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Vector quantinizer with distance measure calculated by using correlations

  • US 5,761,632 A
  • Filed: 05/16/1997
  • Issued: 06/02/1998
  • Est. Priority Date: 06/30/1993
  • Status: Expired due to Fees
First Claim
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1. A speech coder for coding speech signals, said speech coder including a vector quantizer, said vector quantizer comprising:

  • a plurality of auto-correlation calculation means each of which calculates an auto-correlation of an impulse response signal of a weighting function for a corresponding sub-interval of a plurality of sub-intervals of an input signal vector which corresponds to the input speech signal;

    a signal codebook means for storing a plurality of codevectors produced in advance, each of said codevectors having a length equal to a code length of said input signal vector;

    a plurality of auto-correlation codebook means for respectively storing a corresponding one of the plurality of auto-correlations calculated by a corresponding one of said plurality of auto-correlation calculation means;

    a first auto-correlation calculation circuit for calculating an auto-correlation of a first impulse response signal, said first impulse response signal corresponding to a weighting function for a first time interval of an input signal vector which corresponds to the input speech signal;

    a second auto-correlation calculation circuit for calculating an auto-correlation of a second impulse response signal, said second impulse response signal corresponding to said weighting function for a second time interval of said input signal vector, wherein said second time interval has a same time length as said first time interval and wherein said second time interval starts immediately after said first time interval ends;

    a signal codebook for storing a plurality of codevectors, each of said codevectors having a length equal to a code length of said input signal vector;

    a first auto-correlation codebook for storing the auto-correlation of the first impulse response signal as calculated by said first auto-correlation calculation circuit;

    a second auto-correlation codebook for storing the auto-correlation of the second impulse response signal as calculated by said second auto-correlation calculation circuit;

    a cross-correlation codebook for storing a cross-correlation of the first and second sub-intervals for each of the codevectors;

    a weighted cross-correlation calculation circuit for calculating a weighted cross-correlation of the input signal vector and each of the codevectors, with both the input signal vector and said each codevector being weighted by the weighting function, the weighted cross-correlation being performed for each codevector with respect to the input signal vector, the auto-correlations of the first and second impulse response signals, and the cross-correlation for said each codevector that is stored in the cross-correlation codebook;

    a weighted auto-correlation calculation circuit for calculating a weighted auto-correlation for said each codevector,a cross-correlation codebook means for storing a plurality of cross-correlations of the respective sub-intervals for each of the codevectors;

    a weighted cross-correlation calculation means for calculating a weighted cross-correlation of the input signal vector and each of the codevectors by weighting the input signal vector and said each codevector by the weighting function corresponding to each of the sub-intervals, and calculating the weighted cross-correlation by using the input signal vector, the plurality of codevectors and the plurality of impulse response signals;

    a weighted auto-correlation calculation means for calculating an auto-correlation of each of the weighted codevectors, as a weighted auto-correlation, by using the auto-correlations of the plurality of impulse response signals, the plurality of codevectors, and the cross-correlations;

    a distance calculation means for calculating a corresponding distance between the input signal vector and each of the codevectors, by using the cross-correlations of the weighted input signal vector and weighted codevectors, and the auto-correlation of the weighted codevectors; and

    a distance inspection means for supplying an index of one of the codevectors corresponding to a minimum distance of the distances calculated by the distance calculation means,wherein the one of the codevectors is used to quantize the input speech vector.

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