[amsat-bb] Re: D-STAR experiment on Cubesat

Mark Vandewettering 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?   
> I'd
> 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?
> Dave
> Minnesota

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  
amateur radio.

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). [4] 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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