A method, apparatus, and computer program product for combining a subband decomposition and a linear signal processing filter (LSPF). Operations performed include merging the LSPF, via superposition, with each synthesis filter of the first level of the subband decomposition into a set of composite filters; generating an equivalent structure for the low-pass composite filter and its adjacent upsampler to allow combining the equivalent structure with the synthesis filter on the next level of the subband decomposition; repeatedly operating the merging on the next level of the subband decomposition; creating an equivalent structure for the intermediate structure generated by the merging step and its adjacent upsampler in order to allow for combination of the equivalent structure with the at least one synthesis filter on the next level; repeating the operations for each remaining level to generate a composite subband synthesis linear operator, which operates directly on data of the subband decomposition.