Lumi masking

Lumi Masking

Lumi masking is a technique used by video compression software, most notably XviD, which reduces quality in very bright or very dark areas of the picture, as quality loss in these areas is less likely to be visible. It is also used in DivX encoding software, where it is referred to as psychovisual enhancements. The reduction in quality (and therefore bitrate) in certain areas of the picture caused by using lumi masking allows more bits to be allocated to the rest of the video, thus improving overall quality. Lumi masking is not perfect, however, and in some cases the degredation in quality it causes is visible.