Developer Reference

  • 2020
  • 07/15/2020
  • Public Content
Contents

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

/******************************************************************************* * Copyright 2015-2020 Intel Corporation. * * This software and the related documents are Intel copyrighted materials, and * your use of them is governed by the express license under which they were * provided to you (License). Unless the License provides otherwise, you may not * use, modify, copy, publish, distribute, disclose or transmit this software or * the related documents without Intel's prior written permission. * * This software and the related documents are provided as is, with no express * or implied warranties, other than those that are expressly stated in the * License. *******************************************************************************/ #include <stdio.h> #include "ipp.h" /* Next two defines are created to simplify code reading and understanding */ #define EXIT_MAIN exitLine: /* Label for Exit */ #define check_sts(st) if((st) != ippStsNoErr) goto exitLine; /* Go to Exit if Intel(R) Integrated Primitives (Intel(R) IPP) function returned status different from ippStsNoErr */ /* Results of ippMalloc() are not validated because Intel(R) IPP functions perform bad arguments check and will return an appropriate status */ int main() { int len = 512; Ipp64f pDst[512]; Ipp64f magn = 4095; Ipp64f rFreq = 0.2; int tapslen = 27; int numIters = 512; IppsFIRSpec_64f* pSpec = NULL; IppStatus status = ippStsNoErr; int i = 0, bufSize = 0, specSize = 0; Ipp8u* pBuffer = NULL; IppAlgType algType = ippAlgDirect; Ipp64f* pDlySrc = NULL; Ipp64f* pDlyDst = NULL; Ipp64f* FIRDst = ippsMalloc_64f(numIters * sizeof(Ipp64f)); Ipp64f* taps = ippsMalloc_64f(tapslen*sizeof(Ipp64f)); pDlySrc = ippsMalloc_64f(tapslen*sizeof(Ipp64f)); check_sts( status = ippsZero_64f(pDlySrc, tapslen) ) /*generate source vector*/ check_sts( status = ippsVectorJaehne_64f(pDst, len, magn) ) /* create a Jaehne vector */ printf("\nSource vector\n"); for (i = 0; i < 32; i++) printf("%f,", pDst[i]); /*computes tapsLen coefficients for lowpass FIR filter*/ check_sts( status = ippsFIRGenGetBufferSize(tapslen, &bufSize) ) pBuffer = ippsMalloc_8u(bufSize); check_sts( status = ippsFIRGenLowpass_64f(rFreq, taps, tapslen, ippWinBartlett, ippTrue, pBuffer) ) printf("\nGenerated taps:\n"); for (i = 0; i < tapslen; i++) printf("%f,", taps[i]); check_sts( status = ippsFIRSRGetSize(tapslen, ipp64f, &specSize, &bufSize) ) pSpec = (IppsFIRSpec_64f*)ippsMalloc_8u(specSize); pBuffer = ippsMalloc_8u(bufSize); check_sts( status = ippsFIRSRInit_64f(taps, tapslen, algType, pSpec) ) /* filter an input vector */ check_sts( status = ippsFIRSR_64f(pDst, FIRDst, numIters, pSpec, pDlySrc, pDlyDst, pBuffer) ) printf("\nAfter LowPass filter\n"); for (i = 0; i < 32; i++) printf("%f,", FIRDst[i]); printf("\n"); EXIT_MAIN ippsFree(FIRDst); ippsFree(taps); printf("Exit status %d (%s)\n", (int)status, ippGetStatusString(status)); return (int)status; }
Result:

Product and Performance Information

1

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