Digital signal encoding method and apparatus and recording medium

Claim 1

A method for compressing digital signals comprising the steps of: dividing an input signal into at least two bands; obtaining frequency-domain data of said at least two bands of the input signal; and acting on at least one characteristic of said frequency domain data; wherein said step of acting on at least one characteristic acts on frequency-domain characteristics and includes: a multiplication coefficient calculating sub-step of calculating the size of frequency-domain spectral data, allocating the frequency characteristic operating information on said spectral data for normalization and outputting coefficients for multiplication; an overflow check sub-step of checking whether or not a result of multiplication of said spectral data with the multiplication coefficient supplied from said multiplication coefficient calculating sub-step exceeds a pre-set upper limit; a coefficient correcting step of normalizing the coefficients from said multiplication coefficient calculating sub-step in their entirety if, judging from an output of said overflow check sub-step, there are a large number of frequency domain spectral data for which occurs the overflow; a storage step of correcting the coefficients so that an output of said coefficient correction sub-step will exhibit moderate changes; an aliasing noise reducing sub-step of correcting an output of said coefficient correcting sub-step to characteristics maintaining symmetry with respect to a cut-off frequency as an axis of symmetry for canceling previous aliasing noise; and a multiplication sub-step of multiplying the coefficients corrected by said aliasing noise reducing sub-step with the frequency-domain spectral data.

Claim 2

A method for compressing digital signals comprising the steps of: dividing an input signal into at least two bands; obtaining frequency-domain data of said at least two bands of the input signal; and acting on at least one characteristic of said frequency domain data; wherein said step of acting on at least one characteristic acts on frequency-domain characteristics and includes: a multiplication coefficient calculating sub-step of calculating the size of frequency-domain spectral data, allocating the frequency characteristic operating information on said spectral data for normalization and outputting coefficients for multiplication; an overflow check sub-step of checking whether or not a result of multiplication of said spectral data with the multiplication coefficient supplied from said multiplication coefficient calculating sub-step exceeds a pre-set upper limit; a coefficient correcting step of normalizing the coefficients from said multiplication coefficient calculating sub-step in their entirety if, judging from an output of said overflow check sub-step, there are a large number of frequency domain spectral data for which occurs the overflow; a storage step of correcting the coefficients so that an output of said coefficient correction sub-step will exhibit moderate changes; an aliasing noise reducing sub-step of correcting an output of said coefficient correcting sub-step to characteristics maintaining symmetry with respect to a cut-off frequency as an axis of symmetry for canceling previous aliasing noise; and a multiplication sub-step of multiplying the coefficients corrected by said aliasing noise reducing sub-step with the frequency-domain spectral data.

Claim 10

A method for compressing digital signals comprising the steps of: dividing an input signal into at least two bands; obtaining frequency-domain data of said at least two bands of the input signal; and acting on at least one characteristic of said frequency domain data; wherein said step of acting on at least one characteristic acts on frequency-domain characteristics for maintaining the condition of canceling aliasing noise that results from the frequency division; wherein said step of acting on at least one characteristic includes: a multiplication coefficient calculating sub-step of calculating the size of frequency-domain spectral data, allocating the frequency characteristic operating information on said spectral data for normalization and outputting coefficients for multiplication; an overflow check sub-step of checking whether or not a result of multiplication of said spectral data with the multiplication coefficient supplied from said multiplication coefficient calculating sub-step exceeds a pre-set upper limit; a coefficient correcting step of normalizing the coefficients from said multiplication coefficient calculating sub-step in their entirety if, judging from an output of said overflow check sub-step, there are a large number of frequency domain spectral data for which occurs the overflow; a storage step of correcting the coefficients so that an output of said coefficient correction sub-step will exhibit moderate changes; an aliasing noise reducing sub-step of correcting an output of said coefficient correcting sub-step to characteristics maintaining symmetry with respect to a cut-off frequency fs/4 as an axis of symmetry for canceling previous aliasing noise; and a multiplication sub-step of multiplying the coefficients corrected by said aliasing noise reducing sub-step with the frequency-domain spectral data and wherein said step of dividing an input signal into at least two bands uses a QMF filter made up at least of a low-pass filter and a high-pass filter and said step of acting on at least one characteristic affords such characteristics that the equation ##EQU13## is satisfied, an impulse response of the high-pass filter will meet the equation: ##EQU14## and impulse responses g1, g2 of synthesis filters G1, G2 will meet the equation: ##EQU15## where f1 (n) is an impulse response of the low-pass filter and F1(n) its z-transform.

