Abstract: A method of encoding data, involves the steps of comparing an input image from a video camera with an image being built up, and stored in store. The images are processed by an analyser in accordance with a plurality of different algorithms stored in a store to produce a plurality of different data packets each representative of a partial change which can be effected to the image to be built up to bring it closer to the input image. The analyser compares the effects of the different data packets if implemented on the data image to be built up and provides each one with a score in accordance with a predetermined criteria. A comparator selects the packet with the best score under the predetermined criteria and uses it to alter the image in the store accordingly. The cycle is repeated to cause the image to be built up, to progressively converge on the input image.