Video filters
Filter types
Blurry
Bilinear or bicubic filtering smooth out the pixels by blending them to their neighbors, resulting in a blurry video output.
Sharp
Nearest neighbor filtering keeps the pixels sharp smooths out the pixels by blending them to their neighbors, resulting in a blurry video output.
Smooth
Several filters offer to smooth out the pixels when upscaling them y trying to redraw the intended shape, often resulting in a cartoonish look.
Faithful
This family of filters try to mimic how the displays the games were developed for look like.
Relevant info
http://filthypants.blogspot.fr/2016/03/new-and-updated-shaders.html
http://filthypants.blogspot.de/2015/04/more-crt-shaders.html
http://filthypants.blogspot.de/2013/04/customizing-harlequins-gameboy-cg-pixel.html
https://www.extremetech.com/gaming/84040-depixelizing-pixel-art-upscaling-retro-8bit-games