r8b::CDSPRealFFT Class Reference

Real-valued FFT transform class. More...

#include <CDSPRealFFT.h>

Inheritance diagram for r8b::CDSPRealFFT:

Public Member Functions
void	convertToZP (realfft_t *const p) const
	Converts the specified forward-transformed FFT block into "zero-phase" form, suitable for use with the multiplyBlocksZP() function.
realfft_t *	forward (double *const p) const
	Performs in-place forward FFT.
double	getInvMulConst () const
	Return a multiplication constant that should be used after inverse transform to obtain a correct value scale.
int	getLen () const
	Returns the length (the number of real values in a transform) of this FFT object.
int	getLenBits () const
	Returns the length (the number of real values in a transform) of this FFT object, expressed as Nth power of 2.
realfft_t *	getWorkBuf () const
	Returns pointer to the internal work buffer.
void	inverse (realfft_t *const p) const
	Performs in-place inverse FFT.
void	multiplyBlocks (const realfft_t *const ip, realfft_t *const op) const
	Multiplies two complex-valued FFT blocks in-place.
void	multiplyBlocks (const realfft_t *const ip1, const realfft_t *const ip2, realfft_t *const op) const
	Multiplies two complex-valued data blocks and places result in a new data block.
void	multiplyBlocksZP (const realfft_t *ip, realfft_t *op) const
	Multiplies two complex-valued FFT blocks in-place, considering that the ip block contains "zero-phase" response.
realfft_t *	reorderForward (realfft_t *const p, realfft_t *const op) const
	Reorders FFT bins from native ordering (after the forward transform) to sequential ordering.
realfft_t *	reorderInverse (const realfft_t *const ip, double *const op) const
	Reorders FFT bins from sequential ordering (before the inverse transform) to native ordering.

Static Public Member Functions
static void	setBinNyquist (realfft_t *const p, const realfft_t v)
	Replaces the Nyquist FFT bin in the specified block.

Friends
class	CDSPRealFFTKeeper
class	CPtrKeeper< CDSPRealFFT >
class	CSinglyLinkedListItem< CDSPRealFFT >

Detailed Description

Real-valued FFT transform class.

Class implements a wrapper for real-valued discrete fast Fourier transform functions. The object of this class can only be obtained via the CDSPRealFFTKeeper class.

As a general pre-condition, the buffers passed to the functions of this class should be aligned to 32 bytes.

Uses functions from the FFT package: http://www.kurims.kyoto-u.ac.jp/~ooura/fft.html

Also uses functions from the PFFFT and PFFFT DOUBLE packages.

Also uses Intel IPP library functions if available (if the R8B_IPP=1 macro was defined). Note that IPP library's FFT functions are 2-3 times more efficient on the modern Intel Core i7-3770K processor than Ooura's functions. It may be worthwhile investing in IPP. Note, that FFT functions take less than 20% of the overall sample rate conversion time. However, when the "power of 2" resampling is used the performance of FFT functions dominates.

Member Function Documentation

convertToZP()

void r8b::CDSPRealFFT::convertToZP

(

realfft_t *const

p

)

const

Converts the specified forward-transformed FFT block into "zero-phase" form, suitable for use with the multiplyBlocksZP() function.

Parameters

[in,out]

p

Block to transform.

forward()

realfft_t * r8b::CDSPRealFFT::forward

(

double *const

p

)

const

Performs in-place forward FFT.

If FFT's native type differs from double, the result will be placed to p using values of the native type.

Parameters

[in,out]

p

Pointer to data block to transform, length should be equal to this object's getLen().

Returns

The pointer p casted to transform's native type.

getWorkBuf()

realfft_t * r8b::CDSPRealFFT::getWorkBuf

(

)

const

Returns pointer to the internal work buffer.

This buffer can be used for FFT bin reordering.

Returns

The work buffer pointer, or nullptr if FFT produces sequential-ordered FFT bins. This pointer should not be used beyond the calling context.

inverse()

void r8b::CDSPRealFFT::inverse

(

realfft_t *const

p

)

const

Performs in-place inverse FFT.

If FFT's native type differs from double, the result will be placed to p using double values.

Parameters

[in,out]

p

Pointer to data block to transform, length should be equal to this object's getLen().

multiplyBlocks() [1/2]

void r8b::CDSPRealFFT::multiplyBlocks	(	const realfft_t *const	ip,
		realfft_t *const	op ) const

Multiplies two complex-valued FFT blocks in-place.

Length of both blocks should be equal to this object's block length. Blocks should have been produced with the forward() function of this object.

Parameters

	ip	Input FFT block 1.
[in,out]	op	Output/input FFT block 2.

multiplyBlocks() [2/2]

void r8b::CDSPRealFFT::multiplyBlocks	(	const realfft_t *const	ip1,
		const realfft_t *const	ip2,
		realfft_t *const	op ) const

Multiplies two complex-valued data blocks and places result in a new data block.

Length of all data blocks should be equal to this object's block length. Input blocks should have been produced with the forward() function of this object.

Parameters

	ip1	Input FFT block 1.
	ip2	Input FFT block 2.
[out]	op	Output FFT block, should not be equal to ip1 nor ip2.

multiplyBlocksZP()

void r8b::CDSPRealFFT::multiplyBlocksZP	(	const realfft_t *	ip,
		realfft_t *	op ) const

Multiplies two complex-valued FFT blocks in-place, considering that the ip block contains "zero-phase" response.

Length of both blocks should be equal to this object's block length. Blocks should have been produced with the forward() function of this object.

Parameters

	ip	Input FFT block 1, "zero-phase" response. This block should be first transformed via the convertToZP() function.
[in,out]	op	Output/input FFT block 2.

reorderForward()

realfft_t * r8b::CDSPRealFFT::reorderForward	(	realfft_t *const	p,
		realfft_t *const	op ) const

Reorders FFT bins from native ordering (after the forward transform) to sequential ordering.

Parameters

p	Input FFT block.
op	Output FFT block.

Returns

The pointer to the reordered FFT block. May return p if the transform has sequential ordering already.

reorderInverse()

realfft_t * r8b::CDSPRealFFT::reorderInverse	(	const realfft_t *const	ip,
		double *const	op ) const

Reorders FFT bins from sequential ordering (before the inverse transform) to native ordering.

Parameters

ip	Pointer to FFT block (previously returned by the reorderForward() function).
op	Output FFT block (may equal ip).

Returns

The pointer to the reordered FFT block (op casted to the realfft_t type).

setBinNyquist()

static void r8b::CDSPRealFFT::setBinNyquist ( realfft_t *const p, const realfft_t v )

static

Replaces the Nyquist FFT bin in the specified block.

Parameters

p	Pointer to FFT block.
v	New Nyquist bin value.