Abstract

A method of processing a first series of values representing a row of pixels of a digitized image for differentially encoding the first series of pixel values to generate a first series of codes representing a first series of differential values; expanding each code of the first series into a group of codes to form a second series of codes, each group of codes representing a plurality of differential values whose sum is the differential value represented by the corresponding code of the first series; and decoding the second series of codes to generate a second series of pixel values for display. By transmitting or recording the first series of codes and then effectively dividing each received or reproduced differential value into two or more smaller differential values, known apparatus can be made with little modification to expand each line of a received image by a factor of two or more, depending on the number of codes in each group. The extra pixel values generated will be at least approximately linearly interpolated values. This allows improved moving pictures to be reproduced from an optical disc, for example.