Method and circuit for carrying out forward and inverse quantization by

Abstract

A succession of input signals supplied to a quantizer is processed at sampling instants into a succession of quantized codes by step sizes with a current one of the quantized codes produced at each sampling instant with reference to a current step size adaptively decided not only by a next previous quantized code and a next previous step size but also by a reference size which is determined in accordance with an average level derived from a plurality of prior quantized codes produced until production of the next previous quantized code. A decoder decodes the quantized code succession into a reproduction of the quantizer input signal succession with each quantized code decoded with reference to a similarly adaptively decided step size. It is possible that the reference step size to be determined in a digital fashion as one of a few predetermined sizes or in an analog manner to be variable between two predetermined reference sizes. Each quantizer input signal may be given either as an analog signal sample or as a digital signal represented by a plurality of bits which are greater in number than the bits of each quantized code produced by the quantizer.