@leocg Thank you for your reply. Windows 10. My PC won't support Windows 11.
However, after making my initial post, I tried turning off "Ambient Mode" in YouTube. That seemed to solve the problem for now. Curiously, the problem with having it on only happen on Opera; Firefox and Chrome seemed to play videos on with it enabled.
Thanks again,
Dave

The video playback quality of YouTube videos on Opera has been terrible for the last month or so. Low quality with jumpy movement. (Checked against Chrome and Firefox, which are both working just fine.)
Cleared cache and cookies, with no luck.
Any thoughts on what is going on?
Thanks,
Dave