[FFmpeg-devel] [PATCH] avcodec/cbs_h264_syntax_template: fix off by 1 error with slice_group_change_cycle

[Michael Niedermayer]

Fixes: assertion failure
Fixes: 20390/clusterfuzz-testcase-minimized-ffmpeg_BSF_H264_REDUNDANT_PPS_fuzzer-5683400772157440

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavcodec/cbs_h264_syntax_template.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/cbs_h264_syntax_template.c b/libavcodec/cbs_h264_syntax_template.c
index 878d348b94..b65460996b 100644
--- a/libavcodec/cbs_h264_syntax_template.c
+++ b/libavcodec/cbs_h264_syntax_template.c
@@ -1366,7 +1366,7 @@ static int FUNC(slice_header)(CodedBitstreamContext *ctx, RWContext *rw,
                    (sps->pic_height_in_map_units_minus1 + 1);
         max = (pic_size + pps->slice_group_change_rate_minus1) /
               (pps->slice_group_change_rate_minus1 + 1);
-        bits = av_log2(2 * max - 1);
+        bits = av_ceil_log2(max + 1);
 
         u(bits, slice_group_change_cycle, 0, max);
     }
-- 
2.17.1