[FFmpeg-cvslog] avcodec/vorbisdec: Dont treat overread as error

[Michael Niedermayer]

ffmpeg | branch: release/4.2 | Michael Niedermayer <michael at niedermayer.cc> | Sun Apr  6 16:49:31 2025 +0200| [fef450f3c5a22b3a2d91c73a7489fd3a2afaa9c7] | committer: Michael Niedermayer

avcodec/vorbisdec: Dont treat overread as error

This differs from libvorbis by
stddev:    2.44 PSNR: 88.58 MAXDIFF:   41 bytes:   834304/   834304
for the file from the ticket

Fixes: Ticket11427

Regression since: dc89cf804a811c0d25f4649a99f7fab4b5b416fa

This is a similar solution to what james proposed earlier in
[FFmpeg-devel] [PATCH] avcodec/vorbisdec: don't abort on EOD when decoding residuals

Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit fd5a3c5fed2c190446b2beb9bc532887db360cf7)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=fef450f3c5a22b3a2d91c73a7489fd3a2afaa9c7
---

 libavcodec/vorbisdec.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/libavcodec/vorbisdec.c b/libavcodec/vorbisdec.c
index 9a60ed4770..006b9e332b 100644
--- a/libavcodec/vorbisdec.c
+++ b/libavcodec/vorbisdec.c
@@ -1451,8 +1451,10 @@ static av_always_inline int vorbis_residue_decode_internal(vorbis_context *vc,
                             unsigned step = FASTDIV(vr->partition_size << 1, dim << 1);
                             vorbis_codebook codebook = vc->codebooks[vqbook];
 
-                            if (get_bits_left(gb) <= 0)
-                                return AVERROR_INVALIDDATA;
+                            if (get_bits_left(gb) < 0) {
+                                av_log(vc->avctx, AV_LOG_ERROR, "Overread %d bits\n", -get_bits_left(gb));
+                                return 0;
+                            }
 
                             if (vr_type == 0) {