Intel® Integrated Performance Primitives Developer Reference

Developer Reference

  • 2021
  • 06/28/2021
  • Public Content
Contents

SampleDown

Down-samples a signal, conceptually decreasing its sampling rate by an integer factor.

Syntax

IppStatus ippsSampleDown_16s(const Ipp16s*
pSrc
, int
srcLen
, Ipp16s*
pDst
, int*
pDstLen
, int
factor
, int*
pPhase
);
IppStatus ippsSampleDown_32f(const Ipp32f*
pSrc
, int
srcLen
, Ipp32f*
pDst
, int*
pDstLen
, int
factor
, int*
pPhase
);
IppStatus ippsSampleDown_64f(const Ipp64f*
pSrc
, int
srcLen
, Ipp64f*
pDst
, int*
pDstLen
, int
factor
, int*
pPhase
);
IppStatus ippsSampleDown_16sc(const Ipp16sc*
pSrc
, int
srcLen
, Ipp16sc*
pDst
, int*
pDstLen
, int
factor
, int*
pPhase
);
IppStatus ippsSampleDown_32fc(const Ipp32fc*
pSrc
, int
srcLen
, Ipp32fc*
pDst
, int*
pDstLen
, int
factor
, int*
pPhase
);
IppStatus ippsSampleDown_64fc(const Ipp64fc*
pSrc
, int
srcLen
, Ipp64fc*
pDst
, int*
pDstLen
, int
factor
, int*
pPhase
);
Include Files
ipps.h
Domain Dependencies
Headers:
ippcore.h
,
ippvm.h
Libraries:
ippcore.lib
,
ippvm.lib
Parameters
pSrc
Pointer to the source array holding the samples to be down-sampled.
srcLen
Number of samples in the input array
pSrc
.
pDst
Pointer to the destination array.
pDstLen
Pointer to the length of the destination array
pDst
.
factor
Factor by which the signal is down-sampled. That is,
factor
 - 1 samples are discarded from every block of
factor
 samples in
pSrc
.
pPhase
Pointer to the input phase value that determines which of the samples within each block of
factor
 samples from
pSrc
 is not discarded and copied to
pDst
. The value of
pPhase
 is required to be in the range [0;
factor
-1].
Description
This function down-samples the
srcLen
-length source array
pSrc
 by factor
factor
 with phase
pPhase
, and stores the result in the array
pDst
, ignoring its length value by the
pDstLen
 address.
Down-sampling discards
factor
 - 1 samples from
pSrc
, copying one sample from each block of
factor
 samples from
pSrc
 to
pDst
. The
pPhase
 argument determines which of the samples in each block is not discarded and where it lies within each input block of
factor
 samples. The value of
pPhase
 is required to be in the range [0;
factor
-1]. The length of the destination array is stored by the
pDstLen
 address.
The
pPhase
 value is the phase of an source array sample. It is also a returned output phase which can be used as an input phase for the first sample in the next block to process. Use
pPhase
 for block mode processing to get a continuous output signal.
You can use the FIR multi-rate filter to combine filtering and resampling, for example, for antialiasing filtering before the sub-sampling procedure.
The
ippsSampleDown
 functionality can be described as follows:
pDstLen
= (
srcLen
+
factor
 - 1 -
phase
)/
factor
pDst
[n]=
pSrc
[
factor
 * n +
phase
]
,
0
≤
 n <
pDstLen
phase
 = (
factor
+
phase
 -
srcLen
 %
factor
)%
factor
.
Return Values
ippStsNoErr
Indicates no error.
ippStsNullPtrErr
Indicates an error when the
pDst
,
pSrc
,
pDstLen
, or
pPhase
 pointer is
NULL
.
ippStsSizeErr
Indicates an error when
srcLen
 is less than or equal to 0.
ippStsSampleFactorErr
Indicates an error when
factor
 is less than or equal to 0.
ippStsSamplePhaseErr
Indicates an error when
pPhase
 is negative, or bigger than or equal to
factor
.

Example

The example below shows how to use the function
ippsSampleDown
.
void sampling( void ) {
      Ipp16s x[8] = { 1,2,3,4,5,6,7,8 };
      Ipp16s y[8] = {9,10,11,12,13,14,15,16}, z[8];
      int dstLen1, dstLen2, phase = 2;
      IppStatus st = ippsSampleDown_16s(x, 8, z, &dstLen1, 3, &phase);
      st = ippsSampleDown_16s(y, 8, z+dstLen1, &dstLen2, 3, &phase);
      printf_16s(“down-sampling =”, z, dstLen1+dstLen2, st); 
}
Output:
down-sampling = 3 6 9 12 15

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.