Hi Just wanted to say thanks to everyone for their guidance, I am on chapter three of Millers wonderful book which I have printed out. and am just beginning to try out the all stuff you have suggested.
It will take me a while to get to grips with it as I am an absolute beginner on both PD and DSP concepts. Thanks geoff On 22 Jan 2009, at 23:56, Frank Barknecht wrote: > Hallo, > Geoff hat gesagt: // Geoff wrote: > >> The DSP book I have read gives a simple lowpass filter function as >> >> g(n) = (f(n-1) + f(n) + f(n+1))/3 >> >> i.e the average value of three consecutive samples. I understand how >> this is in effect a lowpass filter. >> >> How do I implement that in PD? > > A lot of that is explained in Miller's book: > http://crca.ucsd.edu/~msp/techniques/latest/book-html/node127.html > You better read the previous chapter on Delays first, it contains > important info as well. > > Generally the basic objects for filter design are [rzero~], > [rpole~] and > [czero~], [cpole~] and another one is [biquad~]. > > With the zero/pole objects you directly give the location of poles and > zeroes of your filter while the biquad~ is an alternative way to > express > two zero and two pole objects in one. > > I don't know the meaning of the variables in your formula, > especially the > f(n+1) looks strange: Is this a value of the future or an output > value, > like the "y" variables in many other filter equations? Anyway you > can sum > up the current and the previous samples easily with rzero~: > > [sig~ 1] > | > [rzero~ -1] > | > [snapshot~] > | > [2 \ > > For more complex filters check out Miller's book and the examples > included in Pd. > > I recently also wrote a lot of filter abstractions for the RjDj > library: > see http://trac.rjdj.me/browser/trunk/rjlib/rj The interesting objects > there are e_beequad.pd as a biquad~ clone and these for calculating > various coefficients: u_lowpass, u_lowpassq, u_highpass, > u_highpassq, ... > > e_lop4.pd also is interesting: It's a 4 pole resonant lowpass filter, > good for moogish synths, when combined with the bandlimited > oscillators > of s_osc.pd there. All these filtes use zero/pole objects inside. > > RjDj abstractions are for Pd vanilla, so they run everywhere. > > Ciao > -- > Frank Barknecht > > _______________________________________________ > Pd-list@iem.at mailing list > UNSUBSCRIBE and account-management -> http://lists.puredata.info/ > listinfo/pd-list _______________________________________________ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
