r8b::CDSPRealFFT Class Reference

Real-valued FFT transform class. More...

#include <CDSPRealFFT.h>

Inheritance diagram for r8b::CDSPRealFFT:

Public Member Functions
void	convertToZP (double *const ap) const
void	forward (double *const p) const
double	getInvMulConst () const
int	getLen () const
int	getLenBits () const
void	inverse (double *const p) const
void	multiplyBlocks (const double *const aip, double *const aop) const
void	multiplyBlocks (const double *const aip1, const double *const aip2, double *const aop) const
void	multiplyBlocksZP (const double *const aip, double *const aop) const

Friends
class	CDSPRealFFTKeeper

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.

Uses functions from the FFT package by: Copyright(C) 1996-2001 Takuya OOURA http://www.kurims.kyoto-u.ac.jp/~ooura/fft.html

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 becomes "everything".

Member Function Documentation

convertToZP()

void r8b::CDSPRealFFT::convertToZP

(

double *const

ap

)

const

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

Parameters

[in,out]

ap

Block to transform.

forward()

void r8b::CDSPRealFFT::forward

(

double *const

p

)

const

Function performs in-place forward FFT.

Parameters

[in,out]

p

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

getInvMulConst()

double r8b::CDSPRealFFT::getInvMulConst

(

)

const

Returns

A multiplication constant that should be used after inverse transform to obtain a correct value scale.

getLen()

int r8b::CDSPRealFFT::getLen

(

)

const

Returns

The length (the number of real values in a transform) of *this FFT object.

getLenBits()

int r8b::CDSPRealFFT::getLenBits

(

)

const

Returns

The length (the number of real values in a transform) of *this FFT object, expressed as Nth power of 2.

inverse()

void r8b::CDSPRealFFT::inverse

(

double *const

p

)

const

Function performs in-place inverse FFT.

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 double *const	aip,
		double *const	aop
	)		const

Function multiplies two complex-valued data blocks in-place. Length of both data blocks should be equal to *this object's block length. Blocks should have been produced with the forward() function of *this object.

Parameters

	aip	Input data block 1.
[in,out]	aop	Output/input data block 2.

multiplyBlocks() [2/2]

void r8b::CDSPRealFFT::multiplyBlocks	(	const double *const	aip1,
		const double *const	aip2,
		double *const	aop
	)		const

Function 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

	aip1	Input data block 1.
	aip2	Input data block 2.
[out]	aop	Output data block, should not be equal to aip1 nor aip2.

multiplyBlocksZP()

void r8b::CDSPRealFFT::multiplyBlocksZP	(	const double *const	aip,
		double *const	aop
	)		const

Function multiplies two complex-valued data blocks in-place, considering that the "ip" block contains "zero-phase" response. Length of both data blocks should be equal to *this object's block length. Blocks should have been produced with the forward() function of *this object.

Parameters

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