AES67 for TV applications
audio essence will no longer “follow” video; it will be produced independently and dynamically assembled with metadata in the delivery of the final content, leading to new productivity schemes
B y its nature, the delivery of audio over IP infrastructure enables a distributed approach to handling audio streams. Without the need to rely on specific pieces of equipment, connected in a point-to-point model, broadcast and A/V facilities can realize much greater flexibility in routing, scheduling and managing audio streams. At the same time, audio-over-IP (AoIP) technologies simplify operations by allowing users to maintain synchronized content within complex multiple-source, multiple-destination workflows, and to manage metadata more effectively in terms of end-to-end content management and overall operations.
The AES67 standard
The AES67 standard for AoIP interoperability has evolved to the point that its performance is roughly comparable to that of MADI (AES10). With the industry increasingly focusing on system approaches, technology suppliers are addressing the “discovery gap” — which was deliberately omitted by the AES67 Working Group — by bridging stream discovery at the system level or in equipment. At the same time, vendors are pushing forward control and monitoring specifications, such as AES70, NMOS, and others, that further enhance system implementation of IP-based applications.
Audio essence will no longer “follow” video
The value of AoIP to mission critical IP-based audio distribution applications has been widely demonstrated, firstly outside the studio with the ACIP standard and now inside with AES67, and video broadcasters now are considering integrating AES67 into video-over-IP environments. In fact, through the Alliance for IP Media Solutions (AIMS), broadcast equipment and solution suppliers have come together to ensure an easier transition to IP by supporting VSF TR-03/-04, SMPTE 2022-6, and AES67 standards. With such an approach, audio essence will no longer “follow” video; it will be produced independently and dynamically assembled with metadata in the delivery of the final content, leading to new productivity schemes.
When broadcasters and A/V facilities take full advantage of IP infrastructure’s potential to increase their workflow productivity and flexibility far beyond simple gains such as reduced installation or transmission costs, they realize the optimal cost-benefit ratio. To do so, they must undertake solid IP infrastructure engineering, taking care to establish the multicast routing and PTP clock synchronization capabilities essential to mission critical broadcast operation.
Because audio also needs to be transmitted between facilities, several audio manufacturers propose “Media Gateway” solutions to bridge the LAN-synchronous and ultra-low latency AES67 to outside WANs, using the ACIP standard (EBU Tech 3326 and EBU Tech 3368). As an example, for countrywide studio-to-studio transport of AES/EBU, bit transparency provides for the highest PCM audio quality, Dolby E® and user bits transport. This application benefits from a dedicated QoS priority to transport PTP (Precision Time Protocol) clock reference at reasonable jitter on a managed WAN to accurately synchronize and phase audio at the sample level.
Another important use case consists of quickly installing a high-performance audio link between an AES67-enabled OB and an AES67-enabled venue, such as a theater or a stadium.
Since AES67 avoids both dedicated audio lines and costly hardware routing, all applications requiring flexibility, high performance (high channel count, precise time-alignment, low latency…) and low capex could benefit from AES67 interoperability.