Merge commit '090cd063'

* commit '090cd063':
  vc1: check the source buffer in vc1_mc functions

Conflicts:
	libavcodec/vc1dec.c

See: 3a04c18dMerged-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/vc1dec.c

@@ -408,8 +408,10 @@ static void vc1_mc_1mv(VC1Context *v, int dir)
         use_ic = v->next_use_ic;
     }
 
-    if(!srcY)
+    if (!srcY || !srcU) {
+        av_log(v->s.avctx, AV_LOG_ERROR, "Referenced frame missing.\n");
         return;
+    }
 
     src_x   = s->mb_x * 16 + (mx   >> 2);
     src_y   = s->mb_y * 16 + (my   >> 2);
@@ -587,8 +589,10 @@ static void vc1_mc_4mv_luma(VC1Context *v, int n, int dir, int avg)
         use_ic = v->next_use_ic;
     }
 
-    if(!srcY)
+    if (!srcY) {
+        av_log(v->s.avctx, AV_LOG_ERROR, "Referenced frame missing.\n");
         return;
+    }
 
     if (v->field_mode) {
         if (v->cur_field_type != v->ref_field_type[dir])
@@ -888,8 +892,10 @@ static void vc1_mc_4mv_chroma(VC1Context *v, int dir)
         use_ic = v->next_use_ic;
     }
 
-    if(!srcU)
+    if (!srcU) {
+        av_log(v->s.avctx, AV_LOG_ERROR, "Referenced frame missing.\n");
         return;
+    }
 
     srcU += uvsrc_y * s->uvlinesize + uvsrc_x;
     srcV += uvsrc_y * s->uvlinesize + uvsrc_x;