Estimates the auto-correlation of a vector.
Syntax
IppStatus ippsAutoCorr_G723_16s(const Ipp16s* pSrcSpch, Ipp16s* pResultAutoCorrExp, Ipp16s* pDstAutoCorr);
Parameters
pSrcSpch |
Pointer to the input speech signal vector [180]. |
pResultAutoCorrExp |
Pointer to the exponent for autocorrelation coefficients. |
pDstAutoCorr |
Pointer to the autocorrelation coefficients vector [11]. |
Description
The function ippsAutoCorr_G723 is declared in the ippsc.h file. This function calculates the first 11 autocorrelation coefficients of the input speech signal. This function is applied to the 180 speech samples centered on the current subframe. The functionality is as follows.
1. First, apply to speech samples the Hamming windows, given by the following formula:
i = 0, 1, ...,179
2. Next, calculate the autocorrelations as follows:
k = 0,1,...,10
3. Finally, add the autocorrelation with binomial window, given by:
b(0) = 1025/1024,
i = 1,...,10 .
Note
The functionippsAutoCorr_G723 is actually a combination of ippsAutoScale , ippsMul_NR and ippsAutoCorr_NormE_G723 functions. The following code details the correspondence.
{ int autoScale=3, corrScale; short vect[180];
ippsAutoScale_16s(pSrcSpch, Vect,180, &autoScale );
/* Apply the Hamming window */
ippsMul_NR_16s_ISfs(HammWindow,Vect,180,15);
/* Compute the autocorrelation coefficients */
ippsAutoCorr_NormE_G723_16s(Vect,pDstAutoCorr,&corrScale);
*pResultAutoCorrExp = corrScale+(autoScale<<1);
}
Return Values
ippStsNoErr |
Indicates no error. |
ippStsNullPtrErr |
Indicates an error when one of the specified pointers is NULL. |