2010/9/30 Pierre Massat <pimassat@gmail.com>

So basically, i get a square wave. Then i use the rzero filter with a parameter set to 1, so that i get X(n)-X(n-1), which is equal to 0 all over the flat sections of the wave (except for the first sample), and equal to Delta (or something) or -Delta at the points where is rises and falls. If i clip this again between 0 and 1, i get a pulse everytime the wave rises from -1 to 1. Am i wrong? I have never used such a filter...
Thank you!

Pierre

2010/9/30 Andy Farnell <padawan12@obiwannabe.co.uk>

Yeah its a bitch actually because in Pd
the blocksize sets an effective resolution
for events. You could ask on-list about
tricks with blocksize, Frank might have
a solution.

I'll share a couple of DSP tricks wit you
as used in guitar subharmonic processors,
if you don't mind keeping it all in the audio
domain (which can be more tricky)

Firstly you amplify by about 100 and clip
the signal

[*~ 100]
|
[clip~ -1 1]

this gives you basically a square wave

Next differentiate using a [rzero~]
so that you get a series of pulses.

Rectify them by clipping again [clip~ 0 1]

Use these pulses to drive into a bank of
parallel resonators for the rattle effect.

cheers,

Andy

On Thu, 30 Sep 2010 20:15:15 +0200

Pierre Massat <pimassat@gmail.com> wrote:

> Ok, i think i get it.
> I've tried do make a simple zero-crossing detection patch using threshold~,
> but it doesn't seem to really work. From what i've read here and there about
> zero crossing in Pd it seems like the size of audio blocks is an issue here.
> Using a simple osc~ as a sound generator and a threshold~ set to 0 0 0 0, i
> get a fairly steady bang at very low frequencies, but it gets extremely
> messy for frequencies above 10 Hz or so.
> I ve tried reducing the block size in the subpatch where threshold~ is, to
> no avail.
> I haven't found anything that properly deals with zero crossing detection in
> Pd. So i'm kinda stuck!
>
> Pierre
>
> 2010/9/29 Andy Farnell <padawan12@obiwannabe.co.uk>
>
> > On Wed, 29 Sep 2010 08:42:28 +0200
> > Pierre Massat <pimassat@gmail.com> wrote:
> >
> > > Hi Andy,
> > > Are you talking about something like that:
> > > http://www.complexity.org.au/ci/vol01/fletch01/html/
> >
> > Not quite. THis is very interesting (I've bookmarked it
> > for future reading) but deals with non-linearity
> > in a continuous equation.
> >
> > For rattling, we are interested in dis-continuous
> > coupling.
> >
> >
> > > I m not familiar with zero crossing detection at all. From what i ve read
> > in
> > > the archives it seems to be possible to do it with edge~.
> >
> > If you search you will find other ways using snapshot~ and threshold~
> > too.
> >
> > > So i'd need to
> > > trigger something like a pulsed noise everytime it detects a zero? That'd
> > be
> > > the trick?
> >
> > Yes, basically drive another synth that makes a pulse or resonant click
> > every time the string crosses zero.
> >
> > > Thanks again for your help!
> > >
> > > Pierre
> > >
> > > 2010/9/28 Andy Farnell <padawan12@obiwannabe.co.uk>
> > >
> > > >
> > > >
> > > > Aha! This is a different problem. It's about creating
> > > > a discontinuity such that the string excursion seems to
> > > > cause a point of new impact in a different system.
> > > >
> > > >
> > > > The traditional way is to do zero crossing detection
> > > > and use that to trigger some other sound.
> > > >
> > > > best,
> > > > Andy
> > > >
> > > > On Tue, 28 Sep 2010 13:07:49 +0200
> > > > Pierre Massat <pimassat@gmail.com> wrote:
> > > >
> > > > > So i'm really only interested in modeling the rattling sound, the
> > buzz,
> > > > to
> > > > > get a dirtier sound, like in most african instruments. I don't know
> > if
> > > > > you've ever played a guitar with a strip a paper kind of weaved
> > accross
> > > > the
> > > >
> > > > --
> > > > Andy Farnell <padawan12@obiwannabe.co.uk>
> > > >
> >
> >
> > --
> > Andy Farnell <padawan12@obiwannabe.co.uk>
> >

--

Andy Farnell <padawan12@obiwannabe.co.uk>