[Webkit-unassigned] [Bug 260185] REGRESSION(262173 at main): media/media-source/media-source-fastseek.html is a flaky text failure

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Thu Aug 17 03:46:56 PDT 2023


--- Comment #5 from Jean-Yves Avenard [:jya] <jean-yves.avenard at apple.com> ---
fastSeek with MediaSource is broken as it is.

When performing an accurate seek, the flow is to call MediaSourcePrivate::waitForSeekCompleted() , seek and then MediaSourcePrivate::seekCompleted().

between the two `waitForSeekCompleted` and `seekCompleted` `MediaPlayerPrivate::seeking` will return false.

However, when doing a fast seek, we never call `MediaSourcePrivate::waitForSeekCompleted()` so `MediaPlayerPrivate::seeking` will return a stale value, which is typically the state of the previous seek and so typically `false`

In this particular test, when we perform a `fastSeek` , if the GPU Process sent an earlier `timeChanged` as `MediaPlayerPrivate::seeking` will return `false` and so we fire `seeked` event even before the GPU Process has completed the seek operation and had time to update the currentTime to the actual value.

I also note that in `void HTMLMediaElement::mediaPlayerTimeChanged()` we immediately call `updateActiveTextTrackCues(currentMediaTime());` but at this stage, currentMediaTime() returns the value of currentTime prior the seek operation. And as such it will set the TrackCues to the wrong time.

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