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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 codec\n");
70 st = avformat_new_stream(oc, *codec);
72 fprintf(stderr, "Could not allocate stream\n");
75 st->id = oc->nb_streams-1;
78 switch ((*codec)->type) {
79 case AVMEDIA_TYPE_AUDIO:
81 c->sample_fmt = AV_SAMPLE_FMT_S16;
83 c->sample_rate = 44100;
87 case AVMEDIA_TYPE_VIDEO:
88 avcodec_get_context_defaults3(c, *codec);
89 c->codec_id = codec_id;
92 /* Resolution must be a multiple of two. */
95 /* timebase: This is the fundamental unit of time (in seconds) in terms
96 * of which frame timestamps are represented. For fixed-fps content,
97 * timebase should be 1/framerate and timestamp increments should be
99 c->time_base.den = STREAM_FRAME_RATE;
100 c->time_base.num = 1;
101 c->gop_size = 12; /* emit one intra frame every twelve frames at most */
102 c->pix_fmt = STREAM_PIX_FMT;
103 if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
104 /* just for testing, we also add B frames */
107 if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
108 /* Needed to avoid using macroblocks in which some coeffs overflow.
109 * This does not happen with normal video, it just happens here as
110 * the motion of the chroma plane does not match the luma plane. */
119 /* Some formats want stream headers to be separate. */
120 if (oc->oformat->flags & AVFMT_GLOBALHEADER)
121 c->flags |= CODEC_FLAG_GLOBAL_HEADER;
126 /**************************************************************/
129 static float t, tincr, tincr2;
130 static int16_t *samples;
131 static int audio_input_frame_size;
133 static void open_audio(AVFormatContext *oc, AVCodec *codec, AVStream *st)
140 if (avcodec_open2(c, codec, NULL) < 0) {
141 fprintf(stderr, "Could not open audio codec\n");
145 /* init signal generator */
147 tincr = 2 * M_PI * 110.0 / c->sample_rate;
148 /* increment frequency by 110 Hz per second */
149 tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
151 if (c->codec->capabilities & CODEC_CAP_VARIABLE_FRAME_SIZE)
152 audio_input_frame_size = 10000;
154 audio_input_frame_size = c->frame_size;
155 samples = av_malloc(audio_input_frame_size *
156 av_get_bytes_per_sample(c->sample_fmt) *
159 fprintf(stderr, "Could not allocate audio samples buffer\n");
164 /* Prepare a 16 bit dummy audio frame of 'frame_size' samples and
165 * 'nb_channels' channels. */
166 static void get_audio_frame(int16_t *samples, int frame_size, int nb_channels)
172 for (j = 0; j < frame_size; j++) {
173 v = (int)(sin(t) * 10000);
174 for (i = 0; i < nb_channels; i++)
181 static void write_audio_frame(AVFormatContext *oc, AVStream *st)
184 AVPacket pkt = { 0 }; // data and size must be 0;
185 AVFrame *frame = avcodec_alloc_frame();
188 av_init_packet(&pkt);
191 get_audio_frame(samples, audio_input_frame_size, c->channels);
192 frame->nb_samples = audio_input_frame_size;
193 avcodec_fill_audio_frame(frame, c->channels, c->sample_fmt,
195 audio_input_frame_size *
196 av_get_bytes_per_sample(c->sample_fmt) *
199 ret = avcodec_encode_audio2(c, &pkt, frame, &got_packet);
201 fprintf(stderr, "Error encoding audio frame\n");
208 pkt.stream_index = st->index;
210 /* Write the compressed frame to the media file. */
211 if (av_interleaved_write_frame(oc, &pkt) != 0) {
212 fprintf(stderr, "Error while writing audio frame\n");
215 avcodec_free_frame(&frame);
218 static void close_audio(AVFormatContext *oc, AVStream *st)
220 avcodec_close(st->codec);
225 /**************************************************************/
228 static AVFrame *frame;
229 static AVPicture src_picture, dst_picture;
230 static int frame_count;
232 static void open_video(AVFormatContext *oc, AVCodec *codec, AVStream *st)
235 AVCodecContext *c = st->codec;
238 if (avcodec_open2(c, codec, NULL) < 0) {
239 fprintf(stderr, "Could not open video codec\n");
243 /* allocate and init a re-usable frame */
244 frame = avcodec_alloc_frame();
246 fprintf(stderr, "Could not allocate video frame\n");
250 /* Allocate the encoded raw picture. */
251 ret = avpicture_alloc(&dst_picture, c->pix_fmt, c->width, c->height);
253 fprintf(stderr, "Could not allocate picture\n");
257 /* If the output format is not YUV420P, then a temporary YUV420P
258 * picture is needed too. It is then converted to the required
260 if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
261 ret = avpicture_alloc(&src_picture, AV_PIX_FMT_YUV420P, c->width, c->height);
263 fprintf(stderr, "Could not allocate temporary picture\n");
268 /* copy data and linesize picture pointers to frame */
269 *((AVPicture *)frame) = dst_picture;
272 /* Prepare a dummy image. */
273 static void fill_yuv_image(AVPicture *pict, int frame_index,
274 int width, int height)
281 for (y = 0; y < height; y++)
282 for (x = 0; x < width; x++)
283 pict->data[0][y * pict->linesize[0] + x] = x + y + i * 3;
286 for (y = 0; y < height / 2; y++) {
287 for (x = 0; x < width / 2; x++) {
288 pict->data[1][y * pict->linesize[1] + x] = 128 + y + i * 2;
289 pict->data[2][y * pict->linesize[2] + x] = 64 + x + i * 5;
294 static void write_video_frame(AVFormatContext *oc, AVStream *st)
