Description

Statevar is a new digital implementation of the analogue state-variable filter. This filter has four simultaneous outputs: high-pass, low-pass, band-pass and band-reject. This filter uses oversampling for sharper resonance (default: 3 times oversampling). It includes a resonance limiter that prevents the filter from getting unstable.

Syntax

ahp,alp,abp,abr statevar ain, kcf, kq [, iosamps, istor]

Initialization

iosamps -- number of times of oversampling used in the filtering process. This will determine the maximum sharpness of the filter resonance (Q). More oversampling allows higher Qs, less oversampling will limit the resonance. The default is 3 times (iosamps=0).

istor --initial disposition of internal data space. Since filtering incorporates a feedback loop of previous output, the initial status of the storage space used is significant. A zero value will clear the space; a non-zero value will allow previous information to remain. The default value is 0.

Performance

ahp -- high-pass output signal.

alp -- low-pass output signal.

abp -- band-pass signal.

abr -- band-reject signal.

asig -- input signal.

kcf -- filter cutoff frequency

kq -- filter Q. This value is limited internally depending on the frequency and the number of times of oversampling used in the process (3-times oversampling by default).

Examples

kenv               linseg 0,0.1,1, p3-0.2,1, 0.1, 0
asig               buzz 16000*kenv, 100, 100, 1;  
kf                 expseg 100, p3/2, 5000, p3/2, 1000
ahp,alp,abp,abr    statevar  asig, kf, 200
                   
			outs alp,ahp
        

Credits

New plugin in version 5

January 2005.