PS1:De-dithering Patch

Dithering is a technique used in many retro games to bypass limits of how many colors a game system can display or to fake transparency effects. It works by relying on composite signals and/or CRT televisions natural blurring to blur two pixels next to each other into one pixel. In the case of the PS1, there is a single flag set per-texture or per-game which will overlay any texture or the entire screen with a checkerboard pattern which blurs all pixels slightly. While some textures actually have dithering baked in, the ones that don't can have the dither effect turned off, vastly changing the look of some games.

A good write-up can be found on Chris McOvell's site.

These patches must be done on a game-by-game basis and the effect is different for each game. Some games — like Driver — may look too bright since the full-screen dither effect darkened the screen considerably.