libavcodec/vc1dec.c:5604: error: Uninitialized Value
  The value read from n_slices1 was never initialized.

libavcodec/vc1dec.c:5604:32: 
5602.                 s->end_mb_y = (i == n_slices     ) ? mb_height : FFMIN(mb_height, slices[i].mby_start % mb_height);
5603.             else
5604.                 s->end_mb_y = (i <= n_slices1 + 1) ? mb_height : FFMIN(mb_height, slices[i].mby_start % mb_height);
                                     ^
5605.             ff_vc1_decode_blocks(v);
5606.             if (i != n_slices)
