[LAU] USB period size? (WAS: tracking down xruns)

[david]

Ng Oon-Ee wrote:
> On Tue, 2009-12-22 at 15:44 +1100, Patrick Shirkey wrote:
>> Are you running the usb device at 44100 or 48000? Ideally usb cards 
>> should be run at 48000 with period sizes that divide perfectly into 
>> 48000. i.e 100, 200, 400, etc...
> 
> Could I know more about this, please? 48000 would be the 'generally'
> used (besides 96k) for USB sound cards I understand, but what's this
> about period sizes? I've always thought period sizes were of the series
> 8, 16, 32, 64, 128, 256...

I did some experimenting with period sizes on my USB card (Behringer 
UCA-202 running at 48k) using jackdmp on my Debian Lenny non-RT ordinary 
use laptop. It was a bit better about overruns, but not much better than 
the 1024 (64msec latency) I usually run here on my non-RT kernel.

Let's try it on musicbox (also non RT, but running regular jack). 
Command line reports that frames must be a power of 2: 64, 512, etc. I 
tried a period of 100 (worked with jackdmp). I think it's jack 0.116 on 
musicbox.



-- 
David
gnome at hawaii.rr.com
authenticity, honesty, community