Re: [linux-audio-user] Low latency USB 1.1 card?

From: Frank Barknecht <fbar@email-addr-hidden>
Date: Thu Jun 16 2005 - 00:05:50 EEST

nigel henry hat gesagt: // nigel henry wrote:

> Hi Frank. Using a dodgy kernel eh!

Not anymore since 10 minutes: Now I run my own personal kernel again like it
should be: vanilla 2.6.11-12 from, preempt enabled.

> I've being viewing your posts , and sort of wanting to help, scanned
> the synaptic list. I had 2.4.27 kernel and 2.6.8. Having now found
> also that the 2 modules I've mentioned should really be loaded as
> default. Just giving my 2 cents worth. Hope you get it fixed. Nigel.

Actually I don't have a problem with soundcards not working, I was
just experimenting with Clemens' suggestion of using the "nrpacks=1"
option to snd-usb-audio to get the lowest possible latencies for USB.

With my new kernel with disabled USB bandwidth allocation, I'm
currently test-running alsaplayer over jackd on a cheapo Terratec
Aureon USB with jackd started as:

$ /usr/bin/jackd -R -dalsa -dhw:1 -r48000 -p128 -n3 -S

and that translates to a latency as displayed by qjackctl of 8msec.

(/me plays around with qjacktl ...)

And now it's at:

$ jackd -R -dalsa -dhw:1 -r48000 -p64 -n3 -S

Latency: 4msec, still no xruns with alsaplayer (I even switched to a
virtual console... ;)

And now: a period of 32!

$ /usr/bin/jackd -R -dalsa -dhw:1 -r48000 -p32 -n3 -S
jackd 0.99.54
Copyright 2001-2005 Paul Davis and others.
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details
JACK compiled with System V SHM support.
loading driver ..
apparent rate = 48000
creating alsa driver ... hw:1|hw:1|32|3|48000|0|0|nomon|swmeter|-|16bit
control device hw:1
configuring for 48000Hz, period = 32 frames, buffer = 3 periods
ALSA: cannot set period size to 32 frames for capture
ALSA: cannot configure capture channel
cannot load driver module alsa

Ah, okay, you jus' gotta know when to stop. ;)


 Frank Barknecht                               _ ______footils.org__
          _ __latest track: "scans" _
Received on Thu Jun 16 04:15:04 2005

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