Evolving IP Standards

The earliest deployments of IP video transport began around 2001, when one large cable company sought ways of reducing the quantities of coax associated with the use of ASI for transporting video.

Although initially not standardised, the distribution of MPEG-2 Transport Streams (TS) began the transition to IP video. dB Broadcast became the UK's leading integrator and installer of encoding and compression systems, and by around 2007 they were installing and commissioning fewer ASI coax systems than IP based systems. This major shift meant the company had to develop internal expertise in video over IP, networking technology and, in particular, configuring IP switches.

In the period 2007–2011, SMPTE defined four standards for the transport of MPEG-2 TS over IP (SMPTE ST 2022-1:2007 to ST 2022-4:2011). In 2012 and 2013, SMPTE extended these with the addition of three new ST 2022 standards for the transport of 'high bitrate media signals' (uncompressed video) over IP networks (SMPTE ST 2022-5:2013, ST 2022-6:2012 and ST 2022-7:2011). ST 2022-5 is a standard method for providing forward error correction (FEC), ST 2022-6 is a standard method for the carriage of SDI over IP and ST 2022-7 is a standard method for seamless protection switching of ST 2022-6 streams.

Yet while these new standards would bring enhanced flexibility and demonstrable cost savings over the long term, the pace of change was presenting new challenges as the products, standards and skills necessary to realise this vision fully were not in place. This required workarounds and bespoke approaches – a challenge that dB Broadcast was uniquely placed to address.

For example, a global technology company chose dB as its partner to help design and implement its flagship London production facility for its content creators. Yet in 2016 when this project was undertaken, the move to IP was still at an early stage. One of the biggest challenges at this time was that IP video systems were transitioning from proof-of-concept (PoC) test systems to operational production facilities while many products were not yet interoperable using the SMPTE standards, or had not been tested 'at scale'. Consequently this project was successfully delivered using a proprietary solution for video, audio and metadata over IP and the use of IP infrastructure made this 4K equipped facility extremely versatile.

Also during 2015–16, dB Broadcast was working with industry suppliers to create PoC systems based on the emerging SMPTE ST 2022 suite of standards, and in 2017, dB delivered the first fully IP production centre in the UK based on SMPTE ST 2022-6 and -7, at a major new facility sited in the City of London.

It should be noted that all the of the ST 2022 media transport standards are related to the carriage of multiplexed data, that is video, audio and any metadata are all carried together on a single IP stream as shown below:

As the SDI payload is intended to carry video, audio and metadata, it is quite inflexible. If, for example, an audio mixing desk needed to access a stereo pair, it would have to receive the entire stream and de-embed the required pair. Although it is possible to send audio via separate flows using AES67, this is wasteful of bandwidth as the ST 2022-6 stream uses a constant bandwidth irrespective of whether embedded audio is carried or not.

To address these concerns, in 2015 the Video Services Forum (VSF) proposed TR-03, which separates the video, audio and metadata essence into discrete flows. By using separate flows, TR-03 avoided wasted bandwidth and offered greater flexibility to the production team by accessing only the flows they needed. In the case of the audio desk above, it would need to receive only the flow carrying the required stereo pair.

What the broadcast market needed was a single SMPTE standard that used the same basic principles as TR-03, and with the industry aligning around the Alliance for IP Media Solutions (AIMS) roadmap during 2016/17, that requirement resulted in the development of the new ST 2110 suite of standards.

ST 2110 is founded on TR-03 but goes much further in its ambitions. The core of the new suite is ST 2110-10 'System Timing and session description', with several other parts dealing with 'Uncompressed Active Video' (based on RFC 4175), 'PCM Audio' (based on AES67) and 'Ancillary Data' (based on ST291). The separate video and audio essence flow parts are derived from those specified by TR-03. The basic structure of these flows is shown below:

SMPTE ST 2110 offers all the flexibility and bandwidth advantages of essence-based media IP flows, with the reassurance that comes from a unified industry standard that ensures the same interoperability we have enjoyed with SDI for almost thirty years.

One of dB Broadcast's biggest challenges in seeking to implement emerging standards, such as SMTPE ST 2110 is that it may lead to interoperability challenges between different products, an issue that needs to be carefully managed by the system integrator.

To provide easier interoperability and configurability within IP networks, there has been a trend towards the use of Software Defined Networks (SDNs), which allow networks to be programmatically configured and managed. In the broadcast world, the AMWA Networked Media Open Specifications (NMOS) is a suite of open specifications that, amongst other capabilities, allows device discovery and registration (IS-04), connection management (IS-05) and network control (IS-06). Although NMOS is a work in progress, it will in time provide an open framework for the interoperable configuration and management of broadcast IP networks.

In the UK, the BBC is committing to these emerging standards and for its new BBC Wales headquarters currently being built in Central Square, Cardiff, the BBC have specified a facility based on the new SMPTE ST 2110 standards and AMWA NMOS IS04.

During 2018 and 2019 dB Broadcast will be working closely with customers and key IP video technology suppliers to deliver systems based on ST 2110. dB has extensive experience and capability in broadcast engineering, and already has a proven track record in implementing IP based systems based on emerging standards, and integrating best-of-breed software products from multiple suppliers.

Image: Simplified SMPTE ST 2110 IP Packet Format.

www.dbbroadcast.co.uk

This article also features in the December edition of Broadcast Film & Video.

(JP/LM)