com.tagtraum.jipes.math

Class Filters.IIRFilter

java.lang.Object

com.tagtraum.jipes.math.Filters.IIRFilter

All Implemented Interfaces:

MapFunction<float[]>, StatefulMapFunction<float[]>

Direct Known Subclasses:

Filters.FourthOrderIIRFilter

Enclosing class:

Filters

public static class Filters.IIRFilter
extends Object
implements StatefulMapFunction<float[]>

IIR (infinite impulse response) filter.

To compute the coefficients you might want to use Matlab or the free package Octave (with additional Octave-Forge packages needed for signals). E.g. for a low pass filter you could execute:

[a,b] = butter(3, .4, 'low')

This will compute the coefficients for a third order low pass filter where the first argument (3) is the order and the second (.4) the normalized cutoff frequency, which is defined as fc*2/fs (f_c = cutoff frequency, f_s = sample frequency).

Assuming your audio is sampled at 44.1kHz, and you wanted a cutoff frequency of 11.025kHz, the seconds parameters would be 11025*2/44100 = 0.5.

Date: Jul 20, 2010 Time: 2:13:51 PM

Author:

Hendrik Schreiber

See Also:

Wikipedia on IIR, Filters.FIRFilter, Filters.FourthOrderIIRFilter

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	IIRFilter()
	IIRFilter(double[] inputCoefficients, double[] outputCoefficients)

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object o)
double	filter(double currentInputValue) Deprecated.
int	hashCode()
float[]	map(float[] data) Maps an object (usually an array, an RealAudioBuffer or a List) to another one of the same size.
void	reset() Resets the function's state.
void	setInputCoefficients(double[] inputCoefficients)
void	setOutputCoefficients(double[] outputCoefficients) First b coefficient must always be 1.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

IIRFilter

protected IIRFilter()

IIRFilter

public IIRFilter(double[] inputCoefficients,
                 double[] outputCoefficients)

Method Detail

reset

public void reset()

Description copied from interface: StatefulMapFunction

Resets the function's state.

Specified by:

reset in interface StatefulMapFunction<float[]>

setInputCoefficients

public void setInputCoefficients(double[] inputCoefficients)

Parameters:

inputCoefficients - a (input) coefficients

setOutputCoefficients

public void setOutputCoefficients(double[] outputCoefficients)

First b coefficient must always be 1.

Parameters:

outputCoefficients - b (output) coefficients

map

public float[] map(float[] data)

Description copied from interface: MapFunction

Maps an object (usually an array, an RealAudioBuffer or a List) to another one of the same size.

Specified by:

map in interface MapFunction<float[]>

Parameters:

data - data

Returns:

mapped data

filter

@Deprecated
public double filter(double currentInputValue)

Deprecated.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object