Apparatus for compressing a digital input signal with signal spectrum-dependent and noise spectrum-dependent quantizing bit allocation
First Claim
1. An apparatus for compressing a digital audio input signal to provide a compressed output signal, the apparatus comprising:
- means for deriving plural spectral coefficients from the input signal and for grouping the spectral coefficients into bands;
distributing means, responsive to the input signal, for distributing a total available number of quantizing bits between signal spectrum-dependent quantizing bits and noise spectrum-dependent quantizing bits;
means for determining a magnitude for each band, and in response thereto, for allocating the signal spectrum-dependent quantizing bits among the bands to allocate to each band a number of signal spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band;
means for determining a subjectively-allowable noise spectrum based at least upon the determined magnitude of each band, and in response thereto, for allocating the noise spectrum-dependent quantizing bits among the bands to allocate to each band a number of noise spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band; and
quantizing means for quantizing the spectral coefficients in each band using a total number of quantizing bits determined by summing the number of signal spectrum-dependent quantizing bits allocated to the band and the number of noise spectrum-dependent quantizing bits allocated to the band.
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Abstract
An apparatus for compressing a digital audio input signal to provide a compressed output signal. A circuit derives plural spectral coefficients from the input signal and groups the spectral coefficients into bands. A distributing circuit distributes a total available number of quantizing bits between signal spectrum-dependent quantizing bits and noise spectrum-dependent quantizing bits. A circuit determines a magnitude for each band, and, in response thereto, allocates the signal spectrum-dependent quantizing bits among the bands. This allocates to each band a number of signal spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band. A circuit determines a subjectively-allowable noise spectrum and, in response thereto, allocates the noise spectrum-dependent quantizing bits among the bands. This allocates to each band a number of noise spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band. A quantizing circuit quantizes the spectral coefficients in each band using a total number of quantizing bits determined by summing the number of signal spectrum-dependent quantizing bits allocated to the band and the number of noise spectrum-dependent quantizing bits allocated to the band. The distribution circuit sets the distribution ratio in response to a circuit that calculates the smoothness of the spectrum of the input signal. In this manner, optimum quantizing for both musical signals and single sine wave signals are given by a single processing operation, without the need to repeatedly adjust the quantizing bit allocation.
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Citations
32 Claims
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1. An apparatus for compressing a digital audio input signal to provide a compressed output signal, the apparatus comprising:
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means for deriving plural spectral coefficients from the input signal and for grouping the spectral coefficients into bands; distributing means, responsive to the input signal, for distributing a total available number of quantizing bits between signal spectrum-dependent quantizing bits and noise spectrum-dependent quantizing bits; means for determining a magnitude for each band, and in response thereto, for allocating the signal spectrum-dependent quantizing bits among the bands to allocate to each band a number of signal spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band; means for determining a subjectively-allowable noise spectrum based at least upon the determined magnitude of each band, and in response thereto, for allocating the noise spectrum-dependent quantizing bits among the bands to allocate to each band a number of noise spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band; and quantizing means for quantizing the spectral coefficients in each band using a total number of quantizing bits determined by summing the number of signal spectrum-dependent quantizing bits allocated to the band and the number of noise spectrum-dependent quantizing bits allocated to the band. - View Dependent Claims (2, 3)
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4. An apparatus for compressing a digital audio input signal to provide a compressed output signal, the apparatus comprising:
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means for deriving plural spectral coefficients from the input signal and for grouping the spectral coefficients into bands; distributing means, responsive to a smoothness of the input signal, for distributing a total available number of quantizing bits between signal spectrum-dependent quantizing bits and noise spectrum-dependent quantizing bits; means for determining a magnitude for each band, and in response thereto, for allocating the signal spectrum-dependent quantizing bits among the bands to allocate to each band a number of signal spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band; means for determining a subjectively-allowable noise spectrum based upon at least the determined magnitude of each band, and in response thereto, for allocating the noise spectrum-dependent quantizing bits among the bands to allocate to each band a number of noise spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band; and quantizing means for quantizing the spectral coefficients in each band using a total number of quantizing bits determined by summing the number of signal spectrum-dependent quantizing bits allocated to the band and the number of noise spectrum-dependent quantizing bits allocated to the band. - View Dependent Claims (5, 6, 7, 8)
