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25 * libavformat API example.
27 * @example libavformat/output-example.c
28 * Output a media file in any supported libavformat format.
29 * The default codecs are used.
37 #include "libavutil/mathematics.h"
38 #include "libavformat/avformat.h"
39 #include "libswscale/swscale.h"
41 /* 5 seconds stream duration */
42 #define STREAM_DURATION 5.0
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;
57 * add an audio output stream
59 static AVStream *add_audio_stream(AVFormatContext *oc, enum AVCodecID codec_id)
65 /* find the audio encoder */
66 codec = avcodec_find_encoder(codec_id);
68 fprintf(stderr, "codec not found\n");
72 st = avformat_new_stream(oc, codec);
74 fprintf(stderr, "Could not alloc stream\n");
80 /* put sample parameters */
81 c->sample_fmt = AV_SAMPLE_FMT_S16;
83 c->sample_rate = 44100;
86 // some formats want stream headers to be separate
87 if (oc->oformat->flags & AVFMT_GLOBALHEADER)
88 c->flags |= CODEC_FLAG_GLOBAL_HEADER;
93 static void open_audio(AVFormatContext *oc, AVStream *st)
100 if (avcodec_open2(c, NULL, NULL) < 0) {
101 fprintf(stderr, "could not open codec\n");
105 /* init signal generator */
107 tincr = 2 * M_PI * 110.0 / c->sample_rate;
108 /* increment frequency by 110 Hz per second */
109 tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
111 if (c->codec->capabilities & CODEC_CAP_VARIABLE_FRAME_SIZE)
112 audio_input_frame_size = 10000;
114 audio_input_frame_size = c->frame_size;
115 samples = av_malloc(audio_input_frame_size *
116 av_get_bytes_per_sample(c->sample_fmt) *
120 /* Prepare a 16 bit dummy audio frame of 'frame_size' samples and
121 * 'nb_channels' channels. */
122 static void get_audio_frame(int16_t *samples, int frame_size, int nb_channels)
128 for (j = 0; j < frame_size; j++) {
129 v = (int)(sin(t) * 10000);
130 for (i = 0; i < nb_channels; i++)
137 static void write_audio_frame(AVFormatContext *oc, AVStream *st)
140 AVPacket pkt = { 0 }; // data and size must be 0;
141 AVFrame *frame = avcodec_alloc_frame();
144 av_init_packet(&pkt);
147 get_audio_frame(samples, audio_input_frame_size, c->channels);
148 frame->nb_samples = audio_input_frame_size;
149 avcodec_fill_audio_frame(frame, c->channels, c->sample_fmt,
151 audio_input_frame_size *
152 av_get_bytes_per_sample(c->sample_fmt) *
155 avcodec_encode_audio2(c, &pkt, frame, &got_packet);
159 pkt.stream_index = st->index;
161 /* Write the compressed frame to the media file. */
162 if (av_interleaved_write_frame(oc, &pkt) != 0) {
163 fprintf(stderr, "Error while writing audio frame\n");
166 avcodec_free_frame(&frame);
169 static void close_audio(AVFormatContext *oc, AVStream *st)
171 avcodec_close(st->codec);
176 /**************************************************************/
179 static AVFrame *picture, *tmp_picture;
180 static int frame_count;
182 /* Add a video output stream. */
183 static AVStream *add_video_stream(AVFormatContext *oc, enum AVCodecID codec_id)
189 /* find the video encoder */
190 codec = avcodec_find_encoder(codec_id);
192 fprintf(stderr, "codec not found\n");
196 st = avformat_new_stream(oc, codec);
198 fprintf(stderr, "Could not alloc stream\n");
204 /* Put sample parameters. */
205 c->bit_rate = 400000;
206 /* Resolution must be a multiple of two. */
209 /* timebase: This is the fundamental unit of time (in seconds) in terms
210 * of which frame timestamps are represented. For fixed-fps content,
211 * timebase should be 1/framerate and timestamp increments should be
213 c->time_base.den = STREAM_FRAME_RATE;
214 c->time_base.num = 1;
215 c->gop_size = 12; /* emit one intra frame every twelve frames at most */
216 c->pix_fmt = STREAM_PIX_FMT;
217 if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
218 /* just for testing, we also add B frames */
221 if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
222 /* Needed to avoid using macroblocks in which some coeffs overflow.
