Hi Samuel,Since this an an Open Source project we're not really worried about "conflict" with our GMSK modem, we expect to have many modems. Actually, that developer may have gotten busy as he's not posted to the list for a while. Our assumption has been that the VHF/UHF radios would be purpose-built, and I am hoping to show a prototype portable VHF/UHF SDR at Hamvention. GMSK might be most appropriate for that. But a mode that can be carried over FM radio audio is of course useful. I'd encourage you to contribute the code under an Open Source license.
Thanks
Bruce
On 02/10/2013 10:38 AM, Samuel Hunt wrote:
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
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