VARIABLE RATE VOICE CODING DEVICE

摘要

PURPOSE:To execute efficient quantization by adaptively changing the number of quantization bits by the result of the analysis of an input frame. CONSTITUTION:The signal to noise ratio (S/N: SNR) of the synthesized voice signal and input voice signal from an adaptive code book 1 and the synthesized voice signal and input voice signal from a probability code book 2 is calculated by an SNR calculator 16. If the calculated SNR is larger than the preset threshold value, the input voice signal is expressed only by the synthesized voice signal from either of the adaptive code book 1 and the probability code book 2 and the signal (gain code vector number) corresponding to the information from the other is not transmitted, by which the number of the quantization bits is varied and the quantization bits based in the characteristic of the input voice signal are varied.