Speech signal processing circuit and method for decoding a coded speech signal by controlling operation of a band synthesis filter

Abstract

A speech signal processing circuit includes an input buffer for receiving inverse quantization samples and for temporarily storing those samples. The circuit also includes a band synthesis filter for reading the inverse quantization samples stored in the input buffer one by one, and for conducting quadrature conversion processing and sum-of-product operation processing to decode the samples into speech signals. The circuit further includes a control circuit for controlling operation of the band synthesis filter. When the inverse quantization samples are recognized as being stored in the input buffer, the control circuit controls the band synthesis filter to execute, as an initial operation, the quadrature conversion processing of the inverse quantization samples as many times as a number corresponding to an operation delay time of the band synthesis filter. After completion of the initial operation, the control circuit control the band synthesis filter to continue, as a steady operation, the quadrature conversion processing of the inverse quantization samples stored in the input buffer, as well as to conduct the sum-of-product operation processing with respect to the results of the quadrature conversion processing.