Patent ID: 7519533

Claim:
A fixed codebook searching apparatus that is included in a speech coding apparatus performing a code-excited linear prediction (CELP) encoding of an input speech signal using a pulse excitation vector searched in the fixed codebook searching apparatus and outputting an encoded bit sequence including a parameter corresponding to the pulse excitation vector, the fixed codebook searching apparatus, comprising: a pulse excitation vector generating section that generates a pulse excitation vector specified by a searching section; a first convolution operation section that convolutes an impulse response of a perceptually weighted synthesis filter with an impulse response vector which has one or more values at negative times, to generate a second impulse response vector that has one or more values at negative times; a matrix generating section that generates a Toeplitz-type convolution matrix by the second impulse response vector generated by the first convolution operation section; and the searching section that inputs a target signal obtained from the input speech signal in the speech coding apparatus, performs convolution processing on the pulse excitation vector generated by the pulse excitation vector generating section using the matrix generated by the matrix generating section, and controls the pulse excitation vector generated by the pulse excitation vector generating section for minimizing an error between a perceptually weighted synthesis signal obtained by the convolution processing and the target vector, and outputs a parameter corresponding to the pulse excitation vector that minimizes the error.