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* Libavformat API example: Output a media file in any supported
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* libavformat format. The default codecs are used.
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* Copyright (c) 2003 Fabrice Bellard
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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#define M_PI 3.1415926535897931
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/* 5 seconds stream duration */
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#define STREAM_DURATION 5.0
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#define STREAM_FRAME_RATE 25 /* 25 images/s */
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#define STREAM_NB_FRAMES ((int)(STREAM_DURATION * STREAM_FRAME_RATE))
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/**************************************************************/
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float t, tincr, tincr2;
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uint8_t *audio_outbuf;
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int audio_outbuf_size;
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int audio_input_frame_size;
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* add an audio output stream
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AVStream *add_audio_stream(AVFormatContext *oc, int codec_id)
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st = av_new_stream(oc, 1);
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fprintf(stderr, "Could not alloc stream\n");
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c->codec_id = codec_id;
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c->codec_type = CODEC_TYPE_AUDIO;
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/* put sample parameters */
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c->sample_rate = 44100;
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void open_audio(AVFormatContext *oc, AVStream *st)
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/* find the audio encoder */
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codec = avcodec_find_encoder(c->codec_id);
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fprintf(stderr, "codec not found\n");
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if (avcodec_open(c, codec) < 0) {
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fprintf(stderr, "could not open codec\n");
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/* init signal generator */
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tincr = 2 * M_PI * 110.0 / c->sample_rate;
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/* increment frequency by 110 Hz per second */
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tincr2 = 2 * M_PI * 110.0 / c->sample_rate / c->sample_rate;
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audio_outbuf_size = 10000;
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audio_outbuf = malloc(audio_outbuf_size);
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/* ugly hack for PCM codecs (will be removed ASAP with new PCM
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support to compute the input frame size in samples */
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if (c->frame_size <= 1) {
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audio_input_frame_size = audio_outbuf_size / c->channels;
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switch(st->codec.codec_id) {
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case CODEC_ID_PCM_S16LE:
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case CODEC_ID_PCM_S16BE:
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case CODEC_ID_PCM_U16LE:
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case CODEC_ID_PCM_U16BE:
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audio_input_frame_size >>= 1;
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audio_input_frame_size = c->frame_size;
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samples = malloc(audio_input_frame_size * 2 * c->channels);
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/* prepare a 16 bit dummy audio frame of 'frame_size' samples and
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'nb_channels' channels */
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void get_audio_frame(int16_t *samples, int frame_size, int nb_channels)
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for(j=0;j<frame_size;j++) {
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v = (int)(sin(t) * 10000);
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for(i = 0; i < nb_channels; i++)
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void write_audio_frame(AVFormatContext *oc, AVStream *st)
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get_audio_frame(samples, audio_input_frame_size, c->channels);
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out_size = avcodec_encode_audio(c, audio_outbuf, audio_outbuf_size, samples);
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/* write the compressed frame in the media file */
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if (av_write_frame(oc, st->index, audio_outbuf, out_size) != 0) {
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fprintf(stderr, "Error while writing audio frame\n");
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void close_audio(AVFormatContext *oc, AVStream *st)
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avcodec_close(&st->codec);
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av_free(audio_outbuf);
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/**************************************************************/
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AVFrame *picture, *tmp_picture;
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uint8_t *video_outbuf;
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int frame_count, video_outbuf_size;
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/* add a video output stream */
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AVStream *add_video_stream(AVFormatContext *oc, int codec_id)
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st = av_new_stream(oc, 0);
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fprintf(stderr, "Could not alloc stream\n");
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c->codec_id = codec_id;
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c->codec_type = CODEC_TYPE_VIDEO;
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/* put sample parameters */
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c->bit_rate = 400000;
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/* resolution must be a multiple of two */
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/* frames per second */
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c->frame_rate = STREAM_FRAME_RATE;
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c->frame_rate_base = 1;
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c->gop_size = 12; /* emit one intra frame every twelve frames at most */
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if (c->codec_id == CODEC_ID_MPEG1VIDEO ||
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c->codec_id == CODEC_ID_MPEG2VIDEO) {
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/* just for testing, we also add B frames */
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AVFrame *alloc_picture(int pix_fmt, int width, int height)
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uint8_t *picture_buf;
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picture = avcodec_alloc_frame();
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size = avpicture_get_size(pix_fmt, width, height);
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picture_buf = malloc(size);
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avpicture_fill((AVPicture *)picture, picture_buf,
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pix_fmt, width, height);
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void open_video(AVFormatContext *oc, AVStream *st)
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/* find the video encoder */
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codec = avcodec_find_encoder(c->codec_id);
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fprintf(stderr, "codec not found\n");
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if (avcodec_open(c, codec) < 0) {
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fprintf(stderr, "could not open codec\n");
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if (!(oc->oformat->flags & AVFMT_RAWPICTURE)) {
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/* allocate output buffer */
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/* XXX: API change will be done */
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video_outbuf_size = 200000;
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video_outbuf = malloc(video_outbuf_size);
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/* allocate the encoded raw picture */
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picture = alloc_picture(c->pix_fmt, c->width, c->height);
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fprintf(stderr, "Could not allocate picture\n");
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/* if the output format is not YUV420P, then a temporary YUV420P
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picture is needed too. It is then converted to the required
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if (c->pix_fmt != PIX_FMT_YUV420P) {
