[PlanetCCRMA] JACK 1 vs 2

Don Estabrook don.estabrook at gmail.com
Fri Apr 17 21:16:43 PDT 2015

On 2015-04-17 12:17 -0500, Fernando Lopez-Lezcano <nando at ccrma.stanford.edu>

> On 04/16/2015 01:16 PM, Don Estabrook wrote:
>> . . .
> So, just wondering whether others have seen any of these issues [with
>> JACK2].
> Not really.

Good to know - it wouldn't be the first time it was only me. :-)

>   If so, might it make sense for CCRMA (or, Fedora?) to switch to JACK1 ?
>> Or are there dependencies on JACK2 functionality that would make that
>> problematic?
> I'm all for keeping jack2. Unless this has changed recently, jack2 is the
> only one that can schedule processes on more than one core if the jack
> connection graph dependencies allow it to do so. I think jack1 can't do
> that, and that is a deal breaker for me (I do want to be able to (ab)use
> all cores in modern machines).
> YMMV...

>From what I've read, I think you're correct, and I'm all for utilizing
multiple cores too.  Making a blanket choice between them seems to be not
quite straightforward, with potential pluses and minuses on both sides


and some of those might be more or less important, depending on what one is
trying to do.  As you say, taking advantage of more than 1 core isn't
always possible.  OTOH I think uninterrupted audio when
connecting/disconnecting apps is very nice, especially when the output
potentially goes somewhere that others can hear it.  &c.

So despite how my initial question may have sounded, I'm not on any kind of
ideological mission to get CCRMA or Fedora to change. :-)  If I'm the only
one seeing these issues, I'm quite okay with building JACK1 myself as a
work-around for the time being.  Just thought I'd let you know about it.

A4 can also connect directly to sound devices through ALSA - so no JACK
needed - handy for someone using Ardour stand-alone.  I haven't tried that

> I don't know about Fedora (you would have to file a bug report) but I
> could package git as a test if there are improvements there. I fuzzily seem
> to remember some LAU/LAD post about jack2 improvements recently.

Both of their Git repos have a number of commits since their last tags, and
actually JACK2's latest is chronologically newer than JACK1's.  Indeed,
JACK2 has some very recent commits - within the last few days...  Sometimes
fuzzy memories are good ones!

> From the way you describe things it would appear these are bugs in Ardour4
> (or in jack2 and they are uncovered by corner cases in Ardour4)....

Could be.  Paul has said that at least one issue is a result of A4 using a
command-line option that JACK2 doesn't support.  (I see arg parsing code
for it in 1.9.10 and much earlier, but I'm guessing it doesn't work
underneath.)  AFAIK my issues were not related to this however.  The
hang-on-export problem was apparently a known issue with 1.9.9, and fixed
after that - but for me it was 100% repeatable (well, 2/2 - all I had
patience for) with 1.9.10.

-- Fernando

- Don
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