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9. An apparatus for expanding a compressed digital signal to provide a digital audio output signal, the compressed digital signal being derived from a digital audio input signal having a spectrum by a compression method including the steps of:
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deriving plural spectral coefficients from the input signal, grouping the spectral coefficients into bands, and determining a magnitude for each band; distributing, in response to the input signal, a total available number of quantizing bits between noise spectrum-dependent bits for allocation among the bands depending on a subjectively allowable noise spectrum based upon at least the magnitude determined for each band, and signal spectrum-dependent bits for allocation among the bands according to the magnitudes of the bands; quantizing the spectral coefficients in each band using a total number of bits determined by summing the noise spectrum-dependent bits allocated to the band and the signal spectrum-dependent bits allocated to the band; and including the quantized spectral components in the compressed signal; the expander comprising; extracting means for extracting quantized spectral coefficients from the compressed signal, wherein the allocation of bits among the bands depends on the subjectively allowable noise spectrum based upon at least the magnitude determined for each band; dequantizing means for dequantizing the quantized spectral components; and means for deriving the output signal from the dequantized spectral components. - View Dependent Claims (10)
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11. An apparatus for expanding a compressed digital signal to provide a digital audio output signal, the compressed digital signal being derived from a digital audio input signal having a spectrum having a smoothness, by a compression method including the steps of:
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deriving plural spectral coefficients from the input signal, grouping the spectral coefficients into bands, and determining a magnitude for each band; distributing, in response to the input signal, a total available number of quantizing bits between noise spectrum-dependent bits for allocation among the bands depending on a subjectively allowable noise spectrum, and signal spectrum-dependent bits for allocation among the bands according to the magnitudes of the bands, wherein the input signal has a smoothness and more of the total available number of quantizing bits are distributed as noise spectrum-dependent quantizing bits as the smoothness of the spectrum of the input signal increases; quantizing the spectral coefficients in each band using a total number of bits determined by summing the noise spectrum-dependent bits allocated to the band and the signal spectrum-dependent bits allocated to the band; and
including the quantized spectral components in the compressed signal;the expander comprising; extracting means for extracting quantized spectral coefficients from the compressed signal, wherein the allocation of bits among the bands depends on the subjectively allowable noise spectrum based upon at least the magnitude determined for each band; dequantizing means for dequantizing the .quantized spectral components; and means for deriving the output signal from the dequantized spectral components.
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12. An apparatus for expanding a compressed digital signal to provide a digital audio output signal, the compressed digital signal being derived from a digital audio input signal having a spectrum which includes plural spectral points, each point having a value, by a compression method including the steps of:
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deriving plural spectral coefficients from the input signal, grouping the spectral coefficients into bands, and determining a magnitude for each band; calculating a difference between the values of adjacent spectral points to indicate the smoothness of the spectrum of the input signal; distributing, in response to the input signal, a total available number of quantizing bits between noise spectrum-dependent bits for allocation among the bands depending on a subjectively allowable noise spectrum, and signal spectrum-dependent bits for allocation among the bands according to the magnitudes of the bands, wherein the input signal has a smoothness and more of the total available number of quantizing bits are distributed as noise spectrum-dependent quantizing bits as the smoothness of the spectrum of the input signal increases; quantizing the spectral coefficients in each band using a total number of bits determined by summing the noise spectrum-dependent bits allocated to the band and the signal spectrum-dependent bits allocated to the band; and including the quantized spectral components in the compressed signal; the expander comprising; extracting means for extracting quantized spectral coefficients from the compressed signal, wherein the allocation of bits among the bands depends on the subjectively allowable noise spectrum based upon at least the magnitude determined for each band; dequantizing means for dequantizing the quantized spectral components; and means for deriving the output signal from the dequantized spectral components.
