Method for speech coding and voice-coder

Claim 2

A method for speech coding according to Claim 1, wherein selection of the candidates of the adaptive codevector and each of the excitation codevectors are performed, respectively, in order, from the selection of the candidate with a smaller error.

Claim 3

A method for speech coding according to Claim 1 or 2, wherein, a gain codebook is used for performing quantization of gains of said adaptive codebook and each of said excitation codebooks, respectively; and a gain codevector is determined by using said gain codebook when selection of a combination of the adaptive codevector and each of the excitation codevectors forming the excitation signal of said subframe from the candidates of said adaptive codevector and said excitation codevector is performed.

Claim 5

A method for speech coding according to Claim 1, wherein the step of selecting the combination of the adaptive codevector and each of the excitation codevectors forming the excitation signal of said subframe from the candidates of said adaptive codevector and said excitation codevector, further comprising the steps of: determining the optimum gain codevector from said gain codebook; and reflecting said gain codevector on said adaptive codevector and each of said excitation codevectors forming said excitation signal.

Claim 6

A method for speech coding according to Claim 5, wherein, at least one or more of excitation super codebooks is included in said plurality of excitation codebooks, said super codebook comprising bits with the number of bits larger than the number of bits to be transmitted; and selection of the candidate of the excitation codevector from said excitation super codebook is performed corresponding to the candidate of the excitation codevector already selected.

Claim 7

A voice-coder for coding speech signals divided into frames spaced with a constant interval, comprising: linear prediction analysis means for outputting spectral parameters of input speech signals; an adaptive codebook for storing excitation signals determined in the past; a plurality of excitation codebooks provided for multi-stage vector quantization of the excitation signal of said input speech signals; wherein, in case of searching for a combination of the adaptive codevector and each of the excitation codevectors for every subframe prepared by further division of said frame from said adaptive codebook and each of said excitation codebooks, respectively, said combination of the adaptive codevector and each of the excitation codevectors forming an excitation signal of said subframe: a candidate of a first predetermined number of adaptive codevectors is selected from said adaptive codebook by using said input speech signal and said spectral parameter; candidates of each predetermined number of excitation codevectors are selected from a plurality of said excitation codebooks, respectively, by using said input speech signal, said spectral parameter and the candidate of said adaptive codevector; and a candidate of said adaptive codevector and each of said excitation codevectors forming the excitation signal of said subframe is selected from the candidate of said adaptive codevector and each of said excitation codevectors by using said input speech signal and said spectral parameter.

Claim 8

A voice-coder according to Claim 7, further comprising: a gain codebook for quantization of each gain of said adaptive codebook and each of said excitation codebooks; wherein said input speech signal, said spectral parameter and said gain codebook are used for searching a combination of the adaptive codevector and each of the excitation codevectors which forms the excitation signal of said subframe, from the candidates of said adaptive codevector and said excitation codevectors.

Claim 9

A voice-coder according to Claim 7 or 8, wherein, at least one or more of excitation super codebooks is included in said plurality of excitation codebooks, said super codebook comprising bits with the number of bits larger than the number of bits to be transmitted; and selection of the candidate of the excitation codevector from said excitation super codebook is performed corresponding to the candidate of the excitation codevector already selected.

Claim 10

A voice-coder for coding speech signals divided into frames spaced with a constant interval, comprising: linear prediction analysis means for outputting spectral parameters of input speech signals; an adaptive codebook storing excitation signals determined in the past; a plurality of excitation codebooks provided for multi-stage vector quantization of an excitation signal of said input speech signals; subframe division means for generating subframe signals by dividing said frame into subframes; first selection means for selecting a candidate of a first fixed number of adaptive codevectors from said adaptive codebook in accordance with said subframe signal and said spectral parameter; second selection means provided for every said excitation codebook for selecting the candidate of the excitation codevectors of the number predetermined for every excitation codebook, from the corresponding excitation codebook in accordance with said subframe signal, said spectral parameter and the candidate of said adaptive codevector; and means for searching the candidate of said adaptive codevector and each of said excitation codevectors which forms the excitation signal of said subframe, from the candidate of said adaptive codevector and the candidate of each of said excitation codevectors in accordance with said input speech signal and said spectral parameter.

Claim 11

A voice-coder according to Claim 10, wherein, first and second selecting means select each corresponding candidate, in order, from the candidate with a smaller error; said search means searches the candidate of said codevector on the condition of whose error is lowest.

Claim 12

A voice-coder according to Claim 10, further comprising: a gain codebook for quantization of each gain of said adaptive codebook and each of said excitation codebooks; wherein said search means searches the candidate of said codevector by further consulting said gain codebook.

Claim 13

A voice-coder according to Claim 11, further comprising: a gain codebook for quantization of each gain of said adaptive codebook and each of said excitation codebooks; wherein said search means further determines the optimum gain codevector from said gain codebook by consulting said gain codebook, and reflects said gain codevector on the adaptive codevector and each of the excitation codevector which forms said excitation signal.

Claim 14

A voice-coder according to any of Claims 10 to 13, wherein, at least one or more of excitation super codebooks is included in said plurality of excitation codebooks, said super codebook comprising bits with the number of bits larger than the number of bits to be transmitted; and said second selection means corresponding to said excitation super codebook performs selection of the candidate of the excitation codevector from said excitation super codebook according to the candidate of the excitation codevector already selected.