IIRSparse

Filters a source vector through a sparse IIR filter.

Syntax

IppStatus ippsIIRSparse_32f(const Ipp32f* pSrc, Ipp32f* pDst, int len, IppsIIRSparseState_32f* pState);

Parameters

pState	Pointer to the sparse IIR filter state structure.
pSrc	Pointer to the source vector.
pDst	Pointer to the destination vector.
len	Number of elements that will be filtered.

Description

The function ippsIIRSparse is declared in the ipps.h file. This function applies the sparse IIR filter to the len elements of the source vector pSrc, and stores the results in pDst. The filter parameters - the number of non-zero taps nzTapsLen1, nzTapsLen2, their values pNZTaps and their positions pNZTapPos, and the delay line values pDlyLine - are specified in the sparse IIR filter structure pState that should be previously initialized the function ippsIIRSparseInit.

In the following definition of the sparse IIR filter, the sample to be filtered is denoted x(n), the non-zero taps are denoted B_i and A _i, their positions are denoted BP_i and AP_i.

The non-zero taps are arranged in the array as follows:

B₀, B₁, . . ., B_nzTapsLen1-1, A₀, A₁, . . ., A_{nzTapsLen2-1.}

The non-zero tap positions are arranged in the array as follows:

BP₀, BP₁, . . ., BP_nzTapsLen1-1, AP₀, AP₁, . . ., AP_{nzTapsLen2-1,}AP₀ ≠ 0

The return value is y(n) is defined by the formula for a sparse IIR filter:

After the function has performed calculations, it updates the delay line values stored in the filter state structure.

The example below shows how to use the sparse IIR filter functions.

Return Values

ippStsNoErr	Indicates no error.
ippStsNullPtrErr	Indicates an error if one of the specified pointers is NULL.
ippStsSizeErr	Indicates an error if len is less than or equal to 0.

Using the Sparse IIR Filter Functions

int buflen;

Ipp8u *buf;

int nzTapsLen1 = 5;	//number of non-zero taps in the FIR part of the formula

int nzTapsLen2 = 3;	//number of non-zero taps in the IIR part of the formula

Ipp32f nzTaps [] = {0.5, 0.4, 0.3, 0.2, 0.1, 0.8, 0.7, 0.6};	 
                                               //non-zero taps values (FIR+IIR)

Ipp32s nzTapsPos[] = {0, 10, 20, 30, 40, 1, 5, 15};

                            
                 //non-zero tap positions (FIR+IIR)

IppsIIRSparseState_32f* iirState;

Ipp32f *src, *dst;

/* ............................................. */

ippsIIRSparseGetStateSize_32f(nzTapsLen1, nzTapsLen2, nzTapsPos [nzTapsLen1 - 1],
                                 nzTapsPos [nzTapsLen1 + nzTapsLen2 - 1], &buflen);

buf = ippsMalloc_8u(buflen);

ippsIIRSparseInit_32f(&iirState, nzTaps, nzTapsPos, nzTapsLen1, nzTapsLen2,
                        NULL, buf);

/* . . . . initializing src somehow . . . . */

ippsIIRSparse_32f(src, dst, len, iirState);

/* dst[i] = src[i] * 0.5 + src[i-10] * 0.4 +  src[i-20] * 0.3 +  src[i-30] * 0.2 
           +  src[i-40] * 0.1 + dst[i-1] * 0.8 + dst[i-5] * 0.7 + dst[i-15] * 0.6  */

/* ................................................... */

ippsFree(buf);