On Thu, 2008-07-10 at 17:40 +0200, Harald Hoyer wrote:
> Michal Schmidt wrote:
> > On Thu, 10 Jul 2008 13:40:26 +0200
> > Harald Hoyer <harald@redhat.com> wrote:
> >
> >> Anyone interested in an audio SIG?
> >>
> >> We could create a jacklab like spin ( http://jacklab.org/ ) with
> >> jackd as the main audio daemon.
(or Ubuntu Studio, the Gentoo pro audio overlay, 64Studio, etc, etc,
pretty much all big distros already have it)
> > Would the absence of a real-time kernel variant in Fedora be a problem
> > for such a spin?
Yes.
> > Fedora kernel only has voluntary preemption enabled.
> > All the audio-specialized distributions I've heard about ship with an
> > RT-patched kernel.
> >
>
> Absence is no "problem" on a modern desktop (my desktop :-) ), though a
> real-time kernel would definitely improve the latency for slower systems.
Nope. It is a problem.
A stock Fedora kernel can have latency problems if you use jackd with 64
or 128 frames per period[*]. One hiccup is enough to ruin a performance
or a recording session. That is why other audio oriented distros use a
realtime patched kernel (as does Planet CCRMA, which I maintain).
You could define your "target user base" to not need that level of
performance, and then sidestep the issue. But then you can't compare a
hypothetical Fedora JackStudio or whatever distro with other audio
oriented distros that have a realtime patched kernel.
> Maybe we could "maintain" a kernel-rt package or persuade our RHEL5 kernel team
> to provide a rt-kernel (with the benefit of more QA

).
I've been "maintaining" one for Planet CCRMA since 2001. It is not fun
(well, it used to be, many years ago) and it is a worthy task for
Sisyphus. I made some noise in the fedora audio list a while back about
this, but there's no manpower for doing a realtime kernel on Fedora.
RedHat itself does have a realtime patched MRG kernel for RHEL.
-- Fernando
[*] depends on your particular hardware configuration, sound card model,
interrupt sharing, usage patterns, and the phase of the moon for all I
know :-)
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