[FFmpeg-cvslog] avcodec/vc1dec: Disable error concealment for *IMAGE

[Michael Niedermayer]

ffmpeg | branch: release/4.4 | Michael Niedermayer <michael at niedermayer.cc> | Sat Jul 31 00:01:53 2021 +0200| [674adf0a028bb795dd089ff0ce8d83aedde93f72] | committer: Michael Niedermayer

avcodec/vc1dec: Disable error concealment for *IMAGE

The existing error concealment makes no sense for the image formats, they
use transformed source images which is different from keyframe + MC+difference
for which the error concealment is designed.
Of course feel free to re-enable this if you have a case where it works and
improves vissual results

Fixes: Timeout
Fixes: 36234/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VC1IMAGE_fuzzer-6300306743885824

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 643b2d49bf52d5a3205ce3db732e0c4c396bd457)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=674adf0a028bb795dd089ff0ce8d83aedde93f72
---

 libavcodec/vc1dec.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index ea93e11588..d822240cff 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -1124,7 +1124,9 @@ static int vc1_decode_frame(AVCodecContext *avctx, void *data,
             ret = AVERROR_INVALIDDATA;
             goto err;
         }
-        if (!v->field_mode)
+        if (   !v->field_mode
+            && avctx->codec_id != AV_CODEC_ID_WMV3IMAGE
+            && avctx->codec_id != AV_CODEC_ID_VC1IMAGE)
             ff_er_frame_end(&s->er);
     }