Package net.cspeech.DSP

Class FFT

java.lang.Object

net.cspeech.DSP.FFT

public class FFT
extends java.lang.Object

Constructor Summary

Constructors

Constructor	Description
FFT()

Method Summary

Modifier and Type	Method	Description
float[]	cFFT(float[] sig)	Complex FFT
float[]	dB(float[] spec)
int	getm()
int	getN()
float[]	Hamming(float[] sig)
float[]	normHamming(float[] sig)
float[]	rFFT(float[] sig)
void	setm(int m)

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FFT

public FFT()

Method Detail

setm

public void setm(int m)

Parameters:

m - sets length N = 2^m where default of m = 9 gives length N = 512 complex FFT, length 2N = 1024 real FFT

getm

public int getm()

getN

public int getN()

cFFT

public float[] cFFT(float[] sig)

Complex FFT

Parameters:

sig - is complex valued: the real part goes in the even samples, the imaginary part in the odd samples.

Returns:

length 2N = 2^{m+1} array where even samples are real part of spectrum, odd samples are imaginary part of spectrum.

rFFT

public float[] rFFT(float[] sig)

Parameters:

sig - up to 2*N+2 real-valued elements of this array are the signal.

Returns:

N+1 complex spectrum samples where

spec[0], spec[1] = 0 are the real and imaginary parts of X[k=0],

spec[N], spec[N+1] = 0 are the real and imaginary parts of X[k=N/2] and where N = 2^m

Hamming

public float[] Hamming(float[] sig)

Parameters:

sig - has length N = sig.length.

Returns:

length N Hamming window applied to sig

normHamming

public float[] normHamming(float[] sig)

Parameters:

sig - has length N = sig.length.

Returns:

length N normalized Hamming window applied to sig.

The normalization makes the DC value of the window == 1.

dB

public float[] dB(float[] spec)

Parameters:

spec - has length == 2N+2 for N+1 complex samples returned by rFFT()

Returns:

N+1 real-valued dB samples where N = 2^m