/* Extract structure information about the picture described by pic_num in the current decoding context (frame or field). Note that pic_num is picture number without wrapping (so, 0<=pic_num<max_pic_num).  */
static int pic_num_extract(H264Context *h, int pic_num, int *structure)
/* Extract structure information about the picture described by pic_num in the current decoding context (frame or field). Note that pic_num is picture number without wrapping (so, 0<=pic_num<max_pic_num).  */
static int pic_num_extract(H264Context *h, int pic_num, int *structure)
{
        if (!(pic_num & 1))
            *structure ^= PICT_FRAME;
        pic_num >>= 1;
    }
    return pic_num;
}