4th order Butterworth lowpass filter; Butterworth filters have maximum flat frequency response in the pass band. More...

#include <TTLowpassButterworth4.h>

Inheritance diagram for TTLowpassButterworth4:

Collaboration diagram for TTLowpassButterworth4:

Protected Member Functions
TTErr	updateMaxNumChannels (const TTValue &oldMaxNumChannels, TTValue &)
	Receives notifications when there are changes to the inherited mMaxNumChannels attribute. More...

TTErr	clear ()
	This algorithm uses an IIR filter, meaning that it relies on feedback. More...

TTErr	calculateValue (const TTFloat64 &x, TTFloat64 &y, TTPtrSizedInt channel)
	Standard single value calculate method as used by DSP objects. More...

TTErr	processAudio (TTAudioSignalArrayPtr inputs, TTAudioSignalArrayPtr outputs)
	Standard audio processing method as used by TTBlue objects. More...

TTErr	setFrequency (const TTValue &value)
	Setter for the frequency attribute. More...

virtual TTErr	test (TTValue &returnedTestInfo)
	Unit Tests. More...

Protected Attributes
TTFloat64	mFrequency
	filter cutoff frequency

TTFloat64	mRadians4
	filter coefficients

TTFloat64	mA2
	filter coefficients for input samples

TTFloat64	mB4
	filter coefficients for output samples

TTSampleVector	mX1
	Input sample n-1.

TTSampleVector	mX2
	Input sample n-2.

TTSampleVector	mX3
	Input sample n-3.

TTSampleVector	mX4
	Input sample n-4.

TTSampleVector	mY1
	Output sample n-1.

TTSampleVector	mY2
	Output sample n-2.

TTSampleVector	mY3
	Output sample n-3.

TTSampleVector	mY4
	Output sample n-4.

Detailed Description

4th order Butterworth lowpass filter; Butterworth filters have maximum flat frequency response in the pass band.

Filter equations from:

Second-order IIR Filters will support cascade implementations By Rusty Allred, Texas Instruments, Dallas July 01, 2003 http://www.planetanalog.com/article/printableArticle.jhtml?articleID=12802683

Definition at line 40 of file TTLowpassButterworth4.h.

Member Function Documentation

TTErr TTLowpassButterworth4::calculateValue	(	const TTFloat64 &	x,
		TTFloat64 &	y,
		TTPtrSizedInt	channel
	)

inlineprotected

Standard single value calculate method as used by DSP objects.

Definition at line 134 of file TTLowpassButterworth4.cpp.

References kTTErrNone, mA2, mB4, mX1, mX2, mX3, mX4, mY1, mY2, mY3, and mY4.

Referenced by processAudio().

TTErr TTLowpassButterworth4::clear ( )

protected

This algorithm uses an IIR filter, meaning that it relies on feedback.

If the filter should not be producing any signal (such as turning audio off and then back on in a host) or if the feedback has become corrupted (such as might happen if a NaN is fed in) then it may be neccesary to clear the filter by calling this method.