Re: alsa and jack latency
On Tue, 17 May 2005 22:58:08 +0100, Paul Brossier wrote:
> 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?
I have the same configuration (powerbook) and also problems but never took
any real effort to fix them. If you are using the realtime-lsm (or as
root), you should be fine.
Someone currently having issues as well (but amd64):
http://boudicca.tux.org/hypermail/jackit-devel/2005-May/0121.html
You could try to get latency-test running on ppc:
http://www.alsa-project.org/~iwai/alsa.html#LatencyTest
But that seems to require some special RTC functions.
I uploaded a newer JACK (0.99.61) to experimental. But that is binary
incompatible to the current one. So you have to recompile you applications.
Robert.
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