If you're e.g. using DivX5.1.1. (movie must be loaded):
Rightclick > Options > Filters > DivX Decoder Filter
On "Quality Settings"-tab you can adjust settings of Brightness, Contrast and Saturation under Picture Properties. (Note: "Yuf Extended Mode" must be
deselected; otherwise Picture Properties will not be available)
(Similar for other codecs/filters; not for all though; depends on the possibilities of the codecs/filters themselves).