av_reduce(&den, &num, den, num, (1UL<<31)-1);
avpriv_set_pts_info(st, 33, num, den);
/* flags & 0x80 means that image is interlaced,
av_reduce(&den, &num, den, num, (1UL<<31)-1);
avpriv_set_pts_info(st, 33, num, den);
/* flags & 0x80 means that image is interlaced,