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1 /*
2  * Copyright (c) 2003 Fabrice Bellard
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a copy
5  * of this software and associated documentation files (the "Software"), to deal
6  * in the Software without restriction, including without limitation the rights
7  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8  * copies of the Software, and to permit persons to whom the Software is
9  * furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice shall be included in
12  * all copies or substantial portions of the Software.
13  *
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
17  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
20  * THE SOFTWARE.
21  */
22 
23 /**
24  * @file
25  * libavformat API example.
26  *
27  * Output a media file in any supported libavformat format. The default
28  * codecs are used.
29  * @example muxing.c
30  */
31 
32 #include <stdlib.h>
33 #include <stdio.h>
34 #include <string.h>
35 #include <math.h>
36 
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>
45 
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 */
49 
50 #define SCALE_FLAGS SWS_BICUBIC
51 
52 // a wrapper around a single output AVStream
53 typedef struct OutputStream {
54     AVStream *st;
55     AVCodecContext *enc;
56 
57     /* pts of the next frame that will be generated */
58     int64_t next_pts;
59     int samples_count;
60 
61     AVFrame *frame;
62     AVFrame *tmp_frame;
63 
64     float t, tincr, tincr2;
65 
66     struct SwsContext *sws_ctx;
67     struct SwrContext *swr_ctx;
68 } OutputStream;
69 
log_packet(const AVFormatContext * fmt_ctx,const AVPacket * pkt)70 static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt)
71 {
72     AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
73 
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),
78            pkt->stream_index);
79 }
80 
write_frame(AVFormatContext * fmt_ctx,AVCodecContext * c,AVStream * st,AVFrame * frame)81 static int write_frame(AVFormatContext *fmt_ctx, AVCodecContext *c,
82                        AVStream *st, AVFrame *frame)
83 {
84     int ret;
85 
86     // send the frame to the encoder
87     ret = avcodec_send_frame(c, frame);
88     if (ret < 0) {
89         fprintf(stderr, "Error sending a frame to the encoder: %s\n",
90                 av_err2str(ret));
91         exit(1);
92     }
93 
94     while (ret >= 0) {
95         AVPacket pkt = { 0 };
96 
97         ret = avcodec_receive_packet(c, &pkt);
98         if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
99             break;
100         else if (ret < 0) {
101             fprintf(stderr, "Error encoding a frame: %s\n", av_err2str(ret));
102             exit(1);
103         }
104 
105         /* rescale output packet timestamp values from codec to stream timebase */
106         av_packet_rescale_ts(&pkt, c->time_base, st->time_base);
107         pkt.stream_index = st->index;
108 
109         /* Write the compressed frame to the media file. */
110         log_packet(fmt_ctx, &pkt);
111         ret = av_interleaved_write_frame(fmt_ctx, &pkt);
112         av_packet_unref(&pkt);
113         if (ret < 0) {
114             fprintf(stderr, "Error while writing output packet: %s\n", av_err2str(ret));
115             exit(1);
116         }
117     }
118 
119     return ret == AVERROR_EOF ? 1 : 0;
120 }
121 
122 /* Add an output stream. */
add_stream(OutputStream * ost,AVFormatContext * oc,AVCodec ** codec,enum AVCodecID codec_id)123 static void add_stream(OutputStream *ost, AVFormatContext *oc,
124                        AVCodec **codec,
125                        enum AVCodecID codec_id)
126 {
127     AVCodecContext *c;
128     int i;
129 
130     /* find the encoder */
131     *codec = avcodec_find_encoder(codec_id);
132     if (!(*codec)) {
133         fprintf(stderr, "Could not find encoder for '%s'\n",
134                 avcodec_get_name(codec_id));
135         exit(1);
136     }
137 
138     ost->st = avformat_new_stream(oc, NULL);
139     if (!ost->st) {
140         fprintf(stderr, "Could not allocate stream\n");
141         exit(1);
142     }
143     ost->st->id = oc->nb_streams-1;
144     c = avcodec_alloc_context3(*codec);
145     if (!c) {
146         fprintf(stderr, "Could not alloc an encoding context\n");
147         exit(1);
148     }
149     ost->enc = c;
150 
151     switch ((*codec)->type) {
152     case AVMEDIA_TYPE_AUDIO:
153         c->sample_fmt  = (*codec)->sample_fmts ?
