Eric- > ----- Start Original Message ----- > Sent: Wed, 19 Mar 2008 23:29:57 -0400 > From: "David I. Emery" <[EMAIL PROTECTED]> > To: Rick Parrish <[EMAIL PROTECTED]> > 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 > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio