Monday, August 3, 2015

DMR <-> SIP Translation

When I first got interested in D-Star, there were some discussions on building a D-Star to SIP bridge.

This was back in 2011, now DMR seems to be taking off as I just wrote in my last blog entry titled AMBE proxy.  Once again that nasty AMBE problem?

However Trbonet ( software dispatch thingy does allow you to dispatch from a PC.  So unless this software has some DVSI/AMBE licenseed code in it, there must be a way to address both sides of the AMBE vocoder in the Mototrbo repeater and or radio.  If there is a way to address the input side of the AMBE+2 vocoder in the radio, then you can jack the audio in that way, instead of through a bastardized speaker mic (as an analog hack)

There are a number of interesting DMR related projects on gihub.    The first we stated to play with locally was KD8EYF's TRBO-NET perl scripts:

Showing some interactive text based commands sent from a DMR portable, and the replies from the KD8EYF powered information gateway. Weather reports, sending APRS messages, last heard status of a station, etc.

DMR does actually seem more well suited for a SIP to private call bridge.  D-Star really has no way to know when the call ended to be able to tear down the SIP connection.  It also has no real way to know if a particular D-Star radio is even on.  DMR on the other hand can do all this.

Other ideas:   When mobile it might be nice to have the various responses to the quick texted queries  actually spoken with a text to speech engine.  And since your radio affiliates when you turn it on, maybe even custom repeater greetings/reminders.

When you try and send a text to someone who doesn't have their radio on, obliviously that times out.  In theory it should be possible to see there isn't a reply happening and have server accept the message on their behalf, and when that server sees the user next affiliate, send the message to them then.  (Much like how it works in the cellular world)

The same could apply to a private call that isn't being acknowledged.  The server recognizes this and asks using a text to speech voice if you'd like to leave them a message.  Again playing the message to the user it was original intended for when they next turn on their radio and it phones home to the repeater.

This one seems to incorporate some audio related things: As of this writing, a large multi-national ham radio group has deployed this on TGID 9998 and dubbed it the "parrot". This application can listen to group and/or private voice transmissions and if you trasmit to the group and/or private IDs it's programmed to use, it will record the digital packet stream and then re-play it back. Handy for listening to your audio to see what you actually sound like on the air


Tutorial for Setup of Hytera Phone Patch via SIP: