1. A visual perception threshold unit for image processing, the threshold unit comprising: a parameter generator to generate a multiplicity of parameters that describe at least some of the information content of at least one video frame to be processed; and a threshold generator to generate from said parameters, a plurality of visual perception threshold levels to be associated with the pixels of the at least one video frame, wherein said threshold levels define contrast levels above which a human eye can distinguish a pixel from among its neighboring pixels of said at least one video frame.