Bug 213107

Summary:	timestampOffset doesn't subtract presentationTimestamp from m_groupStartTimestamp
Product:	WebKit	Reporter:	Yuki Sekiguchi <yuki.sekiguchi>
Component:	Media	Assignee:	Nobody <webkit-unassigned>
Status:	RESOLVED CONFIGURATION CHANGED
Severity:	Normal	CC:	ahmad.saleem792, bfulgham, eric.carlson, jer.noble, webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	WebKit Nightly Build
Hardware:	Unspecified
OS:	Unspecified

Description Yuki Sekiguchi 2020-06-11 19:02:07 PDT

Media Source spec defines

https://www.w3.org/TR/media-source/#sourcebuffer-coded-frame-processing
> 1.3.1 Set timestampOffset equal to group start timestamp - presentation timestamp.

The comment matches to the spec, but the code is different from the spec and the comment
https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/Modules/mediasource/SourceBuffer.cpp?rev=%09262766#L1485
> 1485	            // 1.3.1 Set timestampOffset equal to group start timestamp - presentation timestamp.
> 1486	            m_timestampOffset = m_groupStartTimestamp;

I couldn't create a content which reproduce this bug. Sorry.

Comment 1 Radar WebKit Bug Importer 2022-07-01 11:25:57 PDT

<rdar://problem/96304755>

Comment 2 Ahmad Saleem 2023-03-22 13:42:47 PDT

It is now correct:

https://searchfox.org/wubkat/source/Source/WebCore/platform/graphics/SourceBufferPrivate.cpp#684

and Safari is passing all WPT tests as well:

https://wpt.fyi/results/media-source/mediasource-timestamp-offset.html?label=master&label=experimental&aligned=&view=subtest&q=timestamp+offset

Comment 3 Yuki Sekiguchi 2023-03-22 23:54:24 PDT

Thank you for the information!