AOO is a lightweight and flexible peer-to-peer audio streaming and messaging solution, using Open Sound Control 1 as the underlying transport protocol.
It is fundamentally connectionless and allows to send audio and messages in real time and on demand between arbitrary network endpoints.
The C/C++ library can be easily embedded in host applications or plugins. It even runs on embedded devices, such as the ESP32. In addition, the project contains a Pure Data external, and soon also a SuperCollider extension.
For more information please visit https://aoo.iem.at.
WARNING: AOO is still alpha software, there are breaking changes between pre-releases!
-
Peer-to-peer audio networks (IPv4 and IPv6) of any topology with arbitrary ad-hoc connections.
-
Each IP endpoint can have multiple so-called 'sources' (= senders) and 'sinks' (= receivers).
-
Sources can send audio to several sinks. Conversely, sinks can receive from several sources, summing the signals at the output.
-
AOO is connectionless: streams can start/stop at any time, enabling a "message-based audio" approach.
-
AOO sinks can "invite" and "uninvite" sources, i.e. ask them to send resp. stop sending audio. The source may accept the (un)invitation or decline it.
-
Sources can send arbitrary messages with sample-accurate timestamps together with the audio data. For example, this may be used to embed control data, timing information or MIDI messages.
-
Sources and sinks can operate at different blocksizes and samplerates. Streams are resampled and reblocked automatically.
-
Clock differences between machines can be adjusted automatically with dynamic resampling.
-
Support for different audio codecs. Currently, only PCM (uncompressed) and Opus (compressed) are implemented, but additional codecs can be added with the codec plugin API.
-
Network jitter, packet reordering and packet loss are handled by the sink jitter buffer deals. The latency can be adjusted dynamically.
-
Sinks can ask sources to resend dropped packets.
-
Several diagnostic events about packet loss, resent packets, etc.
-
A connection server (
aooserver) facilitates peer-to-peer communication in local networks or over the public internet. -
AOO clients can send each other timestamped messages with optional reliable transmission.
The vision of AOO was first presented in 2009 by Winfried Ritsch together with a proof-of-concept for embedded devices. In 2010 it has been implemented by Wolfgang Jäger as a library (v1.0-b2) with externals for Pure Data (Pd) 2, but its practical use remained limited. AOO 1.0 is the topic of Winfried Ritsch's paper "towards message based audio systems" which he presented at LAC 2014 3.
In 2020 AOO has been reimplemented from scratch by Christof Ressi. The first draft version has been developed in February 2020 for a network streaming project at Kunsthaus Graz with Bill Fontana, using an independent wireless network infrastructure FunkFeuer Graz 4. It was subsequently used for the Virtual Rehearsal Room project 5 which allowed musicians at the University of Arts Graz to rehearse and perform remotely during the early Covid pandemic. The first public pre-release of AOO 2.0 has been published in April 2020. Since then it has been used in several art projects and software applications.
aoo - AOO C/C++ library source code
cmake - CMake helper files
common - shared code
deps - dependencies
doc - documentation
doxygen - doxygen documentation
examples - examples
include - public headers
pd - Pd external
sc - SC extension
server - the aooserver command line program
tests - test suite
The aoo library is written in C++17 and provides a pure C API as well as a C++ API. The public API headers are contained in the include directory.
For build instructions please see INSTALL.md.
The C API may be used for creating bindings to other languages, such as Rust, Python, Java or C#.
NOTE:
In general, C++ does not have a standardized ABI. However, by following certain COM idioms, we provide portable C++ interfaces. This means you can use a pre-build version of the aoo shared library, even though it may have been built with a different compiler (version).
The library features four object classes:
-
AooSource- AOO source object, seeaoo_source.hppresp.aoo_source.h. -
AooSink- AOO sink object, seeaoo_sink.hppresp.aoo_sink.h. -
AooClient- AOO client object, seeaoo_client.hppresp.aoo_client.h. -
AooServer- AOO UDP hole punching server, seeaoo_server.hppresp.aoo_server.h.
Objects:
[aoo_send~] - send an AOO stream
[aoo_receive~] - receive one or more AOO streams
[aoo_client] - connect to AOO peers over the public internet or in a local network
[aoo_server] - AOO connection server
For documentation see the corresponding help patches.
The Pd external is available on Deken (in Pd -> Help -> "Find externals" search for "aoo".)
Classes/UGens:
AooSend - a UGen that sends an AOO stream
AooSendCtl - control an AooSend UGen
AooReceive- a UGen that receives on or more AOO streams
AooReceiveCtl - control an AooReceive UGen
AooClient - connect to AOO peers over the public internet or in a local network
AooServer - AOO connection server
... and many more.
See Guides/AOO_Introduction.schelp for a gentle introduction
and the corresponding help files for detailed documentation.
If you want to host your own (private or public) AOO server, you only have to run aooserver
on the command line or as a service and make sure that clients can connect to your machine.
Run aooserver -h to see all available options.