static AVStream *add_stream(AVFormatContext *oc, AVCodec **codec, enum AVCodecID codec_id) { AVCodecContext *c; AVStream *st; /* find the encoder */ *codec = avcodec_find_encoder(codec_id); if (!(*codec)) { fprintf(stderr, "Could not find encoder for '%s'\n", avcodec_get_name(codec_id)); exit(1); } st = avformat_new_stream(oc, *codec); if (!st) { fprintf(stderr, "Could not allocate stream\n"); exit(1); } st->id = oc->nb_streams-1; c = st->codec; switch ((*codec)->type) { case AVMEDIA_TYPE_AUDIO: st->id = 1; c->sample_fmt = AV_SAMPLE_FMT_S16; c->bit_rate = 64000; c->sample_rate = 44100; c->channels = 2; break; case AVMEDIA_TYPE_VIDEO: avcodec_get_context_defaults3(c, *codec); c->codec_id = codec_id; c->bit_rate = 400000; /* Resolution must be a multiple of two. */ c->width = 352; c->height = 288; /* timebase: This is the fundamental unit of time (in seconds) in terms * of which frame timestamps are represented. For fixed-fps content, * timebase should be 1/framerate and timestamp increments should be * identical to 1. */ c->time_base.den = STREAM_FRAME_RATE; c->time_base.num = 1; c->gop_size = 12; /* emit one intra frame every twelve frames at most */ c->pix_fmt = STREAM_PIX_FMT; if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) { /* just for testing, we also add B frames */ c->max_b_frames = 2; } if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) { /* Needed to avoid using macroblocks in which some coeffs overflow. * This does not happen with normal video, it just happens here as * the motion of the chroma plane does not match the luma plane. */ c->mb_decision = 2; } break; default: break; } /* Some formats want stream headers to be separate. */ if (oc->oformat->flags & AVFMT_GLOBALHEADER) c->flags |= CODEC_FLAG_GLOBAL_HEADER; return st; }