Package processing.sound

Class FFT

java.lang.Object

processing.sound.Analyzer

processing.sound.FFT

public class FFT
extends Analyzer

This is a Fast Fourier Transform (FFT) analyzer. It calculates the normalized power spectrum of an audio stream the moment it is queried with the analyze() method.

Field Summary

Fields

Modifier and Type	Field	Description
float[]	spectrum

Constructor Summary

Constructors

Constructor	Description
FFT(PApplet parent)
FFT(PApplet parent, int bands)

Method Summary

Modifier and Type	Method	Description
float[]	analyze()
float[]	analyze(float[] target)	Calculates the current frequency spectrum of the input signal.
static float[]	analyzeSample(float[] sample, float[] target)	Calculates the frequency spectrum of a given audio sample and returns an array of magnitudes, one for each frequency band.
static float[]	analyzeSample(float[] sample, int numBands)

Methods inherited from class processing.sound.Analyzer

input

Methods inherited from class java.lang.Object

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

Field Details

spectrum

public float[] spectrum

Constructor Details

FFT

public FFT(PApplet parent)

FFT

public FFT(PApplet parent,
 int bands)

Parameters:

parent - typically use "this"

bands - number of frequency bands for the FFT. This parameter needs to be a power of 2 (e.g. 16, 32, 64, 128, ...). The default is 512.

Method Details

analyze

public float[] analyze()

analyze

public float[] analyze(float[] target)

Calculates the current frequency spectrum of the input signal. Returns an array with as many elements as this FFT analyzer's number of frequency bands. The frequency associated with each band of the spectrum is frequency = binIndex * sampleRate / (2*numBands).
The values of the resulting array show the amplitudes of pure tone components contained in the signal. If the signal is a sine with an amplitude of 1, the spectrum will have an absolute value of 1 (0 dB) at the frequency of the sine. For complex real-world signals the spectrum values will be much lower and usually don't exceed 0.05.

Parameters:

target - if provided, writes the frequency spectrum into the given array. The array needs to have as many elements as this FFT analyzer's number of frequency bands.

analyzeSample

public static float[] analyzeSample(float[] sample,
 float[] target)

Calculates the frequency spectrum of a given audio sample and returns an array of magnitudes, one for each frequency band. The frequency associated with each band of the spectrum is frequency = binIndex * sampleRate / (2*numBands).
This version is intended to be used in non-real time processing, particularly when you are creating an animation in non-real time and want to get the FFT for a particular chunk of an audio sample. For stereo samples, you can call this function once for each channel, so you can display the left and right fft values separately.
The values of the resulting array show the amplitudes of pure tone components contained in the signal. If the signal is a sine with an amplitude of 1, the spectrum will have an absolute value of 1 (0 dB) at the frequency of the sine. For complex real-world signals the spectrum values will be much lower and usually don't exceed 0.05.

Parameters:

sample - an array of numbers that describe the waveform to be analyzed

numBands - the number of fft bands requested. Must be a power of 2 (one of 2, 4, 8, 16 etc.)

target - array that the computed spectrum will be written to. The FFT will compute as many frequency bands as the length of this array, which must be a power of 2 (2, 4, 8, 16 etc.)

Returns:

The frequency spectrum of the given audio sample. The array has as many elements as this FFT analyzer's number of frequency bands.

analyzeSample

public static float[] analyzeSample(float[] sample,
 int numBands)