Apparatus, method, and system for compressing a digital input signal in more than one compression mode
First Claim
1. Apparatus for compressing a digital input signal in a selected one of plural compression modes to provide a compressed digital signal, the plural compression modes including a first compression mode and a second compression mode, the compressed digital signal having a higher bit rate in the first compression mode than in the second compression mode, the apparatus comprising:
- deriving means for deriving from the digital input signal spectral coefficients grouped by frequency and time into bands, each band having a frequency width, the deriving means including frequency width setting means for setting the frequency width of at least one of the plural bands according to the selected compression mode;
a quantizer, the quantizer receiving the bands of spectral coefficients from the deriving means, and providing bands of quantized spectral coefficients; and
including means for including in the compressed digital signal the quantized spectral coefficients from the quantizer and sub information for each band.
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Abstract
An apparatus, method, and system in which a compressed digital signal is derived from a digital input signal by compressing the digital input signal in a selected one of plural compression modes. The digital output signal has a different bit rate in each compression mode, but the digital input signal is received at the same bit rate in all the compression modes. In the method, spectral coefficients are derived from the digital input signal, and are grouped by frequency and by time into bands. Each band has a frequency width, and the frequency width of at least one of the bands is set according to the selected compression mode. The spectral coefficients in each band are quantized to provide quantized spectral coefficients. Finally, the quantized spectral coefficients in each band are included in the compressed digital signal, together with sub information for each band.
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Citations
59 Claims
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1. Apparatus for compressing a digital input signal in a selected one of plural compression modes to provide a compressed digital signal, the plural compression modes including a first compression mode and a second compression mode, the compressed digital signal having a higher bit rate in the first compression mode than in the second compression mode, the apparatus comprising:
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deriving means for deriving from the digital input signal spectral coefficients grouped by frequency and time into bands, each band having a frequency width, the deriving means including frequency width setting means for setting the frequency width of at least one of the plural bands according to the selected compression mode; a quantizer, the quantizer receiving the bands of spectral coefficients from the deriving means, and providing bands of quantized spectral coefficients; and including means for including in the compressed digital signal the quantized spectral coefficients from the quantizer and sub information for each band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for compressing a digital input signal in a selected one of plural compression modes to provide a compressed digital signal, the plural compression modes including a first compression mode and a second compression mode, the compressed digital signal having a higher bit rate in the first compression mode than in the second compression mode, the method comprising the steps of:
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deriving from the digital input signal spectral coefficients grouped by frequency and by time into bands, each band having a frequency width, the frequency width of at least one of the bands being set according to the selected one of the compression modes; quantizing the spectral coefficients in each band to provide quantized spectral coefficients; and including the quantized spectral coefficients in each band in the compressed digital signal, together with sub information for each band. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49)
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50. A digital signal processing system for compressing a digital input signal to provide a compressed digital signal and for expanding the compressed digital signal to provide a digital output signal, the system operating in a selected one of at least two different compression modes, including a first compression mode and a second compression mode, the compressed digital signal having a higher bit rate in the first compression mode than in the second compression mode, the system comprising:
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a compressor, including; compressed signal deriving means for analyzing the digital input signal into plural spectral coefficients grouped by frequency into plural bands, each band having a frequency width, for quantizing the spectral coefficients in each band to provide quantized spectral coefficients, and for providing the quantized spectral coefficients as the compressed digital signal, and means for setting the frequency width of at least one of the bands whereinto the spectral coefficients are grouped by frequency, the frequency width being set according to the selected compression mode; and an expander, including; demultiplexing means for receiving the compressed digital signal and extracting the quantized spectral coefficients and the sub information therefrom, dequantizing means for dequantizing the quantized spectral coefficients in each band using the sub information for the band to provide spectral coefficients, the frequency width of at least one of the bands being set according to the selected compression mode, and output signal deriving means for deriving the digital output signal from the spectral coefficients. - View Dependent Claims (51, 52, 53, 54, 55)
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56. Method for deriving a second compressed digital signal from a first compressed digital signal obtained by compressing a digital input signal in a first compression mode, the second compressed digital signal being compressed in a second compression mode, the first compressed digital signal and the second compressed digital signal respectively having a first bit rate and a second bit rate, the second bit rate being less than the second bit rate, the first compressed digital signal including plural quantized spectral coefficients grouped by frequency into bands, the bands being grouped by frequency into frequency ranges, the frequency ranges including a lowest-frequency frequency range, the method comprising the steps of:
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extracting the quantized spectral coefficients from the first compressed digital signal; inversely quantizing the quantized spectral coefficients to provide recovered spectral coefficients; inversely orthogonally transforming the recovered spectral coefficients in the lowest-frequency frequency range to provide a block of a lowest-frequency frequency range signal; joining blocks of the lowest-frequency frequency range signal together to provide super blocks; orthogonally transforming the super blocks of the lowest-frequency frequency range signal to provide new spectral coefficients; re-quantizing the new spectral coefficients and the recovered spectral coefficients not inversely orthogonally transformed in the inverse orthogonal transform step to provide new quantized spectral coefficients; and including the new quantized spectral coefficients in the second compressed digital signal. - View Dependent Claims (57, 58, 59)
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Specification