Does the player have a stats or debug item in the right-click context menu ?

youtube does but that bugs out less than amazon

Can you also provide links to videos are that bad quality? Did you try with Firefox in Safe Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#w_how-to-start-firefox-in-4troubleshoot-modesf5safe-modesf

You can also try Windows Sandbox if you're running Win Pro. https://www.howtogeek.com/399290/how-to-use-windows-10s-new-sandbox-to-safely-test-apps/

launching in troubleshoot mode didnt help, as for links to certain videos its everything on amazon ive tried and every yt video so long as im tabbed out.

It's certainly frustrating to experience video quality issues while streaming content. Your observation that the problem mainly occurs when tabbed out and using your second monitor is interesting and could point to a potential cause. It's great that you've ruled out your computer and Wi-Fi as the sources of the problem.

Considering your situation, it's possible that your browser's hardware acceleration or power management settings might be affecting video playback performance when you're using your second monitor. Here are a few suggestions you could consider:

1. **Adjust Hardware Acceleration:** Try adjusting the hardware acceleration settings in your browser. Enabling or disabling hardware acceleration might have an impact on video playback quality. You can usually find this option in your browser's settings.

2. **Power Management Settings:** Check your computer's power management settings. Some power-saving features might be affecting your system's performance when using multiple monitors. Adjusting these settings could potentially improve video playback.

3. **Browser Extensions:** It's worth checking if any browser extensions are causing conflicts with video playback. Temporarily disabling extensions and testing video playback again could help identify if any particular extension is causing the issue.

4. **Browser Updates:** Make sure your browser is up to date. Sometimes, browser updates include fixes for video playback-related issues.

5. **Graphics Drivers:** Ensure that your graphics drivers are up to date. Outdated or incompatible graphics drivers could potentially impact video quality.

6. **Browser Compatibility:** Since you mentioned that the issue doesn't persist when using a different browser, it could indicate a compatibility issue with your current browser. If other troubleshooting steps don't yield results, using an alternative browser for video streaming might be a temporary solution.

If none of these suggestions resolve the issue, you might consider seeking assistance from the Amazon Prime Video or YouTube support teams. They might have specific insights into how their services interact with different browser settings and configurations.

Ultimately, troubleshooting such issues can involve a bit of trial and error, but with persistence, you're likely to find a solution that ensures smooth video streaming while using your second monitor. Good luck, and I hope you're able to enjoy uninterrupted video playback soon!

mainly effects FPS and only when im tabbed out and using my second monitor.

Go to about:config in the address bar and change widget.windows.window_occlusion_tracking.enabled to false then restart the browser.