libavcodec/vc1dec.c:3679: error: Uninitialized Value
  The value read from is_coded[_] was never initialized.

libavcodec/vc1dec.c:3679:51: 
3677.                 v->mb_type[0][s->block_index[i]] = is_intra[i];
3678.                 if (!coded_inter)
3679.                     coded_inter = !is_intra[i] && is_coded[i];
                                                        ^
3680.             }
3681.             // if there are no coded blocks then don't do anything more
