Opus compression audio for Godot

This is a low level operation of the opus library based on https://github.com/RevoluPowered/one-voip-godot-4/ with a VoIP-over-MQTT demo project.

Build instructions:

Nixos

The build system is defined by the flake.nix file

• makes a result directory that needs to be copied into addons

nix build cp result/addons/twovoip/*so addons/twovoip

• android version:

nix build .#android cp result/addons/twovoip/*so addons/twovoip

Make sure addons/twovoip/twovoip.gdextension point to these files:

Otherwise by hand

Since we've not got submodules here we need to first clone Opus and godot-cpp modules before building them

> git clone git@github.com:goatchurchprime/two-voip-godot-4.git
> cd two-voip-godot-4
> git clone git@github.com:godotengine/godot-cpp.git
> cd godot-cpp
> git checkout 48afa82f29354668c12cffaf6a2474dabfd395ed
> cd ..
> git clone git@github.com:xiph/opus.git
> cd opus
> git checkout c85499757c148fede8604cffa12454206b6138ba
> cmake -Bbuild -DCMAKE_POSITION_INDEPENDENT_CODE=ON
> cd build
> make
> cd ../..
> scons  (or python -m SCons on Windows)

For MAC see the instructions on the one-voip here: https://github.com/RevoluPowered/one-voip-godot-4/?tab=readme-ov-file#mac