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Speech coding

  • US 6,470,313 B1
  • Filed: 03/04/1999
  • Issued: 10/22/2002
  • Est. Priority Date: 03/09/1998
  • Status: Expired due to Term
First Claim
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1. A method of coding a speech signal which signal comprises a sequence of subframes containing digitised speech samples, the method comprising, for each subframe:

  • (a) selecting a quantised vector d(i) comprising at least one pulse, wherein the number m and position of pulses in the vector d(i) may vary between subframes;

    (b) determining a gain value gc for scaling the amplitude of the quantised vector d(i) or of a further vector c(i) derived from the quantised vector d(i), wherein the scaled vector synthesizes a weighted residual signal {tilde over (s)};

    (c) determining a scaling factor k which is a function of the ratio of a predetermined energy level to the energy in the quantised vector d(i);

    (d) determining a predicted gain value ĝ

    c on the basis of one or more previously processed subframes, and as a function of the energy Ec of the quantised vector d(i) or said further vector c(i) when the amplitude of the vector is scaled by said scaling factor k; and

    (e) determining a quantised gain correction factor {circumflex over (γ

    )}gc using said gain value gc and said predicted gain value ĝ

    c.

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