I realize that changing the CODEC would be a breaking change, and DMR repeater/network operations wouldn't like it on their systems, but I would like to demonstrate that there is an alternative to using patent-encumbered CODECs.
While I have been able to compile the OpenGD77 code, and I've located where it calls the CODEC, I don't know enough about codec2 to do the integration -- I'm really hoping that there are some gurus here that will help! -----Original Message----- From: Greg Troxel <g...@lexort.com> Sent: February 3, 2021 13:31 To: e...@jacksch.com Cc: freetel-codec2@lists.sourceforge.net Subject: Re: [Freetel-codec2] Codec2 and OpenGD77 I have long wondered about this sort of thing. A few thoughts: AIUI, DMR specifies lots of things and technically leaves hte codec unspecified. So essentially all "DMR digital voice" is properly called DMR/AMBE2, but because there isn't DMR/somethingelse, it's just called DMR. Using one of the codec2 variants that has a similar bitrate, and trying to leave everything in DMR that is specified the same seems sensible. Ideally DMR, not having specified a codec, would have some bits for a codec choice and some registry of bits but that would be too much like IETF. One could perhaps play games with some kind of CRC, basically saying that for codec2, one includes some specific bytes not in the frame before the frame when calculating the CRC, so that DMR/AMBE2 nodes would drop the bits, and DMR/codec2 nodes receive them. But I think it needs to pass a regular DMR repeater, so it is fairly likely such schemes will not work. Once you have two such radios, they should be able to talk simplex. Probably, they can talk through a DMR repeater, because AIUI those just retransmit the codec bits even though they demod the digital channel. And you could probably even talk across a network but not across familes that require transcoding (perhaps DMR/DSTAR currnetly requires AMBE2/AMBE transcoding). This raises the issue that DMR repeater operators might not like this. But of course with your own, or permission, it seems good. I've also wondered about DSTAR with codec2, but not gotten anywhere near to really thinking about it. I don't think the M17 project is a good reason to refrain from doing this if you feel like doing it. I am a fan of M17, but I don't think it's good for the community to prune things off too aggressively. So far I have declined to get a DMR radio because I don't want to run a proprietary protocol. If this works I might reconsider. 73 de n1dam _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
