I heard one of the guys on the net the other evening mention a new mode called FreeDATA. It sounded like FreeDV and, in fact, I though that was what he was talking about, but on listening further I found that it was, if not a new mode, a new development of an existing mode called codex 2.
You can download the software here: -
https://github.com/DJ2LS/FreeDATA
And find the Wiki here: -
I'll have a play with this and report back once I have worked out how to drive it.