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Brandmeister bridge to mumble

Stream Brandmeister DMR calls using the Simple External Application protocol. This connects a BrandMeister DMR talkgroup to a Mumble bot user, enableing people to listen to a DMR talkgroup without a radio.

Mumble is a free, open source, low latency, high quality voice chat application. It can handle massive amounts of concurrent users.

See this blogpost for a writeup.

What's the difference between this and brandmeister-dmr-opendmr?

This uses the Simple External Applications protocol, brandmeister-dmr-opendmr uses the Open DMR terminal protocol. For bridging purposes, the administrators have asked to use the Simple External Applications protocol instead of the protocol meant for running hotspots.

Can I also talk in Mumble and have the bridge send it to the Brandmeister network?

No: this is too easy to misconfigure so that unlicensed users could transmit, possibly breaking some laws while doing so.

Setup

The setup is considerably easier than my other software stack that uses the Open DMR protocol brandmeister-dmr-opendmr:

  1. Clone this repository with git clone --recurse-submodules -j8 https://github.com/redfast00/brandmeister-dmr-sea.git to make sure
  2. Copy the config file from config/config_example.json to config/config.json and fill in the required information. Note that you will have to ask the Brandmeister administrator of your country for a Simple External Application.
  3. Build the docker container with ./build.sh
  4. Start the docker container with ./start.sh

Software used

  • the tool that talks to the BrandMeister network was adapted from callrec
  • decode49to70.py is adapted from dmr_utils
  • the AMBE-decoder from the MD380-project

Legal (I'm not a lawyer)

The AMBE codec is still under patent until 2023-11-07. This means that using the AMBE decoder/encoder might not be legal where you live.

In my country (Belgium), the rights coming from patents don't apply for actions in the private sphere that are non-commercial (source). There are also laws prohibiting from doing any commercial actions on the amateur radio bands. The code that handles the AMBE encoding and decoding is also not in this repository: it is in the md380 tools repository. In this repository, I am only talking about how to use the md380 software, which is protected under free speech (I think, again, I'm not a lawyer).

If you want to be absolutely sure you're not infringing any patents, use an AMBE decoder USB dongle.