Method of calculating line spectral frequencies
First Claim
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1. A method of encoding a source signal by determining line spectral frequencies for representing linear predictive coding filter coefficients, said method comprising determining real zeros in associated polynomials in cos(mω
- ), where m is an integer and ω
is a variable angle, each of said associated polynomials comprising a series of Chebyshev polynomials, wherein a search for the real zeroes is performed by evaluating the associated polynomials in a series of steps in value of a variable, values of cos(ω
) being determined from an approximation of cos(ω
) as a function of a real variable u.
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Abstract
In a method of encoding a source signal by determining Line Spectral Frequencies (LSFs) for representing Linear Predictive Coding (LPC) filter coefficients, real zeros are determined in associated polynomials P″ and Q″ in cos(mω), with each polynomial being a series of Chebyshev polynomials, a search for real zeroes being performed by evaluating the associated polynomials in a series of steps of a real variable u, an approximation of cos(mω) as a function of the real variable u being employed.
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Citations
14 Claims
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1. A method of encoding a source signal by determining line spectral frequencies for representing linear predictive coding filter coefficients, said method comprising determining real zeros in associated polynomials in cos(mω
- ), where m is an integer and ω
is a variable angle, each of said associated polynomials comprising a series of Chebyshev polynomials, wherein a search for the real zeroes is performed by evaluating the associated polynomials in a series of steps in value of a variable, values of cos(ω
) being determined from an approximation of cos(ω
) as a function of a real variable u. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- ), where m is an integer and ω
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8. An encoder for encoding a source signal, wherein the encoder is arranged for determining line spectral frequencies for representing linear predictive coding filter coefficients by determining real zeros in associated polynomials in cos(mω
- ), where m is an integer and ω
is an angle, each of said associated polynomials comprising a series of Chebyshev polynomials, wherein a search for the real zeroes is performed by evaluating the associated polynomials in a series of steps in value of a real variable, values of cos(ω
) being determined from an approximation of cos(ω
) as a function of a real variable u. - View Dependent Claims (9, 10, 11, 12, 13)
- ), where m is an integer and ω
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14. A communication device comprising an encoder which is arranged for determining line spectral frequencies for representing linear predictive coding filter coefficients by determining real zeros in associated polynomials in cos(ω
- ), where m is an integer and ω
is an angle, each of said associated polynomials comprising a series of Chebyshev polynomials, wherein a search for the real zeroes is performed by evaluating the associated polynomials in a series of steps in value of a real variable u, values of cos(ω
) being determined from an approximation of cos(ω
) as a function of the real variable u which is;
- ), where m is an integer and ω
Specification