Hi all. I have for some time been looking for an alternative to the "AMBE" type vocoders which seem to dominate the low bitrate arena. Having found Codec2, I am very impressed with the quality. Being open source is the main interest, however.
I have had much experience with VHF/UHF data, and have devised systems for RTK (Differential GPS), which is in use by one of the top 5 Agricultural manufacturers. I also have much experience with VoIP, having developed my own higher bitrate (8kbit/sec) codec. I have been thinking for a long time about a project similar to this, but have never had the time nor the inclination to get involved with developing low bitrate codecs. However, I have a great deal of interest in the lower bitrate data side of things. I notice that you have already started on a VHF modem, which appears to use GMSK. I guess you have selected GMSK because at 2400 baud it would permit 6.25khz channel spacing? I have always been more of a fan of FFSK, particularly 2400 baud, because it readily passes through existing transmitters, receivers, repeaters, etc, without any real modification, and seems to be more forgiving than GMSK. I also have written my own Windows 2400 baud FFSK modem, with error correction, etc, for other projects, and this could probably be easily interfaced to the Windows Codec2 DLL. I also have experience with PIC programming, and see huge potential with this codec ported out to a DSPIC, with a modem on the end. I make PCB boards, etc, and own a commercial production facility, so would also be interested in looking into porting to DSPIC and making a nice little PCB to go into radios to retro-convert them to digital. Anyway, I do not know if any of this is of any interest to anyone on the list. I think what you are doing is great, and would be more than happy to look at making a 2400 baud FFSK Soundcard based interface for this Codec2. It would obviously work best with an external circuit to switch audio around. However, I suspect that this would conflict with the GMSK modem you are already working on? Sam Hunt ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
