[FFmpeg-cvslog] avformat/matroskadec: Fix VfW extradata size

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at outlook.com> | Sun May 25 05:12:05 2025 +0200| [92e310eb82e04713e55d248b65c22f0eb95afada] | committer: Andreas Rheinhardt

avformat/matroskadec: Fix VfW extradata size

The structure is padded to an even length with an internal
size field to indicate the real size.
The matroska-matroska-display-metadata test (writing FFV1
in VFW mode) was affected by this.
It should also fix ticket #11613.

Reviewed-by: compn <ff at hawaiiantel.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=92e310eb82e04713e55d248b65c22f0eb95afada
---

 libavformat/matroskadec.c                          | 5 +++++
 tests/ref/fate/matroska-mastering-display-metadata | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index 2750652c51..da5166319e 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -2877,6 +2877,11 @@ static int mkv_parse_video_codec(MatroskaTrack *track, AVCodecParameters *par,
 {
     if (!strcmp(track->codec_id, "V_MS/VFW/FOURCC") &&
         track->codec_priv.size >= 40) {
+        uint32_t size = AV_RL32A(track->codec_priv.data);
+        // VFW extradata is padded to an even length, yet
+        // the size field contains the real length.
+        if (size & 1 && size == track->codec_priv.size - 1)
+            --track->codec_priv.size;
         track->ms_compat    = 1;
         par->bits_per_coded_sample = AV_RL16(track->codec_priv.data + 14);
         par->codec_tag      = AV_RL32(track->codec_priv.data + 16);
diff --git a/tests/ref/fate/matroska-mastering-display-metadata b/tests/ref/fate/matroska-mastering-display-metadata
index 6a2ff15b1b..5984f54131 100644
--- a/tests/ref/fate/matroska-mastering-display-metadata
+++ b/tests/ref/fate/matroska-mastering-display-metadata
@@ -1,7 +1,7 @@
 c1e5e2ecf433cf05af8556debc7d4d0b *tests/data/fate/matroska-mastering-display-metadata.matroska
 1669773 tests/data/fate/matroska-mastering-display-metadata.matroska
 #extradata 0:        4, 0x040901a3
-#extradata 3:      202, 0xfce96279
+#extradata 3:      201, 0x9a706279
 #tb 0: 1/1000
 #media_type 0: video
 #codec_id 0: prores