ocac

AES70/OCA device framework (for embedded devices) C99

WORK IN PROGRESS

AES70/Open Control Architecture (OCA) defines a standard for device control and connection management of (networked) audio devices and is ment to allow for vendor independent control interfaces.

This framework aims to provide a skeleton of the class structure and implementations of core functionalities to be integrated into devices.

The library core resides in directory src and likely will not require any modifications - although it can be configured using a provided ocacopts.h file. The class structure (or skeleton) resides in directory impl and requires customization to interface with a device's architecture; class data members can be made use of or, if preferred, just the class methods that thus would act like protocol callbacks.

For every target platform some basic functionality must be implemented, also see interfaces in src/include/ocac/host/.

See directory docs for further documentation of AES70 ..

Very short and simple intro to AES70

AES70 is an object-oriented protocol which means that it more or less works like a remote API or RPC framework with a predefined basic class structure for common use cases but allows for custom derivations. More precisely speaking, any command targets specific objects and specific functions thereof.

The predefined classes cover a wide range of necessary interfaces like security, network, firmware or power managers and possible objects like actuators and sensors. Somewhat with networked audio devices in mind it entails interfaces for clock and signal/stream management amongst others, structures suitable for DSP architectures (object matrices) and has many datatypes relating to audio metrics.

As a major feature aside from a command interface it also provides an (optional) subscription mechanism for events, (typically) data change events.

The currently specified protocol interfaces use either UDP (suggested for small, non-critical devices), TCP, secure TCP (TLS), and websockets.

At this time the standard does not suggest any means of service description or device categorization.

Service Discovery

For discovery of AES70 devices common mDNS service discovery is used.

Protocol	Service name	Text record data
TCP	_oca._tcp	txtvers=1 [1] protovers=V [2]
Secure TCP (TLS)	_ocasec._tcp	txtvers=1 protovers=V
UDP	_oca._udp	txtvers=1 protovers=V
Websockets	_ocaws._tcp	txtvers=1 protovers=V, optional: path=XYZ [3]

1. OCA service registration version
2. decimal AES70 version as specified in the device's OcaDeviceManager object
3. base path or websocket, if missing / is assumed

Also see header src/include/ocac/mdns.h.

Resources & Related

• AES Standard Models
• AES70-1-2018 (Part1: Framework (OCF))
• AES70-2-2018 (Part2: Class structure (OCC)
• AES70-3-2018 (Part3: Protocol for IP Networks (OCP1))
• OCA Alliance docs
• Official Tools and Demos CPP Implementation
• More on github

In the future ANEMAN - a free connection management tool - is ment to support AES70 and would seem promising.