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Re: [Discuss-gnuradio] DV Dongle - AMBE USB Device

From: Jeff Brower
Subject: Re: [Discuss-gnuradio] DV Dongle - AMBE USB Device
Date: Fri, 21 Mar 2008 23:20:36 -0600


> On Fri, Mar 21, 2008 at 04:23:00PM -0500, Rick Parrish wrote:
> > Jeff Brower wrote:
> > >All the standardized codecs that I know of, both ones with IP rights
> > >requirements and free ones, provide a reference design, typically
> > >fixed-point C code plus test vectors. I wonder why DVSI has not done
> > >the same.
> >
> > Perhaps the APCO and TIA committees did not require it when the
> > algorithm was published ten years ago.
>         I'm sure there was a bit of negotiation to get the best
> available vocoder technology and still preserve MIT's and DVSI's
> interests.   A full reference implementation in C would have been
> immediately employed by a variety of entities seeking to use the
> technology without the royalties and control DVSI and MIT wanted -
> anything published like that would have been impossible to control.

I agree, however it's very easy to get C source for G729 and other standard, 
used telephony codecs.  Yes, the G729 IP rights holders have battles to fight 
have had to take steps, such as consolidating and hiring a manager to handle
licensing and monitor illegal usage (Sipro).  I suspect with the advent of 
and other open source voice software, we're just waiting for a commercial outfit
who's made it big using open source and is handling 100,000s of channels at 
installations -- but without paying the required $10 per channel -- to get sued 
Sipro or their constituents, such as NEC and Siemens.
>         And history indicates they made a choice that served their
> interests well - radio hobby and hacker and far east clone (read
> "Chinese copy") use of P25 IMBE on a PC or in unlicensed hardware has
> not been a major issue for 10 years, though no doubt more than a few
> versions do exist outside of official DVSI licensees.   It is hard to
> believe this would have been true if the standard came with C source
> code... regardless of its license status and the formal restrictions on
> using it.

All good points.  But that's a path leading to non widespread popularity and
non-adoption into worldwide standardization bodies.

With MELPe, NSA has far more serious concerns than MIT + DVSI, with major 
security implications.  NSA has chosen a 2-prong approach:  a) provide access to
voice codec standards but hold the line on encryption, and b) carefully control 
has access to C source (approved agencies and commercial organizations within 
and PfP countries so far).  Unlike DVSI, reference code and test vectors are
important to them because so many disparate entities need to interoperate.

>         And this has no doubt made it easier to collect revenue from the
> hefty fees for licenses... if only because at least some major users
> haven't been as annoyed by hobby software  that scares their law
> enforcement customers away from P25 + IMBE as they no doubt would have
> been if unofficial copies of the C from the standard were available and
> in wide use in PC radio hobby software.  It is at least probably true
> that at least two common VHF/UHF non P25 digital radio systems that
> currently are not supported by readily purchased scanner would be
> readily monitorable by the general public if IMBE source was available,
> even with the  potential patent infringement involved - and I am sure
> this hasn't escaped notice.

Well, without encryption any voice codec is a clear channel if there is strong 
to build a product that can decode.  I have no doubt that a community / group 
could easily and quickly produce C source for IMBE if there were sufficient 
(profit, fame, beat Microsoft, etc).


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