encoding video frame: %s\n", av_err2str(ret));
360 /* If size is zero, it means the image was buffered. */
362 if (c->coded_frame->key_frame)
363 pkt.flags |= AV_PKT_FLAG_KEY;
365 pkt.stream_index = st->index;
367 /* Write the compressed frame to the media file. */
368 ret = av_interleaved_write_frame(oc, &pkt);
374 fprintf(stderr, "Error while writing video frame: %s\n", av_err2str(ret));
380 static void close_video(AVFormatContext *oc, AVStream *st)
382 avcodec_close(st->codec);
383 av_free(src_picture.data[0]);
384 av_free(dst_picture.data[0]);
388 /**************************************************************/
389 /* media file output */
391 int main(int argc, char **argv)
393 const char *filename;
396 AVStream *audio_st, *video_st;
397 AVCodec *audio_codec, *video_codec;
398 double audio_pts, video_pts;
401 /* Initialize libavcodec, and register all codecs and formats. */
405 printf("usage: %s output_file\n"
406 "API example program to output a media file with libavformat.\n"
407 "This program generates a synthetic audio and video stream, encodes and\n"
408 "muxes them into a file named output_file.\n"
409 "The output format is automatically guessed according to the file extension.\n"
410 "Raw images can also be output by using '%%d' in the filename.\n"
417 /* allocate the output media context */
418 avformat_alloc_output_context2(&oc, NULL, NULL, filename);
420 printf("Could not deduce output format from file extension: using MPEG.\n");
421 avformat_alloc_output_context2(&oc, NULL, "mpeg", filename);
428 /* Add the audio and video streams using the default format codecs
429 * and initialize the codecs. */
433 if (fmt->video_codec != AV_CODEC_ID_NONE) {
434 video_st = add_stream(oc, &video_codec, fmt->video_codec);
436 if (fmt->audio_codec != AV_CODEC_ID_NONE) {
437 audio_st = add_stream(oc, &audio_codec, fmt->audio_codec);
440 /* Now that all the parameters are set, we can open the audio and
441 * video codecs and allocate the necessary encode buffers. */
443 open_video(oc, video_codec, video_st);
445 open_audio(oc, audio_codec, audio_st);
447 av_dump_format(oc, 0, filename, 1);
449 /* open the output file, if needed */
450 if (!(fmt->flags & AVFMT_NOFILE)) {
451 ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);
453 fprintf(stderr, "Could not open '%s': %s\n", filename,
459 /* Write the stream header, if any. */
460 ret = avformat_write_header(oc, NULL);
462 fprintf(stderr, "Error occurred when opening output file: %s\n",
470 /* Compute current audio and video time. */
472 audio_pts = (double)audio_st->pts.val * audio_st->time_base.num / audio_st->time_base.den;
477 video_pts = (double)video_st->pts.val * video_st->time_base.num /
478 video_st->time_base.den;
482 if ((!audio_st || audio_pts >= STREAM_DURATION) &&
483 (!video_st || video_pts >= STREAM_DURATION))
486 /* write interleaved audio and video frames */
487 if (!video_st || (video_st && audio_st && audio_pts < video_pts)) {
488 write_audio_frame(oc, audio_st);
490 write_video_frame(oc, video_st);
491 frame->pts += av_rescale_q(1, video_st->codec->time_base, video_st->time_base);
495 /* Write the trailer, if any. The trailer must be written before you
496 * close the CodecContexts open when you wrote the header; otherwise
497 * av_write_trailer() may try to use memory that was freed on
498 * av_codec_close(). */
499 av_write_trailer(oc);
501 /* Close each codec. */
503 close_video(oc, video_st);
505 close_audio(oc, audio_st);
507 /* Free the streams. */
508 for (i = 0; i < oc->nb_streams; i++) {
509 av_freep(&oc->streams[i]->codec);
510 av_freep(&oc->streams[i]);
513 if (!(fmt->flags & AVFMT_NOFILE))
514 /* Close the output file. */
517 /* free the stream */