SPKitButterworthFilter


User's Guide

SPKitButterworthFilter a base class for butterworth filters. It implements functions common to the four Butterworth filter variant classes:

Note: SPKitButterworthFilter serves only as a base class for the filters listed above. It is not intended for direct use.

For a more detailed description of Butterworth filters, see Dodge & Jerse (1985:186-193).


Programmer's Reference

Defined in <spkit/butterwo.h>
Inherits from SPKitProcessor

SPKitButterworthFilter overrides getSample() and setInput(). It also defines a destructor for releasing local buffers allocated by setInput().

Public Members

SPKitError setInput(SPKitProcessor* newInput)
connect an input to the object and initialize it. Allocates a delay buffer for each audio channel of the input object.

Calls SPKitProcessor::setInput().

int getSample(SPKitSample& outputSample)
retrieve a processed audio sample

getSample() multiplies each input sample by the product of previously read and written samples and coefficients.

getSample() stores the processed sample in outputSample. The function returns 0 on end of signal, 1 otherwise.

Protected Members

SPKitFloat C
a temporary variable for calculating filter coefficients
SPKitFloat D
a temporary variable for calculating filter coefficients
SPKitFloat a[3]
coefficients for the current input and previously read samples
SPKitFloat b[2]
coefficients for the previously written samples
BWBuffer* chBuf[]
buffers for previously read and written samples

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Kai Lassfolk / University of Helsinki / kpl@elisir.helsinki.fi