223 * This does not happen with normal video, it just happens here as
224 * the motion of the chroma plane does not match the luma plane. */
227 /* Some formats want stream headers to be separate. */
228 if (oc->oformat->flags & AVFMT_GLOBALHEADER)
229 c->flags |= CODEC_FLAG_GLOBAL_HEADER;
234 static AVFrame *alloc_picture(enum AVPixelFormat pix_fmt, int width, int height)
237 uint8_t *picture_buf;
240 picture = avcodec_alloc_frame();
243 size = avpicture_get_size(pix_fmt, width, height);
244 picture_buf = av_malloc(size);
249 avpicture_fill((AVPicture *)picture, picture_buf,
250 pix_fmt, width, height);
254 static void open_video(AVFormatContext *oc, AVStream *st)
261 if (avcodec_open2(c, NULL, NULL) < 0) {
262 fprintf(stderr, "could not open codec\n");
266 /* Allocate the encoded raw picture. */
267 picture = alloc_picture(c->pix_fmt, c->width, c->height);
269 fprintf(stderr, "Could not allocate picture\n");
273 /* If the output format is not YUV420P, then a temporary YUV420P
274 * picture is needed too. It is then converted to the required
277 if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
278 tmp_picture = alloc_picture(AV_PIX_FMT_YUV420P, c->width, c->height);
280 fprintf(stderr, "Could not allocate temporary picture\n");
286 /* Prepare a dummy image. */
287 static void fill_yuv_image(AVFrame *pict, int frame_index,
288 int width, int height)
295 for (y = 0; y < height; y++)
296 for (x = 0; x < width; x++)
297 pict->data[0][y * pict->linesize[0] + x] = x + y + i * 3;
300 for (y = 0; y < height / 2; y++) {
301 for (x = 0; x < width / 2; x++) {
302 pict->data[1][y * pict->linesize[1] + x] = 128 + y + i * 2;
303 pict->data[2][y * pict->linesize[2] + x] = 64 + x + i * 5;
308 static void write_video_frame(AVFormatContext *oc, AVStream *st)
312 static struct SwsContext *img_convert_ctx;
316 if (frame_count >= STREAM_NB_FRAMES) {
317 /* No more frames to compress. The codec has a latency of a few
318 * frames if using B-frames, so we get the last frames by
319 * passing the same picture again. */
321 if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
322 /* as we only generate a YUV420P picture, we must convert it
323 * to the codec pixel format if needed */
324 if (img_convert_ctx == NULL) {
325 img_convert_ctx = sws_getContext(c->width, c->height,
329 sws_flags, NULL, NULL, NULL);
330 if (img_convert_ctx == NULL) {
332 "Cannot initialize the conversion context\n");
336 fill_yuv_image(tmp_picture, frame_count, c->width, c->height);
337 sws_scale(img_convert_ctx, tmp_picture->data, tmp_picture->linesize,
338 0, c->height, picture->data, picture->linesize);
340 fill_yuv_image(picture, frame_count, c->width, c->height);
344 if (oc->oformat->flags & AVFMT_RAWPICTURE) {
345 /* Raw video case - the API will change slightly in the near
346 * future for that. */
348 av_init_packet(&pkt);
350 pkt.flags |= AV_PKT_FLAG_KEY;
351 pkt.stream_index = st->index;
352 pkt.data = (uint8_t *)picture;
353 pkt.size = sizeof(AVPicture);
355 ret = av_interleaved_write_frame(oc, &pkt);
357 AVPacket pkt = { 0 };
359 av_init_packet(&pkt);
361 /* encode the image */
362 ret = avcodec_encode_video2(c, &pkt, picture, &got_packet);
363 /* If size is zero, it means the image was buffered. */
364 if (!ret && got_packet && pkt.size) {
365 if (pkt.pts != AV_NOPTS_VALUE) {
366 pkt.pts = av_rescale_q(pkt.pts,
367 c->time_base, st->time_base);
369 if (pkt.dts != AV_NOPTS_VALUE) {
370 pkt.dts = av_rescale_q(pkt.dts,
