[linux-audio-user] Re: External interface with many inputs

[Paul Davis]

On Fri, 2005-09-16 at 19:34 -0400, Ross Vandegrift wrote:
> On Fri, Sep 16, 2005 at 05:41:49PM -0400, Lee Revell wrote:
> > Make sure to check the status of Firewire support too.  Last I heard the
> > freebob guys have some 1394 audio interfaces working.
> 
> Oh wow - any word on reverse engineering the MOTU stuff?  Years ago

reverse engineering MOTU stuff is basically impossible. and why bother
when they are free to release new versions that have large or small
design changes at any time?

> they already had pretty cool looking 8+ analog I/O firewire boxes that
> I sadly turned away from.

if you were using ieee1394 for audio "years ago" it was either mLAN or
some utterly proprietary 

> Google didn't turn up anything obvious ::-)

there are currently 3 ways that ieee1394 can be used with audio:
	
	a) proprietary protocol on top of ieee1394 (e.g. RME        
              Firewhatever, MOTU, RME hdsp)
        b) the BeBox chipset and protocol
        c) mLAN

b and c (and possibly (a) but how could we know?) are definitely based
on IEC61883, but have extensions to cover things that IEC61883 doesn't
cover. Bridge Co, the BeBox makers have apparently tried to feed their
extensions back to the IEC standards body. yamaha are still playing the
"our toy" game with mLAN for the most part.

there is no support for (a) on linux (the hdsp is supported because the
use of ieee1394 is transparent to the driver - it does not plug into a
generic ieee1394 interface). 

there is no (actively growing) support for (c) either, despite the fact
that yamaha keep saying they are OK about an open source mLAN
implementation. they still do not appear to have released info on the
parts of mLAN that are outside the IEC61883 specs, making any support
based on that standard pretty poor.

the freebox project supports all devices that use (b), and such devices
can also be physically chained to produce larger meta-devices. the
project has reported success on linux with a number of devices.

if you see ieee1394 h/w advertised, bug the advertiser to say which of
these technologies they use. forget linux - just tell them you are
interested in chaining the device with existing ieee1394 audio h/w that
you have, and you want to know if the advertised device supports it.

--p