Encoder, decoder, coding method, decoding method, coding program, decoding program and recording medium
First Claim
1. An encoder comprising:
- circuitry configured to;
execute a periodic-combined-envelope generating processing in which the circuitry generates a periodic combined envelope sequence, WM[1], . . . , WM[N], which is a frequency-domain sequence by changing values of samples of a spectral envelope sequence, W[1], . . . , W[N], which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input time-domain audio signal in a predetermined time segment based on a frequency-domain period corresponding to a period code obtained from the input time-domain audio signal, wherein values of samples of the spectral envelope sequence are changed as in the following formula;
WM[n]=W[n]·
(1+δ
·
P[n]),wherein P[n] is a periodic envelope sequence P[1], . . . , P[N], and δ
is a predetermined value or a chosen value from candidates;
execute a variable-length-coding-parameter calculating processing in which the circuitry calculates a variable-length coding parameter dependent on an amplitude value from the periodic combined envelope sequence; and
execute a variable-length coding processing in which the circuitry uses the variable-length coding parameter to encode a frequency-domain sequence derived from the input time-domain audio signal by variable-length coding dependent on the amplitude value and to output a variable-length code to a decoder.
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Abstract
An encoder includes a periodic-combined-envelope generating part and a variable-length coding part. The periodic-combined-envelope generating part generates a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input audio signal and on a frequency-domain period. The variable-length coding part encodes a frequency-domain sequence derived from the input audio signal. A decoder includes a periodic-combined-envelope generating part and a variable-length decoding part. The periodic-combined-envelope generating part generates a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code and on a frequency-domain period. The variable-length decoding part decodes a variable-length code to obtain a frequency-domain sequence.
12 Citations
10 Claims
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1. An encoder comprising:
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circuitry configured to; execute a periodic-combined-envelope generating processing in which the circuitry generates a periodic combined envelope sequence, WM[1], . . . , WM[N], which is a frequency-domain sequence by changing values of samples of a spectral envelope sequence, W[1], . . . , W[N], which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input time-domain audio signal in a predetermined time segment based on a frequency-domain period corresponding to a period code obtained from the input time-domain audio signal, wherein values of samples of the spectral envelope sequence are changed as in the following formula;
WM[n]=W[n]·
(1+δ
·
P[n]),wherein P[n] is a periodic envelope sequence P[1], . . . , P[N], and δ
is a predetermined value or a chosen value from candidates;execute a variable-length-coding-parameter calculating processing in which the circuitry calculates a variable-length coding parameter dependent on an amplitude value from the periodic combined envelope sequence; and execute a variable-length coding processing in which the circuitry uses the variable-length coding parameter to encode a frequency-domain sequence derived from the input time-domain audio signal by variable-length coding dependent on the amplitude value and to output a variable-length code to a decoder. - View Dependent Claims (3)
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2. An encoder comprising:
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circuitry configured to; execute a periodic-combined-envelope generating processing in which the circuitry generates a periodic combined envelope sequence, WM[1], . . . , WM[N], which is a frequency-domain sequence by changing values of samples of a spectral envelope sequence, W[1], . . . , W[N], which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input time-domain audio signal in a predetermined time segment based on a frequency-domain period corresponding to a period code obtained from the input time-domain audio signal, wherein values of samples of the spectral envelope sequence are changed as in the following formula;
WM[n]=W[n]·
(1+δ
·
P[n]),wherein P[n] is a periodic envelope sequence P[1], . . . , P[N], and δ
is a predetermined value or a chosen value from candidates; andexecute a variable-length coding processing in which the circuitry encodes a frequency-domain sequence derived from the input time-domain audio signal on the assumption that the amplitude value of the frequency-domain sequence is greater for a frequency with a greater value of the periodic-combined envelope sequence and outputs a variable-length code to a decoder.
