[PD] Introduction to elementary filter components in Pd

Frank Barknecht fbar at footils.org
Sun Sep 12 10:07:00 CEST 2010


Hi,

On Sat, Sep 11, 2010 at 04:03:00PM -0400, brandon zeeb wrote:
> So I'm reading Miller's book hoping for a real world explanation of the
> elementary filter objects in Pd (z~, rpole~, czero~, etc).  Unfortunately,
> this only occupies 3-4 pages.
> 
> Does anyone have a set of tutorials, abstractions, or are their any
> documents available which go into further detail into these objects?  For
> starters, I'd like to build a few simple classic filter types (ie: lpf, hpf
> w/ recirculation).  lop~, hip~, and bp~ are nice, and one can build
> recirculating filters with these, but they don't offer audio-rate control of
> filter cutoff.

A few of these are included in the rj library that you can get at
http://github.com/rjdj/

Basically it includes two kinds of filters: Some are direct implementations
using the c/r_pole or c/r_zero objects directly. An example would be e_resonzq,
the classical two-pole resonator. (We  use "e_..." to designate effects.)

The approach taken with several other filters is to split up the process into a
biquad filter and a set of utility abstractions like "u_lowpass.pd" to generate
filter coefficients for that. In addition to the biquad~ internal the rj
library also includes an interpolating clone built with elementary filters
called "e_beequad.pd".

The coefficient-calculation is made using the filter recipes from the
Audio-EQ-Cookbook: http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt

These objects are all Pd vanilla abstractions, so they should run on every
flavour of Pd and you can change and play around with them easily.

A good read also is the "The Scientist and Engineer's Guide to Digital Signal
Processing": http://www.dspguide.com/

Ciao
-- 
 Frank Barknecht            Do You RjDj.me?          _ ______footils.org__



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