com.softsynth.jsyn
Class Filter_2o2p2z

java.lang.Object
  java.util.Observable
      com.softsynth.jsyn.SynthObject
          com.softsynth.jsyn.SynthSound
              com.softsynth.jsyn.SynthUnit
                  com.softsynth.jsyn.SynthFilter
                      com.softsynth.jsyn.Filter_2o2p2z

public class Filter_2o2p2z
extends SynthFilter

Filter_2o2p2z unit. Second Order, Two Pole, Two Zero filter using the following formula:

     y(n) = 2.0 * (A0*x(n) + A1*x(n-1)  + A2*x(n-2) - B1*y(n-1)  - B2*y(n-2))

where y(n) is Output, x(n) is Input, x(n-1) is a delayed copy of the input, and y(n-1) is a delayed copy of the output.

This filter is a recursive IIR or Infinite Impulse Response filter. It can be unstable depending on the values of the coefficients.

A thorough description of the digital filter theory needed to fully describe this filter is beyond the scope of this document. Calculating coefficients is non-intuitive; the interested user is referred to one of the standard texts on filter theory (e.g., Moore, "Elements of Computer Music", section 2.4).

Special thanks to Robert Bristow-Johnson for contributing his filter equations to the music-dsp list. They were used for calculating the coefficients for the lowPass, highPass, and other parametric filter calculations.

Version:

JSyn Version 011

Author:

(C) 1997 Phil Burk, SoftSynth.com, All Rights Reserved

See Also:

Synth, SynthUnit, Filter_1o1z, Filter_1o1p, Filter_2o2p, Filter_1o1p1z, Filter_LowPass, Filter_HighPass, Filter_BandPass, Filter_PeakingEQ, Filter_BandStop, Filter_LowShelf, Filter_HighShelf, Filter_StateVariable

Field Summary

SynthVariable	A0 Filter coefficient.
SynthVariable	A1 Filter coefficient.
SynthVariable	A2 Filter coefficient.
SynthVariable	B1 Filter coefficient.
SynthVariable	B2 Filter coefficient.

Fields inherited from class com.softsynth.jsyn.SynthFilter

input, output

Constructor Summary

Filter_2o2p2z()

Filter_2o2p2z(SynthContext synthContext)
Create a SynthUnit that runs at Synth.RATE_AUDIO.

Filter_2o2p2z(SynthContext synthContext, int calculationRate)

Method Summary

void	bandPass(double frequency, double bandwidth)
void	bandPass(int time, double frequency, double bandwidth) Set coefficients of filter for Band Pass operation.
void	highPass(double frequency, double bandwidth)
void	highPass(int time, double frequency, double bandwidth) Set coefficients of filter for High Pass operation.
void	highShelf(double frequency, double dBGain, double slope)
void	highShelf(double frequency, double bandwidth, double dBGain, double slope)
void	highShelf(int time, double frequency, double dBGain, double slope) Set coefficients of filter for High Shelf operation.
void	highShelf(int time, double frequency, double bandwidth, double dBGain, double slope)
void	lowPass(double frequency, double bandwidth)
void	lowPass(int time, double frequency, double bandwidth) Set coefficients of filter for Low Pass operation.
void	lowShelf(double frequency, double dBGain, double slope)
void	lowShelf(double frequency, double bandwidth, double dBGain, double slope)
void	lowShelf(int time, double frequency, double dBGain, double slope) Set coefficients of filter for Low Shelf operation.
void	lowShelf(int time, double frequency, double bandwidth, double dBGain, double slope)
void	notch(double frequency, double bandwidth)
void	notch(int time, double frequency, double bandwidth) Set coefficients of filter for Notch operation.
void	peakingEQ(double frequency, double bandwidth, double dBGain)
void	peakingEQ(int time, double frequency, double bandwidth, double dBGain) Set coefficients of filter for Peaking EQ operation.

Methods inherited from class com.softsynth.jsyn.SynthSound

addPort, addPort, findNamedPort, getName, getNumPorts, getPortAt, getPriority, setPriority, setStage, setStage, start, start, stop, stop

Methods inherited from class com.softsynth.jsyn.SynthObject

delete, deleteAll, enableDeletionByGarbageCollector, enableTracking, getPeer, getSynthContext, isTrackingEnabled, toString, track

Methods inherited from class java.util.Observable

addObserver, countObservers, deleteObserver, deleteObservers, hasChanged, notifyObservers, notifyObservers

Methods inherited from class java.lang.Object

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

Field Detail

A0

public SynthVariable A0

Filter coefficient. SIGNAL_TYPE_RAW_SIGNED, default = 0.0.

A1

public SynthVariable A1

Filter coefficient. SIGNAL_TYPE_RAW_SIGNED, default = 0.0.

A2

public SynthVariable A2

Filter coefficient. SIGNAL_TYPE_RAW_SIGNED, default = 0.0.

B1

public SynthVariable B1

Filter coefficient. SIGNAL_TYPE_RAW_SIGNED, default = 0.0.

B2

public SynthVariable B2

Filter coefficient. SIGNAL_TYPE_RAW_SIGNED, default = 0.0.

Constructor Detail

Filter_2o2p2z

public Filter_2o2p2z(SynthContext synthContext,
                     int calculationRate)
              throws SynthException

Throws:

SynthException

Filter_2o2p2z

public Filter_2o2p2z(SynthContext synthContext)
              throws SynthException

Create a SynthUnit that runs at Synth.RATE_AUDIO.

Throws:

SynthException - If resource allocation fails.

