I’m not sure why the preview still plays rather slowly, even after multiple updates. I suspect it’s because proper hardware decoding isn’t implemented. At the least, preview should be as performant as an ordinary video player, players which don’t slow down during AI processing. This could also help fix the AV1 decoding problems that sometimes occur, although I haven’t figured out which videos cause this exactly. To be clear, preview usually works just fine, it just seems not to be lean.
