DATA COMPRESSION SYSTEM INCLUDING SUCCESSIVE APPROXIMATION QUANTIZER

A data processing system augments compression of non-zero values of significant coefficients by coding entries of a significance map independently of coding the values of significant non-zero coefficients. A dedicated symbol represents a zerotree structure encompassing a related association of insignificant coefficients within the tree structure. The zerotree symbol represents that a coefficient is a root of a zerotree if, at a threshold T, the coefficient and all of its descendants that have been found to be insignificant at larger thresholds have magnitudes less than threshold T. The zerotree structure is disclosed in the context of a pyramid-type image subband processor together with successive refinement quantization and entropy coding to facilitate data compression.