Closed Bug 1649515 Opened 1 year ago Closed 1 year 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)


(Depends on 1 open bug)


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: 1 year ago
relnote-firefox: --- → ?
Resolution: --- → FIXED
Target Milestone: --- → 81 Branch
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