Pretty sure StreamFX dev is trying to implement it now for his plugin, and it will be nice to have an alternative.
As for anime4k. There are some shaders that already has been made already by another guy, but they don't work properly with latest OBS versions: https://github.com/ryandash/Anime4k-obs-upscaling-shaders
The main idea is to upscale a small resolution windowed games (old rpg maker games for example), so they don't look like crap when being stretched.
Pretty sure StreamFX dev is trying to implement it now for his plugin, and it will be nice to have an alternative.
As for anime4k. There are some shaders that already has been made already by another guy, but they don't work properly with latest OBS versions: https://github.com/ryandash/Anime4k-obs-upscaling-shaders The main idea is to upscale a small resolution windowed games (old rpg maker games for example), so they don't look like crap when being stretched.