alsa and jack latency
I sent this mail a few days ago to debian-powerpc but had no reply.
Maybe someone here will have an idea.
bye, Paul
----- Forwarded message from Paul Brossier <piem@altern.org> -----
Date: Sat, 14 May 2005 21:56:40 +0100
From: Paul Brossier <piem@altern.org>
To: debian-powerpc@lists.debian.org
Subject: alsa and jack latency
Hi all,
Trying to reduce the latency of jack on my ibook G4, i realised i can go
down to 8.7ms using the oss mode, which is really good. But alsa won't
accept running with less than 22ms and click on most X request:
$ jackd -R -doss -r44100 -p128 -n3 -w16
works perfectly, 128*3/44100=8.7ms latency, hardly any xrun on heavy load
$ jackd -R -doss -r44100 -p256 -n2 -w16
works fine, 11.6ms latency
$ jackd -R -dalsa -r44100 -p128 -n3 -S
runs but no clients can connect
$ jackd -R -dalsa -r44100 -p256 -n2 -S
fails saying ...
ALSA: cannot set number of periods to 2 for capture
ALSA: cannot configure capture channel
$ jackd -R -dalsa -r44100 -p256 -n4 -S
would run with 23.2ms latency, but xruns on most X queries
It looks to me that this is related to the pmac driver. I have similar
problems with snd-usb-audio and an edirol usb, which will only let jack
run in oss mode.
I wonder what prevents the pmac module to do so while the oss emulation
layer does it very well. I am running 2.6.12-rc4, but had this problem
with earlier 2.6 kernels. Any thoughts?
Many thanks, Paul
----- End forwarded message -----
(mmh, pmac should really be powermac in the above)
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