Encoder apparatus and method that perform preliminary signal selection for transform coding before main signal selection for transform coding
First Claim
1. A coding apparatus, comprising:
- a memory; and
a processor, which performs the functions ofa first coding section that outputs a spectrum of a first decoded signal that is generated by decoding a first code obtained by a first encoding of an input audio signal;
a suppressing section that suppresses an amplitude of the spectrum of the first decoded signal using a specified suppressing coefficient that is specified by a preliminary selector from among a plurality of suppressing coefficients, to generate a suppressed spectrum;
a residual spectrum calculating section that calculates a residual spectrum with respect to the specified suppressing coefficient using a spectrum of the input audio signal and the suppressed spectrum;
a preliminary selecting section that specifies the specified suppressing coefficients to the suppressing section from among a plurality of suppressing coefficients and selects a predetermined number of suppressing coefficients from among the specified suppressing coefficients using the spectrum of the input audio signal and the residual spectrum; and
a second coding section that encodes the specified suppressing coefficient using a residual spectrum with respect to each of the predetermined number of suppressing coefficients, and determines one suppressing coefficient with respect to which a coding distortion caused by the second encoding is smallest, among the predetermined number of suppressing coefficients using a spectrum of a second decoded signal that is generated by decoding a second code obtained by the second encoding, the suppressed spectrum and the spectrum of the input audio signal,wherein the preliminary selecting section further comprisesan estimating section that estimates a position of a pulse that is generated with respect to the residual spectrum in the second encoding, using the residual spectrum;
an attenuating section that generates an estimated residual spectrum by attenuating an amplitude at the estimated position of the pulse in the residual spectrum;
a calculating section that calculates an estimated distortion energy that is an estimated energy of the coding distortion, using the estimated residual spectrum and the spectrum of the input audio signal; and
a candidate limiting section that preliminarily selects the predetermined number of suppressing coefficients among the plurality of suppressing coefficients based on the estimated distortion energy;
wherein the attenuating section attenuates an amplitude of the spectrum at the estimated position of the pulse by multiplying the amplitude by a coefficient having a value that is greater than or equal to 0 and less than 1 andwherein the coding apparatus achieves higher processing efficiency and encoding quality by processing separate portions of the input audio signal using different coding.
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Abstract
An encoder apparatus is provided that suppresses the quality degradation of encoding processes. An ultimate selection candidate limiting unit uses the spectrum of an input signal and a residual spectrum to designate a given number of pre-selected suppression factors to a CELP component suppressing unit, which uses the designated suppression factors to generate a suppressed spectrum. A CELP residual signal spectrum calculating unit, to which the suppressed spectrum is input, calculates a residual spectrum. A conversion encoding unit uses the residual spectrum to perform a second encoding process. A distortion evaluating unit determines one of the designated suppression factors by use of the spectrum of a second decoded signal generated by decoding a second code obtained by the second encoding process, and further by use of the suppressed spectrum and the spectrum of the input signal.
12 Citations
15 Claims
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1. A coding apparatus, comprising:
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a memory; and a processor, which performs the functions of a first coding section that outputs a spectrum of a first decoded signal that is generated by decoding a first code obtained by a first encoding of an input audio signal; a suppressing section that suppresses an amplitude of the spectrum of the first decoded signal using a specified suppressing coefficient that is specified by a preliminary selector from among a plurality of suppressing coefficients, to generate a suppressed spectrum; a residual spectrum calculating section that calculates a residual spectrum with respect to the specified suppressing coefficient using a spectrum of the input audio signal and the suppressed spectrum; a preliminary selecting section that specifies the specified suppressing coefficients to the suppressing section from among a plurality of suppressing coefficients and selects a predetermined number of suppressing coefficients from among the specified suppressing coefficients using the spectrum of the input audio signal and the residual spectrum; and a second coding section that encodes the specified suppressing coefficient using a residual spectrum with respect to each of the predetermined number of suppressing coefficients, and determines one suppressing coefficient with respect to which a coding distortion caused by the second encoding is smallest, among the predetermined number of suppressing coefficients using a spectrum of a second decoded signal that is generated by decoding a second code obtained by the second encoding, the suppressed spectrum and the spectrum of the input audio signal, wherein the preliminary selecting section further comprises an estimating section that estimates a position of a pulse that is generated with respect to the residual spectrum in the second encoding, using the residual spectrum; an attenuating section that generates an estimated residual spectrum by attenuating an amplitude at the estimated position of the pulse in the residual spectrum; a calculating section that calculates an estimated distortion energy that is an estimated energy of the coding distortion, using the estimated residual spectrum and the spectrum of the input audio signal; and a candidate limiting section that preliminarily selects the predetermined number of suppressing coefficients among the plurality of suppressing coefficients based on the estimated distortion energy; wherein the attenuating section attenuates an amplitude of the spectrum at the estimated position of the pulse by multiplying the amplitude by a coefficient having a value that is greater than or equal to 0 and less than 1 and wherein the coding apparatus achieves higher processing efficiency and encoding quality by processing separate portions of the input audio signal using different coding. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A coding apparatus, comprising:
