[LAD] LV2 control port (parameter) value scaling and mapping?

Gianfranco Ceccolini gianfranco at portalmod.com.br
Wed May 27 20:00:24 UTC 2015


Here at the MOD we forked the MDA plugins in order to use “real values” instead of the -1 to 1 range.

You can check it at https://github.com/portalmod/mda-lv2 <https://github.com/portalmod/mda-lv2>

Cheers

Gianfranco


> Em 27/05/2015, à(s) 16:42, Christopher Arndt <chris at chrisarndt.de> escreveu:
> 
> Is there a way to have the value range of a control input port of a LV2
> plugin be in one range (e.g. 0.0f..1.0f or 0-127) and have the LV2 host
> display the values scaled or mapped to a different range (e.g. 20-20,000
> Hz or 2 - 2000 ms)?
> 
> I know about lv2:scalePoints and the lv2:enumeration property to handle
> list of discrete values and the units:unit properties to set the value
> unit, but how do I map the actual values of a large continuous range? Is
> there a way to define a transfer function? Or does that need to happen
> inside the plug-in code?
> 
> And what about more advanced parameter display, e.g. a wet/dry setting,
> which I want to display as going from 100:00 through 50:50 to 0:100, but
> the actual parameter value is just 0.0..1.0 (or -1.0..+1.0)?
> 
> 
> Background: I'm trying to improve the JX10.ttl from the mda.lv2
> collection [1], so that the parameter display in the LV2 host generated
> plug-in UI is more useful and intuitive, i.e. instead of e.g. the slider
> for OSC Tuning being going from 0.0 .. 1.0, I want it to be displayed as
> -24 .. +24 cents. All control input ports of the plugin are defined as
> taking a value 0.0f..1.0f.
> 
> [1] http://svn.drobilla.net/lad/trunk/plugins/mda.lv2/
> 
> 
> Chris
> 
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