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Apparatus for compressing a digital input signal with signal spectrum-dependent and noise spectrum-dependent quantizing bit allocation

  • US 5,583,967 A
  • Filed: 06/16/1993
  • Issued: 12/10/1996
  • Est. Priority Date: 06/16/1992
  • Status: Expired due to Term
First Claim
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1. An apparatus for compressing a digital audio input signal to provide a compressed output signal, the apparatus comprising:

  • means for deriving plural spectral coefficients from the input signal and for grouping the spectral coefficients into bands;

    distributing means, responsive to the input signal, for distributing a total available number of quantizing bits between signal spectrum-dependent quantizing bits and noise spectrum-dependent quantizing bits;

    means for determining a magnitude for each band, and in response thereto, for allocating the signal spectrum-dependent quantizing bits among the bands to allocate to each band a number of signal spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band;

    means for determining a subjectively-allowable noise spectrum based at least upon the determined magnitude of each band, and in response thereto, for allocating the noise spectrum-dependent quantizing bits among the bands to allocate to each band a number of noise spectrum-dependent quantizing bits for quantizing each spectral coefficient in the band; and

    quantizing means for quantizing the spectral coefficients in each band using a total number of quantizing bits determined by summing the number of signal spectrum-dependent quantizing bits allocated to the band and the number of noise spectrum-dependent quantizing bits allocated to the band.

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