trx: Realtime audio over IP

Summary

trx is a simple toolset for broadcasting live audio. It is based on the Opus codec http://www.opus-codec.org/ and sends and receives encoded audio over IP networks.

It can be used for point-to-point audio links or multicast, eg. private transmitter links or audio distribution. In contrast to traditional streaming, high quality wideband audio (such as music) can be sent with low-latency and fast recovery from dropouts.

With quality audio hardware and wired ethernet, a total latency of no more than a few milliseconds is possible.

Dependencies

This is only for GNU/Linux systems. This program depends upon the following packages:

• ALSA
• oRTP
• Opus

Installing Dependencies from Debian Systems

# Install build tools
sudo apt install build-essential autoconf automake git autoconf-archive libtool make 
# Install dependencies
sudo apt install libortp-dev libopus-dev libbctoolbox-dev libasound2-dev libgpiod-dev

Installing Dependencies from Fedora Systems

TODO

Build

This is a GNU autotools based build system. To build:

autoreconf -vi
./configure
make

Run

This package contains an audio transmitter and receiver. The transmitter has an optional push-to-talk (PTT) capability. Both programs provide run-time help with the -h command line flag. To gain full perfromance, both programs will request that the program use the real-time scehduler and lock their processes within physical memory. Furthermore, the PTT capability depends upon /dev/input or GPIO. Therefore, they should run as root.

Example server using multicast on the non-routable local network:

sudo ./tx -h 224.0.0.17

Example receiver using multicast on the non-routable local network:

sudo ./rx -h 224.0.0.17

TODO

• [ ] Provide latency and jitter metrics
• [ ] Create unit tests
• [ ] Encrypt RTP payloads using SRTP or ZRTP
• [ ] Conjoin rx & tx into a single application
• [ ] Create Android and iOS apps
• [ ] Explore rnnnoise, echo cancellation and other codecs

Copyright

(C) Copyright 2020 Mark Hills mark@xwax.org

See the COPYING file for licensing terms.

Attribution

This software was obtained from the following URL:

http://www.pogo.org.uk/~mark/trx/