2 * Copyright (c) 2003 Fabrice Bellard
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25 * libavformat API example.
27 * Output a media file in any supported libavformat format. The default
37 #include <libavutil/avassert.h>
38 #include <libavutil/channel_layout.h>
39 #include <libavutil/opt.h>
40 #include <libavutil/mathematics.h>
41 #include <libavutil/timestamp.h>
42 #include <libavformat/avformat.h>
43 #include <libswscale/swscale.h>
44 #include <libswresample/swresample.h>
46 #define STREAM_DURATION 10.0
47 #define STREAM_FRAME_RATE 25 /* 25 images/s */
48 #define STREAM_PIX_FMT AV_PIX_FMT_YUV420P /* default pix_fmt */
50 #define SCALE_FLAGS SWS_BICUBIC
52 // a wrapper around a single output AVStream
53 typedef struct OutputStream {
57 /* pts of the next frame that will be generated */
64 float t, tincr, tincr2;
66 struct SwsContext *sws_ctx;
67 struct SwrContext *swr_ctx;
70 static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt)
72 AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
74 printf("pts:%s pts_time:%s dts:%s dts_time:%s duration:%s duration_time:%s stream_index:%d\n",
75 av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, time_base),
76 av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, time_base),
77 av_ts2str(pkt->duration), av_ts2timestr(pkt->duration, time_base),
81 static int write_frame(AVFormatContext *fmt_ctx, const AVRational *time_base, AVStream *st, AVPacket *pkt)
83 /* rescale output packet timestamp values from codec to stream timebase */
84 av_packet_rescale_ts(pkt, *time_base, st->time_base);
85 pkt->stream_index = st->index;
87 /* Write the compressed frame to the media file. */
88 log_packet(fmt_ctx, pkt);
89 return av_interleaved_write_frame(fmt_ctx, pkt);
92 /* Add an output stream. */
93 static void add_stream(OutputStream *ost, AVFormatContext *oc,
95 enum AVCodecID codec_id)
100 /* find the encoder */
101 *codec = avcodec_find_encoder(codec_id);
103 fprintf(stderr, "Could not find encoder for '%s'\n",
104 avcodec_get_name(codec_id));
108 ost->st = avformat_new_stream(oc, NULL);
110 fprintf(stderr, "Could not allocate stream\n");
113 ost->st->id = oc->nb_streams-1;
114 c = avcodec_alloc_context3(*codec);
116 fprintf(stderr, "Could not alloc an encoding context\n");
121 switch ((*codec)->type) {
122 case AVMEDIA_TYPE_AUDIO:
123 c->sample_fmt = (*codec)->sample_fmts ?
124 (*codec)->sample_fmts[0] : AV_SAMPLE_FMT_FLTP;
126 c->sample_rate = 44100;
127 if ((*codec)->supported_samplerates) {
128 c->sample_rate = (*codec)->supported_samplerates[0];
129 for (i = 0; (*codec)->supported_samplerates[i]; i++) {
130 if ((*codec)->supported_samplerates[i] == 44100)
131 c->sample_rate = 44100;
134 c->channels = av_get_channel_layout_nb_channels(c->channel_layout);
135 c->channel_layout = AV_CH_LAYOUT_STEREO;
136 if ((*codec)->channel_layouts) {
137 c->channel_layout = (*codec)->channel_layouts[0];
138 for (i = 0; (*codec)->channel_layouts[i]; i++) {
139 if ((*codec)->channel_layouts[i] == AV_CH_LAYOUT_STEREO)
140 c->channel_layout = AV_CH_LAYOUT_STEREO;
143 c->channels = av_get_channel_layout_nb_channels(c->channel_layout);
144 ost->st->time_base = (AVRational){ 1, c->sample_rate };
147 case AVMEDIA_TYPE_VIDEO:
148 c->codec_id = codec_id;
150 c->bit_rate = 400000;
151 /* Resolution must be a multiple of two. */
154 /* timebase: This is the fundamental unit of time (in seconds) in terms
155 * of which frame timestamps are represented. For fixed-fps content,
156 * timebase should be 1/framerate and timestamp increments should be
158 ost->st->time_base = (AVRational){ 1, STREAM_FRAME_RATE };
159 c->time_base = ost->st->time_base;
161 c->gop_size = 12; /* emit one intra frame every twelve frames at most */
162 c->pix_fmt = STREAM_PIX_FMT;
163 if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
164 /* just for testing, we also add B-frames */
167 if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
168 /* Needed to avoid using macroblocks in which some coeffs overflow.
