Re: Bridging alsa and jack midi

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On 09/26/2014 04:12 PM, Philipp Überbacher wrote:
On Fri, 26 Sep 2014 10:50:06 -0400
Paul Davis <paul@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Fri, Sep 26, 2014 at 7:17 AM, Philipp Überbacher
<murks@xxxxxxxxxxxxx> wrote:

On Thu, 25 Sep 2014 18:17:56 -0400
Paul Davis <paul@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Thu, Sep 25, 2014 at 4:56 PM, Philipp Überbacher
<murks@xxxxxxxxxxxxx> wrote:

on as far as timing.

So I remember correctly that there used to be issues with -X
seq.


the -X seq option in current JACK1 is just a backward compatible
hack to allow qjackctl and other tools to invoke the relevant
stuff.

the actual implementation is nothing to do with the old -X seq
code, and is actually a2jmidid converted into an internal client.
Note that JACK2 could use this client too - its source code is
even in the theoretically "shared" git repo for JACK tools.

Is there a new, recommended way to do the same thing? I only found
-X alsa_midi in the man page but it does not have the same effect.


the confusion here is that there are two sets of command line
arguments when you start JACK:

    jackd [ SERVER OPTIONS ] -d BACKEND_NAME [ BACKEND OPTIONS ]

for better or for worse, some of the option letters (e.g. -X or -p)
can occur as either server options or backend options.

in the "old" world, there was only -X as a backend option and it had
two arguments ("seq" or "raw"). Both of them are basically not
sensible to use because of the poor implementations they refer to.

in the new world, the preferable use of -X is as a server option:

    jackd ... -X alsa_midi ... -d BACKEND ....

BUT ... given the legacy of qjackctl and other control apps which
don't know about this, I hacked jack1 so that it would look for the
the -X seq argument as a **backend** option and treat that as if the
user had used the new form.

It would have been less confusing to have not done this, but that
would have meant that it would be impossible/harder to use qjackctl
to invoke this new MIDI bridge stuff, since it only knows about -X
(seq|raw) as a backend option.

Alles klar?

Alles klar. Well, mostly. I guess that alsa_midi only makes sense
when alsa is used as a backend, so I don't quite see why it is a server
option instead of a backend option. Anyway, using the -X alsa_midi as
server option works.


on qjackctl settings, you can set the server prefix to "jackd -X alsa_midi" and leave the midi driver to "none", especially when NOT using "alsa" as the driver back-end.

hth.
cheers
--
rncbc aka Rui Nuno Capela
rncbc@xxxxxxxxx
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