[PlanetCCRMA] JACK 1 vs 2

[Fernando Lopez-Lezcano]

On 04/16/2015 01:16 PM, Don Estabrook wrote:
> Hi Fernando and all,

Hi!,

> I've been doing some light testing of an Ardour4 rc build in the last
> day or so, and I ran into some issues with JACK2 1.9.10 - the current
> version for Fedora 21, including:
>
>    - Ardour UI locked up at the end of exporting; had to kill it.
>    - After restarting, UI is "awake" but, eg, clicking on buttons
> doesn't have the intended effect; Session > Quit also didn't quit
> Ardour, so eventually had to kill that one too.
>    - The second kill results in a run-away jackd process.
>
> Other issues have been mentioned in Ardour-land as well, including the
> lack of an option (-T) that allows for Ardour to stop JACK itself, if it
> started JACK when the session was opened.  Apparently that's been added
> to a newer version of JACK2, but it doesn't seem to have been published
> yet -- even in Git, the latest tag is 1.9.10.
>
> I built JACK1 0.124.1 - itself over a year old - from source, and ran
> qjackctl and Ardour with PATH and LD_LIBRARY_PATH augmented to pick up
> my JACK1 installation[1], and with that I haven't seen a single issue so
> far. As a (minor) bonus, qjackctl and Ardour now show 100% DSP load
> during export, whereas JACK2 typically showed 8-10%.  (This has been the
> case for some time, even with A3.)
>
> So, just wondering whether others have seen any of these issues.

Not really.

>  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...

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.

 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)....

-- Fernando