com.jsyn.unitgen

Class FilterBiquad

java.lang.Object

com.jsyn.unitgen.UnitGenerator

com.jsyn.unitgen.UnitFilter

com.jsyn.unitgen.TunableFilter

com.jsyn.unitgen.FilterBiquad

All Implemented Interfaces:

UnitSink, UnitSource

Direct Known Subclasses:

FilterBiquadCommon, FilterBiquadShelf

public abstract class FilterBiquad
extends TunableFilter

Base class for a set of IIR filters.

Author:

Phil Burk (C) 2011 Mobileer Inc

See Also:

FilterBandStop, FilterBandPass, FilterLowPass, FilterHighPass, FilterTwoPolesTwoZeros

Field Summary

Fields

Modifier and Type	Field and Description
protected double	a0
protected double	a1
protected double	a2
UnitInputPort	amplitude
protected double	b1
protected double	b2
protected double	cos_omega
protected static double	MINIMUM_FREQUENCY
protected static double	MINIMUM_GAIN
protected double	omega
protected double	previousFrequency
protected static double	RATIO_MINIMUM
protected double	sin_omega

Fields inherited from class com.jsyn.unitgen.TunableFilter

frequency

Fields inherited from class com.jsyn.unitgen.UnitFilter

input, output

Fields inherited from class com.jsyn.unitgen.UnitGenerator

FALSE, PORT_NAME_AMPLITUDE, PORT_NAME_CUTOFF, PORT_NAME_FREQUENCY, PORT_NAME_FREQUENCY_SCALER, PORT_NAME_INPUT, PORT_NAME_OUTPUT, PORT_NAME_PAN, PORT_NAME_PHASE, PORT_NAME_PRESSURE, PORT_NAME_TIMBRE, PORT_NAME_TIME, synthesisEngine, TRUE, VERY_SMALL_FLOAT

Constructor Summary

Constructors

Constructor and Description
FilterBiquad()

Method Summary

Modifier and Type	Method and Description
protected void	calculateOmega(double ratio)
void	generate(int start, int limit) Generic generate(int start, int limit) method calls this filter's recalculate() and performBiquadFilter(int, int) methods.
void	performBiquadFilter(int start, int limit) Each filter calls performBiquadFilter() through the generate(int, int) method.
protected abstract void	recalculate()

Methods inherited from class com.jsyn.unitgen.UnitFilter

getInput, getOutput

Methods inherited from class com.jsyn.unitgen.UnitGenerator

addPort, addPort, autoStop, convertHalfLifeToMultiplier, convertTimeToRate, flattenOutputs, generate, getCircuit, getFramePeriod, getFrameRate, getId, getPortByName, getPorts, getSynthesisEngine, getSynthesizer, getTopUnit, getUnitGenerator, incrementWrapPhase, isEnabled, isStartRequired, printConnections, printConnections, printConnections, pullData, setCircuit, setEnabled, setFrameRate, setPort, setSynthesisEngine, start, start, start, stop, stop, stop

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.jsyn.unitgen.UnitSink

getUnitGenerator, start, start, stop, stop

Methods inherited from interface com.jsyn.unitgen.UnitSource

getUnitGenerator

Field Detail

amplitude

public UnitInputPort amplitude

MINIMUM_FREQUENCY

protected static final double MINIMUM_FREQUENCY

See Also:

Constant Field Values

MINIMUM_GAIN

protected static final double MINIMUM_GAIN

See Also:

Constant Field Values

RATIO_MINIMUM

protected static final double RATIO_MINIMUM

See Also:

Constant Field Values

a0

protected double a0

a1

protected double a1

a2

protected double a2

b1

protected double b1

b2

protected double b2

previousFrequency

protected double previousFrequency

omega

protected double omega

sin_omega

protected double sin_omega

cos_omega

protected double cos_omega

Constructor Detail

FilterBiquad

public FilterBiquad()

Method Detail

generate

public void generate(int start,
                     int limit)

Generic generate(int start, int limit) method calls this filter's recalculate() and performBiquadFilter(int, int) methods.

Specified by:

generate in class UnitGenerator

Parameters:

start - offset into port buffers

limit - limit offset into port buffers for loop

recalculate

protected abstract void recalculate()

performBiquadFilter

public void performBiquadFilter(int start,
                                int limit)

Each filter calls performBiquadFilter() through the generate(int, int) method. This method has converted Robert Bristow-Johnson's coefficients for the Direct I form in this way: Here is the equation that JSyn uses for this filter:

 y(n) = A0*x(n) + A1*x(n-1) + A2*x(n-2) -vB1*y(n-1) - B2*y(n-2)
 

Here is the equation that Robert Bristow-Johnson uses:

 y[n] = (b0/a0)*x[n] + (b1/a0)*x[n-1] + (b2/a0)*x[n-2] - (a1/a0)*y[n-1] - (a2/a0)*y[n-2]
 

So to translate between JSyn coefficients and RBJ coefficients:

 JSyn => RBJ
 A0 => b0/a0
 A1 => b1/a0
 A2 => b2/a0
 B1 => a1/a0
 B2 => a2/a0
 

Parameters:

start -

limit -

calculateOmega

protected void calculateOmega(double ratio)