net.beadsproject.beads.analysis.featureextractors

Class FFT

java.lang.Object

net.beadsproject.beads.core.Bead

net.beadsproject.beads.analysis.FeatureExtractor<float[][],float[]>

net.beadsproject.beads.analysis.featureextractors.FFT

public class FFT
extends FeatureExtractor<float[][],float[]>

FFT performs a Fast Fourier Transform and forwards the complex data to any listeners. The complex data is a float of the form float[2][frameSize], with real and imaginary parts stored respectively.

Field Summary

Fields

Modifier and Type	Field and Description
protected float[]	fftImag The imaginary part.
protected float[]	fftReal The real part.

Fields inherited from class net.beadsproject.beads.analysis.FeatureExtractor

featureDescriptions, features, name, numFeatures

Constructor Summary

Constructors

Constructor and Description
FFT() Instantiates a new FFT.

Method Summary

Modifier and Type	Method and Description
static float	binFrequency(float samplingFrequency, int blockSize, float binNumber) The frequency corresponding to a specific bin
static float	binNumber(float samplingFrequency, int blockSize, float freq) Returns the average bin number corresponding to a particular frequency.
protected static float[]	calculateImaginary(float[] spectrum, int length) Gets the imaginary part from the complex spectrum.
protected static float[]	calculateReal(float[] spectrum, int length) Gets the real part from the complex spectrum.
protected static void	fft(float[] data, int n, boolean isign)
static float	nyquist(float samplingFrequency) The nyquist frequency for this samplingFrequency
void	process(TimeStamp startTime, TimeStamp endTime, float[] data) Process some data of type P (specified by the class def).

Methods inherited from class net.beadsproject.beads.analysis.FeatureExtractor

addListener, forward, getFeatureDescriptions, getFeatures, getName, getNumberOfFeatures, removeListener, setName, setNumberOfFeatures

Methods inherited from class net.beadsproject.beads.core.Bead

getKillListener, isDeleted, isPaused, kill, message, messageReceived, pause, setKillListener, start, toString

Methods inherited from class java.lang.Object

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

Field Detail

fftReal

protected float[] fftReal

The real part.

fftImag

protected float[] fftImag

The imaginary part.

Constructor Detail

FFT

public FFT()

Instantiates a new FFT.

Method Detail

process

public void process(TimeStamp startTime,
                    TimeStamp endTime,
                    float[] data)

Description copied from class: FeatureExtractor

Process some data of type P (specified by the class def). This method must be overidden by implementing classes.

Specified by:

process in class FeatureExtractor<float[][],float[]>

data - the data.

binFrequency

public static float binFrequency(float samplingFrequency,
                                 int blockSize,
                                 float binNumber)

The frequency corresponding to a specific bin

Parameters:

samplingFrequency - The Sampling Frequency of the AudioContext

blockSize - The size of the block analysed

binNumber -

binNumber

public static float binNumber(float samplingFrequency,
                              int blockSize,
                              float freq)

Returns the average bin number corresponding to a particular frequency. Note: This function returns a float. Take the Math.round() of the returned value to get an integral bin number.

Parameters:

samplingFrequency - The Sampling Frequency of the AudioContext

blockSize - The size of the fft block

freq - The frequency

nyquist

public static float nyquist(float samplingFrequency)

The nyquist frequency for this samplingFrequency

calculateReal

protected static float[] calculateReal(float[] spectrum,
                                       int length)

Gets the real part from the complex spectrum.

Parameters:

spectrum - complex spectrum.

length - length of data to use.

Returns:

real part of given length of complex spectrum.

calculateImaginary

protected static float[] calculateImaginary(float[] spectrum,
                                            int length)

Gets the imaginary part from the complex spectrum.

Parameters:

spectrum - complex spectrum.

length - length of data to use.

Returns:

imaginary part of given length of complex spectrum.

fft

protected static void fft(float[] data,
                          int n,
                          boolean isign)