libavcodec/vp3.c:849: error: Uninitialized Value
  The value read from motion_x[_] was never initialized.

libavcodec/vp3.c:849:29: 
847.                         frag = BLOCK_Y * s->fragment_width[1] + BLOCK_X;
848.                         if (s->macroblock_coding[current_macroblock] == MODE_INTER_FOURMV) {
849.                             s->motion_val[1][frag][0] = motion_x[k];
                                 ^
850.                             s->motion_val[1][frag][1] = motion_y[k];
851.                         } else {
