wrap = s->block_wrap[0];
wrap = s->b8_stride;
static inline int coded_block_pred(MpegEncContext * s, int n, uint8_t **coded_block_ptr){    int xy, wrap, pred, a, b, c;    xy = s->block_index[n];    wrap = s->block_wrap[0];    /* B C     * A X      */    a = s->coded_block[xy - 1       ];    b = s->coded_block[xy - 1 - wrap];    c = s->coded_block[xy     - wrap];        if (b == c) {        pred = a;    } else {        pred = c;    }        /* store value */    *coded_block_ptr = &s->coded_block[xy];    return pred;}