Developer Reference for Intel® Integrated Performance Primitives 2019

FIRGenLowpass

Computes lowpass FIR filter coefficients.

Syntax

IppStatus ippsFIRGenLowpass_64f(Ipp64f rFreq, Ipp64f* pTaps, int tapsLen, IppWinType winType, IppBool doNormal, Ipp8u* pBuffer);

Include Files

ipps.h

Domain Dependencies

Headers: ippcore.h, ippvm.h

Libraries: ippcore.lib, ippvm.lib

Parameters

rFreq

Normalized cutoff frequency, must be in the range (0, 0.5).

pTaps

Pointer to the array where computed tap values are stored. The number of elements in the array is tapsLen.

tapsLen

Number of elements in the array containing the tap values; must be equal or greater than 5.

winType

Specifies what type of window is used in computations. The winType must have one of the following values:
  • ippWinBartlett - Bartlett window

  • ippWinBlackman - Blackman window

  • ippWinHamming - Hamming window

  • ippWinHann - Hann window

doNormal

Specifies normalized or non-normalized sequence of the filter coefficients is computed. The doNormal must have one of the following values:
  • ippTrue for normalized sequence of coefficients

  • ippFalse for non-normalized sequence of coefficients

pBuffer

Pointer to the buffer for internal calculations. To get the size of the buffer, use the ippsFIRGenGetBufferSize function.

Description

This function computes tapsLen coefficients for lowpass FIR filter with the cutoff frequency rFreq by windowing the ideal infinite filter coefficients. The quality of filtering is defined by the number of coefficients. The parameter winType specifies the type of the window. For more information on window types used by the function, see Windowing Functions. The computed coefficients are stored in the array pTaps.

For more information about the used algorithm, see [MIT 93].

Return Values

ippStsNoErr

Indicates no error.

ippStsNullPtrErr

Indicates an error when the pTaps pointer is NULL.

ippStsSizeErr

Indicates an error when the tapsLen is less than 5, or rFreq is out of range.

Example

FIRGenLowpass.c

Result: