22 Jan
2003
22 Jan
'03
1:14 p.m.
Dave Griffiths wrote:
I thought I'd pipe up here, as I use jack on a totally unpatched, untuned
system (with SCHED_FIFO) and get rock solid performance.
Hmmm, that's annoying, I've never had that happen to me >:-|
;-) no, seriously, that's really great! Sadly this is not the case for
all of us...
Would you care to describe your setup, hardware/kernel versions etc...?
Regards,
Robert
It shouldn't be a problem, iwht only a few apps
running the overhead is
very small. If by "isn't perfectly tuned" you mean not running SCHED_FIFO
or a patched kernel that its not that supprising, the context switch will
be causing big problems. But, at worst it should just make xruns a bit more
frequent, not go from none to some.
What I have noticed is subtle, I have xruns in both situations but
the rate increases noticeably. I've been running patched kernels but
there are all kinds of parameters
(as I'm sure you know) to tweak before it is sufficiently solid. I
would consider my findings pretty much expected behaviour with a
less then perfectly tuned system.
22 Jan
22 Jan
1:57 p.m.
I thought
I'd pipe up here, as I use jack on a totally unpatched, untuned
system (with SCHED_FIFO) and get rock solid performance.
Hmmm, that's annoying, I've never had that happen to me >:-|
;-) no, seriously, that's really great! Sadly this is not the case
for all of us...
Would you care to describe your setup, hardware/kernel versions etc...?
2:03 p.m.
I thought
I'd pipe up here, as I use jack on a totally unpatched, untuned
system (with SCHED_FIFO) and get rock solid performance.
Hmmm, that's annoying, I've never had that happen to me >:-|
;-) no, seriously, that's really great! Sadly this is not the case
for all of us...
Would you care to describe your setup, hardware/kernel versions etc...? 
2:23 p.m.
New subject: [linux-audio-dev] RE: [Jackit-devel] Re: k_jack v0.0.0.5
Would you care to describe your setup, hardware/kernel versions etc...?
Robert,
At the risk of looking like Steve's shadow, I run the PlanetCCRMA flow on
two machines. The low-end machine is an older Dell P3-500 with a Hammerfall
light and 768MB of DRAM. In that machine I run Jack with a -r 44100 -p 1024
setting, so latency is pretty high. (43mS?) It runs fluxbox and is
completely solid. I could probably lower the Jack latency settings but
haven't needed to you. I never see xruns.
On my main box, where I run Ardour and Rosegarden, along with
fluid-synth, amSynth and a couple of other synths, I use an Asus A7V266-E
mobo with an Athlon XP 1600+ processor, 256MB DRAM, normal internal drives
and external 1394 drives using reiserfs. On that machine I normally run with
a -p 256 -n 2 setting, which I thin gets the latency down in the 10-11mS
range. I can run at -p 128, but down there I do see xruns too often.
I have noticed that there are still a number of system oriented things
that, on my system, absolutely guarantee an xrun. The simplest is dropping
down to a console. (Alt-Ctl-F2) Normally I like to put Jack in it's own
console instead of running it on my desktop somewhere. With low settings (-p
256 and below) I see xruns coming from and going to console.
I do not see xruns for other reasons, at least for the work model I have
right now, which is admittedly pretty simple. Possibly it will get worse
later. Typically I'm running 10-15 MIDI tracks in Rosegarden, sending them
to an external machine running GigaSampler, and bringing the audio back in
using Ardour. I never, ever see xruns when monitoring audio with Ardour. I
can create them if I try to record too many audio tracks at the same time. I
have not tried to optimize this yet, other than my recently published info
on xruns and file systems. (Thanks Jan!) I presume that there will always be
a limit to what any given system can do in terms of recording tracks, so I'm
not surprised to see this sort of limit in mine.
WRT a previous comment about not using Jack at all, how would I use 5
soft synths, Ardour and Rosegarden at the same time without it, and only
using Alsa? Even if I didn't require low latency which I do) how would I do
that? I'm not clear?
