A differential-index assignment scheme for tree-structured vector quantization

Abstract

A differential index (DI) assignment scheme is proposed for the image encoding system in which a variable-length tree-structured vector quantizer (VLTSVQ) is adopted. Each source vector is quantized into a terminal node of VLTSVQ and each terminal node is represented as a unique binary vector. The proposed index assignment scheme utilizes the correlation between interblocks of the image to increase the compression ratio with the image quality maintained; Simulation results show that the proposed scheme achieves a much higher compression ratio than the conventional one does and that the amount of the bit rate reduction of the proposed scheme becomes large as the correlation: of the image becomes large. The proposed encoding scheme can be effectively used to encode MR images whose pixel values are, in:general, highly correlated with those of the neighbor pixels.