Patent ID: 7392179

Claim:
An LPC parameter vector quantization apparatus comprising: a distortion calculator that calculates distortion between a plurality of codevectors successively read from an LSF codebook storing a plurality of LSF codevectors and a target quantization using a first distortion evaluation measure; an LPC code pre-selector that preliminarily selects indices of codevectors that reduce the amount of distortion according to said first distortion evaluation measure, from said plurality of LSF codevectors, and that generates decoded LSF parameters corresponding to the respective preliminarily selected indices; a first parameter convertor that converts said decoded LSF parameters to first distortion calculation parameters, respectively, with which distance of a spectrum can be calculated; a second parameter convertor that converts an LSF parameter comprising said quantization target to a second distortion calculation parameter with which distance of a spectrum can be calculated; and an LPC code final searcher that calculates distortion between said second distortion calculation parameter, obtained by converting said quantization target and supplied from said second parameter convertor, and said first distortion calculation parameters, obtained by converting said decoded LSF parameters and supplied from said first parameter convertor, using a second distortion evaluation measure that is different from said first distortion evaluation measure, and that outputs, as an LPC code, an index of an LSF codevector corresponding to said first distortion calculation parameter that minimizes the amount of distortion according to said second distortion evaluation measure.