Biquad Class Reference

The Biquad object implements a first or second order H(z) transfer function using one of four standard structures: Direct, Canonical, Transpose Direct, Transpose Canonical. More...

#include <fxobjects.h>

Inheritance diagram for Biquad:

Public Member Functions
virtual bool	reset (double _sampleRate)
virtual bool	canProcessAudioFrame ()
virtual double	processAudioSample (double xn)
	process one sample through the biquad
BiquadParameters	getParameters ()
void	setParameters (const BiquadParameters &_parameters)
void	setCoefficients (double *coeffs)
double *	getCoefficients ()
double *	getStateArray ()
double	getG_value ()
double	getS_value ()
	returns the storage component S(n) for delay-free loop solutions
Public Member Functions inherited from IAudioSignalProcessor
virtual bool	reset (double _sampleRate)=0
virtual double	processAudioSample (double xn)=0
virtual bool	canProcessAudioFrame ()=0
virtual void	setSampleRate (double _sampleRate)
virtual void	enableAuxInput (bool enableAuxInput)
virtual double	processAuxInputAudioSample (double xn)
virtual bool	processAudioFrame (const float *inputFrame, float *outputFrame, uint32_t inputChannels, uint32_t outputChannels)

Protected Attributes
double	coeffArray [numCoeffs] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 }
double	stateArray [numStates] = { 0.0, 0.0, 0.0, 0.0 }
BiquadParameters	parameters
double	storageComponent = 0.0

Detailed Description

The Biquad object implements a first or second order H(z) transfer function using one of four standard structures: Direct, Canonical, Transpose Direct, Transpose Canonical.

Audio I/O:

• Processes mono input to mono output.

Control I/F:

• Use BiquadParameters structure to get/set object params.

Author

Will Pirkle http://www.willpirkle.com

Remarks

This object is included in Designing Audio Effects Plugins in C++ 2nd Ed. by Will Pirkle

Version

Revision : 1.0

Date

Date : 2018 / 09 / 7

Member Function Documentation

canProcessAudioFrame()

virtual bool Biquad::canProcessAudioFrame ( )

inlinevirtual

return false: this object only processes samples

Implements IAudioSignalProcessor.

getCoefficients()

double * Biquad::getCoefficients ( )

inline

get the coefficient array for read/write access to the array (not used in current objects)

getG_value()

double Biquad::getG_value ( )

inline

get the structure G (gain) value for Harma filters; see 2nd Ed FX book

getParameters()

BiquadParameters Biquad::getParameters ( )

inline

get parameters: note use of custom structure for passing param data

Returns

BiquadParameters custom data structure

getS_value()

double Biquad::getS_value

(

)

returns the storage component S(n) for delay-free loop solutions

get the structure S (storage) value for Harma filters; see 2nd Ed FX book

• NOTES:
  the storageComponent or "S" value is used for Zavalishin's VA filters as well as the phaser APFs (Biquad) and is only available on two of the forms: direct and transposed canonical
  

  Returns

  the storage component of the filter

getStateArray()

double * Biquad::getStateArray ( )

inline

get the state array for read/write access to the array (used only in direct form oscillator)

processAudioSample()

double Biquad::processAudioSample ( double  xn )

virtual

process one sample through the biquad

process input x(n) through biquad to produce return value y(n)

Parameters

xn

input

Returns

the processed sample

• RULES:
  1) do all math required to form the output y(n), reading registers as required - do NOT write registers
  2) check for underflow, which can happen with feedback structures
  3) lastly, update the states of the z^-1 registers in the state array just before returning
  
• NOTES:
  the storageComponent or "S" value is used for Zavalishin's VA filters and is only available on two of the forms: direct and transposed canonical
  

  Parameters

  xn	the input sample x(n)

  Returns

  the biquad processed output y(n)

Implements IAudioSignalProcessor.

reset()

virtual bool Biquad::reset ( double  _sampleRate )

inlinevirtual

reset: clear out the state array (flush delays); can safely ignore sampleRate argument - we don't need/use it

Implements IAudioSignalProcessor.

setCoefficients()

void Biquad::setCoefficients ( double *  coeffs )

inline

set the coefficient array NOTE: passing by pointer to array; allows us to use "array notation" with pointers i.e. [ ]

setParameters()

void Biquad::setParameters ( const BiquadParameters &  _parameters )

inline

set parameters: note use of custom structure for passing param data

Parameters

BiquadParameters

custom data structure

Member Data Documentation

coeffArray

double Biquad::coeffArray[numCoeffs] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 }

protected

array of coefficients

parameters

BiquadParameters Biquad::parameters

protected

type of calculation (algorithm structure)

stateArray

double Biquad::stateArray[numStates] = { 0.0, 0.0, 0.0, 0.0 }

protected

array of state (z^-1) registers

storageComponent

double Biquad::storageComponent = 0.0

protected

for Harma loop resolution

---

The documentation for this class was generated from the following files:

• C:/RackAFX_v7/ASPIK_Doxygen/PluginObjects/fxobjects.h
• C:/RackAFX_v7/ASPIK_Doxygen/PluginObjects/fxobjects.cpp