[webkit-changes] [WebKit/WebKit] c6dd1f: [MSE][GStreamer] Avoid unneeded timechanged notifi...

[Enrique Ocaña González]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: c6dd1fbfea75773bdffbf034e532930577168acd
      https://github.com/WebKit/WebKit/commit/c6dd1fbfea75773bdffbf034e532930577168acd
  Author: Enrique Ocaña González <eocanha at igalia.com>
  Date:   2023-04-17 (Mon, 17 Apr 2023)

  Changed paths:
    M Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp

  Log Message:
  -----------
  [MSE][GStreamer] Avoid unneeded timechanged notifications
https://bugs.webkit.org/show_bug.cgi?id=255452

Reviewed by Philippe Normand.

The YouTube MSE Conformance Tests 2021[1][2] added a check to ensure that the initial warm up time
of the player is less than 500 ms in accuracy tests. While these tests pass on a fast desktop
computer, they fail on a lower end device (eg: Raspberry Pi 3). This is because there's a first
timeupdate event triggered as soon as the appended init segment is processed, but the processing
time of the next appended data segment takes too much time, so when playback actually starts, the
next timeupdate event comes later than 500ms from the first one, causing the test to fail on slow
platforms.

Since the default time of the video element should be 0 from the begining and the time reported by
that initial timeupdate is actually 0 (no change), that initial timeupdate event is redundant (and
wasn't happening before the WebKitMediaSrc rework[3]).

This patch honors the original source code comment, which states that the timeupdate notification
makes sense when currentTime has reached the duration, avoiding the notification in other cases,
at least when still waiting for an initial preroll.

[1] https://ytlr-cert.appspot.com/2021/main.html?tests=35,36,37,38&command=run
[2] https://ytlr-cert.appspot.com/2021/media/conformanceTest.js, line 886 (best displayed as https://pastebin.com/fPx1EW22)
[3] https://github.com/WebKit/WebKit/commit/9382c6ef1a5b64d1701c691c63fe84de22cf932b

* Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp:
(WebCore::MediaPlayerPrivateGStreamerMSE::propagateReadyStateToPlayer): Don't notify timeupdate before prerolling unless currentTime has reached the duration.

Canonical link: https://commits.webkit.org/263019@main