Abstract: An adaptive predictive coding (APC) and adaptive kit allocation (ABA) system which splits a speech signal into a plurality of bands, subjecting each signal to adaptive predictive coding and adaptively changes quantization characteristics in the adaptive predictive coding so that quantization noise may become small. An average amplitude (not average power) of the signal of each band is detected for each temporal sub-interval, and a quantization bit number and a quantization step size are adaptively determined from the average amplitude for each sub-interval, thereby permitting reduction of the quantity of hardware used.

Abstract: A speech signal fundamental period extractor which receives a residual value signal from a speech analyzer, such as one using autocorrelators. The residual value signal is first passed through a filter to remove the high-frequency components. Then the signal is quantized to obtain low-bit quantization of the residual value. The output from the quantizer is then sent to an autocorrelator to obtain the correlation coefficient and the fundamental period is extracted by selecting the position of a maximum correlation coefficient. This provides more accurate results and permits the use of low-speed elements and a reduction of components.