Digital signal encoder
First Claim
1. An apparatus for encoding an input digital signal, comprising;
- first frequency analysis means for frequency dividing said input digital signal into frequency components,second frequency analysis means for blocking and frequency analyzing said frequency components to produce blocks of data having analyzed frequency components,first noise level setting means for generating first output signals based on a first allowable noise level set in accordance with an energy of each said analyzed frequency component of said blocks of data output within a predetermined time period from said second frequency analysis means,second noise level setting means for generating second output signals based on a second allowable noise level of each said analyzed frequency component output within said predetermined time period set in accordance with an energy of at least one of said blocks of data which temporally precede and succeed, respectively, said each block, andquantization means for quantizing said blocks of data output from said second frequency analysis means on the basis of a quantization characteristic set in accordance with said first and second output signals from said first and second noise level setting means, respectively.
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Abstract
An apparatus for encoding an input digital signal divides the input digital signal to produce frequency components of increasing bandwidth as the frequency increases, performs blocking on each of the frequency components to produce blocks of decreasing time length as the frequency increases, performs a fast Fourier transformation on each block and quantizes each block using a quantization characteristic set in accordance with a comparison of the energy of each frequency component in each block with a masking spectrum. The masking spectrum includes both a masking effect on the frequency base of the input signal and masking effect on the time base of the input signal and may further include effects of the minimum audible curve of the human hearing sense characteristic. Utilization of both the temporal and frequency masking effects permits reduction in the bit rate of the encoded signal using real time processing and without deterioration in sound quality.
75 Citations
17 Claims
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1. An apparatus for encoding an input digital signal, comprising;
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first frequency analysis means for frequency dividing said input digital signal into frequency components, second frequency analysis means for blocking and frequency analyzing said frequency components to produce blocks of data having analyzed frequency components, first noise level setting means for generating first output signals based on a first allowable noise level set in accordance with an energy of each said analyzed frequency component of said blocks of data output within a predetermined time period from said second frequency analysis means, second noise level setting means for generating second output signals based on a second allowable noise level of each said analyzed frequency component output within said predetermined time period set in accordance with an energy of at least one of said blocks of data which temporally precede and succeed, respectively, said each block, and quantization means for quantizing said blocks of data output from said second frequency analysis means on the basis of a quantization characteristic set in accordance with said first and second output signals from said first and second noise level setting means, respectively. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification