avcodec/dxv: Subtract 12 earlier in dxv_decompress_cocg()

the data_start is after reading 12 bytes and if its subtracted
at the very end the intermediate might overflow

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/dxv.c b/libavcodec/dxv.c
index df63006d04cf63c744bacae8a8ce9931e976178f..b51d6393b040bd15197cd2bd04badeb3ca6220b8 100644 (file)
--- a/libavcodec/dxv.c
+++ b/libavcodec/dxv.c
@@ -783,7 +783,7 @@ static int dxv_decompress_cocg(DXVContext *ctx, GetByteContext *gb,
             return ret;
     }
 
-    bytestream2_seek(gb, data_start + op_offset + skip0 + skip1 - 12, SEEK_SET);
+    bytestream2_seek(gb, data_start - 12 + op_offset + skip0 + skip1, SEEK_SET);
 
     return 0;
 }