[PD] [sqosc~]-issues

Martin Peach martin.peach at sympatico.ca
Tue Mar 27 02:23:23 CEST 2007

Does anyone know how to tell, in c, if you're getting nans? It should be 
easy enough in the dsp routine to replace nans with zeros.
It's just a question of detecting them in time. I remember you could do 
it in SANE, the old Apple math system, there was some function like isnan().
I don't see how [sqosc~] could be generating them though, since it's 
deliberately operating in a fixed range of float, the same way [osc~] does.


Derek Holzer wrote:
> After having done lots of work with recursive feedback structures in PD 
> using delays and filters, I can positively say that PD (rather then 
> Jack) is making the problem in every one of my cases. YMMV. But for me, 
> it always happens when delay lines or resonant filters become feedback 
> saturated to the point of being pure DC. The offending object must then 
> be cut and pasted (i.e. reset) to get rid of the "nan" signal, so try 
> cut/paste rather than restart and see if it helps you next time. I've 
> always considered this something that is inherent in DSP with no sanity 
> checks, as PD often is, rather than a bug specific to PD. The CSound 
> manual mentions this "blowing up" of filters quite frequently, so I know 
> it happens in other applications.
> best,
> d.
> padawan12 wrote:
>> I get this too. It's never seemed worth filing a bug report
>> because it's not clear whether Pd or an external or Jack
>> itself it where the problem occurs. Sometimes a channel
>> just locks up and all I can get is nans until the application
>> is restarted. It's quite rare, but annoying if it happens 
>> during a talk or performance.

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