[OT] Re: rt kernel

Ralf Mardorf ralf.mardorf at alice-dsl.net
Wed Apr 6 14:21:16 UTC 2011

On Wed, 2011-04-06 at 15:36 +0200, ailo wrote:
> Well, if you get a chance, please try them. 2.6.38, that is.
> Also, I'm hoping 2.6.39 will be even better, since it seems we will be
> able to adjust irq priority.

No, I won't use those kernels, just because of issues that might not be
caused by those kernels, but that unfavourable could be the putative
cause for an issue.

Bug reports for DAWs often are a problem, because of outdated libs and
apps. The community of audio coders seems to be very small, so they
maintain their latest software versions only. Distributions like
openSUSE, that often update the complete version, don't provide all
current libs and especially not audio apps. I'm still on 11.2, but the
folks and magazines are at 11.4 at the moment. Audio coders sometimes
use svn libs that aren't official released. For Ubuntu I noticed a trend
to use Natty, I just installed Maverick, only because I've got serious
issues with Ubuntu Studio Lucid, while Maverick is ok.

The choice of the used kernel, distro and apps also depends to the
trends of the Linux community, not only to stability and use.

When KDE 3 became the best desktop environment that ever was programmed
for any OS and it just needed some optimisation, they switch to KDE 4
and gave us another unfinished desktop environment. I needed to switch
to GNOME, with all it's disadvantages, but also with the advantage not
to change the complete workflow.

It's hard to keep an audio Linux stable + up-to-date ... anyway ... if
you run in issues for hard audio work and you do a bug report, you
better use a kernel-rt (+ current libs and apps).

> Perhaps the midi problems are partly because of Alsa? Don't know much,
> but from what I hear, alsa midi is not the most reliable.

ALSA MIDI (not audio)? Yes, perhaps. Most of the times there are no
timing/jitter issues for ALSA MIDI and ALSA MIDI clients. JACK MIDI only
is for internal usage and the bridges 'jackd [snip] -Xseq' or
'a2jmidi_bridge' usually for my needs do a good job too. At least the -X
switch is known as less good. I can't confirm this. JACK transport again
and again was out of sync, dunno the current state, I don't use JACK
transport. It wasn't the bad of JACK all the time, I remember that there
once was a bug for Hydrogen. The doubtful funny thing is, that most
Linux musicians didn't notice this bug, while others, e.g. me, aren't
able to make music, if sync isn't very good.

Regarding to sync, e.g. play a sequence in cycle mode and use a
'virtual' (internal) synth + an external MIDI standalone device in
unison. After a while the two synth will drift completely. Jitter isn't
the only issue.

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