vc1dec: prevent v_edge_pos from becoming negative.

Fixes assertion failure Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
12 years ago · bde6f6eadc
parent b6a7f66f93
commit bde6f6eadc
1 changed files with 2 additions and 1 deletions
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@ -981,7 +981,8 @@ static void vc1_mc_4mv_chroma4(VC1Context *v)
        uvmy_field[i] = (uvmy_field[i] & 3) << 1;

        if (fieldmv && !(uvsrc_y & 1))
-            v_edge_pos--;
+            v_edge_pos = (s->v_edge_pos >> 1) - 1;
+
        if (fieldmv && (uvsrc_y & 1) && uvsrc_y < 2)
            uvsrc_y--;
        if ((v->mv_mode == MV_PMODE_INTENSITY_COMP)