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

A differential index (DI) assignment scheme is proposed for the image encod ing system in which a variable-length tree-structured vector quantizer (VLT SVQ) is adopted. Each source vector is quantized into a terminal node of VL TSVQ and each terminal node is represented as a unique binary vector. The p roposed index assignment scheme utilizes the correlation between interblock s of the image to increase the compression ratio with the image quality mai ntained; Simulation results show that the proposed scheme achieves a much h igher compression ratio than the conventional one does and that the amount of the bit rate reduction of the proposed scheme becomes large as the corre lation: of the image becomes large. The proposed encoding scheme can be eff ectively used to encode MR images whose pixel values are, in:general, highl y correlated with those of the neighbor pixels.