Biquad Struct Reference

Single RBJ biquad, per sample. More...

#include <gin_biquad.h>

Public Member Functions
void	setLowpass (double freq, double q, double sampleRate)
void	setHighpass (double freq, double q, double sampleRate)
void	setBandpass (double freq, double q, double sampleRate)
void	setPeak (double freq, double q, double gainDb, double sampleRate)
	Peaking EQ.
void	setBypass ()
	Passes everything through unchanged.
float	process (float x)
void	reset ()

Public Attributes
float	b0 = 1.0f
float	b1 = 0.0f
float	b2 = 0.0f
float	a1 = 0.0f
float	a2 = 0.0f
float	x1 = 0.0f
float	x2 = 0.0f
float	y1 = 0.0f
float	y2 = 0.0f

Detailed Description

Single RBJ biquad, per sample.

A small, self contained second order section for the places a filter is part of an algorithm rather than a thing the user configures - detector paths, side chain shaping, band limiting inside an effect. Filter is the one to reach for when a plugin exposes a filter to the user: it handles channels, slopes and modulation. This one is a struct with five coefficients and four state variables, and can sit inside a loop.

Coefficients follow Robert Bristow-Johnson's cookbook.

Usage:

Biquad hp;
hp.setHighpass (80.0f, 0.707f, sampleRate);
 
for (int i = 0; i < numSamples; i++)
    data[i] = hp.process (data[i]);

Note: one instance holds the state for one channel.

See also

Filter, EQ

Member Function Documentation

setLowpass()

void Biquad::setLowpass	(	double	freq,
		double	q,
		double	sampleRate )

setHighpass()

void Biquad::setHighpass	(	double	freq,
		double	q,
		double	sampleRate )

setBandpass()

void Biquad::setBandpass	(	double	freq,
		double	q,
		double	sampleRate )

setPeak()

void Biquad::setPeak	(	double	freq,
		double	q,
		double	gainDb,
		double	sampleRate )

Peaking EQ.

Positive gainDb boosts around freq, negative cuts.

setBypass()

void Biquad::setBypass

(

)

Passes everything through unchanged.

process()

float Biquad::process

(

float

x

)

References a1, a2, b0, b1, b2, x1, x2, y1, and y2.

reset()

void Biquad::reset

(

)

References x1, x2, y1, and y2.

Member Data Documentation

b0

float Biquad::b0 = 1.0f

Referenced by process().

b1

float Biquad::b1 = 0.0f

Referenced by process().

b2

float Biquad::b2 = 0.0f

Referenced by process().

a1

float Biquad::a1 = 0.0f

Referenced by process().

a2

float Biquad::a2 = 0.0f

Referenced by process().

x1

float Biquad::x1 = 0.0f

Referenced by process(), and reset().

x2

float Biquad::x2 = 0.0f

Referenced by process(), and reset().

y1

float Biquad::y1 = 0.0f

Referenced by process(), and reset().

y2

float Biquad::y2 = 0.0f

Referenced by process(), and reset().

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

• gin_biquad.h