[linux-audio-dev] Re: MIDI over WiFi

[lazzaro]

On Mar 31, 2007, at 5:26 AM,  Jens M Andreasen wrote:

> What I wonder is; wouldn't it be possible to bypass this USB radio
> transmitter/recaiver dongle-thingie and fast forward to the wireless
> capabilities already built in to most of modern portable devices sold
> today? Hey, even the OLPC aimed at third world children have this
> capability ...


If you access to two OS X machines for a few minutes, run the
Network MIDI Driver over Airport (Network MIDI Driver described here:

http://www.soundonsound.com/sos/jul05/articles/tiger.htm#3

You'll see it works OK, even with the 1-2% packet loss that the IP
layer sees on a typical WiFi network.  Apple's implementation uses
IETF RFC 4695 (a.k.a. RTP MIDI) as the transport layer, which
includes a resiliency system (the recovery journal) for handling
an arbitrary number of lost packets with only transient artifacts.

More on RTP MIDI here:

http://www.cs.berkeley.edu/~lazzaro/rtpmidi/index.html

Note that there are actually third-party products now compatible
with Apple's protocol, although these products are for wired networks.
And, last time I checked didn't implement the recovery journal
part of the RTP MIDI (and so can't be trusted over switches that
lose packets -- although my info on the product might be out of date):

http://www.kiss-box.com/products.pdf


> It kind of puzzles me that this is not happening already ...


I haven't looked into the issue in detail, but for my own use wireless
only makes sense if I don't have to be constantly worrying about
the battery life of the device.  At the moment, what I see in
the state of the art in portable WiFi chips -- the chip in the Sony
PSP and the chip in the Microsoft Zune -- is not too encouraging
in this regard.  But hopefully in a few generations of chip designs
this will get better.  This review:

http://emusician.com/midi/emusic_maudio_midair/

make the point well of how limiting the battery life can be for
a MIDI wireless controller right now.


---
John Lazzaro
http://www.cs.berkeley.edu/~lazzaro
lazzaro [at] cs [dot] berkeley [dot] edu
---