Scalable encoding apparatus, scalable decoding apparatus, and methods thereof
First Claim
Patent Images
1. A scalable coding apparatus, comprising:
- a first layer coder that generates first encoded parameters by encoding a speech signal using a pitch period of the speech signal;
a calculator that calculates a pitch frequency from the pitch period;
a decoder that generates a decoded signal using the first encoded parameters;
a second layer coder that generates second encoded parameters; and
a selector that selects integral multiples of the pitch frequency from both a spectrum of the speech signal and a spectrum of the decoded signal, wherein the second layer coder generates the second encoded parameters by encoding a residual spectrum obtained by subtracting the spectrum of the decoded signal from the spectrum of the speech signal, the residual spectrum being limited to the selected integral multiples of the pitch frequency higher than a predetermined starting-point frequency.
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Abstract
A scalable encoding apparatus capable of reducing the bit rates of encoded parameters and also capable of efficiently encoding audio signals in which a plurality of harmonic structures are coexistent. In the apparatus, an MDCT analyzer MDCT analyzes an audio signal for converting/encoding processes. A pitch frequency converter determines an inverse of a pitch period to calculate a pitch frequency. A selector selects spectra located at frequencies that are integral multiples of the pitch frequency, and a second layer encoder encodes the selected spectra.
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Citations
19 Claims
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1. A scalable coding apparatus, comprising:
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a first layer coder that generates first encoded parameters by encoding a speech signal using a pitch period of the speech signal; a calculator that calculates a pitch frequency from the pitch period; a decoder that generates a decoded signal using the first encoded parameters; a second layer coder that generates second encoded parameters; and a selector that selects integral multiples of the pitch frequency from both a spectrum of the speech signal and a spectrum of the decoded signal, wherein the second layer coder generates the second encoded parameters by encoding a residual spectrum obtained by subtracting the spectrum of the decoded signal from the spectrum of the speech signal, the residual spectrum being limited to the selected integral multiples of the pitch frequency higher than a predetermined starting-point frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14)
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11. A scalable decoding apparatus, comprising:
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a first layer decoder that generates a low-quality decoded signal by decoding first encoded parameters of a speech signal that have been encoded using a pitch period of the speech signal; a calculator that calculates a pitch frequency from the pitch period; a second layer decoder that generates a high-quality decoded signal by adding an arranged residual spectrum obtained by decoding second encoded parameters to a spectrum of the low-quality signal; and an arranger that generates the arranged residual spectrum by arranging a residual spectrum, that represents a difference between the spectrum of the low quality decoded signal and a spectrum of the speech signal, the residual spectrum being obtained by decoding the second encoded parameters into harmonic spectra positioned at frequencies of integral multiples of the calculated pitch frequency calculated by the calculator and higher than a predetermined starting-point frequency. - View Dependent Claims (13, 15)
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16. A scalable coding method, comprising:
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generating first encoded parameters by encoding a speech signal, utilized by a communication system, using a pitch period of the speech signal; calculating a pitch frequency from the pitch period; generating a decoded signal using the first encoded parameters; generating second encoded parameters; and selecting integral multiples of the pitch frequency from both a spectrum of the speech signal and a spectrum of the decoded signal, wherein the second encoded parameters are generated by encoding a residual spectrum obtained by subtracting the spectrum of the decoded signal from the spectrum of the speech signal, the residual spectrum being limited to the selected integral multiples of the pitch frequency higher than a predetermined starting-point frequency.
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17. A scalable decoding method, comprising:
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generating a low-quality decoded signal, utilized by a communication system, by decoding first encoded parameters of a speech signal that have been encoded using a pitch period of the speech signal; calculating a pitch frequency from the pitch period; generating a high-quality decoded signal by adding an arranged residual spectrum obtained by decoding second encoded parameters to a spectrum of the low-quality signal; and generating the arranged residual spectrum by arranging a residual spectrum, representing a difference between the spectrum of the low quality signal and a spectrum of the speech signal, the residual spectrum being obtained by decoding the second encoded parameters into harmonic spectra positioned at frequencies of integral multiples of the calculated pitch frequency and higher than a predetermined starting-point frequency.
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18. A scalable coding apparatus, comprising:
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a first coder that encodes a speech signal using a pitch period of the speech signal; a calculator that calculates a pitch frequency from the pitch period; a second coder that encodes a spectrum of a frequency of an integral multiple of the pitch frequency in spectra of the speech signal; and a corrector that corrects the pitch period based on a nearby pitch period of the pitch period, wherein the calculator calculates the pitch frequency from the corrected pitch period, and the second coder further encodes a difference between the pitch period and the corrected pitch period.
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19. A scalable coding method, comprising:
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encoding a speech signal, utilized by a communication system, using a pitch period of the speech signal; calculating a pitch frequency from the pitch period; encoding a spectrum of a frequency of an integral multiple of the pitch frequency in spectra of the speech signal; correcting the pitch period based on a nearby pitch period of the pitch period; and encoding a difference between the pitch period and the corrected pitch period, wherein calculating a pitch frequency calculates the pitch frequency from the corrected pitch period.
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Specification