169 * This does not happen with normal video, it just happens here as
170 * the motion of the chroma plane does not match the luma plane. */
179 /* Some formats want stream headers to be separate. */
180 if (oc->oformat->flags & AVFMT_GLOBALHEADER)
181 c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
184 /**************************************************************/
187 static AVFrame *alloc_audio_frame(enum AVSampleFormat sample_fmt,
188 uint64_t channel_layout,
189 int sample_rate, int nb_samples)
191 AVFrame *frame = av_frame_alloc();
195 fprintf(stderr, "Error allocating an audio frame\n");
199 frame->format = sample_fmt;
200 frame->channel_layout = channel_layout;
201 frame->sample_rate = sample_rate;
202 frame->nb_samples = nb_samples;
205 ret = av_frame_get_buffer(frame, 0);
207 fprintf(stderr, "Error allocating an audio buffer\n");
215 static void open_audio(AVFormatContext *oc, AVCodec *codec, OutputStream *ost, AVDictionary *opt_arg)
220 AVDictionary *opt = NULL;
225 av_dict_copy(&opt, opt_arg, 0);
226 ret = avcodec_open2(c, codec, &opt);
229 fprintf(stderr, "Could not open audio codec: %s\n", av_err2str(ret));
233 /* init signal generator */
235 ost->tincr = 2 * M_PI * 110.0 / c->sample_rate;
236 /* increment frequency by 110 Hz per second */
237 ost->tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
239 if (c->codec->capabilities & AV_CODEC_CAP_VARIABLE_FRAME_SIZE)
242 nb_samples = c->frame_size;
244 ost->frame = alloc_audio_frame(c->sample_fmt, c->channel_layout,
245 c->sample_rate, nb_samples);
246 ost->tmp_frame = alloc_audio_frame(AV_SAMPLE_FMT_S16, c->channel_layout,
247 c->sample_rate, nb_samples);
249 /* copy the stream parameters to the muxer */
250 ret = avcodec_parameters_from_context(ost->st->codecpar, c);
252 fprintf(stderr, "Could not copy the stream parameters\n");
256 /* create resampler context */
257 ost->swr_ctx = swr_alloc();
259 fprintf(stderr, "Could not allocate resampler context\n");
264 av_opt_set_int (ost->swr_ctx, "in_channel_count", c->channels, 0);
265 av_opt_set_int (ost->swr_ctx, "in_sample_rate", c->sample_rate, 0);
266 av_opt_set_sample_fmt(ost->swr_ctx, "in_sample_fmt", AV_SAMPLE_FMT_S16, 0);
267 av_opt_set_int (ost->swr_ctx, "out_channel_count", c->channels, 0);
268 av_opt_set_int (ost->swr_ctx, "out_sample_rate", c->sample_rate, 0);
269 av_opt_set_sample_fmt(ost->swr_ctx, "out_sample_fmt", c->sample_fmt, 0);
271 /* initialize the resampling context */
272 if ((ret = swr_init(ost->swr_ctx)) < 0) {
273 fprintf(stderr, "Failed to initialize the resampling context\n");
278 /* Prepare a 16 bit dummy audio frame of 'frame_size' samples and
279 * 'nb_channels' channels. */
280 static AVFrame *get_audio_frame(OutputStream *ost)
282 AVFrame *frame = ost->tmp_frame;
284 int16_t *q = (int16_t*)frame->data[0];
286 /* check if we want to generate more frames */
287 if (av_compare_ts(ost->next_pts, ost->enc->time_base,
288 STREAM_DURATION, (AVRational){ 1, 1 }) >= 0)
291 for (j = 0; j <frame->nb_samples; j++) {
292 v = (int)(sin(ost->t) * 10000);
293 for (i = 0; i < ost->enc->channels; i++)
295 ost->t += ost->tincr;
296 ost->tincr += ost->tincr2;
299 frame->pts = ost->next_pts;
300 ost->next_pts += frame->nb_samples;
306 * encode one audio frame and send it to the muxer
307 * return 1 when encoding is finished, 0 otherwise
309 static int write_audio_frame(AVFormatContext *oc, OutputStream *ost)
312 AVPacket pkt = { 0 }; // data and size must be 0;
318 av_init_packet(&pkt);
321 frame = get_audio_frame(ost);
324 /* convert samples from native format to destination codec format, using the resampler */
325 /* compute destination number of samples */
326 dst_nb_samples = av_rescale_rnd(swr_get_delay(ost->swr_ctx, c->sample_rate) + frame->nb_samples,
327 c->sample_rate, c->sample_rate, AV_ROUND_UP);
328 av_assert0(dst_nb_samples == frame->nb_samples);
