1. A method for operating a coding apparatus, the method comprising: for an ordered series of quantized transform coefficients of a block of image data, the series having a most likely-to-occur amplitude, and at least one other amplitude including a next-to-most likely-to-occur amplitude, encoding the position of coefficients having other than the most likely-to-occur amplitude, the position encoding including encoding events using variable length coding such that on average, events that are more likely to occur are encoded by respective codewords that are shorter than the respective codewords for events that are less likely to occur, the variable length coding using a plurality of variable length code mappings that each maps events to codewords, the position encoding including switching between the code mappings based on the context; and encoding amplitudes of the coefficients having values other than the most likely-to-occur amplitude using variable dimensional amplitude coding in the reverse order of the original ordering of the series, such that relatively more likely-to-occur sequences of quantized coefficients are represented by relatively short sets of codewords and relatively less likely-to-occur sequences of quantized coefficients are represented by relatively long sets of codewords, wherein the context is defined by one or more parameters that when encoding a current event are known or derivable from one or more previously encoded events.