libavcodec/vc1.c:666: error: Uninitialized Value
  The value read from mvy[_] was never initialized.

libavcodec/vc1.c:666:18: 
664.         case 0x8:
665.             tx = mid_pred(mvx[0], mvx[1], mvx[2]);
666.             ty = mid_pred(mvy[0], mvy[1], mvy[2]);
                      ^
667.             break;
668.         }
