Module tagtraum.jipesfft

Package com.tagtraum.jipesfft

Class AbstractFFT

java.lang.Object

com.tagtraum.jipesfft.AbstractFFT

All Implemented Interfaces:

AutoCloseable

Direct Known Subclasses:

FFT, PureJavaFFT

public abstract class AbstractFFT
extends Object
implements AutoCloseable

Abstract superclass for FFTs.

Author:

Hendrik Schreiber

Field Summary

Fields

Modifier and Type	Field	Description
static int	FREQUENCY	Index to be used on the result of transform(float[]) and the like.
static int	IMAGINARY	Index to be used on the result of transform(float[]) and the like.
static int	REAL	Index to be used on the result of transform(float[]) and the like.

Constructor Summary

Constructors

Constructor	Description
AbstractFFT(int numberOfSamples)	Constructor for a given number of samples.

Method Summary

Modifier and Type	Method	Description
float[]	getFrequencies()	Array describing the frequency for the different FFT bins.
float	getFrequencyForBin(int bin)	Frequency for a given fourier transform bin.
int	getNumberOfSamples()	Number of samples.
abstract float[][]	inverseTransform(float[] real, float[] imaginary)	Perform inverse transform.
String	toString()
abstract float[][]	transform(float[] real)	Transform for real numbers.
abstract float[][]	transform(float[] real, float[] imaginary)	Transform for complex numbers.

Methods inherited from interface java.lang.AutoCloseable

close

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

REAL

public static final int REAL

Index to be used on the result of transform(float[]) and the like.

See Also:

Constant Field Values

IMAGINARY

public static final int IMAGINARY

Index to be used on the result of transform(float[]) and the like.

See Also:

Constant Field Values

FREQUENCY

public static final int FREQUENCY

Index to be used on the result of transform(float[]) and the like.

See Also:

Constant Field Values

Constructor Detail

AbstractFFT

public AbstractFFT(int numberOfSamples)

Constructor for a given number of samples.

Parameters:

numberOfSamples - number of samples you intend to transform

Throws:

IllegalArgumentException - if the number of samples is negative or not a power of 2

Method Detail

getNumberOfSamples

public int getNumberOfSamples()

Number of samples.

Returns:

number of samples

getFrequencies

public float[] getFrequencies()

Array describing the frequency for the different FFT bins. Note that these still need to be multiplied with your sampling frequency to get actual Hz values. Also note, that values beyond N/2 (Nyquist frequency) are typically not useful.

The returned array is a clone, you may do with it whatever you want.

Returns:

array with frequencies for the FFT (bins == index)

getFrequencyForBin

public float getFrequencyForBin(int bin)

Frequency for a given fourier transform bin. Note that the returned frequencies need to be multiplied with your sampling frequency to get actual Hz values. Also note, that values beyond N/2 (Nyquist frequency) are typically not useful.

Parameters:

bin - bin

Returns:

frequency

Throws:

IllegalArgumentException - if the given bin number is invalid for this FFT instance

toString

public String toString()

Overrides:

toString in class Object

inverseTransform

public abstract float[][] inverseTransform(float[] real,
                                           float[] imaginary)
                                    throws UnsupportedOperationException

Perform inverse transform. For very large number of samples (>32768) the Java version is used.

Parameters:

real - real part

imaginary - imaginary part

Returns:

two-dimensional array for the real and the imaginary parts

Throws:

UnsupportedOperationException

transform

public abstract float[][] transform(float[] real)
                             throws UnsupportedOperationException

Transform for real numbers. For very large number of samples (>32768) the Java version is used.

Parameters:

real - samples

Returns:

three-dimensional array, consisting of the real part, the imaginary, and the frequencies

Throws:

UnsupportedOperationException

transform

public abstract float[][] transform(float[] real,
                                    float[] imaginary)
                             throws UnsupportedOperationException

Transform for complex numbers. Note that the current implementation simply delegates to the pure Java version.

Parameters:

real - real part

imaginary - imaginary part

Returns:

three-dimensional array, consisting of the real part, the imaginary, and the frequencies

Throws:

UnsupportedOperationException