h264_cavlc: check prefix before using it.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
13 years ago · 39f0a45a1a
parent 32e60b6bfe
commit 39f0a45a1a
1 changed files with 2 additions and 1 deletions
--- a/libavcodec/h264_cavlc.c
+++ b/libavcodec/h264_cavlc.c
@ -513,7 +513,7 @@ static int decode_residual(H264Context *h, GetBitContext *gb, DCTELEM *block, in
                else
                    level_code= prefix + get_bits(gb, 4); //part
            }else{
-                level_code= 30 + get_bits(gb, prefix-3); //part
+                level_code= 30;
                if(prefix>=16){
                    if(prefix > 25+3){
                        av_log(h->s.avctx, AV_LOG_ERROR, "Invalid level prefix\n");
@ -521,6 +521,7 @@ static int decode_residual(H264Context *h, GetBitContext *gb, DCTELEM *block, in
                    }
                    level_code += (1<<(prefix-3))-4096;
                }
+                level_code += get_bits(gb, prefix-3); //part
            }

            if(trailing_ones < 3) level_code += 2;