154             (*codec)->sample_fmts[0] : AV_SAMPLE_FMT_FLTP;
155         c->bit_rate    = 64000;
156         c->sample_rate = 44100;
157         if ((*codec)->supported_samplerates) {
158             c->sample_rate = (*codec)->supported_samplerates[0];
159             for (i = 0; (*codec)->supported_samplerates[i]; i++) {
160                 if ((*codec)->supported_samplerates[i] == 44100)
161                     c->sample_rate = 44100;
162             }
163         }
164         c->channels        = av_get_channel_layout_nb_channels(c->channel_layout);
165         c->channel_layout = AV_CH_LAYOUT_STEREO;
166         if ((*codec)->channel_layouts) {
167             c->channel_layout = (*codec)->channel_layouts[0];
168             for (i = 0; (*codec)->channel_layouts[i]; i++) {
169                 if ((*codec)->channel_layouts[i] == AV_CH_LAYOUT_STEREO)
170                     c->channel_layout = AV_CH_LAYOUT_STEREO;
171             }
172         }
173         c->channels        = av_get_channel_layout_nb_channels(c->channel_layout);
174         ost->st->time_base = (AVRational){ 1, c->sample_rate };
175         break;
176 
177     case AVMEDIA_TYPE_VIDEO:
178         c->codec_id = codec_id;
179 
180         c->bit_rate = 400000;
181         /* Resolution must be a multiple of two. */
182         c->width    = 352;
183         c->height   = 288;
184         /* timebase: This is the fundamental unit of time (in seconds) in terms
185          * of which frame timestamps are represented. For fixed-fps content,
186          * timebase should be 1/framerate and timestamp increments should be
187          * identical to 1. */
188         ost->st->time_base = (AVRational){ 1, STREAM_FRAME_RATE };
189         c->time_base       = ost->st->time_base;
190 
191         c->gop_size      = 12; /* emit one intra frame every twelve frames at most */
192         c->pix_fmt       = STREAM_PIX_FMT;
193         if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
194             /* just for testing, we also add B-frames */
195             c->max_b_frames = 2;
196         }
197         if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
198             /* Needed to avoid using macroblocks in which some coeffs overflow.
199              * This does not happen with normal video, it just happens here as
200              * the motion of the chroma plane does not match the luma plane. */
201             c->mb_decision = 2;
202         }
203         break;
204 
205     default:
206         break;
207     }
208 
209     /* Some formats want stream headers to be separate. */
210     if (oc->oformat->flags & AVFMT_GLOBALHEADER)
211         c->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
212 }
213 
214 /**************************************************************/
215 /* audio output */
216 
alloc_audio_frame(enum AVSampleFormat sample_fmt,uint64_t channel_layout,int sample_rate,int nb_samples)217 static AVFrame *alloc_audio_frame(enum AVSampleFormat sample_fmt,
218                                   uint64_t channel_layout,
219                                   int sample_rate, int nb_samples)
220 {
221     AVFrame *frame = av_frame_alloc();
222     int ret;
223 
224     if (!frame) {
225         fprintf(stderr, "Error allocating an audio frame\n");
226         exit(1);
227     }
228 
229     frame->format = sample_fmt;
230     frame->channel_layout = channel_layout;
231     frame->sample_rate = sample_rate;
232     frame->nb_samples = nb_samples;
233 
234     if (nb_samples) {
235         ret = av_frame_get_buffer(frame, 0);
236         if (ret < 0) {
237             fprintf(stderr, "Error allocating an audio buffer\n");
238             exit(1);
239         }
240     }
241 
242     return frame;
243 }
244 
