JackAudio Setup for NI3 Dance

A post that describes NI3 Dance's live software setup:
All free and open-source software, MIDI and Audio routed with Jack.

Seb MondetPosted on: Sun, 28 Jun 2020#NI3Dance, #JackAudio, #LinuxMusicToot, Tweet

I presented Vecosek and Vimebac a couple of years ago at OCaml-2018 and FARM-2018. Afterwards, I swore to some people I'd describe a bit more my particular usage within NI3 Dance; so here it is.

I've never managed to make “native” session management work for me reliably. I need my setup to be resilient to to missing items or some changes in configuration (e.g. presence or not of MIDI/Audio extra hardware, like my “Looptimus”).

⇒ My session management is GNU-Screen 👴

A script just starts the various applications like this:

screen -S ni3_session -X screen -t Sampson ./start_sampson

It seems archaic but it provides easy logging and easier killing.

I start everything 4 phases called manually (they are just different key combinations using Comk ☺).

The first only starts QJackCtl (rncbc/qjackctl); it can be useful to change the configuration before starting the rest. Starting jackd can sometimes just fail, it's nice to have a simple setup to debug.

The second start all the small applications that can live happily by themselves:

• Drumkv1 “is an old-school all-digital drum-kit sampler synthesizer with stereo fx.”
• ZynAddSubFx is a famous synth in the Music-on-Linux community.
• Sampson is a very simple command-line sampler, it is obscure and may be abandoned.
• a2jmidid is a bridge between ASLA-MIDI interfaces and Jack, it is useful to connect to MIDI hardware.
• Vimebac is the visual feedback, band conductor, and MIDI controller (written by me in OCaml).

The third stage only starts Ardour with a custom session. Ardour knows about its Jack-connections, so it's better if all other software is started by the time it initializes. It used here as a mixer and effects host, I use simple things from calf-studio-gear.

The last stage is often restarted and tweaked: it runs Vecosek with a freshly generated “scene” and then runs an OCaml script to connect the various jack-endpoints (with the --start-hook option).

I only ever use patchage to make nice screenshots:

We see a2jmidid and Vimebac being control inputs for vecosek, itself connected to MIDI-instruments as well as back to Vimebac for visual feedback. Then the flow leaves the MIDI-world (in red) onto the Audio world (green) for mixing, effects, and output (“system playback”).

At some point, instead of Ardour, it used to be Non Mixer together with the Calf plugins in standalone mode. But Ardour, while heavy and capricious, simplifies a lot, and provides quick “record snapshot” functionality to get a jam on tape.

There are still a couple of pain points:

• The whole thing is still a bit annoying to kill, Ardour seems to really dislike being quit improperly, and jackd needs to be shutdown explicitly.
• The configuration of jackd is is hard to control, and even harder to automate and make portable. Next thing to do would be to figure out how to configure it manually (incl. to automate the sound-card choice) and manage the jack-server process separately instead of letting QJackCtl start/stop it.