Linear predictive codeword excited speech synthesizer

Claim 1

A linear predictive codeword excited speech synthesizer comprising: linear predictive code analysis means for receiving an input speech signal and generating therefrom a set of linear predictive filter coefficients; codeword selection means responsive to said linear predictive code analysis means for generating a codeword index; inverse filter means responsive to said input speech signal and said linear predictive code analysis means for generating a residual speech signal output; pitch detector means responsive to said inverse filter means for generating pitch lag and pitch tap gain output signals; frame buffer means for receiving and storing samples of said input speech signal and said residual speech signal output; pitch epoch position detector means responsive to said pitch detector means for operating on stored input and residual speech signals in said frame buffer so as to detect a point of maximum excitation over a pitch cycle; gain estimator means for generating a gain output signal in response to segments of said stored input and residual speech signals in said frame buffer means; and means for transmitting said linear predictive filter coefficients, said codeword index, said pitch lag and pitch tap gain output signals, and said gain output signal.

Claim 7

A method for operating a linear predictive codeword excited speech synthesizer, said synthesizer including linear predictive code analysis means for receiving an input speech signal and generating therefrom a set of linear predictive filter coefficients, an all-pole linear predictive coefficient synthesis filter responsive to said linear predictive code analysis means for producing a filter transfer function that closely resembles a gross spectral shape of the input speech signal, and a codebook for providing a selected output signal, said method comprising: analyzing the input speech signal to produce said set of linear predictive filter coefficents; applying said linear predictive filter coefficents to said synthesis filter to generate said filter transfer function; searching said codebook to produce an output signal therefrom; muItiplying said output signal from said codebook by a gain factor to generate an excitation sequence input signal for said synthesis filter; subtracting the output signal of said synthesis filter from a speech samples input signal to produce a codeword index; choosing a new excitation codeword at a start of each frame of voiced speech, in synchronism with an output pitch period; and exciting said synthesis filter with a first P samples of said codeword, where P is the fundamental or pitch period of the input speech signal, the P samples being repeatedly played out to said synthesis filter to create a synthetic voiced output signal.

Claim 8

A method for operating a linear predictive codeword excited speech synthesizer, said synthesizer including linear predictive code analysis means for receiving an input speech signal and generating therefrom a set of linear predictive filter coefficients, an all-pole linear predictive coefficient synthesis filter responsive to said linear predictive code analysis means for producing a filter transfer function that closely resembles a gross spectral shape of the input speech signal, and a codebook for providing a selected output signal, said method comprising: analyzing the input speech signal to produce said set of linear predictive filter coefficents; applying said linear predictive filter coefficents to said synthesis filter to generate said filter transfer function; searching said codebook to produce an output signal therefrom; muItiplying said output signal from said codebook by a gain factor to generate an excitation sequence input signal for said synthesis filter; subtracting the output signal of said synthesis filter from a speech samples input signal to produce a codeword index; choosing a new excitation codeword at a start of each frame of voiced speech, in synchronism with an output pitch period; and exciting said synthesis filter with a first P samples of said codeword, where P is the fundamental or pitch period of the input speech signal, the P samples being repeatedly played out to said synthesis filter to create a synthetic voiced output signal.