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Digital signal coding/decoding apparatus, digital signal coding apparatus, and digital signal decoding apparatus

  • US 5,381,143 A
  • Filed: 09/08/1993
  • Issued: 01/10/1995
  • Est. Priority Date: 09/11/1992
  • Status: Expired due to Term
First Claim
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1. A digital signal processing system wherein a digital input signal is compressed to provide a compressed signal for recording on a medium, and the compressed signal, reproduced from the medium, is expanded to provide a digital output signal, the system comprising:

  • a compressor, the compressor including;

    non-block frequency analysis means for carrying out a frequency analysis of the digital input digital signal to provide a frequency range signal in each of plural frequency ranges, the non-block frequency analysis means carrying out the frequency analysis without dividing the digital input signal into blocks,block frequency analysis means for carrying out a block frequency analysis of the frequency range signals from the non-block frequency analysis means to provide a block of spectral coefficients, the block frequency analysis means including means for dividing the frequency range signals in time into blocks, andmeans for quantizing the block of spectral coefficients from the block frequency analysis means to provide a block of the compressed signal;

    an expander, the expander including;

    block frequency synthesis means for performing a block frequency synthesis to transform, from a frequency base to a time base, the spectral coefficients in each of the frequency ranges in each block of the compressed signal reproduced from the medium, the block frequency synthesis means providing, in each of the frequency ranges, a block of a reproduced frequency range signal, andnon-block frequency synthesis means for conducting frequency synthesis of the reproduced frequency range signals from the block frequency synthesis means to provide the digital output signal, the non-block frequency synthesis means conducting the frequency synthesis without dividing the reproduced frequency range signals into blocks; and

    scale-down means for scaling down values in one of the block frequency analysis performed by the block frequency analysis means and the block frequency synthesis performed by the block frequency synthesis means, the scale-down means operating to cause noise levels resulting from scaling down the values to be different in each of the frequency ranges.

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