Greetings, I would like to report that a DMR transceiver was implemented with SDR hardware and using Codec 2 as the audio payload.
The usual audio codec used in commercial DMR implementations is AMBE2+ at a bitrate of 2450 bits/second. The vocoder socket in each DMR TDMA frame (lasting 30 msec of 4FSK symbols) is transmitted every 60 msec and includes three encoded audio packets of 20 msec each for a total of 216 bits. I have replaced the audio payload with Codec 2 2400 bits/sec packets also consisting of 20 msec each. Some bits in the payload remain unused due to the small bitrate difference and could potentially be used for other in-band signalling. The audio transmission and reception was tested with MMDVM-based DMR repeaters, which allow other types of audio payload to be passed through if the DMR FID is not set to one of the ETSI or DMRA values. This is necessary because otherwise MMDVM will try to run AMBE FEC and clobber useful Codec 2 bits. I can provide other technical details if there is any interest in this. Adrian YO8RZZ _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