open_audio(AVFormatContext * oc,AVCodec * codec,OutputStream * ost,AVDictionary * opt_arg)245 static void open_audio(AVFormatContext *oc, AVCodec *codec, OutputStream *ost, AVDictionary *opt_arg)
246 {
247     AVCodecContext *c;
248     int nb_samples;
249     int ret;
250     AVDictionary *opt = NULL;
251 
252     c = ost->enc;
253 
254     /* open it */
255     av_dict_copy(&opt, opt_arg, 0);
256     ret = avcodec_open2(c, codec, &opt);
257     av_dict_free(&opt);
258     if (ret < 0) {
259         fprintf(stderr, "Could not open audio codec: %s\n", av_err2str(ret));
260         exit(1);
261     }
262 
263     /* init signal generator */
264     ost->t     = 0;
265     ost->tincr = 2 * M_PI * 110.0 / c->sample_rate;
266     /* increment frequency by 110 Hz per second */
267     ost->tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
268 
269     if (c->codec->capabilities & AV_CODEC_CAP_VARIABLE_FRAME_SIZE)
270         nb_samples = 10000;
271     else
272         nb_samples = c->frame_size;
273 
274     ost->frame     = alloc_audio_frame(c->sample_fmt, c->channel_layout,
275                                        c->sample_rate, nb_samples);
276     ost->tmp_frame = alloc_audio_frame(AV_SAMPLE_FMT_S16, c->channel_layout,
277                                        c->sample_rate, nb_samples);
278 
279     /* copy the stream parameters to the muxer */
280     ret = avcodec_parameters_from_context(ost->st->codecpar, c);
281     if (ret < 0) {
282         fprintf(stderr, "Could not copy the stream parameters\n");
283         exit(1);
284     }
285 
286     /* create resampler context */
287     ost->swr_ctx = swr_alloc();
288     if (!ost->swr_ctx) {
289         fprintf(stderr, "Could not allocate resampler context\n");
290         exit(1);
291     }
292 
293     /* set options */
294     av_opt_set_int       (ost->swr_ctx, "in_channel_count",   c->channels,       0);
295     av_opt_set_int       (ost->swr_ctx, "in_sample_rate",     c->sample_rate,    0);
296     av_opt_set_sample_fmt(ost->swr_ctx, "in_sample_fmt",      AV_SAMPLE_FMT_S16, 0);
297     av_opt_set_int       (ost->swr_ctx, "out_channel_count",  c->channels,       0);
298     av_opt_set_int       (ost->swr_ctx, "out_sample_rate",    c->sample_rate,    0);
299     av_opt_set_sample_fmt(ost->swr_ctx, "out_sample_fmt",     c->sample_fmt,     0);
300 
301     /* initialize the resampling context */
302     if ((ret = swr_init(ost->swr_ctx)) < 0) {
303         fprintf(stderr, "Failed to initialize the resampling context\n");
304         exit(1);
305     }
306 }
307 
308 /* Prepare a 16 bit dummy audio frame of 'frame_size' samples and
309  * 'nb_channels' channels. */
get_audio_frame(OutputStream * ost)310 static AVFrame *get_audio_frame(OutputStream *ost)
311 {
312     AVFrame *frame = ost->tmp_frame;
313     int j, i, v;
314     int16_t *q = (int16_t*)frame->data[0];
315 
316     /* check if we want to generate more frames */
317     if (av_compare_ts(ost->next_pts, ost->enc->time_base,
318                       STREAM_DURATION, (AVRational){ 1, 1 }) > 0)
319         return NULL;
320 
321     for (j = 0; j <frame->nb_samples; j++) {
322         v = (int)(sin(ost->t) * 10000);
323         for (i = 0; i < ost->enc->channels; i++)
324             *q++ = v;
325         ost->t     += ost->tincr;
326         ost->tincr += ost->tincr2;
327     }
328 
329     frame->pts = ost->next_pts;
330     ost->next_pts  += frame->nb_samples;
331 
332     return frame;
333 }
334 
335 /*
336  * encode one audio frame and send it to the muxer
337  * return 1 when encoding is finished, 0 otherwise
338  */
write_audio_frame(AVFormatContext * oc,OutputStream * ost)339 static int write_audio_frame(AVFormatContext *oc, OutputStream *ost)
340 {
341     AVCodecContext *c;
342     AVFrame *frame;
343     int ret;
344     int dst_nb_samples;
