[FFmpeg-devel] [PATCH 4/6] avcodec/av1: Add upper bound for the size of a sane sequence header

From: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
To: ffmpeg-devel@ffmpeg.org
Cc: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Subject: [FFmpeg-devel] [PATCH 4/6] avcodec/av1: Add upper bound for the size of a sane sequence header
Date: Tue, 21 Jun 2022 04:34:16 +0200
Message-ID: <DB6PR0101MB22143E20A60A1DED534E72728FB39@DB6PR0101MB2214.eurprd01.prod.exchangelabs.com> (raw)
In-Reply-To: <DB6PR0101MB2214886E62B7920390D6D89F8FB39@DB6PR0101MB2214.eurprd01.prod.exchangelabs.com>

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@outlook.com>
---
 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 */
-- 
2.34.1

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