A video signal is converted into a coefficient signal for each frame in a video image. Each coefficient signal comprises block coefficient signals which represent the pixels in a pixel map block (420) in a pixel map (410) with the coefficients in a hybrid polynomial. The coefficient signal for only selected frames is transmitted to a receiving computer (130). The coefficient signals are selected based on a number of coefficients in the coefficient signal for a current frame that vary from corresponding coefficients in the coefficient signal for a sequentially previous frame.