libavcodec/vp8dsp.c:165: error: Uninitialized Value
  The value read from p0 was never initialized.

libavcodec/vp8dsp.c:165:5: 
163.     const uint8_t *cm = ff_crop_tab + MAX_NEG_CROP;
164. 
165.     a = 3*(q0 - p0);
         ^
166. 
167.     if (is4tap)
