Vector quantization of algebraic codebook with high-pass characteristic for polarity selection

A speech coding apparatus comprising:

• a perceptual weighting filter coefficient calculator that calculates, using a processor, a perceptual weighting filter coefficient using a linear predictive coefficient (LPC) parameter, which is obtained by analyzing an input speech signal;
• a parameter calculator that calculates a parameter related to a speech spectrum characteristic using the perceptual weighting filter coefficient and a LPC synthesis filter coefficient, which is obtained by quantizing the LPC parameter;
• a target vector generator that calculates a target vector to be encoded by subtracting a synthesized signal, which is generated by filtering an adaptive excitation signal multiplied by a gain using a perceptual weighting LPC synthesis filter, from the input speech signal that is weighted using the perceptual weighting filter coefficient;
• a first vector calculator that calculates a first reference vector by applying the parameter to the target vector, and transmits the first reference vector to both a second vector calculator and a polarity selector;
• a matrix calculator that calculates a reference matrix by matrix calculation using the parameter;
• the second vector calculator that calculates a second reference vector by multiplying the first reference vector by a filter having a high-pass characteristic;
• the polarity selector that generates a polarity vector based on a polarity of each element of the second reference vector, generates an adjusted first reference vector by multiplying the first reference vector by the polarity vector, and generates an adjusted reference matrix by multiplying the reference matrix by the polarity vector;
• and
• a pulse position searcher that searches for an optimal pulse position using the adjusted first reference vector and the adjusted reference matrix.