330 /* when we pass a frame to the encoder, it may keep a reference to it
332 * make sure we do not overwrite it here
334 ret = av_frame_make_writable(ost->frame);
338 /* convert to destination format */
339 ret = swr_convert(ost->swr_ctx,
340 ost->frame->data, dst_nb_samples,
341 (const uint8_t **)frame->data, frame->nb_samples);
343 fprintf(stderr, "Error while converting\n");
348 frame->pts = av_rescale_q(ost->samples_count, (AVRational){1, c->sample_rate}, c->time_base);
349 ost->samples_count += dst_nb_samples;
352 ret = avcodec_encode_audio2(c, &pkt, frame, &got_packet);
354 fprintf(stderr, "Error encoding audio frame: %s\n", av_err2str(ret));
359 ret = write_frame(oc, &c->time_base, ost->st, &pkt);
361 fprintf(stderr, "Error while writing audio frame: %s\n",
367 return (frame || got_packet) ? 0 : 1;
370 /**************************************************************/
373 static AVFrame *alloc_picture(enum AVPixelFormat pix_fmt, int width, int height)
378 picture = av_frame_alloc();
382 picture->format = pix_fmt;
383 picture->width = width;
384 picture->height = height;
386 /* allocate the buffers for the frame data */
387 ret = av_frame_get_buffer(picture, 32);
389 fprintf(stderr, "Could not allocate frame data.\n");
396 static void open_video(AVFormatContext *oc, AVCodec *codec, OutputStream *ost, AVDictionary *opt_arg)
399 AVCodecContext *c = ost->enc;
400 AVDictionary *opt = NULL;
402 av_dict_copy(&opt, opt_arg, 0);
405 ret = avcodec_open2(c, codec, &opt);
408 fprintf(stderr, "Could not open video codec: %s\n", av_err2str(ret));
412 /* allocate and init a re-usable frame */
413 ost->frame = alloc_picture(c->pix_fmt, c->width, c->height);
415 fprintf(stderr, "Could not allocate video frame\n");
419 /* If the output format is not YUV420P, then a temporary YUV420P
420 * picture is needed too. It is then converted to the required
422 ost->tmp_frame = NULL;
423 if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
424 ost->tmp_frame = alloc_picture(AV_PIX_FMT_YUV420P, c->width, c->height);
425 if (!ost->tmp_frame) {
426 fprintf(stderr, "Could not allocate temporary picture\n");
431 /* copy the stream parameters to the muxer */
432 ret = avcodec_parameters_from_context(ost->st->codecpar, c);
434 fprintf(stderr, "Could not copy the stream parameters\n");
439 /* Prepare a dummy image. */
440 static void fill_yuv_image(AVFrame *pict, int frame_index,
441 int width, int height)
448 for (y = 0; y < height; y++)
449 for (x = 0; x < width; x++)
450 pict->data[0][y * pict->linesize[0] + x] = x + y + i * 3;
453 for (y = 0; y < height / 2; y++) {
454 for (x = 0; x < width / 2; x++) {
455 pict->data[1][y * pict->linesize[1] + x] = 128 + y + i * 2;
456 pict->data[2][y * pict->linesize[2] + x] = 64 + x + i * 5;
461 static AVFrame *get_video_frame(OutputStream *ost)
463 AVCodecContext *c = ost->enc;
465 /* check if we want to generate more frames */
466 if (av_compare_ts(ost->next_pts, c->time_base,
467 STREAM_DURATION, (AVRational){ 1, 1 }) >= 0)
470 /* when we pass a frame to the encoder, it may keep a reference to it
471 * internally; make sure we do not overwrite it here */
472 if (av_frame_make_writable(ost->frame) < 0)
475 if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
476 /* as we only generate a YUV420P picture, we must convert it
477 * to the codec pixel format if needed */
479 ost->sws_ctx = sws_getContext(c->width, c->height,
483 SCALE_FLAGS, NULL, NULL, NULL);
486 "Could not initialize the conversion context\n");
490 fill_yuv_image(ost->tmp_frame, ost->next_pts, c->width, c->height);
491 sws_scale(ost->sws_ctx,
492 (const uint8_t * const *)ost->tmp_frame->data, ost->tmp_frame->linesize,
493 0, c->height, ost->frame->data, ost->frame->linesize);
495 fill_yuv_image(ost->frame, ost->next_pts, c->width, c->height);
498 ost->frame->pts = ost->next_pts++;
