libavcodec/motionpixels.c:271: error: Uninitialized Value
  The value read from p.u was never initialized.

libavcodec/motionpixels.c:271:17: 
269.             if ((y & 3) == 0) {
270.                 p.v += mp_gradient(mp, 1, mp_get_vlc(mp, gb));
271.                 p.u += mp_gradient(mp, 2, mp_get_vlc(mp, gb));
                     ^
272.             }
273.             mp->vpt[y] = p;
