Why was AES67 Developed

MotiVATION

The scope of the AES initiative is on high performance networks which allow high quality (16 bit / 48 kHz and higher), high capacity (up to several hundred channels) and low latency (less than 10 milliseconds) digital audio transport. The level of network performance needed to meet these requirements is available on local area networks and is achievable on enterprise-scale networks. Besides RAVENNA, a number of networked audio systems have been developed to support high-performance media networking, but until now there were no recommendations for operating these systems in an interoperable manner. The aim of this initiative was to identify common approaches and protocols and to suggest and standardize means for interoperability between these systems.

 

For technical details visit the Resources page to download our Whitepaper and presentations on AES67.

Application

The standard is expected to be useful for distribution within broadcast, music production and post-production facilities as well as for commercial audio applications including fixed and touring live sound reinforcement

Task Group & Project status

An AES standards task group called SC-02-12-H was formed to develop an interoperability standard for high-performance professional digital audio IP networking. The project was designated AES-X192 and inaugurated in October 2010. The Task Group was chaired by Kevin Gross of AVA Networks, Boulder, Co., who is a highly-respected industry veteran on media networking (he was the inventor of the ground-breaking CobraNet technology). Since its inauguration at the end of 2010, the Task group membership list grew up to more than 100 individuals, representing a prestigious spectrum of companies and organizations from the professional audio community.  Through bi-weekly web conferences and several face-to-face meetings, the Task Group concluded on a 40+ page draft, which was published as the "AES67 standard for audio applications of networks - High-performance streaming audio-over-IP interoperability" on September 11th, 2013.

 

The Task Group continues to work under the name SC-02-12-M, maintaining and improving the standard and hosting plug-fests to verify interoperability among various implementations following the standard's rules. A first revision document including some minor corrections and amendments was released in 2015 (AES67-R-2015).

Standard "INgredients

To achieve a sound interoperability definition, AES67 addresses the following topics:

  • Synchronization – defines the mechanism for a common clock system
  • Media clocks – defines which media clocks have to be supported and how they are related to the common clock system
  • Transport – describes how media data is transported across the network
  • Encoding and streaming – describes the means in which audio is digitized and formatted into the sequence of packets that constitutes a stream
  • Stream description – required for connection management, specifies relevant stream information such as network addressing, encoding format and origination information
  • Connection management – the procedure and protocols used to establish a media stream connection between a sender and one or more receivers


RAVENNA & AES67

Since all relevant standard ingredients of AES67 are directly based on RAVENNA or are very similar to RAVENNA's operating principles, RAVENNA naturally fully supports interoperability as defined within AES67. However, since the RAVENNA technology framework is superior to the AES67 interoperability guidelines, AES67 can be seen as one of many possible operational profiles for RAVENNA. Other RAVENNA profiles can offer higher performance, better applicability to routed network environments or means of transporting different types of media.

OUTLOOK

Observing Task Group participation and contribution, it can be expected that several other existing IP-based solutions will be modified or enhanced to support AES67 in the future. Indeed, it is already starting to happen. This will open up the landscape of product diversity and widen the field of application for RAVENNA-enabled devices.

 

Limited interoperability can also be expected with devices compliant to the next revision of the EBU Tech 3326 protocol suite, which is currently work in progress in the EBU ACIP2 Work Group. This all will help to broaden the basis of acceptance for high-performance network-based media distribution systems like RAVENNA.

 

Just recently, the Video Services Forum has released a set of Technical Recommendations (namely VSF TR-03 and TR-04) which cover the transport of SDI content in elementary essence flows (i.e. seperate, but synchronized RTP streams for video, audio and ancillary data). AES67 has been chosen as the transport protocol for the elementary audio streams.