1. A method of filtering an input signal in a filter bank, the method comprising the steps of: downsampling the input signal in each of M channels of the filter bank, where M is greater than two; and processing downsampled versions of the input signal in at least a first predict filter and at least one update filter, wherein the first predict filter and the update filter are associated with a pair of the M channels of the filter bank, and the update filter is selected as the adjoint of a predict filter having an order less than or equal to that of the first predict filter, divided by M.