[gmpi] Re: Requirements

  • From: Marc Poirier <marc@xxxxxxxxxxxxxxxxxxx>
  • To: gmpi@xxxxxxxxxxxxx
  • Date: Tue, 11 Feb 2003 17:19:16 +0100 (CET)

> > Why bother with normalized parameters then?
> Because it's the most convenient way to represent a
> parameter as a knob position (or as Y-axis for a curve).

Yes, but a total nuisance for the DSP plugin component, especially for 
descrete value parameters!  I think that the recent post (sorry, I forgot 
who wrote it, David O?) about separating GUI concerns from the initial 
design in order to achieve a cleaner design applies perfectly to this 
point.  If we were thinking outside of GUI concerns, no one would say that 
they prefer to handle parameter values in a normalized range!  I think 
that this is a chore best offloaded to the GUI.  If we have a parameter 
curve attribute specified, with the possibility even for custom curve 
functions, then the GUI layer, when it's defined, could include simple 
convenience methods for interfacing with parameters in a normalized range, 
taking into account the curve hints.  But there's no need for the DSP 
plugin to suffer from this interface convenience.

> Actually it's important to provide host with a conversion
> function, because mapping based on the generic unit (ie log
> scale for a parameter expressed in Hz) is not generally the
> most convenient way to do it.

Right, that's why I suggested that at least the curve attribute be 
separate from the unit attribute, so that no assumptions are made.  Have 
you ever tried tweaking a log-curved LFO rate parameter that ranges from 
0.1 Hz to 20 Hz, for example?  Ugh, painful!  ;)  But wonderful for a 
pitch parameter that ranges from 40 Hz to 20 kHz...  And then 
additionally, there can be the possiblity for totally custom curves.


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