M17 support

[sp5wwp]

I see NXDN and D-STAR might eventually be added. What about M17?

BTW: https://github.com/M17-Project/libm17

[jketterl]

NXDN and D-Star have been added already.

There hasn't really been a reason to implement another M17 decoder, m17-cxx-demod already took that job...

The reasons for this specific collection of decoders really goes back a few years. dsd did not offer decoding of "meta" information (DMR IDs, talkgroups), and had no support for YSF (I believe that has changed since then). Later on, mbelib dependencies needed to be removed, which is when dsd had to be removed completely and D-Star and NXDN were added.