[LAU] Something odd

Len Ovens len at ovenwerks.net
Sat Aug 15 02:30:54 UTC 2015

On Fri, 14 Aug 2015, Will Godfrey wrote:

> Background.
> I often use my 'office' machine (64 bit dial core Intel - debian 8) to do
> experimental work on audio software as I don't want to take risks with my DAW.
> Sometimes I use a KA6, other times the motherboard sound depending on what I
> want to check. However, I've got into the habit of leaving the KA6 plugged in
> anyway.
> Recently I've noticed that if I have jack running through the motherboard
> audio, I get exactly 1 Xrun approximately every 11 minutes. This doesn't
> happen if the KA6 is not plugged in, nor does it happen if I route jack's audio
> through it.

My first thought was a media clock missmatch. An HDA audio if may have 
more than one media clock. I have a laptop where the internal mic is 48k 
only while the linein/out can be adjusted from 44k1 to 96k. I am pretty 
sure the internal mic clock does not match line in/out even at 48k. But, 
the problem is not always there.

> If this was some USB issue I would have expected it to be there when routing
> through the KA6 as well.
> Any ideas?
Is pulse running? I have had a similar problem: pulse is connected to 
internal (not using it for anything, just connected) Pulse bridged to 
jack, and playing through jack then through ice1712 device... trouble. 
Configure pulse with all device profiles to "off"... no problems. I think 
pulse was trying to service jacksink/source at the same time as the 
"unused" interface.

In my opinion, the trick to happiness with pulseaudio in a jack system is 
to turn all devices off in pulse. (I want to try blacklisting the PA ALSA 
module) and run jackdbus all the time. (jack_control with jackdbus allows 
changing anything in jack while "running" though not glitchless changes 
;) )

> As an aside, I can run the KA6 at 1/2 the buffer size of the motherboard audio
> and still get no Xruns, when the latter is getting quite croaky.

The best I have gotten my HDA to go is 64/3 (64/2 not). Even my 2 channel 
usb1.1 AI does better than that.

Len Ovens

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