Claim 11

A method for compressing digital signals comprising the steps of: dividing an input signal into at least two bands; obtaining frequency-domain data of said at least two bands of the input signal; and acting on at least one characteristic of said frequency domain data; wherein said step of acting on at least one characteristic acts on frequency-domain characteristics for maintaining the condition of canceling aliasing noise that results from the frequency division; wherein said step of acting on at least one characteristic includes: a multiplication coefficient calculating sub-step of calculating the size of frequency-domain spectral data, allocating the frequency characteristic operating information on said spectral data for normalization and outputting coefficients for multiplication; an overflow check sub-step of checking whether or not a result of multiplication of said spectral data with the multiplication coefficient supplied from said multiplication coefficient calculating sub-step exceeds a pre-set upper limit; a coefficient correcting step of normalizing the coefficients from said multiplication coefficient calculating sub-step in their entirety if, judging from an output of said overflow check sub-step, there are a large number of frequency domain spectral data for which occurs the overflow; a storage step of correcting the coefficients so that an output of said coefficient correction sub-step will exhibit moderate changes; an aliasing noise reducing sub-step of correcting an output of said coefficient correcting sub-step to characteristics maintaining symmetry with respect to a cut-off frequency fs/4 as an axis of symmetry for canceling previous aliasing noise; and a multiplication sub-step of multiplying the coefficients corrected by said aliasing noise reducing sub-step with the frequency-domain spectral data and wherein said step of dividing an input signal into at least two bands uses a QMF filter made up at least of a low-pass filter and a high-pass filter and said step of acting on at least one characteristic affords such characteristics that the equation ##EQU13## is satisfied, an impulse response of the high-pass filter will meet the equation: ##EQU14## and impulse responses g1, g2 of synthesis filters G1, G2 will meet the equation: ##EQU15## where f1 (n) is an impulse response of the low-pass filter and F1(n) its z-transform.

Claim 15

A device for compressing digital signals comprising: means for dividing an input signal into at least two bands; means for obtaining frequency-domain data of said at least two bands of the input signal; and means for acting on at least one characteristic of said frequency-domain data; wherein said means for acting on at least one characteristic acts on frequency-domain characteristics for maintaining the condition of canceling the aliasing noise that results from the frequency division wherein said means for acting on at least one characteristic includes: a multiplication coefficient calculating circuit for calculating the size of frequency-domain spectral data, allocating the frequency characteristic operating information on said spectral data for normalization and outputting coefficients for multiplication; an overflow check circuit for checking whether or not a result of multiplication of said spectral data with the multiplication coefficient supplied from said multiplication coefficient calculating means exceeds a pre-set upper limit; a coefficient correcting circuit for normalizing the coefficients from said multiplication coefficient calculating means in their entirety if, judging from an output of said overflow check sub-step, there are a large number of frequency domain spectral data for which occurs the overflow; a memory for correcting the coefficients so that an output of said coefficient correction means will exhibit moderate changes; an aliasing noise reducing circuit for correcting an output of said coefficient correcting means to characteristics maintaining symmetry with respect to a cut-off frequency as an axis of symmetry for canceling previous aliasing noise; and a multiplier for multiplying the coefficients corrected by said aliasing noise reducing means with the frequency-domain spectral data.

Claim 16

A device for compressing digital signals comprising: means for dividing an input signal into at least two bands; means for obtaining frequency-domain data of said at least two bands of the input signal; and means for acting on at least one characteristic of said frequency-domain data; wherein said means for acting on at least one characteristic acts on frequency-domain characteristics for maintaining the condition of canceling the aliasing noise that results from the frequency division wherein said means for acting on at least one characteristic includes: a multiplication coefficient calculating circuit for calculating the size of frequency-domain spectral data, allocating the frequency characteristic operating information on said spectral data for normalization and outputting coefficients for multiplication; an overflow check circuit for checking whether or not a result of multiplication of said spectral data with the multiplication coefficient supplied from said multiplication coefficient calculating means exceeds a pre-set upper limit; a coefficient correcting circuit for normalizing the coefficients from said multiplication coefficient calculating means in their entirety if, judging from an output of said overflow check sub-step, there are a large number of frequency domain spectral data for which occurs the overflow; a memory for correcting the coefficients so that an output of said coefficient correction means will exhibit moderate changes; an aliasing noise reducing circuit for correcting an output of said coefficient correcting means to characteristics maintaining symmetry with respect to a cut-off frequency as an axis of symmetry for canceling previous aliasing noise; and a multiplier for multiplying the coefficients corrected by said aliasing noise reducing means with the frequency-domain spectral data.

