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

A speech coding method comprising:

• calculating, using a processor, a perceptual weighting filter coefficient using a linear predictive coefficient (LPC) parameter, the LPC parameter being obtained by analyzing an input speech signal;
• calculating a speech spectrum characteristic parameter using the perceptual weighting filter coefficient and a LPC synthesis filter coefficient, the LPC synthesis filter coefficient being obtained by quantizing the LPC parameter;
• calculating 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;
• calculating a first reference vector by applying the speech spectrum characteristic parameter to the target vector;
• calculating a reference matrix by matrix calculation using the speech spectrum characteristic parameter;
• high pass filtering the first reference vector by a high pass filter to remove a low-frequency component of the first reference vector and to obtain a high-pass filtered first reference vector;
• selecting a polarity of a pulse in each position of the high-pass filtered first reference vector;
• generating an adjusted first reference vector by incorporating the selected polarity into the first reference vector;
• generating an adjusted reference matrix by incorporating the selected polarity into the reference matrix;
• and
• searching, using the adjusted first reference vector and the adjusted reference matrix, for an optimal pulse position that minimizes a coding distortion
• wherein the first reference vector has a plurality of first reference vector elements identified by first reference vector element indices, and wherein the high pass filter is configured to subtract, from a first reference vector element of the plurality of first reference vector elements identified by a certain reference vector element index, a weighted first reference vector element identified by a lower reference vector element index, or to subtract, from the first reference vector element of the plurality of first reference vector elements identified by the certain reference vector element index, a weighted first reference vector element identified by a higher reference vector element index.

A non-transitory storage medium having stored thereon a software program for performing, when running on a computer or a processor, a speech coding method, the speech coding method comprising:

• calculating a perceptual weighting filter coefficient using a linear predictive coefficient (LPC) parameter, the LPC parameter being obtained by analyzing an input speech signal;
• calculating a speech spectrum characteristic parameter using the perceptual weighting filter coefficient and a LPC synthesis filter coefficient, the LPC synthesis filter coefficient being obtained by quantizing the LPC parameter;
• calculating 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;
• calculating a first reference vector by applying the speech spectrum characteristic parameter to the target vector;
• calculating a reference matrix by matrix calculation using the speech spectrum characteristic parameter;
• high pass filtering the first reference vector by a high pass filter to remove a low-frequency component of the first reference vector and to obtain a high-pass filtered first reference vector;
• selecting a polarity of a pulse in each position of the high-pass filtered first reference vector;
• generating an adjusted first reference vector by incorporating the selected polarity into the first reference vector;
• generating an adjusted reference matrix by incorporating the selected polarity into the reference matrix;
• and
• searching, using the adjusted first reference vector and the adjusted reference matrix, for an optimal pulse position that minimizes a coding distortion
• wherein the first reference vector has a plurality of first reference vector elements identified by first reference vector element indices, and wherein the high pass filter is configured to subtract, from a first reference vector element of the plurality of first reference vector elements identified by a certain reference vector element index, a weighted first reference vector element identified by a lower reference vector element index, or to subtract, from the first reference vector element of the plurality of first reference vector elements identified by the certain reference vector element index, a weighted first reference vector element identified by a higher reference vector element index.