Analysis-by-synthesis 2,4 kbps linear predictive speech codec

Claim 2

A linear predictive speech codec arrangement for performing a closed loop analysis-by-synthesis operation, comprising: an excitation model means for generating a plurality of excitation signals comprising voiced excitation generator means in the form of a codebook for providing a plurality of possible pulse trains for use as an excitation signal; and Gaussian noise generator means in the form of a codebook for providing a plurality of possible random sequences for use as an excitation signal, wherein said voiced excitation generator means and said Gaussian noise generator means are provided in parallel arrangement; sequencing means, coupled to an output of said voiced excitation generator means and said Gaussian noise generator means, for providing all possible pulse trains and random sequences in sequence as possible excitation signals; spectrum synthesizer means, coupled to said sequencing means, for providing reconstructed speech generation in response to each of said plurality of excitation signals; distortion analyzer means, coupled to an output of said spectrum synthesizer means, for comparing said reconstructed speech with original speech, and providing a distortion analysis signal for each of said excitation signals; and means for comparing the distortion analysis signal for each of said excitation signals and selecting the excitation signal that produces the reconstructed speech with a minimum distortion analysis signal so as to provide optimal reconstructed speech.

Claim 3

A speech codec arrangement as claimed in claim 1, further comprising: output means for providing, for speech reconstruction at decoder means, coded output signals according to a 54 bit per speech frame coding scheme, wherein 26 bits are used to define parameters for said spectrum synthesizer means once per frame, and 28 bits are utilized to define a selected optimum excitation signal model twice per frame, with each of two 14 bit groups from said 28 bits being allocated as follows: 1 bit to designate one of a voiced and unvoiced excitation model; if a voiced model is designated, 7 bits are used to define a pitch value and 6 bits are used to define a gain; and, if an unvoiced model is designated, 8 bits being used to designate an excitation signal model from an unvoiced codebook, and 5 bits being used to define a gain; and, decoder means for receiving and utilizing said coded output signals, for producing said optimal reconstructed speech.

Claim 4

A speech codec arrangement as claimed in claim 1 wherein said distortion analyzer means comprises: residual speech means for providing a residual speech which negates effects induced by a memory of said spectrum synthesizer means before a reconstructed speech comparison is performed; and, subtractor means for receiving a reconstructed speech and subtracting therefrom, said residual speech delivered from said residual speech means.

Claim 5

A speech codec arrangement as claimed in claim 1 wherein said distortion analyzer means comprises: perceptual weighting means which introduces a perceptual weighting effect on the mean-squared-error distortion measure with regard to a reconstructed speech.

Claim 6

A speech codec arrangement as claimed in claim 1, wherein said spectrum synthesizer means is a 10th-order all-pole filter.

Claim 7

A linear predictive speech codec arrangement for performing a closed loop analysis-by-synthesis operation, comprising: an excitation model means for generating a plurality of excitation signals comprising voiced excitation generator means in the form of a first order pitch synthesizer for providing a plurality of possible voiced excitation signals for use as an excitation signal; and Gaussian noise generator means in the form of a codebook for providing a plurality of possible random sequences for use as an excitation signal, wherein said voiced excitation generator means and said gaussian noise generator means are provided in parallel arrangement; sequencing means, coupled to an output of said voiced excitation generator means and said Gaussian noise generator means, for providing all possible pulse trains and random sequences in sequence as possible excitation signals; spectrum synthesizer means, coupled to said sequencing means, for providing reconstructed speech generation in response to each of said plurality of excitation signals; distortion analyzer means, coupled to an output of said spectrum synthesizer means, for comparing said reconstructed speech with original speech, and providing a distortion analysis signal for each of said excitation signals; and means for comparing the distortion analysis signal for each of said excitation signals and selecting one of said possible random sequences, or selecting a pitch value and pitch filter coefficient of said first order pitch synthesizer so as to provide optimal reconstructed speech.

Claim 8

A linear predictive speech codec arrangement for performing a closed loop analysis-by-synthesis operation, comprising: an excitation model means for generating a plurality of excitation signals comprising voiced excitation generator means in the form of a first order pitch synthesizer for providing a plurality of possible voiced excitation signals for use as an excitation signal; and Gaussian noise generator means in the form of a codebook for providing a plurality of possible random sequences for use as an excitation signal, wherein said voiced excitation generator means and said gaussian noise generator means are provided in parallel arrangement; sequencing means, coupled to an output of said voiced excitation generator means and said Gaussian noise generator means, for providing all possible pulse trains and random sequences in sequence as possible excitation signals; spectrum synthesizer means, coupled to said sequencing means, for providing reconstructed speech generation in response to each of said plurality of excitation signals; distortion analyzer means, coupled to an output of said spectrum synthesizer means, for comparing said reconstructed speech with original speech, and providing a distortion analysis signal for each of said excitation signals; and means for comparing the distortion analysis signal for each of said excitation signals and selecting one of said possible random sequences, or selecting a pitch value and pitch filter coefficient of said first order pitch synthesizer so as to provide optimal reconstructed speech.

