[PlanetCCRMA] The JACK Story

Fernando Lopez-Lezcano nando at ccrma.Stanford.EDU
Sat Nov 21 19:55:21 PST 2009

On Sat, 2009-11-21 at 22:02 -0500, Orcan Ogetbil wrote:
> There was a recent attempt [1] in the Fedora devel list to discuss
> what to do with jack1 and jack2. But there was not much feedback.
> Upstream just released 0.118.0 and 1.9.4. So they don't seem like they
> are dumping jack1 for the time being.
> Currently we have jack1 in Fedora and jack2 in planetccrma. But these
> can't be installed in parallel. I would like to hear some opinions
> here. Which one do you folks use? 

I have been using jack2 for a long time. One advantage is that for jack
client graphs that can be execute in parallel it uses all cores
available. That is a distinctive advantage in pretty much all
contemporary computers (which have more than one core). 

> Do you alternate for specific tasks?

I have never had to "downgrade" to jack1. 

(I seem to recall somebody having a problem with jack2 and that's why I
have been keeping a jack1 package available as well - hopefully that
person will add to the thread)

> Would you like to have them parallelly installable? We can achieve
> parallel installation via "alternatives". 

I'm not completely sure if that is possible. Keep in mind that all jack
server and client _libraries_ need to be switched in and out (ie: it is
not just a matter of switching the jackd binaries. 

> This is actually what some
> packages do in Fedora, the most popular example being java. It would
> work in the following way:
> $ sudo alternatives --config jack
>   Selection    Library
> -----------------------------------------------
>    1          jack-0.118.4
>  * 2          jack-1.9.4
> The questions boil down to:
> - Is it worth the effort to adapt "alternatives"?
> - Shall we keep things this way?
> - Move the jack2 package to Fedora?

The jack2 (and jack1) package in Planet CCRMA also has a different
default priority that matches the best choice for the rt kernel (plus
optimized irqs using rtirq). That is not really compatible with the
current Fedora kernels (default priority is 60, below the irqs for the
soundcards but above all others). It won't hurt, but I presume it will
not fly either...

The only other difference (AFAIK) is a different netjack but the current
work was to move netjack1 to jack2 (I _think_ 1.9.4 may already have
that, I have not checked yet). 

-- Fernando

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