Digigram: Developing & Delivering Digital Content

By 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.

Digigram's expertise in digital and IP technologies, as well as the company's early involvement in the development of protocols and standards including EBU ACIP, AES67, and RAVENNA, enable it to offer AoIP solutions that address the specific challenges and requirements of media workflows.

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 including Digigram 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. (For example, the AES67-RAVENNA streams sourced by Digigram's LX-IP sound card may be routed by the Dante manager in the AES67 environment thanks to a basic software converter). 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.

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.

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. Digigram has outlined several best practices that help guide successful implementation.

In its AES 2016 Paris e-Brief, Digigram used traffic simulation and actual measurements on almost 800 audio channels with devices from different manufacturers to quantify a set of rules for ensuring the peaceful coexistence of AES67 AoIP traffic and standard network traffic such as web, massive video transfer, and corporate data. First, the company suggests that broadcasters and A/V facilities use the IGMP snooping protocol to distribute predictable bandwidth on a high number of streams. Second, it proposes that facilities activate QoS (Quality-of-Service) to limit disruption and avoid audio glitches. And finally, Digigram strongly recommends that facilities install PTP-enabled switches. Without PTP support, clock jitter on AES67 traffic becomes quite high above 100 audio channels.

To assist broadcasters and A/V facilities in establishing effective IP-based audio distribution using AES67, Digigram offers the LX-IP synchronous AoIP and MADI multichannel sound card. The LX-IP bridges professional PC audio software applications to the ultra-low latency, phase-accurate and high precision clock management of AES67 and RAVENNA AoIP networks.

Because audio also needs to be transmitted between facilities, Digigram proposes different "Media Gateway" solutions to bridge the LAN-synchronous and ultra-low latency AES67 to outside WANs, using the ACIP standard (EBU Tech 3326).

Thus, IQOYA *SERV/LINK supports studio audio I/Os (AES67/RAVENNA, AES/EBU, analog, MADI), to provide up to 128 full-duplex connections using the ACIP standard on managed networks. For countrywide, bit-transparent studio-to-studio transport of AES/EBU, IQOYA *LINK 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.

With the benefit of maturing standards and the availability of robust AES67-compatible AoIP products, the industry is equipped to explore many new possibilities in realizing more flexible, reliable, and efficient delivery of audio streams over IP networks.

www.digigram.com

This article is also available to read at BFV online here, page 28.

(JP/LM)