Adaptive subband scaling method and apparatus for quantization bit allocation in variable length perceptual coding
First Claim
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1. A signal encoding method comprising the steps of:
- transforming an input signal to a frequency spectrum of signal components;
splitting the signal components of the frequency spectrum into a plurality of frequency subbands;
quantizing the signal components in each subband to generate quantized values;
determining the quantization precision needed for the signal components of each subband, wherein the quantization precision is determined to be higher where the quantized values are larger and lower where the quantized values are smaller; and
encoding the quantized values in variable-length codes, wherein the code lengths are set to be longer if the quantization precision value is higher, and shorter if the quantization precision value is lower.
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Abstract
A signal encoding method for encoding input digital data by so-called high-efficiency encoding, wherein it is possible to suppress degradation in the sound quality in case of raising the compression ratio. The range of values of subband-based signal components for quantization to zero, to which a short codelength is given, is set so as to be larger. Consequently the ratio of the subband-based signal components quantized to values of a shorter codelength will become higher than if the subband-based signal components are quantized in such a manner as to minimize the total quantization error energy in each frequency band.
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Citations
42 Claims
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1. A signal encoding method comprising the steps of:
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transforming an input signal to a frequency spectrum of signal components; splitting the signal components of the frequency spectrum into a plurality of frequency subbands; quantizing the signal components in each subband to generate quantized values; determining the quantization precision needed for the signal components of each subband, wherein the quantization precision is determined to be higher where the quantized values are larger and lower where the quantized values are smaller; and encoding the quantized values in variable-length codes, wherein the code lengths are set to be longer if the quantization precision value is higher, and shorter if the quantization precision value is lower. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A recording medium having encoded signals recorded thereon, the encoded signals operative to control, in part, the operation of a decoding apparatus, the recording medium being prepared by the steps of:
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transforming an input signal to a frequency spectrum of signal components; splitting the signal components of the frequency spectrum into a plurality of frequency subbands; quantizing the signal components in each subband to generate quantized values; determining the quantization precision needed for the signal components of each subband, wherein the quantization precision is determined to be higher where the quantized values are larger and lower where the quantized values are smaller; encoding the quantized values in variable-length codes, wherein the code lengths are set to be longer if the quantization precision value is higher, and shorter if the quantization precision value is lower; and recording the encoded quantized values onto the recording medium. - View Dependent Claims (11, 12, 13, 14)
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15. An encoded data signal recorded on a recording medium, the encoded data signal comprising:
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quantized values of signal components in a plurality of frequency subbands of a frequency spectrum; quantization precision values for the signal components of each subband, wherein the quantization precision is higher where the quantized values are larger and lower where the quantized values are smaller; and variable-length codes, wherein the code lengths are longer if the quantization precision value is higher, and shorter if the quantization precision value is lower.
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16. A signal decoding method, comprising the steps of:
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inputting a codestring comprising variable-length codes of quantized spectral signal components, quantization precision information and normalization coefficient information, wherein the quantization precision is higher when the quantized values are larger and lower where the quantized values are smaller, and wherein the codelengths are longer if the quantization precision value is higher and shorter if the quantization precision value is lower; extracting the codes of spectral signal components from the codestring; separating the codes of spectral signal components from codes of the quantization precision information and the normalization coefficient information; decoding the spectral signal components using the quantization precision information and the normalization precision information; transforming the spectral signal components from the frequency domain to the time domain; and outputting the result.
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17. A signal encoding apparatus for encoding acoustic waveform signals, comprising:
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means for inputting time domain signals; means for transforming an input signal to a frequency spectrum of signal components; means for splitting the signal components of the frequency spectrum into a plurality of frequency subbands, means for quantizing the signal components in each subband to generate quantized values; means for determining the quantization precision needed for the signal components of each subband, wherein the quantization precision is determined to be higher where the quantized values are larger and lower where the quantized values are smaller; means for encoding the quantized values in variable-length codes, wherein the code lengths are set to be longer if the quantization precision value is higher, and shorter if the quantization precision value is lower; and means for outputting any of the data generated by the foregoing means. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A signal encoding apparatus for encoding acoustic signals, comprising:
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an input terminal for inputting time domain signals; a conversion circuit for transforming an input signal to a frequency spectrum of signal components and splitting the signal components into a plurality of frequency subbands; a signal component encoding circuit for quantizing the signal components in each subband to generate quantized values and for determining the quantization precision needed for the signal components of each subband, wherein the quantization precision is determined to be higher where the quantized values are larger and lower where the quantized values are smaller; a codestring generating circuit for encoding the quantized values in variable-length codes, wherein the code lengths are set to be longer if the quantization precision value is higher, and shorter if the quantization precision value is lower; and an output terminal for outputting any of the data generated by the conversion circuit, the signal component encoding circuit or the codestring generating circuit. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. A signal decoding apparatus, comprising:
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means for inputting a codestring comprising variable-length codes of quantized spectral signal components, quantization precision information and normalization coefficient information, wherein the quantization precision is higher when the quantized values are larger and lower where the quantized values are smaller, and wherein the codelengths are longer if the quantization precision value is higher and shorter if the quantization precision value is lower; means for extracting codes of spectral signal components from the codestring and separating the spectral signal components from codes of the quantization precision information and the normalization coefficient information; means for decoding the spectral signal components using the quantization precision information and the normalization precision information; means for transforming the spectral signal components from the frequency domain to the time domain; and means for outputting the decoded signal.
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42. A signal decoding apparatus, comprising:
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an input terminal for inputting a codestring comprising variable-length codes of quantized spectral signal components, quantization precision information and normalization coefficient information, wherein the quantization precision is higher when the quantized values are larger and lower where the quantized values are smaller, and wherein the codelengths are longer if the quantization precision value is higher and shorter if the quantization precision value is lower; a codestring resolution circuit, in which codes of spectral signal components are extracted from the codestring and separated from codes of the quantization precision information and the normalization coefficient information; a signal component decoding circuit which decodes the spectral signal components using the quantization precision information and the normalization precision information; an inverse transform circuit which transforms the spectral signal components from the frequency domain to the time domain; and an output terminal.
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Specification