It's been noted that [vcf~] can be obtained with a [cpole~] object - though I didn't do it yet as I find it a bit hard to get to the coeficients from the vcf~ code.
Anyway, if you can get it with a [cpole~] object, it means you could do it with [biquad~] coeficients, right? I suppose so, but then, how exactly? I mean, if I have the coeficients of [cpole~], how do I get to [biquad~]'s?
maybe this will help getting biquad's coefficients from [vcf~]'s parameters... maybe not, I don't know, I need help :)
thanks
2014-07-19 0:44 GMT-03:00 Alexandre Torres Porres porres@gmail.com:
hi all, I've been working on filter patches for my courses and I'm still failing ti get biquad coeficients from the [vcf~] code. Maybe anyone out there could help?
I wanted this to plot the frequency response in realtime...
the [vcf~] filters aren't in the audio Audio-EQ-Cookbook, and the code looks a bit too complicated
thanks
2014-05-26 10:23 GMT-03:00 Joe White white.joe4@gmail.com:
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 fbar@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 cgclepper@gmail.com wrote:
On Wed, May 21, 2014 at 5:31 PM, Joe White white.joe4@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 msp@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 ->
-- Follow me on Twitter @diplojocus
Pd-list@lists.iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list