/* Pullback MV (couldn't find it in the spec, see vc1crop.c in refdec) */
    if (v->fcm == 1) {  // not sure if needed for other types of picture
        int qx, qy;
        int width = s->avctx->coded_width;
        int height = s->avctx->coded_height >> 1;
        qx = (s->mb_x * 16) + (mx >> 2);
        qy = (s->mb_y *  8) + (my >> 3);
        av_log(s->avctx, AV_LOG_DEBUG, "qx = %d, qy = %d\n", qx, qy);

        if (qx < -17)
            mx -= 4 * (qx + 17);
        else if (qx > width)
            mx -= 4 * (qx - width);
        if (qy < -18)
            my -= 8 * (qy + 18);
        else if (qy > height + 1)
            my -= 8 * (qy - height - 1);
        av_log(s->avctx, AV_LOG_DEBUG, "Luma MV Post-Pullback: mx = %d, my = %d\n", mx, my);
    }