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Speech bandwidth extension method and apparatus

  • US 5,455,888 A
  • Filed: 12/04/1992
  • Issued: 10/03/1995
  • Est. Priority Date: 12/04/1992
  • Status: Expired due to Fees
First Claim
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1. Speech bandwidth extension apparatus comprising:

  • an input for receiving a narrowband speech signal sampled at a first rate;

    LPC analysis means for determining, for a speech frame having a predetermined duration of the speech signal, LPC parameters ai ;

    inverse filter means for filtering each speech frame in dependence upon the LPC parameters for the frame to produce a narrowband excitation signal frame;

    excitation extension means for producing a wideband excitation signal sampled at a second rate in dependence upon pitch and power of the narrowband excitation signal;

    lowband shape means for determining a lowband shape vector in dependence upon the LPC parameters;

    voiced/unvoiced means for determining voiced and unvoiced speech frames;

    gain and shape vector quantizer means for selecting predetermined highband shape and gain parameters in dependence upon the lowband shape vector for voiced speech frames and selecting fixed predetermined values for unvoiced speech frames;

    filter bank means responsive to the selected highband shape and gain parameters for filtering the wideband excitation signal to produce a highband speech signal;

    interpolation means for producing a lowband speech signal sampled at the second rate from the narrow band speech signal; and

    adder means for combining the highband speech signal and the lowband speech signal to produce a wideband speech signal.

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