Digital signal encoding with quantizing based on masking from multiple frequency bands
First Claim
1. An apparatus for encoding a digital signal, comprising:
- dividing means for receiving said digital signal and for dividing said digital signal into a plurality of frequency bands to produce a plurality of respective frequency band signals having respective energy levels,noise level setting means for generating an allowable noise level for each of said frequency band signals based on the energy level of the respective frequency band signal and the energy level of at least another one of said frequency band signals in which each of the allowable noise levels is non-linearly related to the energy level of the respective frequency band signal,means for producing a difference signal for each of said frequency band signals which represents a difference between the energy level of the respective frequency band signal and the allowable noise level for said respective frequency band signal, andquantization means for producing a quantized signal by quantizing components of each of said frequency band signals with a respective number of bits corresponding to the respective difference signal for each of said frequency band signals.
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Accused Products
Abstract
An allowable noise level is set for each frequency band of the input digital signal on the basis of the energy level of the respective frequency band and that of another frequency band. The energy level and the allowable noise level are non-linearly related so as to enable high data compression and to provide a satisfactory sound. The signal components of each of the frequency bands are quantized with a number of bits which correspond to the difference between the energy level of each frequency band and the allowable noise level. If the input digital signal is preemphasized, the signal is corrected for preemphasis prior to the setting of the allowable noise level, so that the quantization is performed on a signal which is free from the effects of preemphasis.
53 Citations
5 Claims
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1. An apparatus for encoding a digital signal, comprising:
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dividing means for receiving said digital signal and for dividing said digital signal into a plurality of frequency bands to produce a plurality of respective frequency band signals having respective energy levels, noise level setting means for generating an allowable noise level for each of said frequency band signals based on the energy level of the respective frequency band signal and the energy level of at least another one of said frequency band signals in which each of the allowable noise levels is non-linearly related to the energy level of the respective frequency band signal, means for producing a difference signal for each of said frequency band signals which represents a difference between the energy level of the respective frequency band signal and the allowable noise level for said respective frequency band signal, and quantization means for producing a quantized signal by quantizing components of each of said frequency band signals with a respective number of bits corresponding to the respective difference signal for each of said frequency band signals. - View Dependent Claims (2, 3, 4, 5)
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Specification