1649515 - 60fps YouTube videos on macOS are dropping frames (WebRender, VP9, Intel GPU)

Status: RESOLVED FIXED

(Core :: Audio/Video: Playback, defect)

Description

[Markus Stange [:mstange]]

In Firefox on macOS, 60fps videos drop multiple frames every second. This causes noticeable stutters. I'm getting around 52 to 56 fps rather than the 60fps that are theoretically possible.

Here's a profile: https://share.firefox.dev/3eL7Zw0
It's a profile of playing this 60fps YouTube video in full screen: https://www.youtube.com/watch?v=oakWgLqCwUc

I have a 60fps screen, so the only way to play this video without frame skips is to have a composite at every vsync, with every composite presenting a different frame of the video.

However, you can see that there are many vsyncs where we "skip" a composite, because generateFrame is false. This causes frame skips. Moreover, these frame skips aren't even counted (bug 1578042).

Comment 1

[Alastor Wu [:alwu]]

Hi, Markus,
Does bug1649859 help with this issue? You said the skipping happens because generateFrame [1] is false, so is it a graphic issue?
It's not clear to me what the relationship is between media playback and generateFrame.
Thank you.

[1] https://searchfox.org/mozilla-central/rev/5a4aaccb28665807a6fd49cf48367d47fbb5a19a/gfx/layers/wr/WebRenderBridgeParent.cpp#2035-2036

Comment 2

[Markus Stange [:mstange]]

(In reply to Alastor Wu [:alwu] from comment #1)

Hi, Markus,
Does bug1649859 help with this issue?

Yes, bug 1649859 helps a lot. There's still room for improvement, though, and I'll file bugs for the remaining issues.

Comment 3

[Markus Stange [:mstange]]

All the bugs in the dependency list are now fixed! On my machine, 60fps videos are rock solid now. They play for many minutes without a single frame drop.

Release Note Request (optional, but appreciated)
[Why is this notable]: noticeable smoothness improvement
[Affects Firefox for Android]: no
[Suggested wording]: macOS: Smoother video playback and improved AV sync of 60 fps videos.
[Links (documentation, blog post, etc)]: none