Claim 23

A device for compressing digital signals comprising: means for dividing an input signal into at least two bands; means for obtaining frequency-domain data of said at least two bands of the input signal; and means for acting on at least one characteristic of said frequency-domain data; wherein said means for acting on at least one characteristic acts on frequency-domain characteristics for maintaining the condition of canceling aliasing noise by the frequency division, wherein said means for dividing an input signal into at least two bands uses a QMF filter made up at least of a low-pass filter and a high-pass filter and said means for acting on at least one characteristic affords such characteristics that the equation ##EQU19## is satisfied, an impulse response of the high-pass filter will meet the equation: ##EQU20## and impulse responses g1, g2 of synthesis filters G1, G2 will meet the equation: ##EQU21## where f1(n) is an impulse response of the low-pass filter and F1(n) its z-transform; and wherein said means for acting on at least one characteristic includes: a multiplication coefficient calculating circuit for calculating the size of frequency-domain spectral data, allocating the frequency characteristic operating information on said spectral data for normalization and outputting coefficients for multiplication; an overflow check circuit for checking whether or not a result of multiplication of said spectral data with the multiplication coefficient supplied from said multiplication coefficient calculating means exceeds a pre-set upper limit; a coefficient correcting circuit for normalizing the coefficients from said multiplication coefficient calculating means in their entirety if, judging from an output of said overflow check sub-step, there are a large number of frequency domain spectral data for which occurs the overflow; a memory for correcting the coefficients so that an output of said coefficient correction means will exhibit moderate changes; an aliasing noise reducing circuit for correcting an output of said coefficient correcting means to characteristics maintaining symmetry with respect to a cut-off frequency as an axis of symmetry for canceling previous aliasing noise; and a multiplier for multiplying the coefficients corrected by said aliasing noise reducing means with the frequency-domain spectral data.

Claim 24

A device for compressing digital signals comprising: means for dividing an input signal into at least two bands; means for obtaining frequency-domain data of said at least two bands of the input signal; and means for acting on at least one characteristic of said frequency-domain data; wherein said means for acting on at least one characteristic acts on frequency-domain characteristics for maintaining the condition of canceling aliasing noise by the frequency division, wherein said means for dividing an input signal into at least two bands uses a QMF filter made up at least of a low-pass filter and a high-pass filter and said means for acting on at least one characteristic affords such characteristics that the equation ##EQU19## is satisfied, an impulse response of the high-pass filter will meet the equation: ##EQU20## and impulse responses g1, g2 of synthesis filters G1, G2 will meet the equation: ##EQU21## where f1(n) is an impulse response of the low-pass filter and F1(n) its z-transform; and wherein said means for acting on at least one characteristic includes: a multiplication coefficient calculating circuit for calculating the size of frequency-domain spectral data, allocating the frequency characteristic operating information on said spectral data for normalization and outputting coefficients for multiplication; an overflow check circuit for checking whether or not a result of multiplication of said spectral data with the multiplication coefficient supplied from said multiplication coefficient calculating means exceeds a pre-set upper limit; a coefficient correcting circuit for normalizing the coefficients from said multiplication coefficient calculating means in their entirety if, judging from an output of said overflow check sub-step, there are a large number of frequency domain spectral data for which occurs the overflow; a memory for correcting the coefficients so that an output of said coefficient correction means will exhibit moderate changes; an aliasing noise reducing circuit for correcting an output of said coefficient correcting means to characteristics maintaining symmetry with respect to a cut-off frequency as an axis of symmetry for canceling previous aliasing noise; and a multiplier for multiplying the coefficients corrected by said aliasing noise reducing means with the frequency-domain spectral data.