libavcodec/motion_est.c:597: error: Uninitialized Value
  The value read from ymax was never initialized.

libavcodec/motion_est.c:597:22: 
595. 
596.     if (mx > xmin && mx < xmax &&
597.         my > ymin && my < ymax) {
                          ^
598.         int dx=0, dy=0;
599.         int d, pen_x, pen_y;
