How do I fix video playback randomly stuttering?

Playback occasionally lags really hard for 1-2 seconds anytime I watch a video. This goes for all websites, not just youtube. It seems disconnected from buffering as it will happen even when the video is totally loaded. It doesn't lag out any other tabs, and switching to a different tab and back always fixes it (for that moment). I've already tried disabling hardware acceleration and webgl, but nothing changed. It happens about once every minute no matter what. I have a high-end pc, so that shouldn't be the problem. (or maybe it is, and firefox isn't optimized for some bit of hardware that I have) Thank you ^_^