Method and apparatus of postfiltering using a first spectrum parameter of an encoded sound signal and a second spectrum parameter of a lesser degree than the first spectrum parameter

Claim 2

A postfilter for reproducing a sound signal that has been encoded with an encoder, by using a decoder and compensating a reproduced signal that was output from said decoder, said postfilter comprising: first calculating means for calculating a second spectrum parameter based on a first spectrum parameter supplied from said encoder, said first spectrum parameter being related to said sound signal encoded by said encoder, wherein the degree of said second spectrum parameter is lower than that of said first spectrum parameter; a spectrum postfilter for generating a first transfer function having a denominator and a numerator, wherein said first spectrum parameter is included in said denominator and said second spectrum parameter is included in said numerator, said spectrum postfilter receiving said reproduced signal output from said decoder and filtering said reproduced signal based on said first transfer function; second calculating means for adaptively calculating a compensation coefficient based on said first spectrum parameter and said second spectrum parameter; and a compensation filter for generating a second transfer function based on said compensation coefficient and filtering an output of said spectrum postfilter based on said second transfer function, wherein an output of said compensation filter that corresponds to a filtered reproduced signal is a reproduction of said sound signal.

Claim 3

The postfilter of claim 1, further comprising: said first calculating means for inputting a first linear predictive coefficient as said first spectrum parameter and calculating a second linear predictive coefficient of which degree is lower that that of said first linear predictive coefficient; and said second calculating means for calculating said compensation coefficient based on said first linear predictive coefficient and said second linear predictive coefficient.

Claim 4

The postfilter of claim 1, comprising said spectrum postfilter for generating a transfer function of autoregressive moving average type.

Claim 5

The postfilter of claim 1, wherein said first calculating means further comprises: means for converting said first spectrum parameter to preset k parameters; means for extracting an arbitrary k parameter from among said k parameters; and means for converting said extracted k parameter to a second spectrum parameter.

Claim 6

The postfilter of claim 1, wherein said second calculating means further comprises: means for calculating an impulse response of said spectrum postfilter based on said first spectrum parameter and said second spectrum parameter; means for calculating a preset autocorrelation function based on said calculated impulse response; and means for calculating said compensation coefficient based on said calculated autocorrelation function.

Claim 7

The postfilter of claim 1, further comprising spectrum parameter calculating means for calculating a spectrum parameter in accordance with said reproduced signal, wherein said first calculating means comprising means for inputting said calculated spectrum parameter, instead of said first spectrum parameter, and calculating a spectrum parameter of which degree is lower than that of said calculated spectrum parameter.

Claim 8

A postfilter for reproducing a sound signal that has been encoded with an encoder, by using a decoder and compensating a reproduced signal that was output from said decoder, said postfilter comprising: means for converting a first linear predictive coefficient supplied from said encoder to preset k parameters, said first linear predictive coefficient being related to said sound signal encoded by said encoder; means for extracting an arbitrary k parameter from among said k parameters; means for converting said extracted k parameter to a second linear predictive coefficient, wherein the degree of said second linear predictive coefficient is lower than that of said first linear predictive coefficient; a spectrum postfilter for generating a first transfer function of autoregressive moving average type having a denominator and a numerator, wherein said first spectrum parameter is included in said denominator and said second spectrum parameter is included in said numerator, said spectrum postfilter receiving said reproduced signal output from said decoder and filtering said reproduced signal based on said first transfer function; means for calculating an impulse response of said spectrum postfilter based on said first linear predictive coefficient and said second linear predictive coefficient; means for calculating a preset autocorrelation function based on said calculated impulse response; means for calculating said compensation coefficient based on said calculated autocorrelation function; and a compensation filter for generating a second transfer function based on said compensation coefficient and filtering an output of said spectrum postfilter based on said second transfer function, wherein an output of said compensation filter that corresponds to a filtered reproduced signal is a reproduction of said sound signal.

Claim 9

A postfilter for reproducing a sound signal that has been encoded with an encoder, by using a decoder and compensating a reproduced signal that was output from said decoder, said postfilter comprising: means for converting a first linear predictive coefficient supplied from said encoder to preset k parameters, said first linear predictive coefficient being related to said sound signal encoded by said encoder; means for extracting an arbitrary k parameter from among said k parameters; means for converting said extracted k parameter to a second linear predictive coefficient, wherein the degree of said second linear predictive coefficient is lower than that of said first linear predictive coefficient; a spectrum postfilter for generating a first transfer function of autoregressive moving average type having a denominator and a numerator, wherein said first spectrum parameter is included in said denominator and said second spectrum parameter is included in said numerator, said spectrum postfilter receiving said reproduced signal output from said decoder and filtering said reproduced signal based on said first transfer function; means for calculating an impulse response of said spectrum postfilter based on said first linear predictive coefficient and said second linear predictive coefficient; means for calculating a preset autocorrelation function based on said calculated impulse response; means for calculating said compensation coefficient based on said calculated autocorrelation function; and a compensation filter for generating a second transfer function based on said compensation coefficient and filtering an output of said spectrum postfilter based on said second transfer function, wherein an output of said compensation filter that corresponds to a filtered reproduced signal is a reproduction of said sound signal.

