Ahh yes of course thanks Frank! Have you guys checked out this paper on 'High-Order Digital Parametric Equalizer Design <http://www.aes.org/e-lib/browse.cfm?elib=13397>'? Apparently it reduces the need to cascade filter implementations to achieve high orders.
Cheers, Joe On 24 May 2014 09:53, Frank Barknecht <f...@footils.org> wrote: > Hi Joe, > > versions of these calculations without [expr] are also part of the > rj-library as u_lowpass, u_lowpassq etc. These have been taken straight > from the Audio-EQ-Cookbook. > > Ciao > -- > Frank > > On Fri, May 23, 2014 at 12:06:45PM +0100, Joe White wrote: > > Thanks for the abstractions Chris. Am I correct in thinking the licensing > > issues for [expr] have been resolved now? > > > > Cheers, > > Joe > > > > > > On 21 May 2014 23:22, Chris Clepper <cgclep...@gmail.com> wrote: > > > > > On Wed, May 21, 2014 at 5:31 PM, Joe White <white.j...@gmail.com> > wrote: > > > > > >> > > >> > > >> Is it intentional to not a bank of go-to filters? [biquad~] is the > next > > >> one I would go to, but generating your own coefficients isn't that... > err.. > > >> efficient when you're wanting some that just 'works' :) > > >> > > >> > > > Attached are a set of abstractions wrapping most of the 'Audio EQ > > > Cookbook' formulae around biquad~. It would be nice for Pd to include > > > something like this. > > > > > > The only drawback to [biquad~] is it doesn't take audio rate > coefficients. > > > There are of course externals that do audio rate for cutoff, Q, etc. > > > > > > Chris > > > > > > > > >> > > >> > > >> On 21 May 2014 17:31, Miller Puckette <m...@ucsd.edu> wrote: > > >> > > >>> Hi Joe - > > >>> > > >>> That code is an approximation that works well for low cutoff > > >>> frequencies but badly for high ones. (I should probably warn > > >>> about this in the help window... that'll go on my dolist) > > >>> > > >>> cheers > > >>> M > > >>> > > >>> > > >>> On Fri, May 16, 2014 at 12:58:31PM +0100, Joe White wrote: > > >>> > Hi, > > >>> > > > >>> > I've been looking at the [lop~] implementation (Pd-0.45-4) and > noticed > > >>> > something that seem weird to me. > > >>> > > > >>> > In d_filter, line 176: > > >>> > > > >>> > static void siglop_ft1(t_siglop *x, t_floatarg f) > > >>> > { > > >>> > if (f < 0) f = 0; > > >>> > x->x_hz = f; > > >>> > x->x_ctl->c_coef = f * (2 * 3.14159) / x->x_sr; > > >>> > if (x->x_ctl->c_coef > 1) > > >>> > x->x_ctl->c_coef = 1; > > >>> > else if (x->x_ctl->c_coef < 0) > > >>> > x->x_ctl->c_coef = 0; > > >>> > } > > >>> > > > >>> > > > >>> > Is it correct that for: > > >>> > > > >>> > y[n] = x[n] * a + y[n-1] * b > > >>> > > > >>> > *a = 2π * Fc / Fs* > > >>> > b = 1.0 - a > > >>> > > > >>> > where Fc is the cut-off frequency and Fs the sampling frequency. > > >>> > > > >>> > I appreciate the a coefficient is bounded afterwards but wouldn't > that > > >>> mean > > >>> > that Fc values greater than Fs / 2π will have no impact on the > sound > > >>> being > > >>> > processed. > > >>> > > > >>> > For example if Fs is 44100, then Fc values above ~7020Hz will not > > >>> affect > > >>> > the filter. > > >>> > > > >>> > Have I missed something crucial or could this a bug in the code? > > >>> > > > >>> > The simple IIR filter described in > > >>> > http://en.wikipedia.org/wiki/Low-pass_filter suggests that the > actual > > >>> > coefficient calculation should be more like: > > >>> > > > >>> > a = 2π*Fc / (2π*Fc + Fs) > > >>> > > > >>> > Looking forward to understand this more! > > >>> > > > >>> > Cheers, > > >>> > Joe > > >>> > > > >>> > -- > > >>> > Follow me on Twitter @diplojocus > > >>> > > >>> > _______________________________________________ > > >>> > Pd-list@lists.iem.at mailing list > > >>> > UNSUBSCRIBE and account-management -> > > >>> http://lists.puredata.info/listinfo/pd-list > > >>> > > >>> > > >> > > >> > > >> -- > > >> Follow me on Twitter @diplojocus > > >> > > >> _______________________________________________ > > >> Pd-list@lists.iem.at mailing list > > >> UNSUBSCRIBE and account-management -> > > >> http://lists.puredata.info/listinfo/pd-list > > >> > > >> > > > > > > > > > -- > > Follow me on Twitter @diplojocus > > > _______________________________________________ > > Pd-list@lists.iem.at mailing list > > UNSUBSCRIBE and account-management -> > http://lists.puredata.info/listinfo/pd-list > > -- Follow me on Twitter @diplojocus
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