371 c->time_base, st->time_base);
373 pkt.stream_index = st->index;
375 /* Write the compressed frame to the media file. */
376 ret = av_interleaved_write_frame(oc, &pkt);
382 fprintf(stderr, "Error while writing video frame\n");
388 static void close_video(AVFormatContext *oc, AVStream *st)
390 avcodec_close(st->codec);
391 av_free(picture->data[0]);
394 av_free(tmp_picture->data[0]);
395 av_free(tmp_picture);
399 /**************************************************************/
400 /* media file output */
402 int main(int argc, char **argv)
404 const char *filename;
407 AVStream *audio_st, *video_st;
408 double audio_pts, video_pts;
411 /* Initialize libavcodec, and register all codecs and formats. */
415 printf("usage: %s output_file\n"
416 "API example program to output a media file with libavformat.\n"
417 "The output format is automatically guessed according to the file extension.\n"
418 "Raw images can also be output by using '%%d' in the filename\n"
425 /* Autodetect the output format from the name. default is MPEG. */
426 fmt = av_guess_format(NULL, filename, NULL);
428 printf("Could not deduce output format from file extension: using MPEG.\n");
429 fmt = av_guess_format("mpeg", NULL, NULL);
432 fprintf(stderr, "Could not find suitable output format\n");
436 /* Allocate the output media context. */
437 oc = avformat_alloc_context();
439 fprintf(stderr, "Memory error\n");
443 snprintf(oc->filename, sizeof(oc->filename), "%s", filename);
445 /* Add the audio and video streams using the default format codecs
446 * and initialize the codecs. */
449 if (fmt->video_codec != AV_CODEC_ID_NONE) {
450 video_st = add_video_stream(oc, fmt->video_codec);
452 if (fmt->audio_codec != AV_CODEC_ID_NONE) {
453 audio_st = add_audio_stream(oc, fmt->audio_codec);
456 /* Now that all the parameters are set, we can open the audio and
457 * video codecs and allocate the necessary encode buffers. */
459 open_video(oc, video_st);
461 open_audio(oc, audio_st);
463 av_dump_format(oc, 0, filename, 1);
465 /* open the output file, if needed */
466 if (!(fmt->flags & AVFMT_NOFILE)) {
467 if (avio_open(&oc->pb, filename, AVIO_FLAG_WRITE) < 0) {
468 fprintf(stderr, "Could not open '%s'\n", filename);
473 /* Write the stream header, if any. */
474 avformat_write_header(oc, NULL);
477 /* Compute current audio and video time. */
479 audio_pts = (double)audio_st->pts.val * audio_st->time_base.num / audio_st->time_base.den;
484 video_pts = (double)video_st->pts.val * video_st->time_base.num /
485 video_st->time_base.den;
489 if ((!audio_st || audio_pts >= STREAM_DURATION) &&
490 (!video_st || video_pts >= STREAM_DURATION))
493 /* write interleaved audio and video frames */
494 if (!video_st || (video_st && audio_st && audio_pts < video_pts)) {
495 write_audio_frame(oc, audio_st);
497 write_video_frame(oc, video_st);
501 /* Write the trailer, if any. The trailer must be written before you
502 * close the CodecContexts open when you wrote the header; otherwise
503 * av_write_trailer() may try to use memory that was freed on
504 * av_codec_close(). */
505 av_write_trailer(oc);
507 /* Close each codec. */
509 close_video(oc, video_st);
511 close_audio(oc, audio_st);
513 /* Free the streams. */
514 for (i = 0; i < oc->nb_streams; i++) {
515 av_freep(&oc->streams[i]->codec);
516 av_freep(&oc->streams[i]);
519 if (!(fmt->flags & AVFMT_NOFILE))
520 /* Close the output file. */
523 /* free the stream */