[amsat-bb] Re: D-STAR experiment on Cubesat
kf6kyi at gmail.com
Sun Jun 8 22:59:03 PDT 2008
On Jun 8, 2008, at 9:18 PM, David Donaldson wrote:
> Do we think that anyone other then Icom will ever support the mode?
> love to experiment with it on the birds but until there is
> competition to
> drive the price down will that be possible.
> Maybe a GNU project?
Sadly, it's basically impossible to make a software version which
interacts with D-Star because of the fact that the vocoder they chose
to use is encumbered by patents. This is one of the principle
reasons that I can't generate any enthusiasm for D-Star, despite
having a number of interesting capabilities that would be useful for
The Wikipedia page sums it up pretty well:
D-STAR has been criticized for its use of a patented, closed-source
proprietary voice codec (AMBE).  Hams do not have access to the
detailed specification of this codec or the rights to implement it on
their own without buying a licensed product. Hams have a long
tradition of building, improving upon and experimenting with their own
radio designs. The modern digital age equivalent of this would be
designing and/or implementing codecs in software. Critics say the
proprietary nature of AMBE and its availability only in hardware form
(as ICs) discourages innovation. Even critics praise the openness of
the rest of the D-STAR standard which can be implemented freely. An
open-source replacement for the AMBE codec would resolve this issue.
The problem as I see it is that there really aren't a lot of choices
for low bitrate audio coders. LPC is of course a possibility, and is
free from intellectual property encumberments, but it makes everyone
sound like a speak n' spell. The speex codec is open, but doesn't
really work down into the 2400bps that we'd like to have. There
aren't a lot of other choices that I'm aware of. It sure would be
nice to find one though: with all the experimentation with SDR,
digital voice could be a no-cost addition to radios, and a rich
environment for experimentation.
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