You'd be surprised at what image processing algorithms are fast enough to work in realtime when they have optimised GPU implementations. Anime4K is one of those

You'd be surprised at what image processing algorithms are fast enough to work in realtime when they have optimised GPU implementations. Anime4K is one of those CNN-based anime upscaling tools, and it can run in realtime as a shader in mpv. (I'm not a fan of those upscaling tools myself, but I don't see why they couldn't be used in emulators, for the people who like them.)