345 
346     c = ost->enc;
347 
348     frame = get_audio_frame(ost);
349 
350     if (frame) {
351         /* convert samples from native format to destination codec format, using the resampler */
352         /* compute destination number of samples */
353         dst_nb_samples = av_rescale_rnd(swr_get_delay(ost->swr_ctx, c->sample_rate) + frame->nb_samples,
354                                         c->sample_rate, c->sample_rate, AV_ROUND_UP);
355         av_assert0(dst_nb_samples == frame->nb_samples);
356 
357         /* when we pass a frame to the encoder, it may keep a reference to it
358          * internally;
359          * make sure we do not overwrite it here
360          */
361         ret = av_frame_make_writable(ost->frame);
362         if (ret < 0)
363             exit(1);
364 
365         /* convert to destination format */
366         ret = swr_convert(ost->swr_ctx,
367                           ost->frame->data, dst_nb_samples,
368                           (const uint8_t **)frame->data, frame->nb_samples);
369         if (ret < 0) {
370             fprintf(stderr, "Error while converting\n");
371             exit(1);
372         }
373         frame = ost->frame;
374 
375         frame->pts = av_rescale_q(ost->samples_count, (AVRational){1, c->sample_rate}, c->time_base);
376         ost->samples_count += dst_nb_samples;
377     }
378 
379     return write_frame(oc, c, ost->st, frame);
380 }
381 
382 /**************************************************************/
383 /* video output */
384 
alloc_picture(enum AVPixelFormat pix_fmt,int width,int height)385 static AVFrame *alloc_picture(enum AVPixelFormat pix_fmt, int width, int height)
386 {
387     AVFrame *picture;
388     int ret;
389 
390     picture = av_frame_alloc();
391     if (!picture)
392         return NULL;
393 
394     picture->format = pix_fmt;
395     picture->width  = width;
396     picture->height = height;
397 
398     /* allocate the buffers for the frame data */
399     ret = av_frame_get_buffer(picture, 0);
400     if (ret < 0) {
401         fprintf(stderr, "Could not allocate frame data.\n");
402         exit(1);
403     }
404 
405     return picture;
406 }
407 
open_video(AVFormatContext * oc,AVCodec * codec,OutputStream * ost,AVDictionary * opt_arg)408 static void open_video(AVFormatContext *oc, AVCodec *codec, OutputStream *ost, AVDictionary *opt_arg)
409 {
410     int ret;
411     AVCodecContext *c = ost->enc;
412     AVDictionary *opt = NULL;
413 
414     av_dict_copy(&opt, opt_arg, 0);
415 
416     /* open the codec */
417     ret = avcodec_open2(c, codec, &opt);
418     av_dict_free(&opt);
419     if (ret < 0) {
420         fprintf(stderr, "Could not open video codec: %s\n", av_err2str(ret));
421         exit(1);
422     }
423 
424     /* allocate and init a re-usable frame */
425     ost->frame = alloc_picture(c->pix_fmt, c->width, c->height);
426     if (!ost->frame) {
427         fprintf(stderr, "Could not allocate video frame\n");
428         exit(1);
429     }
430 
431     /* If the output format is not YUV420P, then a temporary YUV420P
432      * picture is needed too. It is then converted to the required
433      * output format. */
434     ost->tmp_frame = NULL;
435     if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
436         ost->tmp_frame = alloc_picture(AV_PIX_FMT_YUV420P, c->width, c->height);
437         if (!ost->tmp_frame) {
438             fprintf(stderr, "Could not allocate temporary picture\n");
439             exit(1);
440         }
441     }
442 
443     /* copy the stream parameters to the muxer */
444     ret = avcodec_parameters_from_context(ost->st->codecpar, c);
445     if (ret < 0) {
446         fprintf(stderr, "Could not copy the stream parameters\n");
447         exit(1);
448     }
