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

• wget http://www.pogo.org.uk/~mark/trx/releases/trx-0.5.tar.gz
• sudo apt-get update
• sudo apt-get install libasound2-dev (gets alsa/asoundlib.h)
• sudo apt-get install opus-tools (trying to get opus/opus.h)
• sudo apt-get install ffmpeg (trying to get opus/opus.h)
• sudo apt-get install -y libopus-dev (get opus/opus.h)
• sudo apt-get install libortp-dev (get ortp/ortp.h)
• make

On transmit side, kept getting directory-not-found errors.

This helped:

https://github.com/eugenehp/trx/issues/3

try something like
 
sudo ./tx -d plughw:2,0 -h 239.0.0.1

I added a USB Logitech Audio “card” on the transmit side. Now it doesn't error. Receive side shows errors.

Try cat /proc/asound/devices to see the inserted Logitech Audio

[4/7/2020]