User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0

Steps to reproduce:

I have two monitors. But is possible in one, no need two.

1. I open a window in primary screen. with an empty tab.
2. Create a new tab and open a video in youtube.
3. Drag the YouTube video to second monitor.
4. In PrimaryScreen, on firefox address bar, try typing randomly.
5. If nothing happening, close the tab, create new tab and repeat from [4].

Actual results:

Sometime the video image is getting stuck, but the sound is good, is working.
Randomly, no matter if i use two monitor, the video image is getting stuck.
And i don't know why, is first time when this is happening.
No Dropped Frames.

https://drive.google.com/open?id=1Se48Vefm5MIWZF6CJnNEfhi3JEBQtOJF

I try this in Nighty, and i cant reproduce there.

Wrong link: https://drive.google.com/open?id=1FYWjGoYK5NNgPgBTvAaRnQAoxyI-U6Aj

In SafeMode works fine but not in normal mode. In Nighty works fine in normal mode.

I try:

1. Uninstall the Firefox.
2. Remove all files from %AppData%, %LocalAppdata%, %ProgramData%, %ProgramFiles%
3. Refresh the Firefox.
4. Create new profile.

And nothing was change.

I can reproduce in Nighty after i create a new Profile in Windows.
After i refresh the Nighty appears to be OK.
If i copy the old Profile the problem appears again.

But in Normal the Refresh not Working. Only the SafeMode is OK.

I added the Bad profile, the first profile that Nighty has created in the new Windows Profile.
The Good profile after i use the Refresh.

Apparently is not for all videos:

This video has the problem, and i thinks is for all that use the codec: https://www.youtube.com/watch?v=aT942ML7P98
I cant reproduce for: https://www.youtube.com/watch?v=3J6o7hcm8bE, the video is fine, no problems.

Andronachi, would you mind posting about:support for the bad profile and good profile? Thank you!

The profiles are for Nighty, but is the same behavior in Normal.

I have another bug problem that triggers this problem: https://bugzilla.mozilla.org/show_bug.cgi?id=1576637

With your "bad" profile can you please check if it is caused by one of your add ons?

I don't have addons. Is clean.

I don't know if help. But i make a video with my steps: https://www.youtube.com/watch?v=-uK2vy4zVIc

I see in the good and bad about:support that your Compositing has change from WebRender to Direct3D 11 (Advanced Layers). Was it an intentional change? Can you change it back to WebRender and check again?

I don't change anything in about:config. The default options is true fin Nighty / Developer. But after refresh was Direct3D 11.

The problem is why the video gets stuck on Direct3D 11 and others not.
I cant use the WebRender, CPU 80%, GPU 80%, and the scroll is jerky, That's the problem with Nighty and Developer because uses the WebRender by default: https://bugzilla.mozilla.org/show_bug.cgi?id=1576637

The Direct3D 11 uses 35% CPU, 30% GPU, the WebRender is insane on resources.
Both are in 1080p 60fps

I wonder if this is related to bug 1559521. NI me to see if I can reproduce when I get some time.

As just a shot in the dark, might be worth trying "gfx.webrender.picture-caching = false" in the config (and restarting FF) to see if the old picture cache tiles aren't invalidated properly.

That option is for webrender and not working. This problem i have found on Direct3D.
I can't reproduce on WebRender, i try so many times but i don't found.

Based on the reported behaviour and that webrender fixes the issues this sounds like bug 1559521, going to mark this as a dupe.

I don't know if is the same bug.
This bug if found with DirectX 11, not WebRender.

I believe that bug too is taking place under DirectX 11.

Yes. I see the Attachment of that bug. Was marked with WebRender and i say to not be wrong.