Converts LSP coefficients to LP coefficients.
Syntax
IppStatus ippsLSPToLPC_G729_16s(const Ipp16s* pSrcLSP, Ipp16s* pDstLPC);
IppStatus ippsLSPToLPC_G729_32f(const Ipp32f* pSrcLsp, Ipp32f* pDstLpc);
Parameters
pSrcLSP |
Pointer to the LSP coefficients vector [10], in Q15 for 16s data. |
pDstLPC |
Pointer to the LP coefficients vector [11], in Q12 for 16s data. |
Description
The function ippsLSPToLPC_G729 is declared in the ippsc.h file. This function converts a set of 10th order LSP coefficients to LP coefficients. It performs the following steps:
1. Calculates the polynomial coefficients of F1(z) and F2(z) , using the recursive relations:
for i = 1 to 5
f1(i) = -2q2i-1 *f1(i-1) + 2f1(i-2)
for j = i-1 down to 1
f1[i](j) = f1[i-1](j) - 2q2i-1 * f1[i-1] (j-1) + f1[i-1] (j-2)
end
end
Here the initial values are set to f1(0) = 1 and f1(-1) = 0. The coefficients f2(i) are computed similarly by replacing q2i-1 by q2i .
2. F1(z) and F2(z) are then multiplied by 1+z-1 and 1-z-1 respectively to obtain F'1(z) and F'2(z) as given by:
f'1(i) = f1(i) + f1(i-1) , i = 1,2,...5
f'2(i) = f2(i) + f2(i-1) , i = 1,2,...5
3. Finally, the function computes the LP coefficients from f'1( i) and f'2(i) as:
Return Values
ippStsNoErr |
Indicates no error. |
ippStsNullPtrErr |
Indicates an error when the pSrcLSP or pDstLPC pointer is NULL. |