[chuck-users] Filter instability

Mark Knecht markknecht at gmail.com
Thu Nov 12 14:52:35 EST 2009

2009/11/11 Kassen <signal.automatique at gmail.com>:
> Dear list,
> Here; http://electro-music.com/forum/viewtopic.php?t=37921 is a discussion
> on instability in the "convenience filters", particularly LPF. It seems like
> LPF sometimes goes unstable while I feel that a filter with this purpose
> (quick&easy filtering with no need to do z-plane transforms ourselves)
> shouldn't go unstable. Could rounding errors in 64bit floats really cause
> issues this bad? Are we verifying that the coefficients we get are indeed
> stable after rounding? That last one is what I'd bet on as a cause for this,
> but I couldn't do a z-plane transform to save my life.
> If one of our residential DSP wizards could kindly have a look at that?
> Maybe Perry?
> Yours,
> Kas.

I wonder if ChucK has done the same things with respect to
denormalization that had to be done in the Ardour/LADSPA world a year
or two ago. They were having many problems with things like filters
and other LADSPA plugins that are reminiscent of this description.
Seems like they went through a big round of fixes, caught most of them
and there haven't been many problems since.


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