Subject: Re: [linux-audio-dev] changing control port values with LADSPA: a serious issue?
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Mon Mar 18 2002 - 14:14:07 EET
On Sat, Mar 16, 2002 at 10:35:46 +0100, David Olofson wrote:
> Complexity: Unless I'm missing something, having LADSPA *requiring*
> plugins to implement linear or cubic ramping will actually make life
> *easier* on plugin coders, as they can just throw in the ramping adds
> for each port, and be done with it.
Agreed. One less design variable will make things easier, but picking the
correct filter/interpolator is not trivial.
> IMHO, linear should do the trick (considering that hosts may split
> buffers as they like, but there may be DSP algorithms that will react
> audibly on the transients you get when changing the linear slope -
> not enough experience with that to tell if it's a real problem.
Most of them do. My experience is that there arn't many parameters that
need smoothing where lerp is sufficient.
> Well, if it wasn't for the problem with plugins that need to
> recalculate stuff when controls change, I'd suggest the <y, dy[,
> ddy]> controls (see above) as that's probably the simplest solution
> there is.
>
> I'm not sure, but I think explicitly specifying in the API that
> control ports should be interpolated, and how, would be the simplest
> solution that doesn't bring in issues that require further extensions.
I don't *think* this is a good idea. Obviously you can exempt integer
ports, but even then it sounds overprescriptive. Remeber, generally it is
the prameter (ie internal value in dsp code) that you are interpolating,
not the port value.
- Steve
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