From: Joel Koltner <[email protected]>
OK, but there's nothing wrong with extending the current protocol and calling
it D*Star+ or just "D*Star Compatible" or whatever.
It's looking more like it would be a competitor to AMBE in a seperate market,
vs overrunning it on the same radio (I.E. reprogramming IC-92ADs, etc.)
(I think he's intending for CODEC2 to be implemented in "whatever processor you
already have around" in your PC or radio anyway, though, so the cost is
effectively free. The AMBE chip is just a pre-programmed TI DSP, after all,
and pretty much any contemporary PC has plenty of CPU cycles around to
implement the algorithm; it's in the form of a chip so that it isn't just
pirated rampantly.)
Unless Alinco, Kenwood or another major radio manufacturer hopped on board,
it'd *have* to start as a "soundcard mode". The to-market cost of soundcards is
nil, compared to DSP chip burning and implementation, as in the case with
AMBE...
Heck, there are already some freely available CODECs out there anyway that seem
to perform pretty well (although weren't specifically designed for wireless
usage): Speex and the Skype-CODEC come to mind. (I'm not up on the specific
licenses, however -- they're "free as in beer" at least, though.)
David Rowe, VK5DGR was one of Speex's initial developers, so he's got a *lot*
of prior experience in the way of vocoder programming. However, Speex doesn't
like lossy mediums like radio. It does wonderfully over TCP/IP, but that's
because it's a LOSSLESS format.
Bruce Perens, K6BP notes on his site (www.codec2.org):
"existing Open Source codecs, like Speex, are designed for VoIP rather than an
imperfect radio link, and are not generally able to cope with single-bit
errors. Thus, they don't match the performance of AMBE over the air."
One thing to keep in mind is that, since most hams operate D*Star through
repeaters anyway, one approach here would be to have the *repeater* have both
AMBE and CODEC2 (or whatever) capabilities, and just translate between them
on-the-fly. (This approach is used with public service radio systems, since
there lots of different companies decided to build their own proprietary
protocols and used different CODECs as well.) I would wager that repeater
usage probably accounts for more than 90% of D*Star voice traffic, and getting
repeater builders to incorporate a backwards compatible radio into their system
(that has the same interface as the current Icom boxes) is nowhere near as
daunting as getting everyone with an HT or mobile D*Star rig to buy something
new.
Now THAT is a brilliant idea!! Of course, CODEC2 to AMBE simplex would be nil.
However you are quite correct - dual-codex repeaters would make the issue null!
Plus, it would translate to and from AMBE over the gateway - I LOVE this idea!
---Joel
KE7CDV
-73, KE7HQY
