Video tearing in Firefox

I'm on Firefox 68.0.1 64bit and recently I've started getting video tearing on all video in the browser. I've tried enabling and disabling hardware acceleration in the settings, as well as "use recommended performance settings", I've tried setting v-sync in my Nvidia driver to on, fast, adaptive - nothing helps. It always tears near the top 1/4 of the screen.

I had unrelated issues with Firefox last month so I completely uninstalled it and deleted my profile and reinstalled it, and I updated my Nvidia driver a few weeks ago. So I have no idea if either of those things triggered this tearing, or if it's something introduced in Firefox 68.

Is there anything I can check for to fix this? I don't seem to have any tearing during page scrolling. Only during video playback.

A quick search did not turn up anything useful. I suggest using Standard Diagnostics; I don't know if it will actually find anything, but if it does not, at least that will eliminate a number of possible causes that otherwise would need to be investigated.

Meanwhile, perhaps some one who knows something specific about this may well show up and offer help. (There was a bug related to this problem, but it apparently was only in Fx 65.x.)

Standard diagnostic - Firefox - MozillaZine Knowledge Base