Thanks,
Mark
2:44 p.m.
New subject: [linux-audio-dev] RE: [Jackit-devel] Re: k_jack v0.0.0.5
I have noticed that there are still a number of
system oriented things
that, on my system, absolutely guarantee an xrun. The simplest is dropping
down to a console. (Alt-Ctl-F2)
It is a known problem and is in the list of "things you should not do"
in Andrew Morton's low latency page (at the bottom):
http://www.zip.com.au/~akpm/linux/schedlat.html
-- Fernando
2:59 p.m.
New subject: [linux-audio-dev] RE: [Jackit-devel] Re: k_jack v0.0.0.5
Thanks Fernando. I hadn't seen that, and it makes me feel better to know
it's just a standard design problem.
I'll still put Jack in the console, I think, to keep it off my desktop, and
just look there occasionally to see how things have been going.
Actually, can I somehow take the jackstart output that goes to the F2
console and pipe it to a file that I could look at from KDE? That would be
nice too.
-----Original Message-----
From: Fernando Pablo Lopez-Lezcano [mailto:nando@ccrma.Stanford.EDU]
Sent: Wednesday, January 22, 2003 10:38 AM
To: Mark Knecht
Cc: Robert Jonsson; jackit-devel(a)lists.sourceforge.net; Linux-audio-dev
Subject: RE: [Jackit-devel] Re: k_jack v0.0.0.5
I have noticed that there are still a number
of system
oriented things
that, on my system, absolutely guarantee an xrun.
The simplest
is dropping
down to a console. (Alt-Ctl-F2)
It is a known problem and is in the list of "things you should not do"
in Andrew Morton's low latency page (at the bottom):
http://www.zip.com.au/~akpm/linux/schedlat.html
-- Fernando
3:05 p.m.
New subject: [linux-audio-dev] RE: [Jackit-devel] Re: k_jack v0.0.0.5
Mark Knecht wrote on Wed, 22-Jan-2003:
Actually, can I somehow take the jackstart output that
goes to the F2
console and pipe it to a file that I could look at from KDE? That would be
nice too.
Sure, if using bash, just run it:
jackstartoptionsblahblah &> /tmp/jack.output &
Then in a terminal under X, you can run:
tail -f -s 0 /tmp/jack.output
and it's just like you were there.
jlc
3:08 p.m.
New subject: [linux-audio-dev] RE: [Jackit-devel] Re: k_jack v0.0.0.5
Actually, can I somehow take the jackstart output that
goes to the F2
console and pipe it to a file that I could look at from KDE? That would be
nice too.
general unix techniques, part 2003.45 (all assume the use of a bourne
shell-like shell, which covers bash, zsh, sh, ksh, ash and many others):
1) divert all regular output to a file:
cmd > filename
2) divert regular output and error output to a file
cmd > filename 2>&1
3) divert regular output to a file but copy it to the screen
cmd | tee filename
4) divert regular output and error output to a file but copy it to the screen
cmd 2>&1 | tee filename
then, to watch it from another shell:
tail -f filename
which will check the file every second by default.
--p
3:08 p.m.
On Wed, Jan 22, 2003 at 10:51:21AM -0800, Mark Knecht wrote:
Thanks Fernando. I hadn't seen that, and it makes
me feel better to know
it's just a standard design problem.
I'll still put Jack in the console, I think, to keep it off my desktop, and
just look there occasionally to see how things have been going.
Actually, can I somehow take the jackstart output that goes to the F2
console and pipe it to a file that I could look at from KDE? That would be
nice too.
man tee
--
Paul Winkler
http://www.slinkp.com
Look! Up in the sky! It's PREPUBESCENT MAESTRO COSMIC!
(courtesy of isometric.spaceninja.com)
3:09 p.m.
