libavcodec/h264_direct.c:388: error: Uninitialized Value
  The value read from mv[_] was never initialized.

libavcodec/h264_direct.c:388:17: 
386.             a = b = 0;
387.             if (ref[0] > 0)
388.                 a = mv[0];
                     ^
389.             if (ref[1] > 0)
390.                 b = mv[1];
