Developer Reference

  • 2020
  • 07/15/2020
  • 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

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804