From 45838561f2f14339acdf53ffa3adbfe8e6db7514 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michaelni@gmx.at>
Date: Sat, 28 Jul 2012 18:07:45 +0600
Subject: [PATCH] vc1dec: Override invalid macroblock quantizer

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Kostya Shishkov <kostya.shishkov@gmail.com>
---
 libavcodec/vc1dec.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index fd515c754e..c6cbfc1270 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -1048,6 +1048,11 @@ static void vc1_mc_4mv_chroma4(VC1Context *v)
             mquant = v->altpq;                                 \
         if ((edges&8) && s->mb_y == (s->mb_height - 1))        \
             mquant = v->altpq;                                 \
+        if (!mquant || mquant > 31) {                          \
+            av_log(v->s.avctx, AV_LOG_ERROR,                   \
+                   "Overriding invalid mquant %d\n", mquant);  \
+            mquant = 1;                                        \
+        }                                                      \
     }
 
 /**