[LAU] MOTU AVB series sample rate issue, JACK, and PulseAudio

Be be.0 at gmx.com
Tue Sep 19 17:26:26 UTC 2017

On 09/19/2017 11:55 AM, Paul Davis wrote:
> On Tue, Sep 19, 2017 at 12:36 PM, Be <be.0 at gmx.com 
> <mailto:be.0 at gmx.com>> wrote:
>     So I have tried using JACK regularly with the PulseAudio to JACK
>     bridge. Unfortunately this has some quirks too. JACK won't start
>     unless I wait several seconds after plugging in the Ultralite AVB. I
> ​I've seen this and I just live with it. I change SR once in a blue 
> moon. It just isn't that important to me. ​ I suspect it really does 
> that the MOTU unit a long time to reset to a new SR. JACK will start 
> eventually.

I don't want to change sample rate either, but the device's sample rate 
changes when I don't want it to. When it starts up it defaults to 192 
kHz and there's also that quirkiness with PulseAudio trying to change 
the sample rate. Perhaps I could ask MOTU to have it set the same rate 
on startup to what it was on the last shutdown in a firmware update. 
That seems like it would be pretty easy for them to implement 
considering it has some persistent storage onboard.

>     Has anyone contacted MOTU about the sample rate switching issue?
>     Ideally they could make it just work when the computer tells the
>     audio interface to switch sample rates.
>     Also, has anyone contacted them about possibly changing the firmware
>     so the web interface is available over USB on Linux? 
> ​if you have an AVB unit, why bother with USB?​ My impression (which 
> could be wrong) was that it would work if you have the correct kernel 
> module loaded. I don't know which module that is.
Do you mean why bother with the web interface over USB? So I don't need 
a router to use the web interface at a gig. At home it's no problem to 
leave an Ethernet cable plugged in. I've tried plugging an Ethernet 
cable directly from the Ultralite AVB to my laptop but that doesn't 
work. I'm getting a new laptop soon and new laptops generally don't have 
space for RJ45 jacks anymore, so that wouldn't be an option.

AFAIK AVB is completely unsupported on Linux. Has something changed 
recently? Even if it is supported in software, doesn't it require a 
special high end NIC?

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