st->cur_dts = AV_NOPTS_VALUE;
AVStream *av_new_stream(AVFormatContext *s, int id){    AVStream *st;    if (s->nb_streams >= MAX_STREAMS)        return NULL;    st = av_mallocz(sizeof(AVStream));    if (!st)        return NULL;    avcodec_get_context_defaults(&st->codec);    if (s->iformat) {        /* no default bitrate if decoding */        st->codec.bit_rate = 0;    }    st->index = s->nb_streams;    st->id = id;    st->start_time = AV_NOPTS_VALUE;    st->duration = AV_NOPTS_VALUE;    /* default pts settings is MPEG like */    av_set_pts_info(st, 33, 1, 90000);    st->last_IP_pts = AV_NOPTS_VALUE;    s->streams[s->nb_streams++] = st;    return st;}