High efficiency digital data encoding and decoding apparatus
First Claim
1. An apparatus for compressing a digital input signal divided into frames of plural samples to provide a compressed signal, the apparatus comprising:
- plural orthogonal transform means for orthogonally transforming the digital input signal in blocks derived by dividing each frame by a different set of divisors, each set of divisors including at least one divisor, each orthogonal transform means deriving spectral coefficients from the digital input signal, quantizing the spectral coefficients by adaptively allocating a number of quantizing bits among the spectral coefficients, each orthogonal transform means allocating an equal number of quantizing bits, and providing the quantized spectral coefficients as an output signal; and
means for selecting the output signal from one of the orthogonal transform means as the compressed signal in response to a selection signal from each of the orthogonal transform means.
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Abstract
An apparatus for compressing a digital input signal compresses a digital input signal arranged into frames of plural samples. The digital input signal is orthogonally transformed by plural orthogonal transform circuits in blocks derived by dividing the frames by a different divisor in each circuit. The resulting spectral coefficients are quantized using an adaptive number of bits. The output of one orthogonal transform circuit is selected based on the outputs of the orthogonal transform circuits. The digital input signal is divided into plural frequency ranges, and frames are formed in each range. A block length decision circuit determines division of the frames of each range signal into blocks in response to range signal dynamics. The range signals are orthogonally transformed in blocks and the spectral coefficients are quantized. The apparatus also includes a frequency analyzing circuit that derives spectral data points from the input data, and groups them in plural bands. A noise level setting circuit finds the energy in each band and sets a allowable noise level in response to the band energy. A block floating coefficient calculating circuit calculates block floating coefficients based on the maximum spectral data point in each band. A quantizing bit number decision circuit determines the number of bits to use for quantizing in response to the allowable noise level and the block floating coefficients. A quantizing circuit quantizes the spectral data points in response to the quantizing bit number decision circuit.
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Citations
29 Claims
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1. An apparatus for compressing a digital input signal divided into frames of plural samples to provide a compressed signal, the apparatus comprising:
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plural orthogonal transform means for orthogonally transforming the digital input signal in blocks derived by dividing each frame by a different set of divisors, each set of divisors including at least one divisor, each orthogonal transform means deriving spectral coefficients from the digital input signal, quantizing the spectral coefficients by adaptively allocating a number of quantizing bits among the spectral coefficients, each orthogonal transform means allocating an equal number of quantizing bits, and providing the quantized spectral coefficients as an output signal; and means for selecting the output signal from one of the orthogonal transform means as the compressed signal in response to a selection signal from each of the orthogonal transform means. - View Dependent Claims (2, 3, 4, 5, 6, 9, 11)
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7. An apparatus for compressing a digital input signal to provide a compressed signal, the apparatus comprising:
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means for dividing the digital input signal into plural frequency ranges to provide plural frequency range signals, each frequency range signal being arranged into frames composed of plural samples; a block length decision means for dynamically determining a division of each frame of each frequency range signal into at least one block in response to a dynamic characteristic of the frame of the frequency range signal; orthogonal transform means for orthogonally transforming each frequency range signal to produce spectral coefficients, the orthogonal transforms means transforming each frequency range signal in blocks determined by the block length decision means; and means for quantizing the spectral coefficients. - View Dependent Claims (8, 10, 12, 17)
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13. A apparatus for compressing a digital input signal, apparatus comprising:
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frequency analyzing means for frequency analyzing the digital input signal to provide plural spectral data points and for forming the spectral data points into plural bands; allowable noise level setting means for determining an energy for each band, and for setting an allowable noise level in response to the energy in each band; block floating coefficient calculating means for calculating a block floating coefficient in response to a maximum spectral data point in each band; quantizing bit number decision means for determining a number of quantizing bits in response to the allowable noise level and the block floating coefficient; and quantizing means for quantizing the spectral data points from the frequency analyzing means using the number of quantizing bits determined by the quantizing bit number decision means. - View Dependent Claims (14, 15, 16)
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18. In combination, a compressor apparatus for compressing a digital input signal comprising plural samples to provide a compressed signal, and an expander apparatus for applying complementary expansion to the compressed signal to provide a digital output signal, the compressor comprising:
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means for arranging the digital input signal in frames of plural samples, means for dividing the digital input signal data into plural frequency ranges to provide plural frequency range signals, means for orthogonally transforming each frequency range signal to provide spectral coefficients, each frequency range signal being transformed by dynamically dividing each frame of the frequency range signal into blocks having a block length determined in response to a dynamic characteristic of the frame of the frequency range signal, and means for quantizing the spectral coefficients using an adaptive bit allocation, means for including in the compressed signal the quantized spectral coefficients and subsidiary information indicating the adaptive bit allocation; and the expander comprising; means for extracting the quantized spectral coefficients and the subsidiary information from the compressed signal, means for dequantizing the quantized spectral coefficients in response to the subsidiary information indicating the adaptive bit allocation to provide plural spectral coefficients, means, including a reverse orthogonal transform circuit, for transforming the spectral coefficients into frequency range signals, and means, including an inverse band division filter, for synthesizing the frequency range signals to produce the digital output signal. - View Dependent Claims (19, 20)
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21. A method for storing in a medium a compressed digital signal derived from a digital input signal divided into frames of plural samples, the method comprising the steps of:
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performing plural orthogonal transforms of the digital input signal each orthogonal transform; orthogonally transforming the digital input signal in blocks derived by dividing a frame of the digital input signal by a different set of divisors, each set of divisors including at least one divisor to provide spectral coefficients, quantizing the spectral coefficients by adaptively allocating a number of quantizing bits among the spectral coefficients using an adaptive bit allocation, each orthogonal transform adaptively allocating an equal number of quantizing bits and providing the quantized spectral coefficients as an output signal for the orthogonal transform; selecting, as the part of the compressed signal, the output signal for one of the orthogonal transforms in response to a selection signal for each orthogonal transform; including subsidiary information indicating the adaptive bit allocation in the compressed signal; and storing the compressed signal in the medium. - View Dependent Claims (22)
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23. A method for storing in a medium a compressed digital signal derived from a digital input signal, the method comprising the steps of:
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dividing the digital input signal into plural frequency ranges to provide plural frequency range signals, each frequency range signal being arranged into frames of plural samples; dynamically determining a division of each frame of each frequency range signal into blocks in response to a dynamic characteristic of the frame of the frequency range signal; orthogonally transforming each frequency range signal in blocks determined by the determining step to produce spectral coefficients; quantizing the spectral coefficients using an adaptive bit allocation; including the quantized spectral coefficients and subsidiary information indicating the adaptive bit allocation in the compressed digital signal; and storing the compressed digital signal in the medium. - View Dependent Claims (24, 25)
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26. A method for storing in a medium a compressed digital signal derived from a digital input signal, the method comprising the steps of:
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frequency analyzing the digital input signal to provide plural spectral data points; forming the spectral data points into plural bands; determining an energy for each band; setting an allowable noise level in response to the energy in each band; calculating a block floating coefficient for each band in response to a maximum level spectral data point in the band; determining a number of quantizing bits for each band in response to the allowable noise level and the block floating coefficient for the band; quantizing the spectral data points in each band using the number of quantizing bits determined in the step of determining the number quantizing bits; including the quantized spectral data points and subsidiary information indicating the number of quantizing bits for each band in the compressed digital signal; and storing the compressed digital signal in the medium. - View Dependent Claims (27, 28, 29)
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Specification