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

From: Eric A. Cottrell
Subject: Re: [Discuss-gnuradio] DV Dongle - AMBE USB Device
Date: Thu, 20 Mar 2008 21:39:49 -0400
User-agent: Thunderbird (X11/20080226)

Jeff Brower wrote:

----- 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).

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

Have you seen one of the IMBE dongle codec chips up close?  Is it a TI DSP, 
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 
or other equipment.  Just a dongle for GNU radio.


This picture of the prototype shows it is a TI chip.

The problem is it may be a ROM or protected Flash version of the DSP chip. I paid for a AMBE codec so I do not want to destroy the internal programming,

However this could be used for another project using a TI DSP for a MELPe dongle. The DV Dongle could be a defacto standard for external CODEC interfacing.

73 Eric

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