You can test older versions with mozregression to see if it worked previously and find when it stopped working.

I turned off acceleration at least a year ago, I noticed Youtube videos now playing not fluent, so I enabled it again. It could me many versions to try. Mozilla team just need to fix this problem. Where is the support email?

The mozregression tool should only take about 10 tests to find the day the problem occurred within the last year or so. This is the first thing a Mozilla developer would request.

app_name: firefox build_date: 2020-01-15 build_file: C:\Users\tulle\.mozilla\mozregression\persist\2020-01-15--mozilla-central--firefox-74.0a1.en-US.win64.zip build_type: nightly build_url: https://archive.mozilla.org/pub/firefox/nightly/2020/01/2020-01-15-21-36-21-mozilla-central/firefox-74.0a1.en-US.win64.zip changeset: c35bb210b8ae793c844bd94c1848d246bf601293 repo_name: mozilla-central repo_url: https://hg.mozilla.org/mozilla-central

Does not have artifacts on webpages with hardware acceleration enabled.

So 2020-01-15 is the last good version and 2020-01-16 is the first bad version?

You can disable hardware acceleration just for video by changing media.hardware-video-decoding.enabled to false in about:config then restart the browser.

Artifacts are on webpages as well. There is an error in the Mozilla software. There are no artifacts in Chrome with hardware acceleration. If I disable hardware accelerations, webpages and videos are slow and notchy. Where are the Mozilla developers, why are they not taking note of this?

Where is the email for Mozilla developers?

Can you attach a screenshot of the artifacts?

Does it still happen in a new profile (without signing into sync account)? An easy way to test a new profile is to install Developer Edition and see if it happens there or refresh your existing profile.