FFTInv_CToC

Computes the inverse fast Fourier transform (FFT) of a complex signal.

Syntax

Case 1: Not-in-place operation on real data type

IppStatus ippsFFTInv_CToC_32f(const Ipp32f* pSrcRe, const Ipp32f* pSrcIm, Ipp32f* pDstRe, Ipp32f* pDstIm, const IppsFFTSpec_C_32f* pFFTSpec, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_64f(const Ipp64f* pSrcRe, const Ipp64f* pSrcIm, Ipp64f* pDstRe, Ipp64f* pDstIm, const IppsFFTSpec_C_64f* pFFTSpec, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_16s_Sfs(const Ipp16s* pSrcRe, const Ipp16s* pSrcIm, Ipp16s* pDstRe, Ipp16s* pDstIm, const IppsFFTSpec_C_16s* pFFTSpec, int scaleFactor, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_32s_Sfs(const Ipp32s* pSrcRe, const Ipp32s* pSrcIm, Ipp32s* pDstRe, Ipp32s* pDstIm, const IppsFFTSpec_C_32s* pFFTSpec, int scaleFactor, Ipp8u* pBuffer);

Case 2: Not-in-place operation on complex data type

IppStatus ippsFFTInv_CToC_32fc(const Ipp32fc* pSrc, Ipp32fc* pDst, const IppsFFTSpec_C_32fc* pFFTSpec, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_64fc(const Ipp64fc* pSrc, Ipp64fc* pDst, const IppsFFTSpec_C_64fc* pFFTSpec, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_16sc_Sfs(const Ipp16sc* pSrc, Ipp16sc* pDst, const IppsFFTSpec_C_16sc* pFFTSpec, int scaleFactor, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_32sc_Sfs(const Ipp32sc* pSrc, Ipp32sc* pDst, const IppsFFTSpec_C_32sc* pFFTSpec, int scaleFactor, Ipp8u* pBuffer);

Case 3: In-place operation on real data type

IppStatus ippsFFTInv_CToC_32f_I(Ipp32f* pSrcDstRe, Ipp32f* pSrcDstIm, const IppsFFTSpec_C_32f* pFFTSpec, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_64f_I(Ipp64f* pSrcDstRe, Ipp64f* pSrcDstIm, const IppsFFTSpec_C_64f* pFFTSpec, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_16s_ISfs(Ipp16s* pSrcDstRe, Ipp16s* pSrcDstIm, const IppsFFTSpec_C_16s* pFFTSpec, int scaleFactor, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_32s_ISfs(Ipp32s* pSrcDstRe, Ipp32s* pSrcDstIm, const IppsFFTSpec_C_32s* pFFTSpec, int scaleFactor, Ipp8u* pBuffer);

Case 4: In-place operation on complex data type

IppStatus ippsFFTInv_CToC_32fc_I(Ipp32fc* pSrcDst, const IppsFFTSpec_C_32fc* pFFTSpec, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_64fc_I(Ipp64fc* pSrcDst, const IppsFFTSpec_C_64fc* pFFTSpec, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_16sc_ISfs(Ipp16sc* pSrcDst, const IppsFFTSpec_C_16sc* pFFTSpec, int scaleFactor, Ipp8u* pBuffer);

IppStatus ippsFFTInv_CToC_32sc_ISfs(Ipp32sc* pSrcDst, const IppsFFTSpec_C_32sc* pFFTSpec, int scaleFactor, Ipp8u* pBuffer);

Parameters

pFFTSpec	Pointer to the FFT specification structure.
pSrc	Pointer to the input array containing complex values.
pDst	Pointer to the output array containing complex values.
pSrcRe	Pointer to the input array containing real parts of the signal.
pSrcIm	Pointer to the input array containing imaginary parts of the signal.
pDstRe	Pointer to the output array containing real parts of the signal.
pDstIm	Pointer to the output array containing imaginary parts of the signal.
pSrcDst	Pointer to the input and output array containing complex values (for the in-place operation).
pSrcDstRe	Pointer to the input and output array containing real parts of the signal(for the in-place operation).
pSrcDstIm	Pointer to the input and output array containing imaginary parts of the signal(for the in-place operation).
pBuffer	Pointer to the external work buffer, can be NULL.
scaleFactor	Scale factor, refer to Integer Scaling.

Description

The function ippsFFTInv_CToC is declared in the ipps.h file. This function computes the inverse FFT of a complex signal according to the pFFTSpec specification parameters: the transform order, the normalization flag, and the specific code hint. The FFT specification structure must be initialized by the functions ippsFFTInitAlloc_C or ippsFFTInit_C beforehand.

The function flavors using the complex data type, for example with the 32fc suffixes, process the input complex array pSrc and store the result in pDst. Their in-place flavors use the complex array pSrcDst.

The function flavors using the real data type and processing complex signals represented by separate real pSrcRe and imaginary pSrcIm parts, for example with the 32f suffixes, store the result separately in pDstRe and pDstIm, respectively. Their in-place flavors uses separate real and imaginary arrays pSrcDstRe and pSrcDstIm, respectively.

For integer data types the output result is scaled according to the scaleFactor value, thus the output signal range and precision are retained.

The function may be used with the external work buffer pBuffer to avoid memory allocation within the functions. Once the work buffer is allocated, it can be used for all following calls to the functions computing FFT. As internal allocation of memory is too expensive operation and depends on operating system and/or runtime libraries used - the use of an external buffer improves performance significantly, especially for the small size transforms.

The size of the external buffer must be previously computed by the function ippsFFTGetBufSize_C or ippsFFTGetSize_C.

If the external buffer is not specified (pBuffer is set to NULL), then the function itself allocates the memory needed for operation.

The length of the FFT must be a power of 2.

Return Values

ippStsNoErr	Indicates no error.
ippStsNullPtrErr	Indicates an error when one of the specified pointers with exception of pBuffer is NULL.
ippStsContextMatchErr	Indicates an error when the specification identifier pFFTSpec is incorrect.
ippStsMemAllocErr	Indicates an error when no memory is allocated.