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Speech coding system utilizing a recursive computation technique for improvement in processing speed

  • US 5,230,036 A
  • Filed: 10/17/1990
  • Issued: 07/20/1993
  • Est. Priority Date: 10/17/1989
  • Status: Expired
First Claim
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1. A speech coding system, comprising:

  • means for receiving an input speech signal and outputting said input speech signal in the form of an input speech vector having one frame of unit;

    analyzing means for analyzing said input speech vector by means of a linear predictive coding method and extracting a predictive parameter rom said input speech vector;

    weighting means for weighting said input speech vector with said predictive parameter from said analyzing means, and for outputting a first weighted input speech vector;

    a first synthesis filter for outputting a zero-input speech vector;

    a first subtraction means for producing a difference between said first weighted input speech vector and said zero-input speech vector;

    a means for preventing influence of a last frame and influence of a pitch from said first weighted input speech vector;

    an excitation signal vector generating means for generating a first excitation signal vector when a target pitch period exceeds a predetermined value, and for generating a second excitation signal vector when said target pitch period is below said predetermined value;

    a computing means for recursively executing one or more operations using a drive signal matrix using one of said first and second excitation signal vectors in the form of a first Toeplitz matrix when executing said one or more operations to determine an optimal pitch period at which an error between said first weighted input speech vector and said one of said first and second excitation signal vectors is a minimum;

    a second synthesis filter for generating a synthesis speech vector corresponding to said optimal pitch period;

    a third synthesis filter;

    a codebook for generating a code vector for input to said third synthesis filter, said code vector being expressible in terms of a second Toeplitz matrix;

    a second subtraction means for producing a difference between the output of said first subtraction means and said synthesis speech vector corresponding to said optimal pitch period;

    a third subtraction means for producing a difference between the output of said second subtraction means and said second synthesis filter; and

    a selection means for selecting from said codebook an optimal code vector used to provide stable quality vector quantization such that said difference between the output from said third synthesis filter and said second weighted input speech vector is minimized.

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