[LAU] MOTU Ultralite AVB - possible to configure two connected devices without 430 EUR switch?

Fernando Lopez-Lezcano nando at ccrma.Stanford.EDU
Wed Oct 17 19:44:23 CEST 2018

On 10/17/2018 07:31 AM, Paul Davis wrote:
> On Wed, Oct 17, 2018 at 2:28 AM Fernando Lopez-Lezcano
> <nando at ccrma.stanford.edu <mailto:nando at ccrma.stanford.edu>> wrote:
>     I think that is the case, sorry. On exotic operating systems like OSX
>     there is a proxy in the driver that serves http through usb (I
>     think) so
>     you can access the configuration pages without an ethernet cable.
> It's much simpler than this, AFAIU. OS X and Windows have drivers for
> IP-over-USB (compared to the more normal IP-over-Ethernet or
> IP-over-Wifi). The MOTU box supports this on the other end too, so
> you're really just connecting entirely normally to the http server on
> the MOTU, but via IP-over-USB.

Ah, thanks for the clarification (the proxy thing was just speculation)

> There is some evidence of a Linux version of IP-over-USB but from what I
> could tell it isn't ready for use for this particular purpose.
>     WARNING: the latest versions of Motu AVB cards seem to break the class
>     compliant driver. The symptom is that on the receiving end (a Linux
>     computer running Jack) the channels seem to rotate in blocks of 8. So,
> I don't know how "latest" you mean. I bought mine well over a year ago,
> and it has had this behaviour since I bought it. I was not convinced
> that it was the MOTU's fault, or rather that it just need some USB audio
> quirk added to stop it from happening.

Well, "latest" actually is old old. For the 24ao/24ai/16A cards 1.2.8+ 
supported 64 channels over USB with the class compliant driver and 
worked fairly well, 1.2.9+ killed that feature (which was _added_ to the 
originally released firmware - that feature enabled me to use the card 
for my purposes, killing the feature made the card useless for me unless 
I downgraded). You might want to try 1.2.x in your card.

For the 1248 1.3.x has the "channels hop all over" feature, 1.2.8 fixes 
that. I don't exactly remember my quick test of the UltraLite AVB which 
I bought very recently (same issue), but I think I downgraded again to 
1.2.x to make it work - but that was a very quick test before a trip, 
and I gave up on using it, so my memory is fuzzy...

So, 1.3.x is bad, 1.2.8 good, 1.2.9 maybe good depending on your needs.

BTW, I went through all the hoops in Motu's site to report the drop of 
the "64 channels over USB2" feature as a bug. It took them a while to 
understand, but eventually they got it and said it was not coming back 
as it was causing them "problems". I never mentioned Linux by name but 
only spoke about the broken behavior in the class compliant driver (but 
anyone that knows a bit about audio would realize what was it being used 

Obviously they told me they still support 64 channels over USB2 using 
their proprietary driver (you can see their endpoints in a detailed 
lsusb)... Oh well.

As you say, maybe it is possible to add a quirk or whatever to make this 
work with the latest firmware (but in my case I do need 64 channels over 
USB2 so the latest firmware is a no-no). I'm not going to dive into the 
kernel either :-(

The real solution to all this (at least from my point of view) would be 
to get the full AVB stack working in Linux for a native connection to 
the AVB streams - and the Jack support needed to bring it to the Jack 
world. I'm forever meaning to do this but I suspect I will never have 
the time (some time ago I managed to get Linux to see the card and sync 
to it, but never even tried discovery and streaming). Still 24 hours in 
a day last time I checked...

To all that have seen this bug I strongly encourage you to waste some 
good time and report the bug in the class compliant driver to Motu. I 
don't know for a fact it is a bug in their firmware but it was working 
before and it is broken now.

-- Fernando

>Alas, the days of me diving into
> the kernel driver to figure out what is happening are long over.

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