libavcodec/vp3.c:821: error: Uninitialized Value
  The value read from motion_x[_] was never initialized.

libavcodec/vp3.c:821:21: 
819.                                              motion_y[2] + motion_y[3], 2);
820.                     }
821.                     motion_x[0] = (motion_x[0] >> 1) | (motion_x[0] & 1);
                         ^
822.                     motion_y[0] = (motion_y[0] >> 1) | (motion_y[0] & 1);
823.                     frag = mb_y * s->fragment_width[1] + mb_x;
