1887639 - Video playback stutters when monitors are connected

Status: NEW

(Core :: Graphics, defect, P3)

Description

[m.perkovic]

User Agent: Mozilla/5.0 (X11; CrOS x86_64 10.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Steps to reproduce:

1. Connect two 4K monitors to the Macbook pro M1 pro
2. Open Firefox and play a video (like YouTube, Dropbox)
3. Don't move your mouse

Additional info:

• While the mouse pointer is moving, the playback runs smoothly
• It works perfectly with chrome
• if no monitors are connected, then it also works with Firefox
• tested without addons

Actual results:

Video playback stutters and does not run smoothly

Expected results:

The video playback should run smoothly

Comment 1

[m.perkovic]

I believe that it worked before Firefox version 124.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Audio/Video: Playback' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 3

[Karl Tomlinson (:karlt)]

Thanks for the report.
Is the playback better on any of the monitors?

Is the playback similar whether fullscreen or not?

Comment 4

[m.perkovic]

• The error does not occur on any monitor in full screen mode.

• The error does not occur at all on the integrated Macbook monitor. When I move the FF window to one of the two external monitors, it starts to stutter. Both external monitors feel the same FPS drop. (If I move the mouse pointer continuously over the Firefox window, it temporarily runs smoothly again)

Comment 5

[Karl Tomlinson (:karlt)]

Are you able to try setting the preference "gfx.core-animation.specialize-video" in about:config to false, please?

Comment 6

[m.perkovic]

With the recommended setting ("gfx.core-animation.specialize-video" -> "false"), the error no longer occurs.

Comment 7

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1839425

:bradwerth, since you are the author of the regressor, bug 1839425, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 8

[Brad Werth [:bradwerth]]

Interesting. Seems like it might be related to refresh rates. If your setup allows you to choose different refresh rates for the external monitors, please see if that has any effect. I'll figure it out.

Comment 9

[m.perkovic]

I own these two external monitors:

• LG 27UD68-W
• LG 27UL850-W

Both are connected to the docking station "CalDigit TS3 Plus" via HDMI and DP.

Set refresh rates:

• Integrated monitor: ProMotion (120 fps)
• Both external monitors: 60 fps

I'll play around with the refresh rates later and report back.

Comment 10

[Donal Meehan [:dmeehan]]

Setting Fx125 and Fx126 to Fixed since the regressor Bug 1839425 was backed out of central and beta