(57) A method for speech coding and a voice-coder for coding speech signals divided into
frames spaced with a constant interval are disclosed. An adaptive codebook storing
excitation signal determined in advance and a plurality of excitation codebooks for
multi-stage vector quantization are provided. Each frame is divided into subframes.
For each subframe, a candidate of a first predetermined number of adaptive codevectors
is selected, and then candidates of each predetermined number of excitation codevectors
are selected from each excitation codebook, respectively, by using the candidate of
the adaptive codevector. Finally, a combination of the adaptive codevector and each
of the excitation codevector is selected from the candidates of the adaptive codevector
and each of the sound codevectors.
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