Add metadata for JACK

[nicolasdanet]

Fixes #225

Proposed changes

• Add global messages to set/unset metadata for JACK on GNU/Linux (see below).
• Note that it is not documented (it could change as everything here).
• I can NOT tested it since it is a feature too recent for QjackCtl on Ubuntu 18.04 and Raspbian.
• Seems too recent for Ubuntu 20.04 also!
• For now Spaghettis is targeted on LTS system only.
• I'm alone sadly and sadly i don't have the time to check all configs (such KXStudio stuff).
• Thanks for feedback.

[ ; pd metadata input 1 cv 1 (
[ ; pd metadata input 1 minimum 0 (
[ ; pd metadata input 1 maximum 10 (
[ ; pd metadata output 2 name Foo (
[ ; pd metadata reset (

[nicolasdanet]

I can add (improve) more metadata if somebody is able to fully test them!

[mxmilkiib]

Carla has had it's version bumped to 2.1-RC1 but not tagged/announced yet, it comes with more robust CV support and I've been trying to work through recreating the LMP example though there a few wrinkles to iron out.

After that, I'd very much love to test Spaghettis for driving CV things.

I mentioned Spaghettis in #dataflow on Freenode, there was a bit of feedback;

...
<IOhannes> although i'd prefer the messages to be (more) stateless...
<IOhannes> e.g. why can you set the "minimum" value without the "maximum" value?
<IOhannes> what do those values mean if the port is not a CV port?
<IOhannes> how can I reset the metadata for the audio I/O *only*? (that is: "metadata" seems to be *quite* generic and probably should not be restricted to only JACK-metadata on the long run)

If you're on IRC, I'd recommend #lad on Freenode.

[mxmilkiib]

I've added Spaghettis to the AUR: https://aur.archlinux.org/packages/spaghettis-git

[nicolasdanet]

The metadata settings are just labels. They currently doesn't clamp anything. Except that marking a port cv disable internal [-1 1] audio clipping. Probably that in the futur it would be possible to set minimum and maximum only if the port is cv. Anyway i think that only usage of that feature will help to improve the feature. That is the benefit of work-in-progress. Experiment and if it is bad, change it. Personally i have no opinion about for what it can be useful for! If anybody want to make it differently, just propose it.

[nicolasdanet]

At first i was thinking about something like below, but i doubt that the metadata label could be used in other situations. But as said above, i'm open to suggestions.

[ ; pd JACK metadata output 1 cv 1 (

[nicolasdanet]

Note that I quickly tested it with QjackCtl 0.6 on Manjaro and it seems OK.