[gmpi] Re: MIDI: Proposed Reqs (try #2)

On Wed, Jul 07, 2004 at 02:07:44PM -0700, Chris Grigg wrote:
> Sure, the Actor can map a MIDI message to a parameter, but I don't 
> think that's what the map's for.  The map tells the host, for a given 
> thing in the plug, what MIDI message you send to the plug to target 
> that thing.  So the arrow flows in the opposite direction.

I think you MEAN the same thing I am thinking, but you didn't SAY it, so
I'm going to say what I think:

The MIDI map allows the host to map incoming MIDI to GMPI.  Example:

A plugin has a "Frobnicate Level" parameter ("FROB").  The FROB parameter
is a float value, with the range [-100.0, 13.6].  The plugin's MIDI map
indicates that 7-bit CC #39 maps to FROB.

Now, when the host sees a CC #39 change to the value 64 it can do this:

convert MIDI to float: 64/127 = 0.50393700787
figure FROB range: (13.6 - (-100.0)) = 113.6
scale the MIDI: (113.6 * 0.50393700787) = 57.247244094032
offset by FROB's min: (57.247244094032 + (-100.0)) = -42.752755905968
set FROB to -42.752755905968

The plugin only ever sees the FROB parameter set to values that are
in-bounds and natural for FROB.  The plugin does not handle raw MIDI.
MIDI control works.

Is that the same as what you meant?

Tim

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