Patent ID: 7398206

Claim:
An apparatus for performing speech coding in a CELP system, comprising: an adaptive codebook that stores previously synthesized excitation signals; a stochastic codebook that stores a plurality of excitation vectors; a synthesized speech obtainer that obtains synthesized speech from excitation information acquired from the adaptive codebook and the stochastic codebook and linear predictive coding coefficients obtained by performing linear predictive coding analysis on an input speech signal; a gain information obtainer that obtains gain information for the synthesized speech using a relation of the synthesized speech and the input speech signal; and a transmitter that transmits the linear predictive coding coefficients, the excitation information and the gain information, wherein the stochastic codebook comprises: a first subcodebook that stores first sub-excitation vectors comprising pulses and outputs one of the first sub-excitation vectors corresponding to an inputted index; a second subcodebook that stores second sub-excitation vectors comprising a larger number of pulses than the first sub-excitation vectors, and outputs one of the second sub-excitation vectors corresponding to the inputted index; a control section that controls an addition gain based on information about pulses of the first sub-excitation vector outputted from the first subcodebook, the second sub-excitation vector outputted from the second subcodebook being multiplied by the addition gain; and a computation section that adds the second sub-excitation vector multiplied by the addition gain and the first excitation vector outputted from the first subcodebook, and obtains an excitation vector.