Source : https://github.com/knatterfunker/codecserver-softmbe

First, install openwebrx as usual. We desceribe how to compile and install codecserver-softmbe on Debian Linux and distributions derived from Debian (Raspbian, armbian, Ubuntu, Mint etc.). For other distributions, you can compile and install the project and the libmbe dependency using the standard cmake approach.

Install the build dependencies and download, build and install the libmbe dependency:

apt install git-core debhelper cmake libprotobuf-dev protobuf-compiler libcodecserver-dev
git clone https://github.com/szechyjs/mbelib.git
cd mbelib
dpkg-buildpackage
cd ..
sudo dpkg -i libmbe1_1.3.0_*.deb libmbe-dev_1.3.0_*.deb

Then, download, build and install codecserver-softmbe:

git clone https://github.com/knatterfunker/codecserver-softmbe.git
cd codecserver-softmbe
dpkg-buildpackage
cd ..
sudo dpkg -i codecserver-driver-softmbe_0.0.1_*.deb

Finally, add the following lines at the end of /etc/codecserver/codecserver.conf:

[device:softmbe]
driver=softmbe

Digital voice decode should now be available in openwebrx after restarting the openwebrx and codecserver services.