FilterEffectBase Class Reference

A Base class for filter based effects including methods for simple high, low and band pass filtering. More...

#include <AudioEffectsSuite.h>

Inheritance diagram for FilterEffectBase:

Public Member Functions
	FilterEffectBase ()
	FilterEffectBase (FilterEffectBase &copy)=default
	~FilterEffectBase ()=default
virtual bool	active ()
	determines if the effect is active
virtual effectsuite_t	applyFilter (effectsuite_t sampVal)
virtual AudioEffect *	clone ()=0
effectsuite_t	envelope (effectsuite_t sample)
int	id ()
	Allows to identify an effect.
virtual effect_t	process (effect_t inputSample) override
	see applyFilter
virtual effectsuite_t	processDouble (effectsuite_t inputSample) override
	Main process block for applying audio effect. More...
virtual void	setActive (bool value)
	sets the effect active/inactive
bool	setChebyICoefficients (effectsuite_t cutFreq, bool shelfType, effectsuite_t ripple)
void	setId (int id)
	Allows to identify an effect.

Protected Member Functions
void	allocateBufferMemory ()
bool	changeChebyICoefficients (effectsuite_t cutFreq, bool shelfType, effectsuite_t ripple, int poles)
void	clearMemory ()
int16_t	clip (int32_t in, int16_t clipLimit=32767, int16_t resultLimit=32767)
	generic clipping method
void	copyParent (AudioEffect *copy)
void	incBufferIndex ()
effectsuite_t	rms (effectsuite_t sample)
bool	setSimpleLpf (int order)

Protected Attributes
bool	active_flag = true
int	bufferIndex = 0
int	filterOrder = 0
effectsuite_t *	firBuffer = 0
effectsuite_t *	firCoefficients = 0
effectsuite_t *	firTemp = 0
int	id_value = -1
effectsuite_t *	iirBuffer = 0
effectsuite_t *	iirCoefficients = 0
effectsuite_t *	iirTemp = 0
effectsuite_t *	rmsBuffer = new effectsuite_t[rmsWindowSize]
int	rmsBufferIndex = 0
const int	rmsWindowSize = 128
int	samplingRate = 0

Static Protected Attributes
constexpr static const effectsuite_t	pi = 3.141592653589793

Detailed Description

A Base class for filter based effects including methods for simple high, low and band pass filtering.

See also

FilterEffectBase

Author

Matthew Hamilton

Copyright

MIT License

Constructor & Destructor Documentation

FilterEffectBase()

FilterEffectBase ( )

inline

Constructor.

~FilterEffectBase()

~FilterEffectBase ( )

default

Destructor.

Member Function Documentation

allocateBufferMemory()

void allocateBufferMemory ( )

inlineprotected

will allocate memory to a buffer given the current filter order and set all values == 0.00

applyFilter()

virtual effectsuite_t applyFilter ( effectsuite_t  sampVal )

inlinevirtual

with the current filter coefficients this method filters a sample then stores it the sample Buffer and increments the index

Parameters

sampVal

is the sample to be processed

Returns

filtered audio sample

changeChebyICoefficients()

bool changeChebyICoefficients ( effectsuite_t  cutFreq, bool  shelfType, effectsuite_t  ripple, int  poles  )

inlineprotected

set firCoefficients and iirCoefficients for required chebyshev type I filter sampleBuffer memory is also set @params cutFreq normalised cutoff frequency (0 < x < .5) @params shelfType bool filter shelf type, false = low pass, true = high pass @params ripple percentage ripple (<.2929) @params poles number of poles

Returns

boolean false on error and true on success

clearMemory()

void clearMemory ( )

inlineprotected

checks internal memory storage of filter coeffcients and deletes if required

envelope()

effectsuite_t envelope ( effectsuite_t  sample )

inline

detect the envelop of an incoming signal

Parameters

sample

the incoming signal sample value

Returns

returns envelope dection signal sample value

incBufferIndex()

void incBufferIndex ( )

inlineprotected

increment the buffer index and wrap it to the filter order

processDouble()

virtual effectsuite_t processDouble ( effectsuite_t  inputSample )

inlineoverridevirtual

Main process block for applying audio effect.

Parameters

inputSample

The input audio sample for the effect to be applied to

Returns

an audio sample as a effectsuite_t with effect applied

Implements EffectSuiteBase.

Reimplemented in EnvelopeFilter, FilteredDelay, and SimpleChorus.

rms()

effectsuite_t rms ( effectsuite_t  sample )

inlineprotected

root mean square of signal over a specific sample window

setChebyICoefficients()

bool setChebyICoefficients ( effectsuite_t  cutFreq, bool  shelfType, effectsuite_t  ripple  )

inline

changes the current Chebyshev type 1 coefficients without altering the filter order. This allows for use in an audio process thread as it avoids dynamic allocation of memory. Filter sample and coefficient buffers are unaltered for initialising a chebyshev type 1 filter

See also

setChebyICoefficients @params cutFreq normalised cutoff frequency (0 < x < .5) @params shelfType bool Filters shelf type, false = low pass, true = high pass @params ripple percentage ripple (<.2929)

Returns

boolean false on error and true on success

setSimpleLpf()

bool setSimpleLpf ( int  order )

inlineprotected

a simple normalised fir low pass filter @params order number of delay coefficients

Member Data Documentation

bufferIndex

int bufferIndex = 0

protected

current buffer index

filterOrder

int filterOrder = 0

protected

order of delay filter including the zero delay coefficients

firBuffer

effectsuite_t* firBuffer = 0

protected

buffer to hold forward delay sample data

firCoefficients

effectsuite_t* firCoefficients = 0

protected

Numerator coefficients in delay filter firCoefficients[0] z^0 coeffcieint firCoefficients[1] z^-1 coefficient

firTemp

effectsuite_t* firTemp = 0

protected

hold temporary values for fir coeffcient buffer

iirBuffer

effectsuite_t* iirBuffer = 0

protected

buffer to hold backward delay sample data

iirCoefficients

effectsuite_t* iirCoefficients = 0

protected

Denomiator coefficients in delay filter

See also

firCoefficients

iirTemp

effectsuite_t* iirTemp = 0

protected

hold temporary values for iir coeffcient buffer

rmsBuffer

effectsuite_t* rmsBuffer = new effectsuite_t[rmsWindowSize]

protected

RMS window buffer

rmsBufferIndex

int rmsBufferIndex = 0

protected

current write index of rmsBuffer

rmsWindowSize

const int rmsWindowSize = 128

protected

window size in samples of rms window

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

• src/AudioEffects/AudioEffectsSuite.h