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13. An apparatus for expanding a compressed digital signal to provide a digital audio output signal, the compressed digital signal being derived from a digital audio input signal having a spectrum by a compression method including the steps of:
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deriving plural spectral coefficients from the input signal, grouping the spectral coefficients into bands, and determining a magnitude for each band; calculating a difference between the magnitudes of the bands to indicate the smoothness of the spectrum of the input signal; distributing, in response to the input signal, a total available number of quantizing bits between noise spectrum-dependent bits for allocation among the bands depending on a subjectively allowable noise spectrum, and signal spectrum-dependent bits for allocation among the bands according to the magnitudes of the bands, wherein the input signal has a smoothness and more of the total available number of quantizing bits are distributed as noise spectrum-dependent quantizing bits as the smoothness of the spectrum of the input signal increases; quantizing the spectral coefficients in each band using a total number of bits determined by summing the noise spectrum-dependent bits allocated to the band and the signal spectrum-dependent bits allocated to the band; and including the quantized spectral components in the compressed signal; the expander comprising; extracting means for extracting quantized spectral coefficients from the compressed signal, wherein the allocation of bits among the bands depends on the subjectively allowable noise spectrum based upon at least the magnitude determined for each band; dequantizing means for dequantizing the quantized spectral components; and means for deriving the output signal from the dequantized spectral components.
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14. An apparatus for expanding a compressed digital signal to provide a digital audio output signal, the compressed digital signal being derived from a digital audio input signal having a spectrum by a compression method including the steps of:
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deriving plural spectral coefficients from the input signal, grouping the spectral coefficients into bands, and determining a magnitude for each band; applying block floating to each band, and calculating a block floating coefficient for each band; calculating a difference between the block floating coefficients of adjacent bands to indicate the smoothness of the spectrum of the input signal; distributing, in response to the input signal, a total available number of quantizing bits between noise spectrum-dependent bits for allocation among the bands depending on a subjectively allowable noise spectrum, and signal spectrum-dependent bits for allocation among the bands according to the magnitudes of the bands, wherein the input signal has a smoothness and more of the total available number of quantizing bits are distributed as noise spectrum-dependent quantizing bits as the smoothness of the spectrum of the input signal increases; quantizing the spectral coefficients in each band using a total number of bits determined by summing the noise spectrum-dependent bits allocated to the band and the signal spectrum-dependent bits allocated to the band; and including the quantized spectral components in the compressed signal; the expander comprising; extracting means for extracting quantized spectral coefficients from the compressed signal, Wherein the allocation of bits among the bands depends on the subjectively allowable noise spectrum based upon at least the magnitude determined for each band; dequantizing means for dequantizing the quantized spectral components; and means for deriving the output signal from the dequantized spectral components.
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15. An apparatus for expanding a compressed digital signal to provide a digital audio output signal, the compressed digital signal being derived from a digital audio input signal having a spectrum by a compression method including the steps of:
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deriving plural spectral coefficients from the input signal by dividing the input signal in frequency without dividing the input signal in time to provide plural frequency range signals, and dividing each frequency range signal in time into blocks, and further dividing the frequency range signal in each block in frequency to provide the spectral coefficients, grouping the spectral coefficients into bands, and determining a magnitude for each band; distributing, in response to the input signal, a total available number of quantizing bits between noise spectrum-dependent bits for allocation among the bands depending on a subjectively allowable noise spectrum based upon at least the magnitude determined for each band, and signal spectrum-dependent bits for allocation among the bands according to the magnitudes of the bands; quantizing the spectral coefficients in each band using a total number of bits determined by summing the noise spectrum-dependent bits allocated to the band and the signal spectrum-dependent bits allocated to the band; and including the quantized spectral components in the compressed signal; the expander comprising; extracting means for extracting quantized spectral coefficients from the compressed signal, wherein the allocation of bits among the bands depends on the subjectively allowable noise spectrum based upon at least the magnitude determined for each band; dequantizing means for dequantizing the quantized spectral components; and means for deriving the output signal from the dequantized spectral components, wherein the means for deriving includes an orthogonal transform circuit.
