30 Jan
2009
30 Jan
'09
12:53 a.m.
On Fri, 2009-01-30 at 03:23 +0100, torbenh(a)gmx.de wrote:
On Thu, Jan 29, 2009 at 03:41:48PM -0800, Fernando
Lopez-Lezcano wrote:
Hmmm, I'm not sure, the load on pci itself by a soundcard should be
nothing really hard. What would the internal card use? Would not that be
pci or pci express anyway?
On Tue, 2009-01-27 at 14:06 +0100, Peder Hedlund
wrote:
i am running with -p64 -n3 on an intel-hda with 2.6.28
of course internal cards have the greatest potential for lowlatencies.
so this might be unfair, compared to pci. Quoting Ken Restivo <ken(a)restivo.org>rg>:
It depends on your usage (this question seems to come up every couple of
months lately). The current kernels are much better in low latency
applications than three years ago. They are usable if you don't require
"low" latencies (64 or 128 x 2). What you get also strongly depends on
the hardware mix you have.
If you want to use 64 or 128 frame periods (or less) you probably will
need at rt patched kernel in most cases. Then again if an occasional
xrun is not a problem then you would be fine with the stock kernel. And here is the next installment in the saga of
trying to get Ingo
RT going on my Asus EEE.
I successfully built and ran the 2.6.26.8-rt12 with the alsa_seq
patch. It ran.
The problem is that neither the Ethernet (atl1e) or wireless
(rt2860sta) work. So I pretty much had to reboot back out of it
immediately.
I've been running the standard kernel from openSUSE 11.0 on my Athlon
2000+ and can get down to at least 5.3ms latency on an Audiophile 2496
using the limits.conf "trick".
Do people really need lower latencies for music purposes or are we
just thinking "well, I needed the RT patch three years ago; I ain't
stopping now" ? and i havent really seen xruns which i could not
relate to some
programm which wasnt RT-safe, and i am compiling stuff most of the day...
though perhaps i am not pushing the DSP load hard enough.
i did not even turn preemptible RCU on.
the latency measurement instrumentation is also in 2.6.28 btw.
Well, that's very good news then!
I think the last time I tried to use a non-preempt was 2.6.27.x (maybe,
I would have to double check). Playing 24 channels in ardour would
result in xruns, not very often but they would happen, this is with
128x2 on an RME hdsp card runing on a quad core intel system. I should
try again with the latest available.
-- Fernando
While going down to, say, 1 or 2 mSecs of latency might be thought of as
unnecessarily low, if your system can work at those levels then you are
going to be more likely to never get an xrun when running at 5 mSecs
latency. And if you are performing in a concert situation you _don't_
want an xrun, not even one. Linux, even rt patched, does not have a hard
realtime scheduler with deadline guarantees, etc.
-- Fernando
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