1. A method for processing an ordered series of digital signals that each have an amplitude from a finite set of amplitudes consisting of the most likely-to-occur amplitude and at least one other amplitude, the at least one other amplitude including a next most likely-to-occur amplitude to the most likely-to-occur amplitude, the processing to reduce the amount of data used to represent the digital signals and to form codewords such that the relatively more likely-to-occur values or sequences of values of digital signals are represented by relatively short codewords and the relatively less likely-to-occur values or sequences of values of digital signals are represented by relatively long codewords, the method comprising: (a) using a position event identifying method to identify position events that each include a cluster of at least one consecutive signal having any amplitude other than the most likely-to-occur amplitude, such that the position events define the relative positions and runlengths of the clusters and of any intervening runs of consecutive coefficients having the most likely-to-occur amplitude; (b) using an amplitude event identifying method to identify the amplitudes of the signals having amplitudes other than the most likely-to-occur amplitude; and (c) encoding the identified position events, encoding the identified amplitude events, and encoding the signs of the amplitudes other than the most likely-to-occur amplitude in the identified amplitude events, such that for at least some of the signals having amplitudes other than the most likely-to-occur amplitude, clusters of signals having relatively more likely-to-occur signal amplitudes are encoded on average by shorter codeword(s) than are clusters of signals having relatively less likely-to-occur signal amplitudes, wherein the position event identifying method uses Cluster Runlength Identifying and the amplitude event identifying method uses Multi-Dimensional Amplitude Event Identifying.