Speech specific adaptive transform coder

Claim 1

Apparatus for developing pitch information in relation to a given speech signal in a transform coder, which coder operates on a sampled time domain information signal composed of information samples by sequentially segregating groups of information samples into blocks, by transforming each block of samples from the time domain to a transform domain, and by generating an auto-correlation function of the transformed signal for each block, and which coder includes a data memory, said apparatus comprising, pitch means for determining the pitch period and the pitch gain from said auto-correlation function; striation means for determining the striation magnitude and energy from said pitch period and pitch gain; reference means for retrieving from said data memory a reference pitch, model which model includes a number of data points wherein said data points are representative of a model pitch striation; scaling means for generating a striation scaling factor in response to said magnitude and energy; multiplication means for multiplying said striation scaling factor by each of said data points thereby generating a current pitch model having a number of adaptively determined points; and sampling means for sampling said adaptively determined points which sampling establishes said pitch information.

Claim 5

A method for developing pitch information in relation to a given speech signal in a transform coder, which coder operates on a sampled time domain information signal composed of information samples by sequentially segregating groups of information samples into blocks, by transforming each block of samples from the time domain to a transform domain, and by generating an auto-correlation function of the transformed signal for each block, said method comprising the steps of: generating a reference pitch model which model includes a number of data points and storing said model in said data memory; determining the pitch period and the pitch gain from said auto-correlation function; determining the striation magnitude and energy from said pitch period and pitch gain. retrieving from said data memory a reference pitch model which model includes a number of data points wherein said data points are representative of a model pitch striation; generating a striation scaling factor in response to said magnitude and energy; multiplying said striation scaling factor by each of said data points thereby generating a current pitch model having a number of adaptively determined points; and sampling said adaptively determined points which sampling establishes said pitch information.

Claim 6

A method for developing pitch information in relation to a given speech signal in a transform coder, which coder operates on a sampled time domain information signal composed of information samples by sequentially segregating groups of information samples into blocks, by transforming each block of samples from the time domain to a transform domain, and by generating an auto-correlation function of the transformed signal for each block, said method comprising the steps of: generating a reference pitch model which model includes a number of data points and storing said model in said data memory; determining the pitch period and the pitch gain from said auto-correlation function; determining the striation magnitude and energy from said pitch period and pitch gain. retrieving from said data memory a reference pitch model which model includes a number of data points wherein said data points are representative of a model pitch striation; generating a striation scaling factor in response to said magnitude and energy; multiplying said striation scaling factor by each of said data points thereby generating a current pitch model having a number of adaptively determined points; and sampling said adaptively determined points which sampling establishes said pitch information.

Claim 9

A method for generating a reference pitch model comprising the steps of: defining a time domain impulse sequence, p(n) as follows: ##EQU15## where P gain is a predetermined value and P is one; generating a finite sequence of length 2N of said time domain impulse sequence utilizing a rectangular window; generating a spectral response of values of said finite sequence using a 2N-point complex FFT; determining the magnitude of said values of said spectral response; determining the energy of values of said spectral response; scaling said magnitude by said energy; and taking the logarithm to a predetermined base of the result of scaling said values.

Claim 10

A method for generating a reference pitch model comprising the steps of: defining a time domain impulse sequence, p(n) as follows: ##EQU15## where P gain is a predetermined value and P is one; generating a finite sequence of length 2N of said time domain impulse sequence utilizing a rectangular window; generating a spectral response of values of said finite sequence using a 2N-point complex FFT; determining the magnitude of said values of said spectral response; determining the energy of values of said spectral response; scaling said magnitude by said energy; and taking the logarithm to a predetermined base of the result of scaling said values.

Claim 13

A method for developing pitch information in relation to a given speech signal in a transform coder, which coder operates on a sampled time domain information signal composed of information samples, which coder sequentially segregates groups of information samples into blocks, transforms each block of samples from the time domain to a transform domain, and generates an autocorrelation function of the transformed signal for each block, said method comprising the steps of: generating a reference pitch model which model includes a number of data points and storing said model in said data memory; determining the pitch period and the pitch gain from said auto-correlation function; retrieving from said data memory a reference pitch model which model includes a number of data points, wherein said data points are representative of a model pitch striation; generating a striation scaling factor in relation to said pitch period and pitch gain; modifying said data points in relation to said scaling factor thereby generating a current pitch model having a number of adaptively determined points; and sampling said adaptively determined points which sampling establishes said pitch information.

Claim 14

A method for developing pitch information in relation to a given speech signal in a transform coder, which coder operates on a sampled time domain information signal composed of information samples, which coder sequentially segregates groups of information samples into blocks, transforms each block of samples from the time domain to a transform domain, and generates an autocorrelation function of the transformed signal for each block, said method comprising the steps of: generating a reference pitch model which model includes a number of data points and storing said model in said data memory; determining the pitch period and the pitch gain from said auto-correlation function; retrieving from said data memory a reference pitch model which model includes a number of data points, wherein said data points are representative of a model pitch striation; generating a striation scaling factor in relation to said pitch period and pitch gain; modifying said data points in relation to said scaling factor thereby generating a current pitch model having a number of adaptively determined points; and sampling said adaptively determined points which sampling establishes said pitch information.