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

[Jeff Brower]

Eric-

> ----- Start Original Message -----
> Sent: Wed, 19 Mar 2008 23:29:57 -0400
> From: "David I. Emery" <address@hidden>
> To: Rick Parrish <address@hidden>
> Subject: Re: [Discuss-gnuradio] DV Dongle - AMBE USB Device
> 
> > On Wed, Mar 19, 2008 at 07:38:13PM -0500, Rick Parrish wrote:
> > > Jeff Brower wrote:
> > > >If you're looking at low bitrate codecs for GNU radio, why use a
> > > >hardware (dongle)dependent solution? You might look at MELPe, which
> > > >provides 600, 1200, and 2400 bps,and can be implemented as a software
> > > >solution. MELPe is a US/NATO standard (STANAG4591). Common
> > > >applications are HF radio and L band satellite apps where bandwidth is
> > > >very limited.
> > > My interest is what is actually being used - which in the case of public
> > > safety communications is the P25 variant of IMBE. FWIW, a closed source
> > > PC hosted IMBE vocoder exists now.
> >
> >       Is this a DVSI licensed and publically available closed source
> > module or something "unofficial" or not generally available to the world
> > at large ?  It has obviously long been possible to recode some reverse
> > engineered DSP chip based IMBE implemenation into C++ source code for
> > Wintel/Unix/BSD use, but this would not be free of license and patent
> > issues... and could not be made part of an open sourced project or
> > product without a DVSI deal (and it appears they don't see this as in
> > their interest).
> Hello,
> 
> In the case of the DV Dongle they buy the DVSI chips and designed a USB
> interface to connect to a PC.  DVSI gets paid for their work.  It is a
> neat solution for the problem of providing PC and Network support for
> D-Star.  The open source part is the interface to the CODEC chip.  It
> is similar to the MadWiFi drivers where there is a closed source HAL
> provided by Atheros and the open source part is the interface of the
> HAL to the OS.  Not the best solution but otherwise there would be
> nothing.

Have you seen one of the IMBE dongle codec chips up close?  Is it a TI DSP, 
maybe
something like a TMS320VC5509, or similar?  DVSI typically uses TI DSPs.

I'm wondering, because IP rights issues for MELPe go away for 2400 bps rate if 
a TI
chip is used; TI will normally waive royalty fees in that case.  Maybe a similar
approach could be taken for MELPe, it would be cheap and not tied to a radio 
receiver
or other equipment.  Just a dongle for GNU radio.

-Jeff

> DVSI does make a PC solution for their licensees.  I have the APCO P25 Voice 
> Module for my WinRadio G305e and it is keyed to the radio serial number.
> 
> Because the DV Dongle has a published API I was able to see that it should be 
> possible to run the CODEC at different rates.  That is one area of 
> exploration I want to do.
> 
> I also want to see if the AMBE codec can be used on a IMBE stream.  I have 
> seen comments online that they are totally different yet I also see comments 
> from the TIA P25 group that the AMBE codec is an improvement over the IMBE 
> codec and it should be implemented by equipment makers.  This seems to 
> indicate that the stream format is the same at least at P25 rates.  I find 
> that new products of a company tend to be built on past products of the 
> company.  Companies tend not to throw out stuff that works if it still works 
> on the new products.  So the improvements could be in the quality of the 
> encoding and decoding rather than changes in stream formats.
> 
> 73 Eric
> 
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