[LAD] USB2 audio?! (Re: Alesis AudioLink)

[Jonathan Woithe]

Hi

> On Wednesday 08 July 2009 17:43:47 Juhana Sadeharju wrote:
> > Why Linux does not support USB2 audio devices?
> > Where is the problem? (How can I help?)
> 
> Repeating the archive: For a rather long time, there was no usb2 audio 
> standard. Each device had its own proprietary protocoll only the vendors know. 
> Hard to support in linux. Now there is a standard. But no device actually uses 
> it because they all already have their own protocols. So in the end nothing 
> has changed.
> 
> And except from making the vendors publish their specs, there is nothing you 
> can do.

This is of course very close to the problems we had with firewire devices:
there were published standards but they weren't always used.  The difference
here was that some vendors *did* adopt the standard which made things a bit
easier.  Even so, most still utilised vendor-specific extensions (especially
for device control).

AFAIK FFADO got started through the cooperation of one or two vendors and as
momentum has built additional vendors have come on board to a greater or
lesser extent.  I expect something similar will have to happen for
professional USB2 audio devices to be generally supported under Linux.

Of course the other way around the problem is to do protocol analysis, but
this really is the "last resort".  However, in many ways this is harder on
USB because as I understand it you can't have two USB bus hosts (ie: two
PCs) connected to the same bus.  You can probably do it using virtualisation
so long as the virtualiser supports USB passthrough.  The kernel's usbmon
facility may then give access to the traffic as it flows.  For this to work
you'll need a pretty fast PC since you'll be running audio applications
under a virtualised environment - I'm not sure the required timing can be
met even on today's fastest hardware.  In any case, there will be a lot of
work involved in getting a start on this if vendor documentation is not
forthcoming.

I should add that from my point of view, drivers written without vendor
support are really to assist those moving to Linux from other platforms who
already have considerable investment in interfaces which they cannot or will
not replace just to switch platforms.  If considering the purchase of an
interface specifically for use under Linux I would encourage you to purchase
from a vendor who actively supports Linux - thereby giving them a reason to
keep doing so.

Regards
  jonathan