Abstract: The disclosure is directed to an apparatus and method for encoding and/or decoding video signals for use in a compatible high definition television system or in other applications. In a form of the disclosure there is provided an encoder which includes means for storing an input frame as an array of digital pixel values, and means for interrogating the stored array and for generating a sum signal and at least one difference signal. The sum signal is representative of the sum of the pixel values in a group of pixels. The difference signal is representative of the difference between the total of the pixel values in some of the pixels in the group and the total of the pixel values of other pixels in the group. The sum signal and the difference signal are generated for a multiplicity of groups which cover the video frame. The sum signal is generated at a relatively high information refresh rate and the difference signal is generated at a relatively low information refresh rate.