libavcodec/vp3.c:751: error: Uninitialized Value
  The value read from motion_y[_] was never initialized.

libavcodec/vp3.c:751:35: 
749.                 if (s->macroblock_coding[current_macroblock] == MODE_INTER_FOURMV) {
750.                     motion_x[0] = RSHIFT(motion_x[0] + motion_x[1] + motion_x[2] + motion_x[3], 2);
751.                     motion_y[0] = RSHIFT(motion_y[0] + motion_y[1] + motion_y[2] + motion_y[3], 2);
                                       ^
752.                 }
753.                 motion_x[0] = (motion_x[0]>>1) | (motion_x[0]&1);
