1725658 - 4k60FPS videos stop playing / drop frames when out of focus in fullscreen on second monitor on macOS Big Sur

Status: RESOLVED INCOMPLETE

(Core :: Audio/Video, defect, P3)

Description

[strayer]

Attachment: about-support.json

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.131 Safari/537.36

Steps to reproduce:

I opened a new window and started playing this 4k60FPS video on YouTube in fullscreen on my MacBooks internal display: https://www.youtube.com/watch?v=H88ECrI6B1M&t=599s

I then focused the main Firefox window on my primary, external screen browsing various websites or having only about:blank open.

Hardware: MacBook Pro 16" 2019 with AMD Radeon Pro 5500M
macOS Version: macOS Big Sur 11.5.1 (20G80)

Actual results:

Even when doing nothing in the primary window, having only about:blank open, the video starts dropping frames or completely drops all frames. It only gets "unstuck" by focusing the window and seeking to a different video position.

Apart from the video performance is good. The whole device performs well, other tabs perform well. Only the video gets stuck. Not leaving focus in the secondary window shows no dropped frames in the video.

I tried this in safe mode and it happened too. Creating a new profile also didn't help.

Expected results:

The video should continue to play without stuttering or getting stuck/dropping frames like crazy. This does not happen in Chrome on the same machine.

Comment 1

[strayer]

Testing this in another new profile without any sync or addons enabled the video didn't even play when in focus at 4K60FPS. It dropped 2580 of 4500 frames. I uploaded a profiler run here: https://share.firefox.dev/2Xptgrs

Comment 2

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

The Bugbug bot thinks this bug should belong to the 'Core::Widget: Cocoa' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 3

[C.M.Chang[:chunmin]]

Hi Alastor, would you mind having a look? This seems a drop frames issue.

Comment 4

[Alastor Wu [:alwu]]

Hi,

So you were saying that you have two screens, and uses Firefox on both of them. If you play 4k60fps in fullscreen on the secondary screen, it would start dropping frames when you are not focusing on that secondary window? If you keep focus on the secondary screen, the video won't drop any frames?

If you doing the same thing but not in fullscreen, would the video still drop frames? And if you play video on the main screen, would the video drop any frame in fullscreen and non-fullscreen? Is this issue only happening when you have multiple screens, or it happens on one screen as well?

Also, would you mind to do profiling again but this time use the media preset?

Thank you so much.

Comment 5

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

A needinfo is requested from the reporter, however, the reporter is inactive on Bugzilla. Closing the bug as incomplete.

For more information, please visit BugBot documentation.