[Ardour-Dev] gain-mapping - was Re: OSC next

Len Ovens len at ovenwerks.net
Sat May 14 12:39:16 PDT 2016

On Sat, 14 May 2016, Felix Homann wrote:

> Len Ovens <len at ovenwerks.net> schrieb am Sa., 14. Mai 2016, 20:35:
>       Nevertheless, it might be interesting to know how some common OSC
>       > controllable hardware is handling faders. 
>       I would hesitate to call the x32/air "Common" :) The tablet OSC
>       controller
>       seems to be by far the most common.
> I can't think of any OSC *controllable* hardware that is more mainstream than the
> X32/M32/X Air mixer family but I may be missing something ;-)
> They are definitely not used as control surfaces, usually.

Ah, maybe I am the one missing something. As a controlable yes that makes 
sense. There are indeed lots of x32/airs around.

> In the end, I just wanted to show how others do the gain mapping. That's all.

Gain mapping in the X32 is fader possition to gain. The OSC message is 
exactly position 0->1 float. The formula just tells the user how to 
convert that to dB gain. While Ardour's position would not line up with 
the right dB markings printed on the surface, that is mostly the 
difference from +6 to +10. +10 is much more common... from Analog days. 
There are some with +12 (easy math like +6, +12 = 4)

I like the: send any message with no value means send me an update. 
However, that would mean a complete rewrite I think. Right now, liblo 
does a direct call to a function based on it's own parse of the incoming 
message. Adding things like path having channel embedded or value being 
present or not breaks that. That may or not be a bad thing. Certainly 
there are a lot of OSC apps (in the tablet world) that can only do a path 
with one value. However, all it takes is one good tablet app that works 
right and is stable to change that. It is ok to support the device rather 
than any or all applets that can run on it. Right now Open Stage Control 
shows it can be done. (though it is in effect a type of middleware in this 

I think I need to have a better understanding of what liblo can do.

Len Ovens

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