[LAU] MOTU AVB discussion from LAC

Max abonnements at revolwear.com
Sat Mar 30 00:56:38 CET 2019

Fernando Lopez-Lezcano discussed the pitfalls of using the MOTU AVB 
external audio interfaces with Linux in his paper [1] and also in the 
keynote at LAC-19.
Let's start another thread around this card.

Fernando mentioned that different firmwares expose different issues, but 
downgrading is possible. Issues are:
1. Channels are not persistent and swap around.
2. Total number of channels has been reduced in newer firmwares.
3. An endless card aquisition loop between Jack and Pulseaudio caused by 
the long time the card needs to switch sampling rate.
4. Seemingly erratic behavior, opening the device fails, fails again, 
again, then works suddenly.

I have a couple of questions and experiences.

Is there a table of the firmware versions somewhere (linuxaudio wiki?) 
which tell me which versions has which features (removed)?

Are all the Class Compliant models having the same quirks as listed 
above? For example the
MOTU UltraLite AVB versus the MOTU 624 AVB?

Is it possible to use the Thunderbolt port to connect the card to a 
Linux computer?

Why can't I tell ALSA to use only the first 2, 4 whatever channels of 
the device? I can only open the device if all channels are connected. Is 
this always like that or is that a limitation of MOTU's implementation?

On my laptop with only one USB bus, If I connected the  MOTU 624 AVB and 
then another high speed usb device, the computer could not connect the 
later, because the MOTU reserved all the bandwith for itself. Connecting 
the other device and then the MOTU worked.

[1] http://lac.linuxaudio.org/2019/doc/lopez.pdf


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