libavcodec/vc1dec.c:5589: error: Uninitialized Value
  The value read from n_slices1 was never initialized.

libavcodec/vc1dec.c:5589:38: 
5587.             if (i) {
5588.                 v->pic_header_flag = 0;
5589.                 if (v->field_mode && i == n_slices1 + 2)
                                           ^
5590.                     vc1_parse_frame_header_adv(v, &s->gb);
5591.                 else if (get_bits1(&s->gb)) {
