Re: [gentoo-user] [Completely and totally OT] FVWM-Crystal...!!!

[Mark Knecht]

On 9/29/05, Holly Bostick <motub@××××××.nl> wrote:
> Mark Knecht schreef:
> > On 9/28/05, Mark Knecht <markknecht@×××××.com> wrote:
> >
> >> Great. Tried it. It worked fine and didn't upset Jack which means
> >> my experiment goes on.
> >>
> >> This is working so much better for me than Gnome on my AMD64 box.
> >> I'll have to go back and try the standard Gentoo kernel instead of
> >>  ck-sources.
> >>
> >> <snip>
> >>
> > In the end the xruns came back so FVWM-Crystal didn't magically solve
> >  my problems. (unfortunately...)
> >
> > My quest goes on. Now running 2.6.14-rc2-mm1, looking for
> > 2.6.14-rc2-mm1-rt6
> >
>
> Am I the only one who doesn't know what are 'xruns'? Whatever they are,
> it would seem that the problem can be minimized, but not eliminated by
> choice of WM, but obviously we couldn't go any further in actually
> eliminating them without knowing what they are (or at least I couldn't,
> since I don't actually know what you're referring to).
>
> Holly

Holly,
    I'm so very sorry. Of course you would have no reason to know
about xruns if you are not part of the Linux audio community. My
apologies.

   One of the Linux 'methods', if you will, for moving audio between
sound cards and applications is a server called Jack (jackd) which is
supplied by emerging jack-audio-connection-kit. Jack provides for the
movement of digital audio between a sound card and essentially an
unlimited number of apps (really 'ports') with a known latency. It's
the latency that's really important to those of us doing live
recording. If I'm listening to a piano and recording my guitar then I
need the two to sound like they are in time or it is virtually
impossible to play a part correctly.

   An 'xrun', standing I think for overrun - go figure - is when
something in the system has not taken or delivered digital audio at
the agreed upon time. This leads to clicks and pops. If you were to
look at the waveform in an oscilloscope there would be some sort of
discontinuity.

   With my 32-bit machines I have been blessed. I have been able, for
at least the last year, to run the standard Gentoo kernel at <3mS
latency with no xruns. I've been writing and recording music on Gentoo
and had no problems while others running on other distros have had to
build specialized kernels utilizing patches from Andrew Morton and
Ingo Molnar to get equivalent results. On guy in Australia didn't
really beleive me so I helped him build a Gentoo box over the net.
When that machien came up it worked so well, with the standard kernel,
that he converted all the machines in his studio to Gentoo and no
brags about how stable his environment is.

   I looked forward to such an experience with my new AMD64 machine.
It did not come to be true.

   Every 64-bit kernel I've tried so far either has terrible xrun
problems or will not build. This includes:

gentoo-sources - xruns
ck-sources - xruns
kernel.org - 2.6.13.3 & 2.6.14-rc2 - xruns
2.6.14-rc2-rt6 - Ingo's patches - won't build

   I'm currently running 2.6.14-rc2-mm1 - with Andrew Morton's
patches. I have not yet tested it but at least it built.

   The major change to the kernel to get better real time results is
(apparently) to make pretty much everything preemptable. When Ingo's
patches are added then a new preemption model shows up in make
menuconfig. Unfortunately for me it won't build on 64-bit yet, at
least for me.

   The window manager choice is just one choice those of us playing
with low latency audio make. KDE has never worked well for me. Gnome
has been fine for the last year until this new AMD64 experience. In
the old days we used fluxbox over KDE and Gnome and got good, but not
great, results.

   Anyway, I hope that helps explain my xrun comments.

Cheers,
Mark

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