libavcodec/vc1_pred.c:669: error: Uninitialized Value
  The value read from px was never initialized.

libavcodec/vc1_pred.c:669:24: 
667. 
668.     /* store MV using signed modulus of MV range defined in 4.11 */
669.     s->mv[dir][n][0] = s->current_picture.motion_val[dir][xy][0] = ((px + dmv_x + r_x) & ((r_x << 1) - 1)) - r_x;
                            ^
670.     s->mv[dir][n][1] = s->current_picture.motion_val[dir][xy][1] = ((py + dmv_y + r_y) & ((r_y << 1) - 1)) - r_y;
671.     if (mvn == 1) { /* duplicate motion data for 1-MV block */