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a memory; and a processor, which performs the functions of a first coding section that outputs a spectrum of a first decoded signal that is generated by decoding a first code obtained by a first encoding of an input audio signal; a suppressing section that suppresses an amplitude of the spectrum of the first decoded signal using a specified suppressing coefficient that is specified by a preliminary selector from among a plurality of suppressing coefficients, to generate a suppressed spectrum; a residual spectrum calculating section that calculates a residual spectrum with respect to the specified suppressing coefficient using a spectrum of the input audio signal and the suppressed spectrum; a preliminary selecting section that specifies the specified suppressing coefficients to the suppressing section from among a plurality of suppressing coefficients and selects a predetermined number of suppressing coefficients from among the specified suppressing coefficients using the spectrum of the input audio signal and the residual spectrum; and a second coding section that encodes the specified suppressing coefficient using a residual spectrum with respect to each of the predetermined number of suppressing coefficients, and determines one suppressing coefficient with respect to which a coding distortion caused by the second encoding is smallest, among the predetermined number of suppressing coefficients using a spectrum of a second decoded signal that is generated by decoding a second code obtained by the second encoding, the suppressed spectrum and the spectrum of the input audio signal, wherein the preliminary selecting section further comprises an estimating section that estimates a position of a pulse that is generated with respect to the residual spectrum in the second encoding, using the residual spectrum; an attenuating section that generates an estimated residual spectrum by attenuating an amplitude at the estimated position of the pulse in the residual spectrum; a calculating section that calculates an estimated distortion energy that is an estimated energy of the coding distortion, using the estimated residual spectrum and the spectrum of the input audio signal; and a candidate limiting section that preliminarily selects the predetermined number of suppressing coefficients among the plurality of suppressing coefficients based on the estimated distortion energy; wherein the attenuating section attenuates an amplitude of the spectrum at the estimated position of the pulse in accordance with a feature of the residual spectrum, and wherein the coding apparatus achieves higher processing efficiency and encoding quality by processing separate portions of the input audio signal using different coding. - View Dependent Claims (12, 13, 14)
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15. A coding method, which is executed by a coding apparatus having a memory and a processor, comprising:
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outputting a spectrum of a first decoded signal that is generated by decoding a first code obtained by a first encoding of an input audio signal; suppressing an amplitude of the spectrum of the first decoded signal using a specified suppressing coefficient that is specified from among a plurality of suppressing coefficients, to generate a suppressed spectrum; calculating a residual spectrum with respect to the specified suppressing coefficient using a spectrum of the input audio signal and the suppressed spectrum; specifying the specified suppressing coefficients to the suppressor from among a plurality of suppressing coefficients and selecting a predetermined number of suppressing coefficients that are used in the suppressing from among the specified suppressing coefficients using the spectrum of the input audio signal and the residual spectrum, and setting the preliminarily selected suppressing coefficients as the specified suppressing coefficients; and encoding the specified suppressing coefficient using a residual spectrum with respect to each of the predetermined number of suppressing coefficients, and determining one suppressing coefficient with respect to which a coding distortion caused by the second encoding is smallest, among the predetermined number of suppressing coefficients using a spectrum of a second decoded signal that is generated by decoding a second code obtained by the second encoding, the suppressed spectrum and the spectrum of the input audio signal, wherein the preliminary selecting further comprises estimating a position of a pulse that is generated with respect to the residual spectrum in the second encoding using the residual spectrum; generating an estimated residual spectrum by attenuating an amplitude at the estimated position of the pulse in the residual spectrum; calculating an estimated distortion energy that is an estimated energy of the coding distortion, using the estimated residual spectrum and the spectrum of the input audio signal; and preliminarily selecting the predetermined number of suppressing coefficients among the plurality of suppressing coefficients based on the estimated distortion energy, wherein the attenuating attenuates an amplitude of the spectrum at the estimated position of the pulse by multiplying the amplitude by a coefficient having a value that is greater than or equal to 0 and less than 1, and wherein the coding method achieves higher processing efficiency and encoding quality by processing separate portions of the input audio signal using different coding.
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Specification