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

Melanie Bernkopf melaniebernkopf at gmail.com
Mon May 16 11:43:44 PDT 2016


This mapping is very nice tried it today with several Faders. Big advantage
is that you don´t overshoot the target  but still get to the position
desired reproduce able and constant.

Something like this will work on Micro controllers. Sending might be
possible with this with just one float which would not hurt too much.

Thank you for posting this.

2016-05-14 18:52 GMT+02:00 Felix Homann <linuxaudio at showlabor.de>:

> I must admit I have missed the start of this conversation which is a bad
> thing to begin with. Nevertheless, it might be interesting to know how some
> common OSC controllable hardware is handling faders. So here's how the
> Midas M32, Behringer X32 and X Air mixers handle fader/dB values over OSC:
>
> 0. The faders range from -90/-oo dB to +10 dB.
> 1. Internally fader values are represented as "index" values within [0,
> 1023].
> 2. The mapping from "index" idx to dB is piecewise linear like this
> dblevel = 40  * idx / (steps - 1) - 30; if idx >= steps / 2
>                                  80  * idx / (steps - 1) - 50; if idx >=
> steps / 4
>                                  160 * idx / (steps - 1) - 70; if idx >=
> steps / 16
>                                  480 * idx / (steps - 1) - 90; if idx > 0
>                                  -144;                         if idx = 0
> with steps = 1024. The -144 representing -inf.
>
> 3. Fader values are being send from the mixer as float "level" values
> with level = idx/1023.f.
> 4. Fader values can be received from the mixer as
> 4.a)  floats within [0.f, 1.f]. The value is being rounded to one of the
> allowed values.
> 4.b)  strings representing the dB value e.g. "-2.3" for -2.3 dB.
> 5. The OSC address for dB and level values is the same. The mixer decides
> depending on the parameter type.
>
> Kind regards,
> Felix
>
>
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>
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