[FFmpeg-cvslog] vc1dec: prevent a crash due missing pred_flag parameter

[Vladimir Pantelic]

ffmpeg | branch: release/1.1 | Vladimir Pantelic <vladoman at gmail.com> | Wed Jan  9 17:04:09 2013 +0100| [58baa367d696f206709a5eb195bbc514467ac82a] | committer: Luca Barbato

vc1dec: prevent a crash due missing pred_flag parameter

Handle pred_flag parameter not given to get_mvdata_interlaced()

Signed-off-by: Vladimir Pantelic <vladoman at gmail.com>
Signed-off-by: Luca Barbato <lu_zero at gentoo.org>
(cherry picked from commit 7b8c5b263bc680eff5710bee5994de39d47fc15e)

Signed-off-by: Luca Barbato <lu_zero at gentoo.org>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=58baa367d696f206709a5eb195bbc514467ac82a
---

 libavcodec/vc1dec.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index d5d6884..c29f91c 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -1133,8 +1133,12 @@ static av_always_inline void get_mvdata_interlaced(VC1Context *v, int *dmv_x,
         *dmv_x = get_bits(gb, v->k_x);
         *dmv_y = get_bits(gb, v->k_y);
         if (v->numref) {
-            *pred_flag = *dmv_y & 1;
-            *dmv_y     = (*dmv_y + *pred_flag) >> 1;
+            if (pred_flag) {
+                *pred_flag = *dmv_y & 1;
+                *dmv_y     = (*dmv_y + *pred_flag) >> 1;
+            } else {
+                *dmv_y     = (*dmv_y + (*dmv_y & 1)) >> 1;
+            }
         }
     }
     else {
@@ -1160,7 +1164,7 @@ static av_always_inline void get_mvdata_interlaced(VC1Context *v, int *dmv_x,
             *dmv_y = (sign ^ ((val >> 1) + offs_tab[index1 >> v->numref])) - sign;
         } else
             *dmv_y = 0;
-        if (v->numref)
+        if (v->numref && pred_flag)
             *pred_flag = index1 & 1;
     }
 }