A signal processing method comprises the steps of: receiving an image frame including a plurality of rows of pixel data words, wherein each of the rows includes a start pixel data word and a plurality of successive pixel data words; processing each row by subtracting each successive pixel data word in the row from the start pixel data word in the row to produce a plurality of difference pixel data words; and storing and/or transmitting the difference pixel data words. An apparatus that performs the method is also included.