[LAU] jackd without MIDI

Paul Davis paul at linuxaudiosystems.com
Wed Nov 18 03:40:45 UTC 2015

On Tue, Nov 17, 2015 at 9:56 PM, jonetsu at teksavvy.com <jonetsu at teksavvy.com>

> On Tue, 17 Nov 2015 12:13:30 -0500
> jonetsu <jonetsu at teksavvy.com> wrote:
> > I did have a reply from Bitwig today with a series of steps to do and
> > I will give it a try.
> Basically it boils down to this.  After booting the workstation, bitwig
> is started, audio set to jack (not ALSA).  There is sound and the MIDI
> keyboard works.  This is as it should be.  Why didn't I see it
> before ?  Because I was loading what I'm used to work with first, that
> is, Ardour.  So now bitwig is OK.  I start Ardour and load a session.
> In this session there is a VST synth plugin.  Since the MIDI keyboard
> is not seen in the MIDI tab (only in the ALSA tab) in qjackctl (where
> Ardour MIDI connections are seen) I have to do:
> % a2j_control ehw start
> Now the MIDI keyboard and Ardour are found in the same MIDI tab in
> qjackctl and a connection can be made between them.  Note that apart
> from the audio tab, there's no bitwig elsewhere in qjackctl.  The
> problem is, no MIDI is reaching the VST plugin in Ardour.
> What I see is the first app to run gets the MIDI.  The other app that
> is launched thereafter will not get.  It works in both ways: bitwig
> first then no MIDI for Ardour.  Ardour first then no MIDI for bitwig.
> This is extremely reproducible.
> The question is now, how to share MIDI between the applications (let
> alone which MIDI channel controls what) ?

As I've explained previously:

    * the ALSA "raw" MIDI API implies exclusive device access. Devices
      accessed with this API cannot be shared. No data can be exchanged
      between applications either (not with this API, at least)

   * the ALSA "sequencer" MIDI API implies shared device access, and
     allows applications to exchange data as well.

   * JACK MIDI backend(s) exist for both of these APIs.

   * the JACK MIDI API implies shared device access and allows
     applications to exchange data as well.

try running this while JACK + Bitwig are running:

          lsof | grep /dev/snd

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