IIRFilter Class Reference

An IIR filter that can perform low, high, or band-pass filtering on an audio signal. More...

Public Member Functions
	IIRFilter ()
	Creates a filter.
	IIRFilter (const IIRFilter &other)
	Creates a copy of another filter.
	~IIRFilter ()
	Destructor.
void	reset () throw ()
	Resets the filter's processing pipeline, ready to start a new stream of data.
void	processSamples (float *samples, int numSamples) throw ()
	Performs the filter operation on the given set of samples.
float	processSingleSampleRaw (float sample) throw ()
	Processes a single sample, without any locking or checking.
void	makeLowPass (double sampleRate, double frequency) throw ()
	Sets the filter up to act as a low-pass filter.
void	makeHighPass (double sampleRate, double frequency) throw ()
	Sets the filter up to act as a high-pass filter.
void	makeLowShelf (double sampleRate, double cutOffFrequency, double Q, float gainFactor) throw ()
	Sets the filter up to act as a low-pass shelf filter with variable Q and gain.
void	makeHighShelf (double sampleRate, double cutOffFrequency, double Q, float gainFactor) throw ()
	Sets the filter up to act as a high-pass shelf filter with variable Q and gain.
void	makeBandPass (double sampleRate, double centreFrequency, double Q, float gainFactor) throw ()
	Sets the filter up to act as a band pass filter centred around a frequency, with a variable Q and gain.
void	makeInactive () throw ()
	Clears the filter's coefficients so that it becomes inactive.
void	copyCoefficientsFrom (const IIRFilter &other) throw ()
	Makes this filter duplicate the set-up of another one.
Protected Member Functions
void	setCoefficients (double c1, double c2, double c3, double c4, double c5, double c6) throw ()
IIRFilter &	operator= (const IIRFilter &)
Protected Attributes
CriticalSection	processLock
bool	active
float	coefficients [6]
float	x1
float	x2
float	y1
float	y2

Detailed Description

An IIR filter that can perform low, high, or band-pass filtering on an audio signal.

See also:: IIRFilterAudioSource

Constructor & Destructor Documentation

IIRFilter::IIRFilter ( )

Creates a filter.

Initially the filter is inactive, so will have no effect on samples that you process with it. Use the appropriate method to turn it into the type of filter needed.

IIRFilter::IIRFilter ( const IIRFilter & other )

Creates a copy of another filter.

IIRFilter::~IIRFilter ( )

Destructor.

Member Function Documentation

void IIRFilter::reset ( ) throw ()

Resets the filter's processing pipeline, ready to start a new stream of data.

Note that this clears the processing state, but the type of filter and its coefficients aren't changed. To put a filter into an inactive state, use the makeInactive() method.

void IIRFilter::processSamples	(	float *	samples,
		int	numSamples
	)			throw ()

Performs the filter operation on the given set of samples.

float IIRFilter::processSingleSampleRaw ( float sample ) throw ()

Processes a single sample, without any locking or checking.

Use this if you need fast processing of a single value, but be aware that this isn't thread-safe in the way that processSamples() is.

void IIRFilter::makeLowPass	(	double	sampleRate,
		double	frequency
	)			throw ()

Sets the filter up to act as a low-pass filter.

void IIRFilter::makeHighPass	(	double	sampleRate,
		double	frequency
	)			throw ()

Sets the filter up to act as a high-pass filter.

void IIRFilter::makeLowShelf	(	double	sampleRate,
		double	cutOffFrequency,
		double	Q,
		float	gainFactor
	)			throw ()

Sets the filter up to act as a low-pass shelf filter with variable Q and gain.

The gain is a scale factor that the low frequencies are multiplied by, so values greater than 1.0 will boost the low frequencies, values less than 1.0 will attenuate them.

void IIRFilter::makeHighShelf	(	double	sampleRate,
		double	cutOffFrequency,
		double	Q,
		float	gainFactor
	)			throw ()

Sets the filter up to act as a high-pass shelf filter with variable Q and gain.

The gain is a scale factor that the high frequencies are multiplied by, so values greater than 1.0 will boost the high frequencies, values less than 1.0 will attenuate them.

void IIRFilter::makeBandPass	(	double	sampleRate,
		double	centreFrequency,
		double	Q,
		float	gainFactor
	)			throw ()

Sets the filter up to act as a band pass filter centred around a frequency, with a variable Q and gain.

The gain is a scale factor that the centre frequencies are multiplied by, so values greater than 1.0 will boost the centre frequencies, values less than 1.0 will attenuate them.

void IIRFilter::makeInactive ( ) throw ()

Clears the filter's coefficients so that it becomes inactive.

void IIRFilter::copyCoefficientsFrom ( const IIRFilter & other ) throw ()

Makes this filter duplicate the set-up of another one.