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TwoPole Class Reference

#include <TwoPole.h>

Inheritance diagram for TwoPole:

Filter Stk List of all members.

Detailed Description

STK two-pole filter class.

This protected Filter subclass implements a two-pole digital filter. A method is provided for creating a resonance in the frequency response while maintaining a nearly constant filter gain.

by Perry R. Cook and Gary P. Scavone, 1995 - 2007.


Public Member Functions

 TwoPole ()
 Default constructor creates a second-order pass-through filter.
 ~TwoPole ()
 Class destructor.
void ignoreSampleRateChange (bool ignore=true)
 A function to enable/disable the automatic updating of class data when the STK sample rate changes.
void clear (void)
 Clears the internal states of the filter.
void setB0 (StkFloat b0)
 Set the b[0] coefficient value.
void setA1 (StkFloat a1)
 Set the a[1] coefficient value.
void setA2 (StkFloat a2)
 Set the a[2] coefficient value.
void setResonance (StkFloat frequency, StkFloat radius, bool normalize=false)
 Sets the filter coefficients for a resonance at frequency (in Hz).
void setGain (StkFloat gain)
 Set the filter gain.
StkFloat getGain (void) const
 Return the current filter gain.
StkFloat lastOut (void) const
 Return the last computed output value.
StkFloat tick (StkFloat sample)
 Input one sample to the filter and return one output.
StkFramestick (StkFrames &frames, unsigned int channel=0)
 Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs.


Member Function Documentation

void TwoPole::setResonance StkFloat  frequency,
StkFloat  radius,
bool  normalize = false
 

Sets the filter coefficients for a resonance at frequency (in Hz).

This method determines the filter coefficients corresponding to two complex-conjugate poles with the given frequency (in Hz) and radius from the z-plane origin. If normalize is true, the coefficients are then normalized to produce unity gain at frequency (the actual maximum filter gain tends to be slightly greater than unity when radius is not close to one). The resulting filter frequency response has a resonance at the given frequency. The closer the poles are to the unit-circle (radius close to one), the narrower the resulting resonance width. An unstable filter will result for radius >= 1.0. For a better resonance filter, use a BiQuad filter.

See also:
BiQuad filter class

void TwoPole::setGain StkFloat  gain  )  [virtual]
 

Set the filter gain.

The gain is applied at the filter input and does not affect the coefficient values. The default gain value is 1.0.

Reimplemented from Filter.

StkFrames& TwoPole::tick StkFrames frames,
unsigned int  channel = 0
[virtual]
 

Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs.

The channel argument should be zero or greater (the first channel is specified by 0). An StkError will be thrown if the channel argument is equal to or greater than the number of channels in the StkFrames object.

Reimplemented from Filter.


The documentation for this class was generated from the following file:
The Synthesis ToolKit in C++ (STK)
©1995-2007 Perry R. Cook and Gary P. Scavone. All Rights Reserved.