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BiQuad Class Reference

#include <BiQuad.h>

Inheritance diagram for BiQuad:

Filter Stk FormSwep List of all members.

Detailed Description

STK biquad (two-pole, two-zero) filter class.

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

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


Public Member Functions

 BiQuad ()
 Default constructor creates a second-order pass-through filter.
virtual ~BiQuad ()
 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 all internal states of the filter.
void setB0 (StkFloat b0)
 Set the b[0] coefficient value.
void setB1 (StkFloat b1)
 Set the b[1] coefficient value.
void setB2 (StkFloat b2)
 Set the b[2] 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 setNotch (StkFloat frequency, StkFloat radius)
 Set the filter coefficients for a notch at frequency (in Hz).
void setEqualGainZeroes ()
 Sets the filter zeroes for equal resonance gain.
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.
virtual StkFloat tick (StkFloat sample)
 Input one sample to the filter and return one output.
virtual 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 BiQuad::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 filter zeros are placed at z = 1, z = -1, and the coefficients are then normalized to produce a constant unity peak gain (independent of the filter gain parameter). 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.

void BiQuad::setNotch StkFloat  frequency,
StkFloat  radius
 

Set the filter coefficients for a notch at frequency (in Hz).

This method determines the filter coefficients corresponding to two complex-conjugate zeros with the given frequency (in Hz) and radius from the z-plane origin. No filter normalization is attempted.

void BiQuad::setEqualGainZeroes  ) 
 

Sets the filter zeroes for equal resonance gain.

When using the filter as a resonator, zeroes places at z = 1, z = -1 will result in a constant gain at resonance of 1 / (1 - R), where R is the pole radius setting.

void BiQuad::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 & BiQuad::tick StkFrames frames,
unsigned int  channel = 0
[inline, 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.