[LAD] LV2 Achievement of GMPI Requirement

Fons Adriaensen fons at linuxaudio.org
Tue Aug 7 21:50:52 UTC 2012

On Wed, Aug 08, 2012 at 09:28:39AM +1200, Jeff McClintock wrote:
> I think I good experiment is to imagine you have to write both an LV2 host
> and 100 LV2 plugins, and you have to write MIDI-binding code. Do you put it
> in the plugin OR the host?
> -If a feature consumes 100 kB RAM and disk space, and it's implemented on
> the host side - that's 100 kB.
> -If it's implemented on the plugins side, that's 100,000 kB.
> Which choice is more 'bloated'?

If the MIDI-binding code is in a shared library (and it probably should
be) then there's little difference between these two. Code is shared.
Per-instance data isn't, in the first case the host would allocate it
if it loads a plugin and in the second case the plugin would do it, but
again the total size would be the same.

> A very real scenario is you write this MIDI-binding support, ship 50
> plugins, then 6 months later discover a bug. Now if that feature is in the
> host - that's one fix and everyone is happy. If that bug is in the 50
> plugins, already shipped to 1000 customers. Then you have a much bigger
> problem.

Again if the code is an a shared library that is the only thing that
will need to be updated.
> It's not a question of 'bloat' YES/NO. The code has to go *somewhere*, there
> is only a tradeoff - HOST vs PLUGIN.

Yes, and the choice should IMHO be made based on *operational*

Does a MIDI controller control

1. a GUI element (e.g. a fader) which in turn controls a
   parameter, or

2. does it control the parameter, updating the GUI as a
   side effect. 

In case (1) the midi controller can use the mapping (e.g. linear
or logarithmic) of the GUI element, which may be a desirable

Also imagine that the plugin GUI and DSP code (and host) run on
separate machines. For example the host is some complex rendering
engine placed in a technical room while the plugin GUI runs on
your on-stage laptop. To which one would you want the MIDI controller
connected ? 



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