Hi Kristoff, OK - so you are suggesting we could test a Codec 2 Digital Voice mode over using DSTAR in data mode? Hmmm, interesting.
Couple of possibilities. I guess people with DSTAR radios already have an interest in DV. So I guess anyone with a DSTAR radio and a laptop could then start using Codec 2 over the air. Then there is the approach you are using to run the "open" parts of DSTAR on a PC, integrated with Codec 2 and possibly on a low cost embedded board. Nice. A good start for adding FEC to Codec 2 is to test the effect of bit errors on each bit. Not all bits need protection. So strong codes can be used to protect the most sensitive bits, leaving some bits unprotected. Or if we have a big enough overhead, just use a rate 1/2 code but we will perhaps need to watch delay with some codes. A way to test bit-error sensitivity is to apply bit errors to each bit and evaluate the results, either subjectively (listening) or objectively (e.g. look at the SNR measure with errors in the LSP bits). Re fixed point port - a first step is to profile Codec 2 on a fixed point CPU. On a modern (500MHz) CPU we might find that just a few chunks of Codec 2 need to be ported to fixed point to get it running in real time. Cheers, David On Tue, 2011-11-01 at 19:28 +0100, Kristoff Bonne wrote: > Hi, > > > With the discussion on the 2100 bps candidate (and even lower) and > remarks on "testing it on-air" and "porting it to fix-point"; one of the > other discussion in this is related to what FEC to use. > > > I'm now working on porting the low-level software of G4KLX's pcrepeater > software to the friendlyarm mini2440, using just a USB audio-dongle (now > have "alpha" code for the D-STAR receiver running). Next step would be > to port this to a more powerfull board (like the pandaboard I also have) > and try to play around with a DV-variant using codec2). > > However, we do need a FEC protocol for that. > Are there FEC-protocols out there that are know not to be patended? > > > While writing the code for D-STAR, I've seen that a 1/2 FEC is used on > the header; a system that is apparently well documented (althou I do not > know its status). > > > If a 2.1 Kbps codec2 vocoder would work OK, the 4.8 Kbps of a VHF or UHF > DV-channel (using the same modulation parameters are D-STAR), would > allow for a 2/1 FEC on a 2.1 Kbps DV communication, and even have some > plave left for some other data (like syncronisation sequences). > > > > 73 > Kristoff - ON1ARF > > ------------------------------------------------------------------------------ > RSA® Conference 2012 > Save $700 by Nov 18 > Register now! > http://p.sf.net/sfu/rsa-sfdev2dev1 > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 ------------------------------------------------------------------------------ RSA® Conference 2012 Save $700 by Nov 18 Register now! http://p.sf.net/sfu/rsa-sfdev2dev1 _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