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tmp_picture = alloc_picture(PIX_FMT_YUV420P, c->width, c->height);
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fprintf(stderr, "Could not allocate temporary picture\n");
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/* prepare a dummy image */
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void fill_yuv_image(AVFrame *pict, int frame_index, int width, int height)
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for(y=0;y<height;y++) {
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for(x=0;x<width;x++) {
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pict->data[0][y * pict->linesize[0] + x] = x + y + i * 3;
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for(y=0;y<height/2;y++) {
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for(x=0;x<width/2;x++) {
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pict->data[1][y * pict->linesize[1] + x] = 128 + y + i * 2;
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pict->data[2][y * pict->linesize[2] + x] = 64 + x + i * 5;
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void write_video_frame(AVFormatContext *oc, AVStream *st)
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AVFrame *picture_ptr;
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if (frame_count >= STREAM_NB_FRAMES) {
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/* no more frame to compress. The codec has a latency of a few
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frames if using B frames, so we get the last frames by
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passing a NULL picture */
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if (c->pix_fmt != PIX_FMT_YUV420P) {
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/* as we only generate a YUV420P picture, we must convert it
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to the codec pixel format if needed */
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fill_yuv_image(tmp_picture, frame_count, c->width, c->height);
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img_convert((AVPicture *)picture, c->pix_fmt,
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(AVPicture *)tmp_picture, PIX_FMT_YUV420P,
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c->width, c->height);
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fill_yuv_image(picture, frame_count, c->width, c->height);
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picture_ptr = picture;
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if (oc->oformat->flags & AVFMT_RAWPICTURE) {
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/* raw video case. The API will change slightly in the near
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ret = av_write_frame(oc, st->index,
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(uint8_t *)picture_ptr, sizeof(AVPicture));
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/* encode the image */
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out_size = avcodec_encode_video(c, video_outbuf, video_outbuf_size, picture_ptr);
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/* if zero size, it means the image was buffered */
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/* write the compressed frame in the media file */
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/* XXX: in case of B frames, the pts is not yet valid */
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ret = av_write_frame(oc, st->index, video_outbuf, out_size);
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fprintf(stderr, "Error while writing video frame\n");
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void close_video(AVFormatContext *oc, AVStream *st)
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avcodec_close(&st->codec);
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av_free(picture->data[0]);
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av_free(tmp_picture->data[0]);
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av_free(tmp_picture);
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av_free(video_outbuf);
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/**************************************************************/
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/* media file output */
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int main(int argc, char **argv)
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const char *filename;
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AVStream *audio_st, *video_st;
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double audio_pts, video_pts;
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/* initialize libavcodec, and register all codecs and formats */
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printf("usage: %s output_file\n"
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"API example program to output a media file with libavformat.\n"
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"The output format is automatically guessed according to the file extension.\n"
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"Raw images can also be output by using '%%d' in the filename\n"
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/* auto detect the output format from the name. default is
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fmt = guess_format(NULL, filename, NULL);
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printf("Could not deduce output format from file extension: using MPEG.\n");
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fmt = guess_format("mpeg", NULL, NULL);
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fprintf(stderr, "Could not find suitable output format\n");
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/* allocate the output media context */
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oc = av_mallocz(sizeof(AVFormatContext));
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fprintf(stderr, "Memory error\n");
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snprintf(oc->filename, sizeof(oc->filename), "%s", filename);
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/* add the audio and video streams using the default format codecs
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and initialize the codecs */
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if (fmt->video_codec != CODEC_ID_NONE) {
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video_st = add_video_stream(oc, fmt->video_codec);
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if (fmt->audio_codec != CODEC_ID_NONE) {
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audio_st = add_audio_stream(oc, fmt->audio_codec);
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/* set the output parameters (must be done even if no
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if (av_set_parameters(oc, NULL) < 0) {
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fprintf(stderr, "Invalid output format parameters\n");
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dump_format(oc, 0, filename, 1);
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/* now that all the parameters are set, we can open the audio and
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video codecs and allocate the necessary encode buffers */
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open_video(oc, video_st);
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open_audio(oc, audio_st);
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/* open the output file, if needed */
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if (!(fmt->flags & AVFMT_NOFILE)) {
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if (url_fopen(&oc->pb, filename, URL_WRONLY) < 0) {
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fprintf(stderr, "Could not open '%s'\n", filename);
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/* write the stream header, if any */
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/* compute current audio and video time */
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audio_pts = (double)audio_st->pts.val * oc->pts_num / oc->pts_den;
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video_pts = (double)video_st->pts.val * oc->pts_num / oc->pts_den;
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if ((!audio_st || audio_pts >= STREAM_DURATION) &&
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(!video_st || video_pts >= STREAM_DURATION))
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/* write interleaved audio and video frames */
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if (!video_st || (video_st && audio_st && audio_pts < video_pts)) {
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write_audio_frame(oc, audio_st);
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write_video_frame(oc, video_st);
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/* close each codec */
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close_video(oc, video_st);
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close_audio(oc, audio_st);
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/* write the trailer, if any */
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av_write_trailer(oc);
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/* free the streams */
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for(i = 0; i < oc->nb_streams; i++) {
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av_freep(&oc->streams[i]);
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if (!(fmt->flags & AVFMT_NOFILE)) {
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/* close the output file */
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/* free the stream */