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4. A decoder comprising:
circuitry configured to; execute a periodic-combined-envelope generating processing in which the circuitry generates a periodic combined envelope sequence, WM[1], . . . , WM[N], which is a frequency-domain sequence by changing values of samples of a spectral envelope sequence, W[1], . . . , W[N], which is a frequency-domain sequence corresponding to an inputted linear predictive coefficient code based on a frequency-domain period corresponding to an inputted period code, the inputted linear predictive coefficient code being received from an encoder and obtained from an input time-domain audio signal at the encoder, wherein values of samples of the spectral envelope sequence are changed as in the following formula;
WM[n]=W[n]·
(1+δ
·
P[n]),wherein P[n] is a periodic envelope sequence P[1], . . . , P[N], and δ
is a predetermined value or a chosen value from candidates;execute a variable-length-coding-parameter calculating processing in which the circuitry calculates a variable-length coding parameter dependent on an amplitude value from the periodic combined envelope sequence; and execute a variable-length decoding processing in which the circuitry uses the variable-length coding parameter to perform decoding an inputted variable-length code. - View Dependent Claims (6)
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5. A decoder comprising:
circuitry configured to; execute a periodic-combined-envelope generating processing in which the circuitry generates a periodic combined envelope sequence WM[1], . . . , WM[N], which is a frequency-domain sequence by changing values of samples of a spectral envelope sequence, W[1], . . . , W[N], which is a frequency-domain sequence corresponding to an inputted linear predictive coefficient code based on a frequency-domain period corresponding to an inputted period code, the inputted linear predictive coefficient code being received from an encoder and obtained from an input time-domain audio signal at the encoder, wherein values of samples of the spectral envelope sequence are changed as in the following formula;
WM[n]=W[n]·
(1+δ
·
P[n]),wherein P[n] is a periodic envelope sequence P[1], . . . , P[N], and δ
is a predetermined value or a chosen value from candidates; andexecute a variable-length decoding processing in which the circuitry decodes an inputted variable-length code to obtain a frequency-domain sequence, on the assumption that the amplitude value of the frequency-domain sequence is greater for a frequency with a greater value of the periodic combined envelope sequence.
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7. A coding method executing:
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generating a periodic combined envelope sequence, WM[1], . . . , WM[N], which is a frequency-domain sequence by changing values of samples of a spectral envelope sequence, W[1], . . . , W[N], which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input time-domain audio signal in a predetermined time segment based on a frequency-domain period corresponding to a period code obtained from the input time-domain audio signal, wherein values of samples of the spectral envelope sequence are changed as in the following formula;
WM[n]=W[n]·
(1+δ
·
P[n]),wherein P[n] is a periodic envelope sequence P[1], . . . , P[N], and δ
is a predetermined value or a chosen value from candidates;calculating a variable-length coding parameter dependent on an amplitude value from the periodic combined envelope sequence; and using the variable-length coding parameter to encode a frequency-domain sequence derived from the input time-domain audio signal by variable-length coding dependent on the amplitude value and to output a variable-length code to a decoder.
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8. A coding method executing:
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generating a periodic combined envelope sequence, WM[1], . . . , WM[N], which is a frequency-domain sequence by changing values of samples of a spectral envelope sequence, W[1], . . . , W[N], which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input time-domain audio signal in a predetermined time segment based on a frequency-domain period corresponding to a period code obtained from the input time-domain audio signal, wherein values of samples of the spectral envelope sequence are changed as in the following formula;
WM[n]=W[n]·
(1+δ
·
P[n]),wherein P[n] is a periodic envelope sequence P[1], . . . , P[N], and δ
is a predetermined value or a chosen value from candidates; andencoding a frequency-domain sequence derived from the input time-domain audio signal on the assumption that the amplitude value of the frequency-domain sequence is greater for a frequency with a greater value of the periodic-combined envelope sequence and outputting a variable-length code to a decoder.
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9. A decoding method executing:
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generating a periodic combined envelope sequence, WM[1], . . . , WM[N], which is a frequency-domain sequence by changing values of samples of a spectral envelope sequence, W[1], . . . , W[N], which is a frequency-domain sequence corresponding to an inputted linear predictive coefficient code based on a frequency-domain period corresponding to an inputted period code, the inputted linear predictive coefficient code being received from an encoder and obtained from an input time-domain audio signal at the encoder, wherein values of samples of the spectral envelope sequence are changed as in the following formula;
WM[n]=W[n]·
(1+δ
·
P[n]),wherein P[n] is a periodic envelope sequence P[1], . . . , P[N], and δ
is a predetermined value or a chosen value from candidates;calculating a variable-length coding parameter dependent on an amplitude value from the periodic combined envelope sequence; and using the variable-length coding parameter to perform decoding an inputted variable-length code.
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10. A decoding method executing:
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generating a periodic combined envelope sequence, WM[1], . . . , WM[N], which is a frequency-domain sequence by changing values of samples of a spectral envelope sequence, W[1], . . . , W[N], which is a frequency-domain sequence corresponding to an inputted linear predictive coefficient code based on a frequency-domain period corresponding to an inputted period code, the inputted linear predictive coefficient code being received from an encoder and obtained from an input time-domain audio signal at the encoder, wherein values of samples of the spectral envelope sequence are changed as in the following formula;
WM[n]=W[n]·
(1+δ
·
P[n]),wherein P[n] is a periodic envelope sequence P[1], . . . , P[N], and δ
is a predetermined value or a chosen value from candidates; anddecoding an inputted variable-length code to obtain a frequency-domain sequence, on the assumption that the amplitude value of the frequency-domain sequence is greater for a frequency with with a greater value of the periodic combined envelope sequence.
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Specification