Bug 213107 – timestampOffset doesn't subtract presentationTimestamp from m_groupStartTimestamp

• Status: RESOLVED
• Resolution: CONFIGURATION CHANGED
• Component: Media

[Yuki Sekiguchi]

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.

[Radar WebKit Bug Importer]

<rdar://problem/96304755>

[Ahmad Saleem]

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

[Yuki Sekiguchi]

Thank you for the information!