User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:85.0) Gecko/20100101 Firefox/85.0

Steps to reproduce:

Play a YouTube video in windowed mode.

Actual results:

Video tears and sections freeze. Doesn't happen in full screen.

Expected results:

Should've played smoothly.

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Please provide the output of about:support.

Make sure that in Compositing, you either use OpenGL or WebRender.

If basic, you will see tearing.

The compositing is set as WebRender

Hi, is this a new issue or a regression? Do you encouter this issue before in the previous version Firefox?
If it's a regression, would you mind to use mozregression to bisect the changeset and find the culprit?
Do you have a specific link for that Youtube video? Or this issue would happen on all videos on Youtube?
Thank you.

(In reply to Alastor Wu [:alwu] from comment #5)

Hi, is this a new issue or a regression? Do you encouter this issue before in the previous version Firefox?
If it's a regression, would you mind to use mozregression to bisect the changeset and find the culprit?
Do you have a specific link for that Youtube video? Or this issue would happen on all videos on Youtube?
Thank you.

It's a new issue. It's happening for all videos.

Opening about:config and changing gfx.webrender.all to true seems to have fixed the issue. It shouldn't be happening with the default settings though.

Based on comment7, it seems a graphic issue.

We enabled Software WebRender for some Linux users recently; you are using the NVIDIA binary drivers which we intend to ship accelerated WebRender on, but still have bugs to fix. With that said, the video tearing with SW-WR should have been fixed in bug 1678954. Can you confirm whether or not this is fixed in the latest nightly? Thanks!

Yes, I can confirm that it's been fixed on 86.0a1 (2020-12-21) (64-bit).

Thanks for testing! :)