Voice coding apparatus with synthesized speech LPC code book

Abstract

A voice coding apparatus has a first linear prediction analyzer for acquiring linear prediction coefficients based on a received input speech sampled at a given time interval. A synthesized speech LPC code book stores linear prediction coefficients of a speech resynthesized based on an old input speech. An excitation code book has predetermined excitation vectors. A first error minimizer receives a signal representing an error between the linear prediction coefficient from the first linear prediction analyzer and one linear prediction coefficient of the synthesized speech LPC code book and acquires an index of the synthesized speech LPC code book which minimizes the error. A linear predictor computes a predictive speech based on the index, acquired by the first error minimizer, and an excitation vector of the excitation code book. A second error minimizer receives a signal representing an error between the input speech and the predictive speech from the linear predictor, and acquires the predictive speech that minimizes the error and an index of the excitation code book at that time while scanning indexes of the excitation code book. A second linear prediction analyzer converts the predictive speech from the second error minimizer into a linear prediction coefficient again and supplies the converted linear prediction coefficient to the synthesized speech LPC code book.