Nippon Telegraph and Telephone Public Corporation

Fumitada Itakura

Masaaki Honda

Nobuhiko Kitawaki

Noboru Sugamura

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.

Adaptive predictive processing system

The spectral envelope of speech signals are characterized by LSP (line spectral pair) parameters, termed w.sub.i and .theta..sub.i. In a speech synthesizer the control parameters for the filter may be a.sub.i =-2 cos w.sub.i and b.sub.i =-2 cos .theta..sub.i. The synthesizer filter is essentially an all pole filter consisting of two feedback paths each of which has a transfer function having zeroes on a unit circle in the complex plane.

Growing community of inventors

Houya, Japan

Fumitada Itakura