Performs LP to ISP coefficients conversion.
Syntax
IppStatus ippsLPCToISP_AMRWB_16s( const Ipp16s* pSrcLpc, Ipp16s* pDstIsp, const Ipp16s* pSrcPrevIsp);
Parameters
pSrcLpc |
Pointer to the input predictor coefficients. |
pDstIsp |
Pointer to the output immittance spectral pairs. |
pSrcPrevIsp |
Pointer to the input previous immittance spectral pairs. |
Description
This function is declared in ippsc.h file. The function performs the following steps:
1. Calculates the polynomial coefficients of F1(z) and F2(z) , using the following recursive relations:
i = 0,1,...,7 ,
f1(i) = a i + am-i
f2(i) = a i - am-i
f1(8) = 2a 8
where f2(-2) = f2(-1) = 1.0.
2. Uses Chebyshev polynomials to evaluate F1(z) and F2(z). The Chebyshev polynomials are given by:
F1(z) and F2(z) polynomials are evaluated at 100 points in equally spaced intervals between 0 and π and are checked for sign changes. A sign change indicates the existence of a root in the corresponding interval. In this case the interval is divided four times to track the root.
3. If the function cannot find all 16 roots needed to determine ISP coefficients, it returns the previous set of ISP coefficients instead.
Return Values
ippStsNoErr |
Indicates no error. |
ippStsNullPtrErr |
Indicates an error when one of the specified pointers is NULL. |