Closed Bug 1649515 Opened 4 years ago Closed 4 years ago

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


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




81 Branch
Tracking Status
relnote-firefox --- 81+
firefox-esr68 --- wontfix
firefox-esr78 --- wontfix
firefox78 --- wontfix
firefox79 --- wontfix
firefox80 --- wontfix
firefox81 --- fixed


(Reporter: mstange, Assigned: 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:
It's a profile of playing this 60fps YouTube video in full screen:

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).

Depends on: 1649859

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.


Severity: -- → S3
Flags: needinfo?(mstange.moz)
Depends on: 1653355

(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.

Flags: needinfo?(mstange.moz)
Depends on: 1654091
See Also: → 1655221

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

Assignee: nobody → mstange.moz
Closed: 4 years ago
relnote-firefox: --- → ?
Resolution: --- → FIXED
Target Milestone: --- → 81 Branch
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