Speech coding system utilizing a recursive computation technique for improvement in processing speed
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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Abstract
This invention provides a novel speech coding system which recursively executes a filter-applied "Toeplitz characteristic" by causing a drive signal (i.e., an excitation signal) to be converted into a "Toeplitz matrix" when detecting a pitch period in which distortion of the input vector and the vector subsequent to the application of filter-applied computation to the drive signal vector in the pitch forecast called either "closed loop" or "compatible code book" is minimized. The vector quantization method substantially making up the speech coding system of the invention is characteristically used by the system.
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Citations
6 Claims
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1. A speech coding system, comprising:
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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. - View Dependent Claims (2, 3, 4)
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5. A speech coding system, comprising:
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an input speech means which, upon receipt of an input speech signal, generates an input speech vector; a weighting means which weights the input speech vector by means of a predetermined parameter and generates a weighted input speech vector; an excitation signal vector generating means which extracts and generates an excitation signal vector from a filter excitation signal for driving a linear predictive coding check filter; a computing means for recursively executing operations by using a drive signal matrix having the excitation signal vector represented by a Toeplitz matrix when executing the operations to determine an optical pitch period at which an error between the weighted input speech vector and the excitation signal vector is at a minimum; and output generating means for outputting a speech vector corresponding to the optimal pitch period. - View Dependent Claims (6)
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Specification