297 static struct SwsContext *sws_ctx;
298 AVCodecContext *c = st->codec;
300 if (frame_count >= STREAM_NB_FRAMES) {
301 /* No more frames to compress. The codec has a latency of a few
302 * frames if using B-frames, so we get the last frames by
303 * passing the same picture again. */
305 if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
306 /* as we only generate a YUV420P picture, we must convert it
307 * to the codec pixel format if needed */
309 sws_ctx = sws_getContext(c->width, c->height, AV_PIX_FMT_YUV420P,
310 c->width, c->height, c->pix_fmt,
311 sws_flags, NULL, NULL, NULL);
314 "Could not initialize the conversion context\n");
318 fill_yuv_image(&src_picture, frame_count, c->width, c->height);
320 (const uint8_t * const *)src_picture.data, src_picture.linesize,
321 0, c->height, dst_picture.data, dst_picture.linesize);
323 fill_yuv_image(&dst_picture, frame_count, c->width, c->height);
327 if (oc->oformat->flags & AVFMT_RAWPICTURE) {
328 /* Raw video case - directly store the picture in the packet */
330 av_init_packet(&pkt);
332 pkt.flags |= AV_PKT_FLAG_KEY;
333 pkt.stream_index = st->index;
334 pkt.data = dst_picture.data[0];
335 pkt.size = sizeof(AVPicture);
337 ret = av_interleaved_write_frame(oc, &pkt);
339 /* encode the image */
343 av_init_packet(&pkt);
344 pkt.data = NULL; // packet data will be allocated by the encoder
347 ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
349 fprintf(stderr, "Error encoding video frame\n");
353 /* If size is zero, it means the image was buffered. */
355 if (c->coded_frame->key_frame)
356 pkt.flags |= AV_PKT_FLAG_KEY;
358 pkt.stream_index = st->index;
360 /* Write the compressed frame to the media file. */
361 ret = av_interleaved_write_frame(oc, &pkt);
367 fprintf(stderr, "Error while writing video frame\n");
373 static void close_video(AVFormatContext *oc, AVStream *st)
375 avcodec_close(st->codec);
376 av_free(src_picture.data[0]);
377 av_free(dst_picture.data[0]);
381 /**************************************************************/
382 /* media file output */
384 int main(int argc, char **argv)
386 const char *filename;
389 AVStream *audio_st, *video_st;
390 AVCodec *audio_codec, *video_codec;
391 double audio_pts, video_pts;
394 /* Initialize libavcodec, and register all codecs and formats. */
398 printf("usage: %s output_file\n"
399 "API example program to output a media file with libavformat.\n"
400 "This program generates a synthetic audio and video stream, encodes and\n"
401 "muxes them into a file named output_file.\n"
402 "The output format is automatically guessed according to the file extension.\n"
403 "Raw images can also be output by using '%%d' in the filename.\n"
410 /* allocate the output media context */
411 avformat_alloc_output_context2(&oc, NULL, NULL, filename);
413 printf("Could not deduce output format from file extension: using MPEG.\n");
414 avformat_alloc_output_context2(&oc, NULL, "mpeg", filename);
421 /* Add the audio and video streams using the default format codecs
422 * and initialize the codecs. */
426 if (fmt->video_codec != AV_CODEC_ID_NONE) {
427 video_st = add_stream(oc, &video_codec, fmt->video_codec);
429 if (fmt->audio_codec != AV_CODEC_ID_NONE) {
430 audio_st = add_stream(oc, &audio_codec, fmt->audio_codec);
433 /* Now that all the parameters are set, we can open the audio and
434 * video codecs and allocate the necessary encode buffers. */
436 open_video(oc, video_codec, video_st);
438 open_audio(oc, audio_codec, audio_st);
440 av_dump_format(oc, 0, filename, 1);
442 /* open the output file, if needed */
443 if (!(fmt->flags & AVFMT_NOFILE)) {
444 if (avio_open(&oc->pb, filename, AVIO_FLAG_WRITE) < 0) {
445 fprintf(stderr, "Could not open '%s'\n", filename);
450 /* Write the stream header, if any. */
451 if (avformat_write_header(oc, NULL) < 0) {
452 fprintf(stderr, "Error occurred when opening output file\n");
459 /* Compute current audio and video time. */
461 audio_pts = (double)audio_st->pts.val * audio_st->time_base.num / audio_st->time_base.den;
466 video_pts = (double)video_st->pts.val * video_st->time_base.num /
467 video_st->time_base.den;
471 if ((!audio_st || audio_pts >= STREAM_DURATION) &&
472 (!video_st || video_pts >= STREAM_DURATION))
475 /* write interleaved audio and video frames */
476 if (!video_st || (video_st && audio_st && audio_pts < video_pts)) {
477 write_audio_frame(oc, audio_st);
479 write_video_frame(oc, video_st);
480 frame->pts += av_rescale_q(1, video_st->codec->time_base, video_st->time_base);
484 /* Write the trailer, if any. The trailer must be written before you
485 * close the CodecContexts open when you wrote the header; otherwise
486 * av_write_trailer() may try to use memory that was freed on
487 * av_codec_close(). */
488 av_write_trailer(oc);
490 /* Close each codec. */
492 close_video(oc, video_st);
494 close_audio(oc, audio_st);
496 /* Free the streams. */
497 for (i = 0; i < oc->nb_streams; i++) {
498 av_freep(&oc->streams[i]->codec);
499 av_freep(&oc->streams[i]);
502 if (!(fmt->flags & AVFMT_NOFILE))
503 /* Close the output file. */
506 /* free the stream */