DFTOutOrdInv

Computes the inverse out-of-order discrete Fourier transform.

Syntax

IppStatus ippsDFTOutOrdInv_CToC_32fc(const Ipp32fc* pSrc, Ipp32fc* pDst, const IppsDFTOutOrdSpec_C_32fc* pDFTSpec, Ipp8u* pBuffer);

IppStatus ippsDFTOutOrdInv_CToC_64fc(const Ipp64fc* pSrc, Ipp64fc* pDst, const IppsDFTOutOrdSpec_C_64fc* pDFTSpec, Ipp8u* pBuffer);

Parameters

pSrc	Pointer to the source data.
pDst	Pointer to the output data.
pDFTSpec	Pointer to the DFT specification structure.
pBuffer	Pointer to the work buffer, can be NULL.

Description

The function ippsDFTOutOrdInv_CToC is declared in the ipps.h file. This function computes the inverse out-of-order DFT of a complex signal pSrc according to the pDFTSpec specification parameters: the transform len, the normalization flag, and the specific code hint, and store the result in pDst.

This function is analogous to ippsDFTInv_CToC and has the similar functionality. The difference is that the elements in frequency domain pSrc can be rearranged if this helps to speed up computations. This procedure is hidden from the user and depends on the specific implementation of the functions.However, the reversibility of each pair of functions for forward/inverse transforms is ensured.

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 DFT. 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.

Required buffer size must be computed by the function ippsDFTOutOrdGetBufSize_C prior to using the DFT computation functions.

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

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 pDFTSpec is incorrect.
ippStsMemAllocErr	Indicates an error when no memory is allocated.