O2

O2 is a communication protocol and implementation for music systems that aims to replace Open Sound Control (OSC). Many computer musicians routinely deal with problems of interconnection in local area networks, unreliable message delivery, and clock synchronization. O2 solves these problems, offering named services, automatic network address discovery, clock synchronization, and a reliable message delivery option, as well as interoperability with existing OSC libraries and applications. Aside from these new features, O2 owes much of its design to OSC and is mostly compatible with and similar to OSC. O2 addresses the problems of inter-process communication with a minimum of complexity.

O2 now supports asynchronous sends, WebSockets, a simplified subset protocol O2lite, Bonjour/Avahi for discovery and service property lists.

More on O2

An informal demo/overview.

Bibliography.

Teaser video.

Building O2

O2 uses CMake. There are a lot of configuration options, so I recommend the CMake GUI (MacOS or Windows) or ccmake (Linux: in the o2 directory just run ccmake . and type h for help) to build either a project for Xcode or Visual Studio, or a Makefile for Linux (then on Linux, simply type make).

The default for O2 discovery is Bonjour/Avahi, so on Linux you need the avahi-client-dev package to be installed.

Using o2host

o2host is a simple command-line application that can serve as a host to o2lite processes (including browser-based applications using o2lite over websockets through o2ws.js (in o2/test/www/o2ws.js), and can also serve as a bridge between MIDI, OSC, and O2.

See doc/o2host.txt for more details on building and running o2host.

Documentation

O2 web pages with documentation

src/o2.h -- the O2 API and most Doxygen sources are here.

src/o2.cpp -- contains implementation details.

src/o2lite.h -- the O2lite API. O2lite connects to an O2 host to obtain O2 services with a very small implementation built using the O2 bridge protocol. o2lite.h is a particular implementation of the O2lite protocol for microcontrollers (e.g. ESP32).

src/o2lite.c -- contains implementation details for the "microcontroller with WIFI and Bonjour" implementation of O2lite.

doc/* -- most of these files contain early design notes. The "real" API is in src/o2.h, which is translated to docs/* by Doxygen. The final description of the implementation is described in src/o2.cpp. It is hard to keep the documentation consistent with the code, so I have kept original notes in doc/* for reference. Anything wrong or missing from src/o2.cpp should be considered a mistake, so doc/* should mostly be unnecessary.