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OT (for the debian-list): Re: [Rosegarden-user] Questions about audio playback and MIDI connections

(Intentionally cross posted)

The following quotes are from an email to a rosegarden mail list -- Rosegarden 
is a music notation (mcow) program.

A user is describing a problem in which it appears the MIDI ports (connected 
via USB ports) change on each boot (or maybe even each start of the Rosegarden 

I just wondered if this is similar to the current Linux behavior related to 
disks wherein, in the old days, disks came up in a consistent order, but 
nowadays (maybe because of systemd?) they (or some of them) can start in 
parallel and thus their device numbers are not consistent.

If a similar problem does exist with USB ports, is there a way to force them 
to be identified in a consistent way on each boot (i.e., something like using 
UUIDs or labels for disks)?


On Tuesday, June 30, 2020 10:46:30 AM Ted Felix wrote:
> On 6/30/20 5:20 AM, Malhaire Christophe wrote:
> > 1) While using Rosegarden, I cannot play a video on Youtube, or play a
> > piece of music using Parole Media Player.
>    Off the top of my head, it sounds like those programs likely use
> ALSA, but you have JACK running.  When JACK is running, it takes over
> ALSA and anything trying to use ALSA will be "broken".
>    There may be a way to get ALSA and JACK apps to cooperate.  I seem to
> remember an article on the JACK website.  This is a common complaint.
> > 2) Each time the PC and Rosegarden are restarted, I have to check and
> > change my MIDI connections because the MIDI ports of my external USB
> > sound modules are systematically inconsistent (MIDI Playback devices
> > related to MIDI Outputs).
>    This is interesting as we've had this complaint before.  I really
> would like to work on fixing this, if possible, but the other user
> reported that the problem went away.
>    To get a closer look at what rg is doing to make those connections,
> load a composition, then go to Edit > Preferences... and press the
> "Details..." button next to "Sequencer Status".  This should show you
> the connections it is trying to make.  If you can post what's in there,
> that might help with figuring out what we might be able to do to fix this.
> > I believe Rosegarden has an internal function
> > for "smartly" attaching a MIDI device, according to its name, but it
> > doesn't work for me. Surely I must miss something but what?
>    It's all automated, so not really anything you can do.  We need to
> have a closer look and see if anything can be done at all.
> > Is there anything to add to the .rgd file?
>    .rgd files are only relevant when you create a new device.  It is the
> .rg file that is driving things from that point on.  It's the exact same
> info, though.
> > But since the port number can change at each boot, or depending on the
> > order in which the devices are turned on, maybe this is not a good
> > method?
>    I suspect that is what is really happening.  There's a limit to what
> we can obtain from the drivers.  Therefore there is a limit as to how
> good of a job we can do matching things up.
> > 3) And by the way, where can we find a complete manual about the xml
> > format of .rgd files?
>    You'll have to read the code.  We've barely got time to write code
> let alone documentation.  Feel free to create some, though.  We'd be
> happy to post it to the wiki.
> Ted.
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