Supersampling
From Avisynth wiki
Supersampling refers to the technique of upscaling the source video to a high resolution for the purpose of applying filters (some filters give better results if they have more pixels to work with). After filtering, the supersampled video is then downscaled to the required output resolution. See the Wikipedia supersampling page for more information.
LimitedSharpen is an example of an external script function filter that uses supersampling.