Claim 10

A postfilter for reproducing a sound signal that has been encoded with an encoder, by using a decoder and compensating a reproduced signal that was output from said decoder, said postfilter comprising: means for calculating a first linear predictive coefficient in accordance with said reproduced signal received from said decoder; means for converting a first linear predictive coefficient to preset k parameters; means for extracting an arbitrary k parameter from among said k parameters; means for converting said extracted k parameter to a second linear predictive coefficient, wherein the degree of said second linear predictive coefficient is lower than that of said first linear predictive coefficient; a spectrum postfilter for generating a first transfer function of autoregressive moving average type having a denominator and a numerator, wherein said first spectrum parameter is included in said denominator and said second spectrum parameter is included in said numerator, said spectrum postfilter receiving said reproduced signal output from said decoder and filtering said reproduced signal based on said first transfer function; means for calculating an impulse response of said spectrum postfilter based on said first linear predictive coefficient and said second linear predictive coefficient; means for calculating a preset autocorrelation function based on said calculated impulse response; means for calculating said compensation coefficient based on said calculated autocorrelation function; and a compensation filter for generating a second transfer function based on said compensation coefficient and filtering an output of said spectrum postfilter based on said second transfer function, wherein an output of said compensation filter that corresponds to a filtered reproduced signal is a reproduction of said sound signal.

Claim 11

A postfilter for reproducing a sound signal that has been encoded with an encoder, by using a decoder and compensating a reproduced signal that was output from said decoder, said postfilter comprising: means for calculating a first linear predictive coefficient in accordance with said reproduced signal received from said decoder; means for converting a first linear predictive coefficient to preset k parameters; means for extracting an arbitrary k parameter from among said k parameters; means for converting said extracted k parameter to a second linear predictive coefficient, wherein the degree of said second linear predictive coefficient is lower than that of said first linear predictive coefficient; a spectrum postfilter for generating a first transfer function of autoregressive moving average type having a denominator and a numerator, wherein said first spectrum parameter is included in said denominator and said second spectrum parameter is included in said numerator, said spectrum postfilter receiving said reproduced signal output from said decoder and filtering said reproduced signal based on said first transfer function; means for calculating an impulse response of said spectrum postfilter based on said first linear predictive coefficient and said second linear predictive coefficient; means for calculating a preset autocorrelation function based on said calculated impulse response; means for calculating said compensation coefficient based on said calculated autocorrelation function; and a compensation filter for generating a second transfer function based on said compensation coefficient and filtering an output of said spectrum postfilter based on said second transfer function, wherein an output of said compensation filter that corresponds to a filtered reproduced signal is a reproduction of said sound signal.

Claim 14

The method of postfiltering of claim 9, wherein said first spectrum parameter and said second spectrum parameter are linear predictive coefficients.

Claim 15

The method of postfiltering of claim 9, wherein said first transfer function is of an autoregressive moving average type.

Claim 16

The method of postfiltering of claim 9, wherein said second transfer function is of an autoregressive moving average type.

Claim 17

The method of postfiltering of claim 9, wherein said step of calculating said second spectrum parameter further comprises the steps of: converting said first spectrum parameter to preset k parameters; extracting an arbitrary k parameter from among said k parameters; and converting said extracted k parameter to a second spectrum parameter.

Claim 18

The method of postfiltering of claim 9, wherein said step of calculating said compensation coefficient comprises the steps of: calculating an impulse response of said spectrum postfilter based on said first spectrum parameter and said second spectrum parameter; calculating a preset autocorrelation function based on said calculated impulse response; and calculating said compensation coefficient based on said calculated autocorrelation function.

Claim 19

The method of postfiltering of claim 14, wherein said step of calculating said compensation coefficient is a step of calculating a compensation coefficient from zero degree autocorrelation and one degree autocorrelation.

Claim 20

The method of postfiltering of claim 9, comprising a step of calculating said first spectrum parameter from said reproduced signal instead of said step of sampling said first spectrum parameter from said encoder.

Claim 21

The postfilter of claim 1, wherein the reproduced signal output by said decoder is based on reception of a signal that corresponds to said sound signal encoded by said encoder.

Claim 22

The postfilter of claim 7, wherein the reproduced signal output by said decoder is based on reception of a signal that corresponds to said sound signal encoded by said encoder.

Claim 23

The postfilter of claim 8, wherein the reproduced signal output by said decoder is based on reception of a signal that corresponds to said sound signal encoded by said encoder.

Claim 24

The method of postfiltering of claim 9, wherein the reproduced signal output by said decoder is based on reception of a signal that corresponds to said sound signal encoded by said encoder.