[FFmpeg-cvslog] avcodec/av1: Add upper bound for the size of a sane sequence header

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at outlook.com> | Fri Jun 17 01:54:22 2022 +0200| [a367e435d816dfe6939ab9932e87c089fb1f3f73] | committer: Andreas Rheinhardt

avcodec/av1: Add upper bound for the size of a sane sequence header

It will be used by the Matroska muxer to reserve a certain number
of bytes for the CodecPrivate in case no extradata is initially
available (as it is for the libaom-av1 encoder).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a367e435d816dfe6939ab9932e87c089fb1f3f73
---

 libavcodec/av1.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libavcodec/av1.h b/libavcodec/av1.h
index 951a18ecb2..384f7cddc7 100644
--- a/libavcodec/av1.h
+++ b/libavcodec/av1.h
@@ -175,4 +175,10 @@ enum {
     AV1_RESTORE_SWITCHABLE = 3,
 };
 
+// Sequence Headers are actually unbounded because one can use
+// an arbitrary number of leading zeroes when encoding via uvlc.
+// The following estimate is based around using the lowest number
+// of bits for uvlc encoding.
+#define AV1_SANE_SEQUENCE_HEADER_MAX_BITS           3138
+
 #endif /* AVCODEC_AV1_H */