Claim 9

A speech codec arrangement as claimed in claim 6, further comprising: output means for providing, for speech reconstruction at decoder means, coded output signals according to a 54 bit per speech frame coding scheme, wherein 26 bits are used to define parameters for said spectrum synthesizer means once per frame, and 28 bits are utilized to define a selected optimum excitation signal model twice per frame, with each of two 14 bit groups from said 28 bits being allocated as follows: one bit to designate one of a voiced and unvoiced excitation model; if a voiced model is designated, 7 bits are used to define a pitch value and 6 bits are used to define a pitch filter coefficient; and, if an unvoiced model is designated, 8 bits being used to designate an excitation signal model from an unvoiced codebook, and 5 bits being used to define a gain; and, decoder means for receiving and utilizing said coded output signals, for producing said optimal reconstructed speech.

Claim 10

A linear predictive speech codec arrangement for performing a closed loop analysis-by-synthesis operation, comprising: an excitation model means for generating a plurality of excitation signals comprising voiced excitation generator means in the form of a first order pitch synthesizer for providing a plurality of possible voice excitation signals for use as an excitation signal; and Gaussian noise generator means in the form of a codebook for providing a plurality of possible random sequences for use as an excitation signal, wherein said voice excitation generator means and said Gaussian noise generator means are provided in parallel arrangement; sequencing means, coupled to an output of said voiced excitation generator means and said Gaussian noise generator means, for providing all possible pulse trains and random sequences in sequence as possible excitation signals; spectrum synthesizer means, coupled to said sequencing means, for providing reconstructed speech generation in response to each of said plurality of excitation signals; distortion analyzer means, coupled to an output of said spectrum synthesizer means, for comparing said reconstructed speech with original speech, and providing a distortion analysis signal for each of said excitation signals; and means for comparing the distortion analysis signal for each of said excitation signals and selecting one of said possible random sequences and a pitch value and pitch filter coefficient of said first order pitch synthesizer, and computing a summation of excitation signals according to the selected random sequence and pitch value and pitch filter coefficient so as to provide optimal reconstructed speech.

Claim 11

A linear predictive speech codec arrangement for performing a closed loop analysis-by-synthesis operation, comprising: an excitation model means for generating a plurality of excitation signals comprising voiced excitation generator means in the form of a first order pitch synthesizer for providing a plurality of possible voice excitation signals for use as an excitation signal; and Gaussian noise generator means in the form of a codebook for providing a plurality of possible random sequences for use as an excitation signal, wherein said voice excitation generator means and said Gaussian noise generator means are provided in parallel arrangement; sequencing means, coupled to an output of said voiced excitation generator means and said Gaussian noise generator means, for providing all possible pulse trains and random sequences in sequence as possible excitation signals; spectrum synthesizer means, coupled to said sequencing means, for providing reconstructed speech generation in response to each of said plurality of excitation signals; distortion analyzer means, coupled to an output of said spectrum synthesizer means, for comparing said reconstructed speech with original speech, and providing a distortion analysis signal for each of said excitation signals; and means for comparing the distortion analysis signal for each of said excitation signals and selecting one of said possible random sequences and a pitch value and pitch filter coefficient of said first order pitch synthesizer, and computing a summation of excitation signals according to the selected random sequence and pitch value and pitch filter coefficient so as to provide optimal reconstructed speech.

Claim 12

A speech codec arrangement as claimed in claim 8, further comprising: output means for providing, for speech reconstruction at decoder means, coded output signals according to a 54 bit per speech frame coding scheme, wherein 26 bits are used to define parameters for said spectrum synthesizer means once per frame, and 28 bits are utilized to define a selected optimum excitation signal model once per frame, with said 28 bits being allocated as follows: 7 bits are used to define a pitch value; 6 bits are used to define a pitch filter coefficient; 10 bits being used to designate an excitation signal model from an unvoiced codebook, and 5 bits being used to define a gain; and, decoder means for receiving and utilizing said coded output signals, for producing said optimal reconstructed speech.