Speech parameter encoding method capable of transmitting a spectrum parameter at a reduced number of bits

摘要

In a speech parameter encoding method of encoding an input speech signal into a sequence of encoded signals, vector quantization is carried out through a plurality of vector quantizers which are connected in cascade to one another through subtractors and which cooperate with code books, respectively. Such a cascade connection of the vector quantizers may be supplied with the input speech signal either at every frame or at every subframe shorter than the frame to produce a set of code vector candidates from each of the vector quantizers. A sequence of coefficients which represent a spectrum parameter is calculated at every frame and is divided into a plurality of coefficient groups each of which is subjected to vector quantization to produce a plurality of code vector candidates for each coefficient group. Cumulative distortions are calculated for combinations of the code vector candidates to select an optimum combination.