1. A method of processing a video signal in an electronic video preprocessor, the video signal comprising a sequence of frames, each of the frames comprising a plurality of pixels, the method comprising the steps of: determining a neighborhood maximum or a neighborhood minimum for a pixel of interest; comparing a sum of an intensity of the pixel of interest and an offset to the neighborhood minimum, or a sum of the neighborhood maximum and an offset to the intensity of the pixel of interest, to determine whether the pixel of interest should be replaced; replacing the pixel of interest with a minimum replacement value if the sum of the intensity of the pixel of interest and an offset is less than the neighborhood minimum; and replacing the pixel of interest with a maximum replacement value if the intensity of the pixel of interest is greater than the sum of the neighborhood maximum and an offset.