BiquadUG Class Reference

BiquadUG is a two-pole, two-zero filter useful for adding resonances. More...

#import <BiquadUG.h>

Inheritance diagram for BiquadUG:

List of all members.

Public Member Functions
(id)	- setInput:
	Sets filter input.
(id)	- setOutput:
	Sets filter output.
(id)	- clear
	Clear internal filter state.
(id)	- setFirstDelayedSample:
	Sets the internal filter state of the first delayed sample.
(id)	- setSecondDelayedSample:
	Sets the internal filter state of the second delayed sample.
(id)	- setA1:
	Sets the A1 filter coefficient.
(id)	- setA2:
	Sets the A2 filter coefficient..
(id)	- setB1:
	Sets the B1 filter coefficient..
(id)	- setB2:
	Sets the B2 filter coefficient..
(id)	- setGain:
	Sets gain of filter.
(id)	- setComplexPolesRadius:angle:
	This method provides a convenient way to set the filter feedback coefficients.
(id)	- setComplexZerosRadius:angle:
	This method provides a convenient way to set the filter feedforward coefficients.
(id)	- setComplexPolesFrequency:bandwidth:
	This method provides a convenient way to set the filter feedback coefficients.
(id)	- setComplexZerosFrequency:bandwidth:
	This method provides a convenient way to set the filter feedforward coefficients.
(id)	- setComplexPolesFrequency:t60:
	Sets the coefficients such as to place the poles at the specified freq with the given t60 value.
Static Public Member Functions
(BOOL)	+ shouldOptimize:
	Specifies that all arguments are to be optimized if possible except the state variable.

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Detailed Description

BiquadUG is a two-pole, two-zero filter useful for adding resonances.

The BiquadUG unit-generator implements a two-pole, two-zero filter section in direct form. The output space can only be y DSP memory. Therefore, only two leaf classes exist, BiquadUGx and BiquadUGy, corresponding to the two possible input spaces.

The biquad transfer function is

                        -1         -2
            1  +  b1 * z   + b2 * z
H(z) = g * -------------------------
                        -1         -2
            1  +  a1 * z   + a2 * z

The biquad difference equation which implements H(z) is

v(n) = g * x(n) - a1 * v(n-1) - a2 * v(n-2);
y(n) =  v(n) + b1 * v(n-1) + b2 * v(n-2);

where n denotes the current sample time, x(n) is the input signal at time n, y(n) is the output signal, and v(n) is an intermediate signal. This is the so-called "transposed direct form II" digital filter structure, which avoids the possibility of internal overflow. See Digital Signal Processing by A.V. Oppenheim and R.W. Schafer (Prentice-Hall, 1975, p. 155) for further discussion.

Memory Spaces

BiquadUGab a output b input

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Member Function Documentation

- (id) setInput:

(id)

aPatchPoint

Sets filter input.

Parameters:

aPatchPoint

is an id.

Returns:

Returns an id.

- (id) setOutput:

(id)

aPatchPoint

Sets filter output.

Parameters:

aPatchPoint

is an id.

Returns:

Returns an id.

- (id) clear

Clear internal filter state.

Returns:

Returns an id.

- (id) setFirstDelayedSample:

(double)

d1

Sets the internal filter state of the first delayed sample.

Parameters:

d1

is a double.

Returns:

Returns an id.

- (id) setSecondDelayedSample:

(double)

d2

Sets the internal filter state of the second delayed sample.

Parameters:

d2

is a double.

Returns:

Returns an id.

- (id) setA1:

(double)

a1

Sets the A1 filter coefficient.

Parameters:

a1

is a double.

Returns:

Returns an id.

- (id) setA2:

(double)

a2

Sets the A2 filter coefficient..

Parameters:

a2

is a double.

Returns:

Returns an id.

- (id) setB1:

(double)

b1

Sets the B1 filter coefficient..

Parameters:

b1

is a double.

Returns:

Returns an id.

- (id) setB2:

(double)

b2

Sets the B2 filter coefficient..

Parameters:

b2

is a double.

Returns:

Returns an id.

- (id) setGain:

(double)

g

Sets gain of filter.

Parameters:

g

is a double.

Returns:

Returns an id.

+ (BOOL) shouldOptimize:

(unsigned)

arg

Specifies that all arguments are to be optimized if possible except the state variable.

Parameters:

arg

is an unsigned.

Returns:

Returns an BOOL.

Reimplemented from MKUnitGenerator.

- (id) setComplexPolesRadius:		(double)	r
angle:		(double)	t

This method provides a convenient way to set the filter feedback coefficients.

Parameters:

	r	is a double.
	t	is a double.

Returns:

Returns an id. Sets the coefficients such as to provide the specified pole radius and angle. The angle is in radians.

- (id) setComplexZerosRadius:		(double)	r
angle:		(double)	t

This method provides a convenient way to set the filter feedforward coefficients.

Parameters:

	r	is a double.
	t	is a double.

Returns:

Returns an id. Sets the coefficients such as to provide the specified zero radius and angle. The angle is in radians.

- (id) setComplexPolesFrequency:		(double)	f
bandwidth:		(double)	b

This method provides a convenient way to set the filter feedback coefficients.

Parameters:

	f	is a double.
	b	is a double.

Returns:

Returns an id. Sets the coefficients such as to provide the specified center frequency and bandwidth. The angle is in radians.

- (id) setComplexZerosFrequency:		(double)	f
bandwidth:		(double)	b

This method provides a convenient way to set the filter feedforward coefficients.

Parameters:

	f	is a double.
	b	is a double.

Returns:

Returns an id. Sets the coefficients such as to provide the specified center frequency and bandwidth. The angle is in radians.

- (id) setComplexPolesFrequency:		(double)	f
t60:		(double)	t60

Sets the coefficients such as to place the poles at the specified freq with the given t60 value.

Parameters:

	f	is a double.
	t60	is a double.

Returns:

Returns an id. t60 is the time, in seconds, to decay to -60 dB.

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

• BiquadUG.h