Claude Heiland-Allen wrote: > Frank Barknecht wrote: >> Hallo, >> martin brinkmann hat gesagt: // martin brinkmann wrote: >> >>> Claude Heiland-Allen wrote: >>> >>>> cpole~ czero~ rpole~ rzero~ have signal inlets for filter control, so i >>>> assume sufficiently smooth changes will not cause clicks >>> that is true, but it looks like no one has made a (usual lp,hp,etc.) >>> filter with these objects until now. >> Except Miller. [1] >> >> Though I agree that some more of these would be handy. I tried to make >> a biquad~ clone with the elementary filters, but failed so far. I >> assume from [2] that the transfer function of two rzero~ and two >> rpole~ in series should be the same as a biquad~, > > You need two cpole~ and two czero~ here, admittedly in complex-conjugate > pairs.
(oops) : either conjugate pairs, or both on the real line. > >> however I don't know >> how to convert the ff1, ff2, ff3, fb1 and fb2 coefficients of biquad~ >> into the coefficients to use at the second inlets of the elemetary >> filters. Can anyone help? > > http://ccrma.stanford.edu/~jos/filters/BiQuad_Section.html > > you need to munge the biquad coefficients from the form expected by Pd's > biquad~ to the form of the difference equation at the bottom - should > just be some scaling and sign stuff. > > then you can factorize the transfer function's numerator and denominator > to get the locations of the (complex) zeroes and poles (using the > quadratic formula would do the trick) > > then feed them to [czero~] [cpole~], and an additional [*~] for the > global gain. > >> [1] http://crca.ucsd.edu/~msp/techniques/latest/book-html/node160.html >> [2] http://crca.ucsd.edu/~msp/techniques/latest/book-html/node136.html >> >> Ciao > > > Claude _______________________________________________ [email protected] mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
