st2->time_base.den * (int64_t)st ->time_base.num, st ->time_base.den * (int64_t)st2->time_base.num);
st->time_base.den * (int64_t)ref_st->time_base.num, st->time_base.num * (int64_t)ref_st->time_base.den);
static void av_update_cur_dts(AVFormatContext *s, AVStream *st, int64_t timestamp){    int i;    for(i = 0; i < s->nb_streams; i++) {        AVStream *st2 = s->streams[i];        st->cur_dts = av_rescale(timestamp,                                  st2->time_base.den * (int64_t)st ->time_base.num,                                 st ->time_base.den * (int64_t)st2->time_base.num);    }}