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16. An apparatus for expanding a compressed digital signal to provide a digital audio output signal, the compressed digital signal being derived from a digital audio input signal having a spectrum by a compression method including the steps of:
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deriving plural spectral coefficients from the input signal by dividing the input signal in frequency without dividing the input signal in time to provide plural frequency range signals, orthogonally transforming each frequency range signal to provide plural spectral coefficients therefrom, grouping the spectral coefficients into bands, and determining a magnitude for each band; distributing, in response to the input signal, a total available number of quantizing bits between noise spectrum-dependent bits for allocation among the bands depending on a subjectively allowable noise spectrum based upon at least the magnitude determined for each band, and signal spectrum-dependent bits for allocation among the bands according to the magnitudes of the bands; quantizing the spectral coefficients in each band using a total number of bits determined by summing the noise spectrum-dependent bits allocated to the band and the signal spectrum-dependent bits allocated to the band; and including the quantized spectral components in the compressed signal; the expander comprising; extracting means for extracting quantized spectral coefficients from the compressed signal, wherein the allocation of bits among the bands depends on the subjectively allowable noise spectrum based upon at least the magnitude determined for each band; dequantizing means for dequantizing the quantized spectral components; and means for deriving the output signal from the dequantized spectral components, wherein the means for deriving includes an orthogonal transform circuit.
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17. A system for recording on a recording medium a digital audio input signal having a bit rate, and for reproducing the digital input signal from the recording medium to provide a digital audio output signal, the system deriving from the input signal a compressed signal for recording on the recording medium, and deriving the output signal from the compressed signal reproduced from the recording medium, the compressed signal having a bit rate lower than the bit rate of the input signal, the system comprising:
a compressor comprising; means for deriving plural spectral coefficients from the input signal and for grouping the spectral coefficients into bands; distributing means, responsive to the input signal, for distributing a total available number of quantizing bits between signal spectrum-dependent quantizing bits and noise spectrum-dependent quantizing bits; means for determining a magnitude for each band, and in response thereto, for allocating the signal spectrum-dependent quantizing bits among the bands to allocate to each band a number of signal spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band; means for determining a subjectively-allowable noise spectrum based upon at least the determined magnitude of each band; and
in response thereto, for allocating the noise spectrum-dependent quantizing bits among the bands to allocate to each band a number of noise spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band;quantizing means for quantizing the spectral coefficients in each band using a total number of quantizing bits determined by summing the number of signal spectrum-dependent quantizing bits allocated to the band and the number of noise spectrum-dependent quantizing bits allocated to the band, and including means for including the quantized spectral coefficients in the compressed signal; and
an expander, comprising;extracting means for extracting quantized spectral coefficients from the compressed signal; dequantizing means for dequantizing the quantized spectral components; and means for deriving the output signal from the dequantized spectral components. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A method of compressing a digital audio input signal to provide a compressed output signal, comprising the steps of:
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deriving plural spectral coefficients from the input signal, grouping the spectral coefficients into bands, and determining a magnitude for each band; distributing, in response to the input signal, a total available number of quantizing bits between noise spectrum-dependent bits for allocation among the bands depending on a subjectively allowable noise spectrum, the subjectively-allowable noise spectrum based upon the determined magnitudes of the bands, and signal spectrum-dependent bits for allocation among the bands according to the determined magnitudes of the bands; quantizing the spectral coefficients in each band using a total number of bits determined by summing the noise spectrum-dependent bits allocated to the band and the signal spectrum-dependent bits allocated to the band; and including the quantized spectral components in the compressed signal. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32)
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Specification