Re: [Sc-devel] Amplitude.kr problem

["Dan Stowell" <danstowell@xxxxxxxxx>]

In fact Julian's code for k-rate modulation (Amplitude_next_kk) looks
wrong to me. This bit:

if(ZIN0(1) != unit->m_clamp_in) {
	clampcoef = exp(log1/(ZIN0(1) * SAMPLERATE));
	unit->m_clamp_in = clampcoef;
} else {
	clampcoef = unit->m_clamp_in;
}

should be

if(ZIN0(1) != unit->m_clamp_in) {
	clampcoef = unit->m_clampcoef =  exp(log1/(ZIN0(1) * SAMPLERATE));
	unit->m_clamp_in = ZIN0(1);
} else {
	clampcoef = unit->m_clampcoef;
}

The same goes for the "relax" input.

Julian, please correct me if I'm wrong, but it looks to me like you've
conflated the clamp-input and clamp-coefficient variables. The UGen
works correctly but is not as optimal as you intended, because the
recalculation of the coefficient would still happen once every control
period.

I'll fix this later (and do the a-rate calc func too); let me know if
I've got this right or not...

Dan



2007/12/14, Dan Stowell <danstowell@xxxxxxxxx>:
> A while ago Julian reworked the Amplitude UGen slightly to allow the
> coefficients to be modulated. Julian, you left some old calc-func code
> in there, deactivated using some "#if" macros. Is it OK to remove the
> old code? Would make it easier to work on fixing the current code...
>
> Dan
>
>
> 2007/12/13, Josh Parmenter <josh@xxxxxxxxxxxxxxxxx>:
> > I think option 1 makes sense. Pitch.kr can take an audio input, so it
> > makes sense (to me at least) that Amplitude should be able to also.
> >
> > Josh
> >
> > On Dec 13, 2007, at 1:50 PM, Dan Stowell wrote:
> >
> > > Hi all,
> > >
> > > Applying Amplitude.kr to an audio-rate signal is allowed, in fact all
> > > the examples in the helpfile do this. However, I noticed that the UGen
> > > doesn't really handle this case "correctly" - if run at control-rate
> > > it simply expects its input to be control rate; the end result on
> > > audio-rate input is a dodgy downsampling which can lead to incorrect
> > > results.
> > >
> > > For example, these two should really give similar results but they
> > > don't (give them a few seconds to converge):
> > >
> > > x = {(Amplitude.kr(Impulse.ar(44100/64, 0.0),1,1)).poll}.play // 1
> > > x = {(Amplitude.kr(Impulse.ar(44100/64, 0.02),1,1)).poll}.play // 0
> > >
> > > Same goes for these:
> > >
> > > x = {(Amplitude.kr(SinOsc.ar(44100/64, 0.0),1,1)).poll}.play // 0.098
> > > x = {(Amplitude.kr(SinOsc.ar(44100/64, pi/4),1,1)).poll}.play // 0.77
> > >
> > > Options for fixing this:
> > >
> > > (1) Alter the UGen source, add a new calc func to deal with the a-to-k
> > > (2) Make Amplitude a subclass of Filter, so it refuses to run k-rate
> > > on an a-rate input (unhelpful!)
> > > (3) Alter the Amplitude class so it automatically replaces
> > > Amplitude.kr(x.ar) with A2K.kr(Amplitude.ar(x.ar))
> > >
> > > Any particular thoughts?
> > >
> > > Dan
> > >
> > > --
> > > http://www.mcld.co.uk
> > > _______________________________________________
> > > Sc-devel mailing list
> > > Sc-devel@xxxxxxxxxxxxxxx
> > > http://www.create.ucsb.edu/mailman/listinfo/sc-devel
> >
> > ******************************************
> > /* Joshua D. Parmenter
> > http://www.realizedsound.net/josh/
> >
> > "Every composer – at all times and in all cases – gives his own
> > interpretation of how modern society is structured: whether actively
> > or passively, consciously or unconsciously, he makes choices in this
> > regard. He may be conservative or he may subject himself to continual
> > renewal; or he may strive for a revolutionary, historical or social
> > palingenesis." - Luigi Nono
> > */
> >
> >
> > _______________________________________________
> > Sc-devel mailing list
> > Sc-devel@xxxxxxxxxxxxxxx
> > http://www.create.ucsb.edu/mailman/listinfo/sc-devel
> >
>
>
> --
> http://www.mcld.co.uk
>


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