[linux-audio-user] latency issues

[Robert Jonsson]

Monday 06 October 2003 13.20 skrev dwillis at stx.rr.com:
> two years ago i did a bunch of testing on latency to find the best kernel
> and patches for my system, and got some damn good results with several
> kernels (the best being 2.4.12-ac3-pe (alan cox's patch and pre-emptive
> kernel patch using alsa on suse 7.3 with gcc 2.96 20000731).  i now have a
> new computer with gentoo linux and alsa 0.9.6, and can only get 16 ms
> latency with perfect results.  same soundcard - m-audio audiophile 2496
> (ice1712).  i've used kernel 2.4.20 with pe, ll, and some other options,
> compiling with gcc version 3.2.3 20030422, and i get the same result with
> all of them (as well as without pe or ll).
>
> does anyone know what the problem could be?  alsa version? gcc version?
> kernel version? hardware (eth0 and soundcard share irq - never thought to
> test without eth0 loaded)?  i'd like to get latency under 4 ms.
>
> thanks for your input,
> dave


First, I'd like to know if you by "latency testing" mean that you ran Benno's 
latency test program?

For some info do check (seems to be down at the moment)
http://myweb.cableone.net/eviltwin69/ALSA_JACK_ARDOUR.html

Did you check what IRQ your card was assigned? There's lots of interesting 
info in the above document.

Performance optimizing is something of a black art. Both the hardware and the 
software needs to be in good condition and go well together...

As a sidenote, my system doesn't do much better than the 16ms scenario 
either... I don't know if it's hardware or software problems... Trying the 
"tricks" in the document above did help though...

Do let us know if there was something specific that helped.

/Robert