beenull/ladybird
1
0
Fork 0
mirror of https://github.com/LadybirdBrowser/ladybird.git synced 2024-09-29 16:21:29 +00:00
Code Issues Actions 5 Packages Projects Releases Wiki Activity

LibMedia/Matroska: Handle negative timestamp offsets correctly

Browse source 
The timestamp offset of a block was being converted from i16 to u64, so
negative values would overflow and cause timestamps that fall before
the cluster's timestamp from being close to the minimum representable
i64.

The math is also now done using saturating operations to prevent any
other similar issues from occurring.
This commit is contained in:
Zaggy1024 2024-06-19 22:03:07 -05:00 committed by Andrew Kaster
parent bbd8a218a5
commit ef99e701b7
Notes: sideshowbarker 2024-07-17 01:23:08 +09:00 
Author: https://github.com/Zaggy1024
Commit: https://github.com/LadybirdBrowser/ladybird/commit/ef99e701b7
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/230
Reviewed-by: https://github.com/ADKaster
1 changed files with 6 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

9
Userland/Libraries/LibMedia/Containers/Matroska/Reader.cpp
View file

@ -7,6 +7,7 @@
#include <AK/Debug.h>
#include <AK/Function.h>
#include <AK/Math.h>
#include <AK/Optional.h>
#include <AK/Time.h>
#include <AK/Utf8View.h>
@ -616,11 +617,13 @@ static DecoderErrorOr<Block> parse_simple_block(Streamer& streamer, Duration clu
// of that track. To get the timestamp in nanoseconds of the first frame in a Block or
// SimpleBlock, the formula becomes:
// `( ( Cluster\Timestamp + ( block timestamp * TrackTimestampScale ) ) * TimestampScale ) - CodecDelay`
Duration timestamp_offset = Duration::from_nanoseconds(static_cast<i64>(static_cast<double>(TRY_READ(streamer.read_i16()) * segment_timestamp_scale) * track.timestamp_scale()));
timestamp_offset -= Duration::from_nanoseconds(static_cast<i64>(track.codec_delay()));
auto raw_timestamp_offset = TRY_READ(streamer.read_i16());
Checked<i64> timestamp_offset_ns = AK::clamp_to<i64>(static_cast<double>(raw_timestamp_offset * AK::clamp_to<i64>(segment_timestamp_scale)) * track.timestamp_scale());
timestamp_offset_ns.saturating_sub(AK::clamp_to<i64>(track.codec_delay()));
// This is only mentioned in the elements specification under TrackOffset.
// https://www.matroska.org/technical/elements.html
timestamp_offset += Duration::from_nanoseconds(static_cast<i64>(track.timestamp_offset()));
timestamp_offset_ns.saturating_add(AK::clamp_to<i64>(track.timestamp_offset()));
Duration timestamp_offset = Duration::from_nanoseconds(timestamp_offset_ns.value());
block.set_timestamp(cluster_timestamp + timestamp_offset);
auto flags = TRY_READ(streamer.read_octet());