504 * encode one video frame and send it to the muxer
505 * return 1 when encoding is finished, 0 otherwise
507 static int write_video_frame(AVFormatContext *oc, OutputStream *ost)
513 AVPacket pkt = { 0 };
517 frame = get_video_frame(ost);
519 av_init_packet(&pkt);
521 /* encode the image */
522 ret = avcodec_encode_video2(c, &pkt, frame, &got_packet);
524 fprintf(stderr, "Error encoding video frame: %s\n", av_err2str(ret));
529 ret = write_frame(oc, &c->time_base, ost->st, &pkt);
535 fprintf(stderr, "Error while writing video frame: %s\n", av_err2str(ret));
539 return (frame || got_packet) ? 0 : 1;
542 static void close_stream(AVFormatContext *oc, OutputStream *ost)
544 avcodec_free_context(&ost->enc);
545 av_frame_free(&ost->frame);
546 av_frame_free(&ost->tmp_frame);
547 sws_freeContext(ost->sws_ctx);
548 swr_free(&ost->swr_ctx);
551 /**************************************************************/
552 /* media file output */
554 int main(int argc, char **argv)
556 OutputStream video_st = { 0 }, audio_st = { 0 };
557 const char *filename;
560 AVCodec *audio_codec, *video_codec;
562 int have_video = 0, have_audio = 0;
563 int encode_video = 0, encode_audio = 0;
564 AVDictionary *opt = NULL;
567 /* Initialize libavcodec, and register all codecs and formats. */
571 printf("usage: %s output_file\n"
572 "API example program to output a media file with libavformat.\n"
573 "This program generates a synthetic audio and video stream, encodes and\n"
574 "muxes them into a file named output_file.\n"
575 "The output format is automatically guessed according to the file extension.\n"
576 "Raw images can also be output by using '%%d' in the filename.\n"
582 for (i = 2; i+1 < argc; i+=2) {
583 if (!strcmp(argv[i], "-flags") || !strcmp(argv[i], "-fflags"))
584 av_dict_set(&opt, argv[i]+1, argv[i+1], 0);
587 /* allocate the output media context */
588 avformat_alloc_output_context2(&oc, NULL, NULL, filename);
590 printf("Could not deduce output format from file extension: using MPEG.\n");
591 avformat_alloc_output_context2(&oc, NULL, "mpeg", filename);
598 /* Add the audio and video streams using the default format codecs
599 * and initialize the codecs. */
600 if (fmt->video_codec != AV_CODEC_ID_NONE) {
601 add_stream(&video_st, oc, &video_codec, fmt->video_codec);
605 if (fmt->audio_codec != AV_CODEC_ID_NONE) {
606 add_stream(&audio_st, oc, &audio_codec, fmt->audio_codec);
611 /* Now that all the parameters are set, we can open the audio and
612 * video codecs and allocate the necessary encode buffers. */
614 open_video(oc, video_codec, &video_st, opt);
617 open_audio(oc, audio_codec, &audio_st, opt);
619 av_dump_format(oc, 0, filename, 1);
621 /* open the output file, if needed */
622 if (!(fmt->flags & AVFMT_NOFILE)) {
623 ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);
625 fprintf(stderr, "Could not open '%s': %s\n", filename,
631 /* Write the stream header, if any. */
632 ret = avformat_write_header(oc, &opt);
634 fprintf(stderr, "Error occurred when opening output file: %s\n",
639 while (encode_video || encode_audio) {
640 /* select the stream to encode */
642 (!encode_audio || av_compare_ts(video_st.next_pts, video_st.enc->time_base,
643 audio_st.next_pts, audio_st.enc->time_base) <= 0)) {
644 encode_video = !write_video_frame(oc, &video_st);
646 encode_audio = !write_audio_frame(oc, &audio_st);
650 /* Write the trailer, if any. The trailer must be written before you
651 * close the CodecContexts open when you wrote the header; otherwise
652 * av_write_trailer() may try to use memory that was freed on
653 * av_codec_close(). */
654 av_write_trailer(oc);
656 /* Close each codec. */
658 close_stream(oc, &video_st);
660 close_stream(oc, &audio_st);
662 if (!(fmt->flags & AVFMT_NOFILE))
663 /* Close the output file. */
664 avio_closep(&oc->pb);
666 /* free the stream */
667 avformat_free_context(oc);