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Dynamic bit allocation subband excited transform coding method and apparatus

DC
  • US 5,235,671 A
  • Filed: 10/15/1990
  • Issued: 08/10/1993
  • Est. Priority Date: 10/15/1990
  • Status: Expired due to Term
First Claim
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1. A speech coding system comprising:

  • transform means for performing a discrete transform of a window of speech to generate a discrete transform spectrum of coefficients comprising a plurality of subbands of coefficients;

    envelope defining and encoding means for defining an approximate envelope of the discrete spectrum of coefficients in each of the plurality of subbands of coefficients and for encoding the defined envelope of each subband of coefficients;

    means for scaling each spectrum coefficient relative to the encoded defined envelope of the respective subband of coefficients;

    a plurality of quantizers having different bit lengths for encoding the scaled spectrum coefficients within each subband; and

    means for determining a quantizer from the plurality of quantizers having different bit lengths, if any, to be used to encode the scaled spectrum coefficients of each subband within each window of speech wherein the selection of available quantizers used in successive windows is variable.

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