Converts LSPs to LP coefficients.
IppStatus ippsLSPToLPC_GSMAMR_16s(const Ipp16s* pSrcLsp, Ipp16s* pDstLpc);
|Pointer to the LSP coefficient vector with ten elements, represented using Q0.15.|
|Pointer to the LP coefficient vector with 11 elements, represented using Q3.12.|
The function ippsLSPToLPC_GSMAMR is declared in ippsc.h file. This function converts a set of 10th-order LSPs to LP coefficients. The functionality is as follows:
for i = 1 .. 5
f1(i) = 2q2i-1 * f1(i-1) + 2f1(i-2)
for j = i-1 .. 1
f1(j) = f1(j) - 2q2i-1 * f1(j-1) + 2f1(j-2)
where initial values f1(0) = 1 and f1 (-1) = 0.
The coefficients f2(i) are computed similarly by replacing q2i-1 by q2i.
2. MultiplyF1(z) and F2(z) by 1+z-1 and 1-z-1 , respectively, to obtain F'1(z) and F'2(z), using the following relations:
f'1(i) = f1(i) + f1(i-1),
f'2(i) = f2(i) + f2(i-1), for i = 1,2, ..., 5.
3. Compute the LP coefficients from the polynomials F'1(z) and F'2(z) as follows:
ai = 0.5f'1(i) + 0.5f'2(i) for i = 1,2, ..., 5, and
ai = 0.5f'1(11 - i) + 0.5f'2(11 - i) for i = 6,7, ..., 11.
|Indicates no error.|
|Indicates an error when one of the specified pointers is NULL.|
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