libavcodec/vc1.c:657: error: Uninitialized Value
  The value read from mvx[_] was never initialized.

libavcodec/vc1.c:657:18: 
655.             break;
656.         case 0x2:
657.             tx = mid_pred(mvx[0], mvx[2], mvx[3]);
                      ^
658.             ty = mid_pred(mvy[0], mvy[2], mvy[3]);
659.             break;
