HTML5 Fullcreen Youtube 720p60 1080p60 Firefox

[Valtam]

I was putting up with choppy videos for a while on fullcreen Youtube 720p60 1080p60 videos in Firefox.
I have 2 x 4k, 28" Screens.

This also worked for 2160p 4k Youtube content

Today I found the solution:

1. Put about:config into Firefox's address bar and hit enter.
2. Search for layers.acceleration.force-enabled
3. When this value comes up, double click the word false under the value column to change it to true
4. Restart Firefox.

FYI, in Chrome I experienced no such issues.

Hurrah, no more chop!