Filter_2o2p2z

public Filter_2o2p2z()
              throws SynthException

Throws:

SynthException

Method Detail

lowPass

public void lowPass(int time,
                    double frequency,
                    double bandwidth)
             throws SynthException

Set coefficients of filter for Low Pass operation. Frequencies below the given frequency parameter will be passed. Frequencies above will be cut off to varying degrees.

Parameters:

time - Time at which to set ports..

frequency - Cutoff frequency in Hertz.

bandwidth - Bandwidth in octaves (between midpoint (dBgain/2) gain frequencies for peaking or between -3 dB frequencies for BPF and notch).

Throws:

SynthException - If port setting fails.

lowPass

public void lowPass(double frequency,
                    double bandwidth)
             throws SynthException

Throws:

SynthException

highPass

public void highPass(int time,
                     double frequency,
                     double bandwidth)
              throws SynthException

Set coefficients of filter for High Pass operation. Frequencies above the given frequency parameter will be passed. Frequencies below will be cut off to varying degrees.

Parameters:

time - Time at which to set ports..

frequency - Cutoff frequency in Hertz.

bandwidth - Bandwidth in octaves (between midpoint (dBgain/2) gain frequencies for peaking or between -3 dB frequencies for BPF and notch).

Throws:

SynthException - If port setting fails.

highPass

public void highPass(double frequency,
                     double bandwidth)
              throws SynthException

Throws:

SynthException

bandPass

public void bandPass(int time,
                     double frequency,
                     double bandwidth)
              throws SynthException

Set coefficients of filter for Band Pass operation. Frequencies near the given frequency parameter will be passed. Frequencies above and below will be cut off to varying degrees.

Parameters:

time - Time at which to set ports..

frequency - Center frequency in Hertz.

bandwidth - Bandwidth in octaves (between midpoint (dBgain/2) gain frequencies for peaking or between -3 dB frequencies for BPF and notch).

Throws:

SynthException - If port setting fails.

bandPass

public void bandPass(double frequency,
                     double bandwidth)
              throws SynthException

Throws:

SynthException

notch

public void notch(int time,
                  double frequency,
                  double bandwidth)
           throws SynthException

Set coefficients of filter for Notch operation. Frequencies near the given frequency parameter will be cut. Frequencies above and below will be passed to varying degrees.

Parameters:

time - Time at which to set ports..

frequency - Center frequency in Hertz.

bandwidth - Bandwidth in octaves (between midpoint (dBgain/2) gain frequencies for peaking or between -3 dB frequencies for BPF and notch).

Throws:

SynthException - If port setting fails.

notch

public void notch(double frequency,
                  double bandwidth)
           throws SynthException

Throws:

SynthException

peakingEQ

public void peakingEQ(int time,
                      double frequency,
                      double bandwidth,
                      double dBGain)
               throws SynthException

Set coefficients of filter for Peaking EQ operation. Frequencies near the given frequency parameter will be passed. Frequencies above and below will be cut off to varying degrees.

Parameters:

time - Time at which to set ports..

frequency - Center frequency in Hertz.

bandwidth - Bandwidth in octaves (between midpoint (dBgain/2) gain frequencies for peaking or between -3 dB frequencies for BPF and notch).

dBGain - Gain in decibels at the center frequency. If dBGain is zero then the signal is unmodified.

Throws:

SynthException - If port setting fails.

peakingEQ

public void peakingEQ(double frequency,
                      double bandwidth,
                      double dBGain)
               throws SynthException

Throws:

SynthException

lowShelf

public void lowShelf(int time,
                     double frequency,
                     double dBGain,
                     double slope)
              throws SynthException

Set coefficients of filter for Low Shelf operation. This is similar to the Bass control on a stereo.

Parameters:

time - Time at which to set ports..

frequency - Center frequency in Hertz.

bandwidth - Bandwidth in octaves (between midpoint (dBgain/2) gain frequencies for peaking or between -3 dB frequencies for BPF and notch).

dBGain - Gain in decibels past the edge of the shelf. If dBGain is zero then the signal is unmodified.

slope - Slope of the edge of the shelf. Should be < 1.0 to prevent irregularities in the frequency response curve.

Throws:

SynthException - If port setting fails.

lowShelf

public void lowShelf(double frequency,
                     double dBGain,
                     double slope)
              throws SynthException

Throws:

SynthException

lowShelf

public void lowShelf(double frequency,
                     double bandwidth,
                     double dBGain,
                     double slope)
              throws SynthException

Throws:

SynthException

lowShelf

public void lowShelf(int time,
                     double frequency,
                     double bandwidth,
                     double dBGain,
                     double slope)
              throws SynthException

Throws:

SynthException

highShelf

public void highShelf(int time,
                      double frequency,
                      double dBGain,
                      double slope)
               throws SynthException

Set coefficients of filter for High Shelf operation. This is similar to the Treble control on a stereo.

Parameters:

time - Time at which to set ports..

frequency - Center frequency in Hertz.

bandwidth - Bandwidth in octaves (between midpoint (dBgain/2) gain frequencies for peaking or between -3 dB frequencies for BPF and notch).

dBGain - Gain in decibels past the edge of the shelf. If dBGain is zero then the signal is supposed to be unmodified but isn't.

slope - Slope of the edge of the shelf. Should be < 1.0 to prevent irregularities in the frequency response curve.

Throws:

SynthException - If port setting fails.

highShelf

public void highShelf(double frequency,
                      double dBGain,
                      double slope)
               throws SynthException

Throws:

SynthException

highShelf

public void highShelf(double frequency,
                      double bandwidth,
                      double dBGain,
                      double slope)
               throws SynthException

Throws:

SynthException

highShelf

public void highShelf(int time,
                      double frequency,
                      double bandwidth,
                      double dBGain,
                      double slope)
               throws SynthException

Throws:

SynthException