449 }
450 
451 /* Prepare a dummy image. */
fill_yuv_image(AVFrame * pict,int frame_index,int width,int height)452 static void fill_yuv_image(AVFrame *pict, int frame_index,
453                            int width, int height)
454 {
455     int x, y, i;
456 
457     i = frame_index;
458 
459     /* Y */
460     for (y = 0; y < height; y++)
461         for (x = 0; x < width; x++)
462             pict->data[0][y * pict->linesize[0] + x] = x + y + i * 3;
463 
464     /* Cb and Cr */
465     for (y = 0; y < height / 2; y++) {
466         for (x = 0; x < width / 2; x++) {
467             pict->data[1][y * pict->linesize[1] + x] = 128 + y + i * 2;
468             pict->data[2][y * pict->linesize[2] + x] = 64 + x + i * 5;
469         }
470     }
471 }
472 
get_video_frame(OutputStream * ost)473 static AVFrame *get_video_frame(OutputStream *ost)
474 {
475     AVCodecContext *c = ost->enc;
476 
477     /* check if we want to generate more frames */
478     if (av_compare_ts(ost->next_pts, c->time_base,
479                       STREAM_DURATION, (AVRational){ 1, 1 }) > 0)
480         return NULL;
481 
482     /* when we pass a frame to the encoder, it may keep a reference to it
483      * internally; make sure we do not overwrite it here */
484     if (av_frame_make_writable(ost->frame) < 0)
485         exit(1);
486 
487     if (c->pix_fmt != AV_PIX_FMT_YUV420P) {
488         /* as we only generate a YUV420P picture, we must convert it
489          * to the codec pixel format if needed */
490         if (!ost->sws_ctx) {
491             ost->sws_ctx = sws_getContext(c->width, c->height,
492                                           AV_PIX_FMT_YUV420P,
493                                           c->width, c->height,
494                                           c->pix_fmt,
495                                           SCALE_FLAGS, NULL, NULL, NULL);
496             if (!ost->sws_ctx) {
497                 fprintf(stderr,
498                         "Could not initialize the conversion context\n");
499                 exit(1);
500             }
501         }
502         fill_yuv_image(ost->tmp_frame, ost->next_pts, c->width, c->height);
503         sws_scale(ost->sws_ctx, (const uint8_t * const *) ost->tmp_frame->data,
504                   ost->tmp_frame->linesize, 0, c->height, ost->frame->data,
505                   ost->frame->linesize);
506     } else {
507         fill_yuv_image(ost->frame, ost->next_pts, c->width, c->height);
508     }
509 
510     ost->frame->pts = ost->next_pts++;
511 
512     return ost->frame;
513 }
514 
515 /*
516  * encode one video frame and send it to the muxer
517  * return 1 when encoding is finished, 0 otherwise
518  */
write_video_frame(AVFormatContext * oc,OutputStream * ost)519 static int write_video_frame(AVFormatContext *oc, OutputStream *ost)
520 {
521     return write_frame(oc, ost->enc, ost->st, get_video_frame(ost));
522 }
523 
close_stream(AVFormatContext * oc,OutputStream * ost)524 static void close_stream(AVFormatContext *oc, OutputStream *ost)
525 {
526     avcodec_free_context(&ost->enc);
527     av_frame_free(&ost->frame);
528     av_frame_free(&ost->tmp_frame);
529     sws_freeContext(ost->sws_ctx);
530     swr_free(&ost->swr_ctx);
531 }
532 
533 /**************************************************************/
534 /* media file output */
535 
main(int argc,char ** argv)536 int main(int argc, char **argv)
537 {
538     OutputStream video_st = { 0 }, audio_st = { 0 };
539     const char *filename;
540     AVOutputFormat *fmt;
541     AVFormatContext *oc;
542     AVCodec *audio_codec, *video_codec;
543     int ret;
544     int have_video = 0, have_audio = 0;
545     int encode_video = 0, encode_audio = 0;
546     AVDictionary *opt = NULL;
547     int i;
548 
549     if (argc < 2) {
