> well, it's got 2 (different) outputs, so it's like 2 filters in there [vcf~] is one filter, it just outputs both the real and imaginary part (which have to be computed anyway), so the idea is you get two filters for the price of one. I have no idea what causes the relatively high CPU load. maybe the tabfudge stuff?
> how about bob~? [bob~] is cool, but it's a bit expensive. Moreover, it's not a bandpass ;-) Gesendet: Sonntag, 16. Oktober 2016 um 13:39 Uhr Von: "Alexandre Torres Porres" <por...@gmail.com> An: "Christof Ressi" <christof.re...@gmx.at> Cc: katja <katjavet...@gmail.com>, pd-list <pd-l...@iem.at> Betreff: Re: [PD] could vanilla borrow iemlib's hi pass filter recipe? > But [bp~] and [vcf~] are almost unusable IMHO and should probably be replaced > by better filters in the future (while keeping the old ones for compatibility > reasons). how about bob~? 2016-10-14 21:34 GMT-03:00 Christof Ressi <christof.re...@gmx.at[mailto:christof.re...@gmx.at]>:There are a number of big problems with all build-in filters in Pd (expect for the raw filters). Problem number 1: [lop~] and [hip~] both use a weird (you could also say: wrong) formula for the cutoff frequency which makes them gradually converge to a fixed output state (reached by about 7000 Hz). The same is true for [vcf~] and [bp~] with Q <= 1. Therefore the actual cutoff frequency is only correct for very low frequencies and approximately gets more and more off until it doesn't move at all. Problem number 2: [bp~] and [vcf~] don't have zeros at DC and Nyquist. For low Q values, the slope is different for each side and changes with frequency. Problem number 3: the gain at the center frequency is not 1 for both [bp~] and [vcf~]. It rather depends on frequency and Q. [bp~] even has has a gain of 2 for Q <= 1! I did some FFT plots, see the attachment. I remember Miller saying somewhere that these filters are not designed for high cutoff frequencies - but even for low frequencies, the behaviour of [bp~] and [vcf~] is horrible. I can see these filters are mere approximations to reduce CPU usage. [hip~] is indeed much more efficient than iemlib's [hp1~], so it's well suited for DC removal (but not much else). [bp~] only is a little bit more CPU friendly than iemlib's [bp2~] - but the latter one has a correct and stable frequency response. [vcf~], however, is a real CPU sucker!!! 100 [vcf~] objects need 3,40% on my laptop whereas 100 of iemlib's [vcf_bp2~] only need 1,80%! But you have to consider that [vcf_bp2~] not only acts correctly but lets you set the Q at audio rate. The high CPU usage of [vcf~] seems like a bug to me... I only use the vanilla filters for the most basic stuff like DC removal and smoothing. I guess these are the use cases which Miller had in mind and that way [lop~] and [hip~] have their justification (although there should be some more warning about the 'wrong' frequency response in the help file). But [bp~] and [vcf~] are almost unusable IMHO and should probably be replaced by better filters in the future (while keeping the old ones for compatibility reasons). Christof > Gesendet: Freitag, 14. Oktober 2016 um 23:51 Uhr > Von: katja <katjavet...@gmail.com[mailto:katjavet...@gmail.com]> > An: pd-list <pd-l...@iem.at[mailto:pd-l...@iem.at]> > Betreff: [PD] could vanilla borrow iemlib's hi pass filter recipe? > > In pd 0.47.1 [hip~] is still not perfect. Attenuation at cutoff is not > constant over the frequency range: -6 dB with cutoff=SR/8, -3 dB with > cutoff=SR/4, 0 DB with cutoff=SR/2. In contrast, iemlib's [hp1~] has > -3 dB at cutoff consistently. > > Could vanilla pd implement iemlib's hipass filter recipe? I don't know > if the license also covers the math. Documentation in > https://git.iem.at/pd/iemlib/tree/master[https://git.iem.at/pd/iemlib/tree/master] > points to external literature > for part of the math (bilinear transform). I've implemented the recipe > with vanilla objects for comparison, see attached. > > Katja> _______________________________________________ > Pdemail@example.com[mailto:Pdfirstname.lastname@example.org] mailing list > UNSUBSCRIBE and account-management -> > https://lists.puredata.info/listinfo/pd-list[https://lists.puredata.info/listinfo/pd-list] > _______________________________________________ Pdemail@example.com[mailto:Pdfirstname.lastname@example.org] mailing list UNSUBSCRIBE and account-management -> https://lists.puredata.info/listinfo/pd-list[https://lists.puredata.info/listinfo/pd-list] _______________________________________________ Pdemail@example.com mailing list UNSUBSCRIBE and account-management -> https://lists.puredata.info/listinfo/pd-list