An IIR filter that can perform low, band and high-pass filtering on an audio signal, with 12 dB of attenuation per octave, using a TPT structure, designed for fast modulation (see Vadim Zavalishin's documentation about TPT structures for more information). More...

#include <juce_StateVariableTPTFilter.h>

Collaboration diagram for juce::dsp::StateVariableTPTFilter< SampleType >:

[legend]

Public Types
using	Type = StateVariableTPTFilterType

Public Member Functions
	StateVariableTPTFilter ()
	Constructor. More...

SampleType	getCutoffFrequency () const noexcept
	Returns the cutoff frequency of the filter. More...

SampleType	getResonance () const noexcept
	Returns the resonance of the filter. More...

Type	getType () const noexcept
	Returns the type of the filter. More...

void	prepare (const ProcessSpec &spec)
	Initialises the filter. More...

template<typename ProcessContext >
void	process (const ProcessContext &context) noexcept
	Processes the input and output samples supplied in the processing context. More...

SampleType	processSample (int channel, SampleType inputValue)
	Processes one sample at a time on a given channel. More...

void	reset ()
	Resets the internal state variables of the filter. More...

void	reset (SampleType newValue)
	Resets the internal state variables of the filter to a given value. More...

void	setCutoffFrequency (SampleType newFrequencyHz)
	Sets the cutoff frequency of the filter. More...

void	setResonance (SampleType newResonance)
	Sets the resonance of the filter. More...

void	setType (Type newType)
	Sets the filter type. More...

void	snapToZero () noexcept
	Ensure that the state variables are rounded to zero if the state variables are denormals. More...

Private Member Functions
void	update ()

Private Attributes
SampleType	cutoffFrequency = static_cast<SampleType> (1000.0)

Type	filterType = Type::lowpass

SampleType	g

SampleType	h

SampleType	R2

SampleType	resonance = static_cast<SampleType> (1.0 / std::sqrt (2.0))

std::vector< SampleType >	s1 { 2 }

std::vector< SampleType >	s2 { 2 }

double	sampleRate = 44100.0

Detailed Description

template<typename SampleType>
class juce::dsp::StateVariableTPTFilter< SampleType >

An IIR filter that can perform low, band and high-pass filtering on an audio signal, with 12 dB of attenuation per octave, using a TPT structure, designed for fast modulation (see Vadim Zavalishin's documentation about TPT structures for more information).

Its behaviour is based on the analog state variable filter circuit.

Note: The bandpass here is not the one in the RBJ CookBook as its gain can be higher than 0 dB. For the classic 0 dB bandpass, we need to multiply the result by R2.

Note 2: Using this class prevents some loud audio artefacts commonly encountered when changing the cutoff frequency using other filter simulation structures and IIR filter classes. However, this class may still require additional smoothing for cutoff frequency changes.

see IIRFilter, SmoothedValue

@tags{DSP}

Member Typedef Documentation

◆ Type

template<typename SampleType >

using juce::dsp::StateVariableTPTFilter< SampleType >::Type = StateVariableTPTFilterType

Constructor & Destructor Documentation

◆ StateVariableTPTFilter()

template<typename SampleType >

juce::dsp::StateVariableTPTFilter< SampleType >::StateVariableTPTFilter ( )

Constructor.

Member Function Documentation

◆ getCutoffFrequency()

template<typename SampleType >

SampleType juce::dsp::StateVariableTPTFilter< SampleType >::getCutoffFrequency ( ) const

inlinenoexcept

Returns the cutoff frequency of the filter.

References juce::dsp::StateVariableTPTFilter< SampleType >::cutoffFrequency.

◆ getResonance()

template<typename SampleType >

SampleType juce::dsp::StateVariableTPTFilter< SampleType >::getResonance ( ) const

inlinenoexcept

Returns the resonance of the filter.

References juce::dsp::StateVariableTPTFilter< SampleType >::resonance.

◆ getType()

template<typename SampleType >

Type juce::dsp::StateVariableTPTFilter< SampleType >::getType ( ) const

inlinenoexcept

Returns the type of the filter.

References juce::dsp::StateVariableTPTFilter< SampleType >::filterType.

◆ prepare()

template<typename SampleType >

void juce::dsp::StateVariableTPTFilter< SampleType >::prepare ( const ProcessSpec & spec )

Initialises the filter.

◆ process()

template<typename SampleType >

template<typename ProcessContext >

void juce::dsp::StateVariableTPTFilter< SampleType >::process ( const ProcessContext & context )

inlinenoexcept

Processes the input and output samples supplied in the processing context.

References jassert, juce::dsp::StateVariableTPTFilter< SampleType >::processSample(), juce::dsp::StateVariableTPTFilter< SampleType >::s1, and juce::dsp::StateVariableTPTFilter< SampleType >::snapToZero().

◆ processSample()

template<typename SampleType >

SampleType juce::dsp::StateVariableTPTFilter< SampleType >::processSample	(	int	channel,
		SampleType	inputValue
	)

Processes one sample at a time on a given channel.

Referenced by juce::dsp::StateVariableTPTFilter< SampleType >::process().

◆ reset() [1/2]

template<typename SampleType >

void juce::dsp::StateVariableTPTFilter< SampleType >::reset ( )

Resets the internal state variables of the filter.

◆ reset() [2/2]

template<typename SampleType >

void juce::dsp::StateVariableTPTFilter< SampleType >::reset ( SampleType newValue )

Resets the internal state variables of the filter to a given value.

◆ setCutoffFrequency()

template<typename SampleType >

void juce::dsp::StateVariableTPTFilter< SampleType >::setCutoffFrequency ( SampleType newFrequencyHz )

Sets the cutoff frequency of the filter.

Parameters

newFrequencyHz the new cutoff frequency in Hz.

◆ setResonance()

template<typename SampleType >

void juce::dsp::StateVariableTPTFilter< SampleType >::setResonance ( SampleType newResonance )

Sets the resonance of the filter.

Note: The bandwidth of the resonance increases with the value of the parameter. To have a standard 12 dB / octave filter, the value must be set at 1 / sqrt(2).