krotos::MoogVcf Class Reference

Apply the Moog voltage controlled filter to an audio signal. More...

#include <MoogVcf.h>

Public Member Functions
void	setUpFirst (double sampleRate, int)
	setUpFirst
float	getSr ()
	getSr()
void	updateCutoff (float _f0)
	updateCutoff
void	updateResonance (float _r)
	updateResonance
float	process (float inputSampleNow, float inputSampleBefore)
	process()

Private Attributes
const float	initialF = 20.0f
float	m_sr
float	om0 = tau * initialF
	Resonant filter frequency.
float	om0New
float	r = 0.0f
	Feedback coefficient.
float	rNew
float	k
	Time step.
float	A0P
float	A0PNew
float	A0M
float	A1
float	A1New
float	A3
float	A3New
float	xf [4] = {0.0}

Static Private Attributes
static constexpr float	tau = 2.0f * 3.1415926535f

Detailed Description

Apply the Moog voltage controlled filter to an audio signal.

This class implements a virtual analogue model of the Moog VCF. The system of equations describing the state of the capacitors of the electrical circuit are solved for each input sample using the Trapezoid Integration Rule. The structure is modified to fit into the Kwidget technology. It is robust and computationally efficient.

TODO: Try and emulate the non linear version...

Member Function Documentation

getSr()

float krotos::MoogVcf::getSr ( )

inline

getSr()

Returns the sampleRate value in float.

process()

float krotos::MoogVcf::process ( float inputSampleNow, float inputSampleBefore )

inline

process()

main filtering process - updates state and writes sample to output. For each input sample, the linear system of equations updates the values of the state vector xf and updates the parameters if they have been changed by the user.

Parameters

float	inputSampleNow: the current input sample from the buffer
float	inputSampleBefore: the former input sample from the buffer.

setUpFirst()

void krotos::MoogVcf::setUpFirst ( double sampleRate, int  )

inline

setUpFirst

Sets up sampleRate and time step k . Gets called in the Processors prepare function.

Parameters

_sampleRate
samplesPerBlock,not	used.

updateCutoff()

void krotos::MoogVcf::updateCutoff ( float _f0 )

inline

updateCutoff

Sets filter cutoff and updates the state coefficients from the input parameter value. Gets called from the Processor's setCutoff function. To avoid loud high frequency - resonance amplitude spikes it performs a custom check and for certain cutoff - resonance pairs it readjusts the resonance, calling the updateResonace function.

Parameters

float

_f0 is the cutoff frequency in Hz parameter value

updateResonance()

void krotos::MoogVcf::updateResonance ( float _r )

inline

updateResonance

Sets filter resonance and updates the state coefficients from the input parameter. Gets called from the Processor's setCutoff function. It also performs check for high frequency - resonance spikes.

Parameters

float

_r is the input resonance parameter value

Member Data Documentation

A0M

float krotos::MoogVcf::A0M

private

A0P

float krotos::MoogVcf::A0P

private

A0PNew

float krotos::MoogVcf::A0PNew

private

A1

float krotos::MoogVcf::A1

private

A1New

float krotos::MoogVcf::A1New

private

A3

float krotos::MoogVcf::A3

private

A3New

float krotos::MoogVcf::A3New

private

initialF

const float krotos::MoogVcf::initialF = 20.0f

private

k

float krotos::MoogVcf::k

private

Time step.

m_sr

float krotos::MoogVcf::m_sr

private

om0

float krotos::MoogVcf::om0 = tau * initialF

private

Resonant filter frequency.

om0New

float krotos::MoogVcf::om0New

private

r

float krotos::MoogVcf::r = 0.0f

private

Feedback coefficient.

rNew

float krotos::MoogVcf::rNew

private

tau

float krotos::MoogVcf::tau = 2.0f * 3.1415926535f

staticconstexprprivate

xf

float krotos::MoogVcf::xf[4] = {0.0}

private

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

• krotos_dsp/processors/moogvcf/MoogVcf.h