17 Oct
2018
17 Oct
'18
11:23 p.m.
On 10/17/2018 07:31 AM, Paul Davis wrote:
On Wed, Oct 17, 2018 at 2:28 AM Fernando
Lopez-Lezcano
<nando(a)ccrma.stanford.edu <mailto:nando@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
for).
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.