Biquadratic (Second Order IIR) Filter

The 'biquadratic-filter controller can be created using the following Lisp syntax:

The 'biquadratic-filter controller takes four arguments:

• dimension: number of dimensions of the input and output controllers.
• period: the time between the updates of the controller. If zero is given then it updates every sample.
• coef_controller: a five-dimensional controller specifying the three bilinear filter coefficients.
• input_controller: filter input (a controller).

The number of dimensions should be the same as that of the input controller.

The coefficient controller should have 5 dimensions which represent the a0, a1, a2, b1 and b2 coefficients.

This filter implements a general second-order (two-pole two-zero) filter which can be used for a variety of purposes, including smoothing out envelopes, and filtering sound-file, signal or other controllers. The following example is shown in one of the graphs (with a 1 Hz cutoff) in the above image:

You should probably consider using it or the biquadratic-filter, instead of the older filtering functions (because you can design any type of filter you want). However, you will first need to generate your own sets of coefficients from higher level parameters such as center/cutoff frequency, etc....

There are no special options for this controller.