1. A method of processing a first sequence of images and a second sequence of images with a physical computing device to compare the first and second sequences, the method comprising the physical computing device: (a) processing each of a plurality of the images in the first sequence and each of a plurality of the images in the second sequence by: processing the image data for each of a plurality of pixel neighborhoods in the image to generate at least one respective descriptor element for each of the pixel neighborhoods, each descriptor element comprising one or more bits; and forming a plurality of words from the descriptor elements of the image such that each word comprises a unique combination of descriptor element bits; wherein the words for the second sequence are generated from the same respective combinations of descriptor element bits as the words for the first sequence; and (b) performing processing to compare the first and second sequences by comparing the words generated for the plurality of images in the first sequences with the words generated for the plurality of images in the second sequence.