ast->codec->channels = 1;
ast->codec->bits_per_coded_sample = 8;
ast->codec->bit_rate = ast->codec->sample_rate * 8;
avpriv_set_pts_info(vst, 64, msecs_per_frame, 1000000);
vst->codec->codec_type = AVMEDIA_TYPE_VIDEO;
ast->codec->channels = 1;
ast->codec->bits_per_coded_sample = 8;
ast->codec->bit_rate = ast->codec->sample_rate * 8;
avpriv_set_pts_info(vst, 64, msecs_per_frame, 1000000);
vst->codec->codec_type = AVMEDIA_TYPE_VIDEO;