New subject: [linux-audio-dev] RE: [Jackit-devel] Re: k_jack v0.0.0.5
I'll still put Jack in the console, I think, to
keep it off my desktop, and
just look there occasionally to see how things have been going.
Actually, can I somehow take the jackstart output that goes to the F2
console and pipe it to a file that I could look at from KDE? That would be
nice too.
cd somedir
jackstart -R -d alsa -d hw &>jack.log
(if using the bash shell)
somewhere else:
cd somedir
tail -f jack.log
(checks at 1 second intervals for new stuff in the file)
Obviously jack.log keeps growing and growing without bounds...
-- Fernando
7:38 p.m.
New subject: [linux-audio-dev] RE: [Jackit-devel] Re: k_jack v0.0.0.5
On Wed, 2003-01-22 at 10:51, Mark Knecht wrote:
Thanks Fernando. I hadn't seen that, and it makes
me feel better to know
it's just a standard design problem.
I'll still put Jack in the console, I think, to keep it off my desktop, and
just look there occasionally to see how things have been going.
Actually, can I somehow take the jackstart output that goes to the F2
console and pipe it to a file that I could look at from KDE? That would be
nice too.
I think in this type of situation the "screen" utility could come in
handy. You can run a program like "screen jackstart" or whatever from a
virtual terminal and then do a "CTRL-A D" to detach from it (it is still
running) and then in an X terminal you can do a "screen -r" at any time
to re-attach to the running program. I'm not sure how to do this between
different users so you will probably need to su to root in your X
terminal (if you are running the application as root) before this will
work (or perhaps there is a way to grab screen sessions from other
users, after entering a password or something, donno). Cheers.
Josh Green
3:55 p.m.
Hi Mark and thanks for an extensive answer.
I've read parts of Jan's paper, a lot of good info, very interesting
your parts regarding filesystem. I wouldn't have guessed that ReisterFS
would have been the least intrusive of the tested filesystems!
My current system is an Athlon XP 1700+, MSI 266(something) m/b with
256MB ram and two ide disks 60gb,80gb. Using an sb-live and an Delta44
(envy24) soundcard.
I've only recently starting to trim it for lowlatency for _real_. And
this system needs trimming. By taking your advice of shuffling the
actual cards and also trying different settings in the bios has made
noticable difference wrt latency.
Right now I'm stuck on the freezing kernel problem that Fernando has
been reporting about. Since he has posted a patch today(yesterday) I'm
in the process of building it, hopefully the problems will disappear and
latency is in the right ballpark :)
WRT a previous comment about not using Jack at all,
how would I use 5
soft synths, Ardour and Rosegarden at the same time without it, and only
using Alsa? Even if I didn't require low latency which I do) how would I do
that? I'm not clear?
For a pro/semipro this is probably not an option, unless you are content
working with just one program at the time, with MusE this works pretty
good since MusE has internal softsynths, but they aren't that many.
Also, there are cards, e.g the SB-Live/Audigy that supports multiple
open of the output port. I think it supports up to 64 simultaneous
streams that then will be mixed on the card. But I don't think
SB-Live/Audigy would suffice for a pro/semipro user. (it's ok for me,
but I don't do much serious work). Mixdown is a real pain in this
situation, what you do is that you set the soundcards mixer to record
from the output stream.
This would not work for jack based applications like ardour, then you'd
need jack anyway. I guess you could run multiple instances of jack, one
for each app, if you really wanted to. But then you would be missing the
point by a few thousand square kilometers.
Jack is a much cleaner solution that has the possibility to really bring
Linux audio together and sustain it for a very long time!
That is, if I ever succeed with running it without xruns ;-)
Regards
/Robert
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linux-audio-dev@lists.linuxaudio.org
11 comments
8 participants
participants (8)
-
Dave Griffiths -
Fernando Pablo Lopez-Lezcano -
Jesse Chappell -
Josh Green -
Mark Knecht -
Paul Davis -
Paul Winkler -
Robert Jonsson