Oequalizer

INSTRUMENT design – multi-purpose equalizer (filter) object

The Oequalizer object uses a biquad filter algorithm to instantiate a number of different filter types (low-pass, high-pass, band-pass, etc.). The code was based on work done by Tom St. Denis, using formulas for the filter coeeficients from Robert Bristow-Johnson’s on-line document The Audio-EQ-Cookbook.

The older functions reson and resonz do similar signal-processing actions, but using different and somewhat less flexible algorithms. For very simple filtering, the Oonepole object may be more appropriate.

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Constructors

Oequalizer(float SR, OeqType filter_type)

*SR* is the current sampling rate (an Instrument class variable).
*filter\_type* is the kind of filter that will be implemented by the biquad equation. These types are defined in the OeqType structure found in the RTcmix/genlib/Oequalizer.h file:

• OeqLowPass – low-pass filter
• OeqHighPass – high-pass filter
• OeqBandPassCSG – band-pass filter with “constant skirt gain”, the peak gain will be related to the “Q” of the filter
• OeqBandPassCPG/OeqBandPass – band-pass filter with “constant peak gain”, the peak gain will be 0 dB
• OeqNotch – notch filter
• OeqAllPass – allpass filter
• OeqPeaking – peaking filter (good for creating “quacking” sounds; used in… oh, you figure it out :-))
• OeqLowShelf – low shelf filter
• OeqHighShelf – high shelf filter

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Access Methods

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Examples

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See Also