FIXED CODEBOOK SEARCHING DEVICE AND FIXED CODEBOOK SEARCHING METHOD

摘要

A fixed codebook searching apparatus which slightlysuppresses an increase in the operation amount, even if thefilter applied to the excitation pulse has the characteristicthat it cannot be represented by a lower triangular matrix andrealizes a quasi-optimal fixed codebook search. This fixedcodebook searching apparatus is provided with an algebraiccodebook (101) that generates a pulse excitation vector; aconvolution operation section (151) that convolutes an impulseresponse of an auditory weighted synthesis filter into an impulseresponse vector that has a value at negative times, to generatea second impulse response vector that has a value at secondnegative times; a matrix generating section (152) that generatesa Toeplitz-type convolutionmatrix by means of the second impulseresponse vector; and a convolution operation section (153) thatconvolutes the matrix generated by matrix generating section(152) into the pulse excitation vector generated by algebraiccodebook (101) .