550         printf("usage: %s output_file\n"
551                "API example program to output a media file with libavformat.\n"
552                "This program generates a synthetic audio and video stream, encodes and\n"
553                "muxes them into a file named output_file.\n"
554                "The output format is automatically guessed according to the file extension.\n"
555                "Raw images can also be output by using '%%d' in the filename.\n"
556                "\n", argv[0]);
557         return 1;
558     }
559 
560     filename = argv[1];
561     for (i = 2; i+1 < argc; i+=2) {
562         if (!strcmp(argv[i], "-flags") || !strcmp(argv[i], "-fflags"))
563             av_dict_set(&opt, argv[i]+1, argv[i+1], 0);
564     }
565 
566     /* allocate the output media context */
567     avformat_alloc_output_context2(&oc, NULL, NULL, filename);
568     if (!oc) {
569         printf("Could not deduce output format from file extension: using MPEG.\n");
570         avformat_alloc_output_context2(&oc, NULL, "mpeg", filename);
571     }
572     if (!oc)
573         return 1;
574 
575     fmt = oc->oformat;
576 
577     /* Add the audio and video streams using the default format codecs
578      * and initialize the codecs. */
579     if (fmt->video_codec != AV_CODEC_ID_NONE) {
580         add_stream(&video_st, oc, &video_codec, fmt->video_codec);
581         have_video = 1;
582         encode_video = 1;
583     }
584     if (fmt->audio_codec != AV_CODEC_ID_NONE) {
585         add_stream(&audio_st, oc, &audio_codec, fmt->audio_codec);
586         have_audio = 1;
587         encode_audio = 1;
588     }
589 
590     /* Now that all the parameters are set, we can open the audio and
591      * video codecs and allocate the necessary encode buffers. */
592     if (have_video)
593         open_video(oc, video_codec, &video_st, opt);
594 
595     if (have_audio)
596         open_audio(oc, audio_codec, &audio_st, opt);
597 
598     av_dump_format(oc, 0, filename, 1);
599 
600     /* open the output file, if needed */
601     if (!(fmt->flags & AVFMT_NOFILE)) {
602         ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);
603         if (ret < 0) {
604             fprintf(stderr, "Could not open '%s': %s\n", filename,
605                     av_err2str(ret));
606             return 1;
607         }
608     }
609 
610     /* Write the stream header, if any. */
611     ret = avformat_write_header(oc, &opt);
612     if (ret < 0) {
613         fprintf(stderr, "Error occurred when opening output file: %s\n",
614                 av_err2str(ret));
615         return 1;
616     }
617 
618     while (encode_video || encode_audio) {
619         /* select the stream to encode */
620         if (encode_video &&
621             (!encode_audio || av_compare_ts(video_st.next_pts, video_st.enc->time_base,
622                                             audio_st.next_pts, audio_st.enc->time_base) <= 0)) {
623             encode_video = !write_video_frame(oc, &video_st);
624         } else {
625             encode_audio = !write_audio_frame(oc, &audio_st);
626         }
627     }
628 
629     /* Write the trailer, if any. The trailer must be written before you
630      * close the CodecContexts open when you wrote the header; otherwise
631      * av_write_trailer() may try to use memory that was freed on
632      * av_codec_close(). */
633     av_write_trailer(oc);
634 
635     /* Close each codec. */
636     if (have_video)
637         close_stream(oc, &video_st);
638     if (have_audio)
639         close_stream(oc, &audio_st);
640 
641     if (!(fmt->flags & AVFMT_NOFILE))
642         /* Close the output file. */
643         avio_closep(&oc->pb);
644 
645     /* free the stream */
646     avformat_free_context(oc);
647 
648     return 0;
649 }
650