[LAD] [LAU] Ardour MIDI tracer

Len Ovens len at ovenwerks.net
Mon Aug 18 01:34:25 UTC 2014

On Sun, 17 Aug 2014, Will Godfrey wrote:

> On Sun, 17 Aug 2014 16:15:58 +0000
> Fons Adriaensen <fons at linuxaudio.org> wrote:
>> On Sun, Aug 17, 2014 at 08:24:38AM -0700, Len Ovens wrote:
>>> So Allen & Heath uses 127 levels on their top end digital control
surfaces, How do they do it? Well they have two different scales: - fader:
((Gain+54)/64)*7f - also used for sends
>>> - Gain: ((Gain-10)/55)*7f - this is preamp gain
>> Suppose you have *real* faders which have a range of 127 mm.
>> That's not far from a typical size on a pro mixer.
>> Would you ever adjust them by half a millimeter ?
>> 127 steps, provided they are mapped well, and zipper noise
>> is avoided by interpolation or filtering, should be enough.
>> The real problem is that many SW mixers
>> * don't use a good mapping,
>> * and don't have any other gain controls.
>> The latter may force you to use the fader in a range
>> where it has bigger steps.
> Well that got me thinking!
> Presumably this should be set up as a proper log law, so even if the
> represent (say) 0.5dB that still gives a control range of over 60dB

I forgot to add:

I would think ((Gain+54)/64)*7f uses a lot less CPU time than a real
(proper) log. Think 8 fingers (plus thumbs?) fading around 80 steps in a
small time. Remember that this calculation has to be done at both ends too
and the receiving end also has to deal with doing more calculation on as
many as 64 tracks of low latency audio at the same time (amongst other

Also remember, this is only of use if you are building a control surface
(I am) and not buying one where "you get what you get". Add to that, even
if you are building your own control surface, do you want to use Yet
Another standard that you then have to make middle-ware for so that the SW
you are talking to will understand? A&H does supply middle-ware (for OSX)
that takes the above values and converts them (both ways) so that their
control surface looks to the sw like a Mackie (just about put Wackie)
control surface. Talk about lot of computations in you music box!

Len Ovens

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