| 摘要 |
A fixed codebook searching apparatus is provided which slightly suppresses an increase in the operation amount, even if the filter applied to the excitation pulse has the characteristic that it cannot be represented by a lower triangular matrix, and realizes a quasi-optimal fixed codebook search. This fixed codebook searching apparatus is provided with an algebraic codebook (101) that generates a pulse excitation vector; a convolution operation section (151) that convolves an impulse response of an auditory weighted synthesis filter with an impulse response vector that has a value at negative times, to generate a second impulse response vector that has a value at negative times; a matrix generating section (152) that generates a Toeplitz-type convolution matrix by means of the second impulse response vector; and a convolution operation section (153) that convolves the matrix generated by matrix generating section (152) with the pulse excitation vector generated by algebraic codebook (101).
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