ST 2059 Archives – Page 4 of 8 – The Broadcast Knowledge

PTP, Precision Time Protocol, underpins the recent uncompressed video and audio over IP standards. It takes over the role of facility-wide synchronisation from black and burst signals. So it’s no surprise that The Broadcast Bridge invited Meinberg to speak at their ‘Real World IP’ event exploring all aspects of video over IP.

David Boldt, head of software engineering at Meinberg, explains how you can accurately transmit time over a network. He summarises the way that PTP accounts for the time taken for messages to move from A to B. David covers different types of clock explaining the often-heard terms ‘boundary clock’ and ‘transparent clock’ exploring their pros and cons.

Unlike black and burst which is a distributed signal, PTP is a system with bi-directional communication which makes redundancy all the more critical and, in some ways, complicated. David talks about different ways to attack the main/reserve problem.

PTP is a cross-industry standard which needs to be interpreted by devices to map the PTP time into an understanding of how the signal should look in order for everything to be in time. SMPTE 2059 does this task which David cover.

PTP-over-WAN: David looks at a case study of delivering PTP over a WAN. Commonly assumed not practical by many, David shows how this was done without using a GPS antenna at the destination. To finish off the talk, there’s a teaser of the new features coming up in the backwards-compatible PTP Version 2.1 before a Q&A.

This is part of a series of videos from The Broadcast Bridge

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Speakers

Daniel Boldt
Head of Software Engineering
Meinberg

When it comes to IP, audio has always been ahead of video. Whilst audio often makes up for it in scale, its relatively low bandwidth requirements meant computing was up to the task of audio-over-IP long before uncompressed video-over-IP. Despite the early lead, audio-over-IP isn’t necessarily trivial. However, this talk aims to give you a heads up to the main hurdles so you can address them right from the beginning.

Matt Ward, Head of Video for UK-based Jigsaw24, starts this talk revising the reasons to go audio over IP (AoIP). The benefits vary for each company. For some, reducing cabling is a benefit, many are hoping it will be cheaper, for others achievable scale is key. Matt’s quick to point out the drawbacks we should be cautious of, not least of which are complexity and skill gaps.

Matt fast-tracks us to better installations by hitting a list of easy wins some of which are basic, but a disproportionately important as the project continues i.e. naming paths and devices and having IP addresses in logical groups. Others are more nuanced like ensuring cable performance. For CAT6 cabling, it’s easy to get companies to test each of your cables to ensure the cable and all terminations are still working at peak performance.

Planning your timing system is highlighted as next on the road to success with smaller facilities more susceptible to problems if they only have one clock. But any facility has to be carefully considered and Matt points out that the Best Master Clock Algorithm (BMCA).

Network considerations are the final stop on the tour, underlining that audio doesn’t have to run in its own network as long as QoS is used to maintain performance. Matt details his reasons to keep Spanning Tree Protocol off, unless you explicitly know that you need it on. The talk finishes by discussing multicast distribution and IGMP snooping.

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Speaker

Matt Ward
Head of Audio,
Jigsaw24

It’s being closely watched throughout the industry, a long-in-the-making project to deploy SMPTE ST 2110 throughout a fully green-field development. Its failure would be a big setback for the push to a completely network-based broadcast workflow.

The BBC Cardiff Central Square project is nearing completion now and is a great example of the early-adopter approach to bringing cutting-edge, complex, large-scale projects to market. They chose a single principle vendor so that they could work closely in partnership at a time when the market for ST 2110 was very sparse. This gave them leverage over the product roadmap and allowed to the for the tight integration which would be required to bring this project to market.

Nowadays, the market for ST 2110 products continues to mature and whilst it has still quite a way to go, it has also come a long way in the past four years. Companies embarking similar projects now have a better choice of products and some may now feel they can start to pick ‘best of breed’ rather than taking the BBC approach. Whichever approach is taken there is still a lot to be gained by following and learning from the mistakes and successes of others. Fortunately, Mark Patrick, Lead Architect on the project is here to provide an update on the project.

Mark starts by giving and overview of the project, its scale and its aims. He presents the opportunities and challenges it presents and the key achievements and milestones passed to date.

Live IP has benefits and risks. Mark takes some time to explain the benefits of the flexibility and increasingly lower cost of the infrastructure and weighs them agains the the risks which include the continually developing standards and skills challenges

The progress overview names Grass Vally as the main vendor, control via BNCS having being designed and virtualised, ST 2110 network topology deployed and now the final commissioning and acceptance testing is in progress.

The media topology for the system uses an principal of an A and a B network plus a separate control network. It’s fundamentally a leaf and spine network and Mark shows how this links in to both the Grass Valley equipment but also the audio equipment via Dante and AES67. Mark takes some time to discuss the separate networks they’ve deployed for the audio part of the project, driven by compatibility issues but also within the constraints of this project, it was better to separate the networks rather than address the changes necessary to force them together.

PTP timing is discussed with a nod to the fact that PTP design can be difficult and that it can be expensive too. NMOS issues are also actively being worked on and remains an outstanding issue in terms of getting enough vendors to support it, but also having compatible systems once an implementation is deployed. This has driven the BBC to use NMOS in a more limited way than desired and creating fall-back systems.

From this we can deduce, if it wasn’t already understood, that interoperability testing is a vital aspect of the project, but Mark explains that formalised testing (i.e. IT-style automated) is really important in creating a uniform way of ensuring problems have been fully addressed and there are no regressions. ST 2110 systems are complex and fault finding can be similarly complex and time consuming.

Mark leaves us by explaining what keeps him awake at night which includes items such as lack of available test equipment, lack of single-stream UHD support and NMOS which leads him to a few comments on ST 2110 readiness such as the need for vendors to put much more effort into configuration and management tools.

Anyone with an interest in IP in broadcast will be very grateful at Mark’s, and the BBC’s, willingness to share the project’s successes and challenges in such a constructive way.

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Speaker

Mark Patrick
Lead Architect,
BBC Major Projects Infrastructure

As the industry gains more and more experience in implementing PTP, AKA SMPTE 2059-2, timing systems it’s natural to share the experiences so we can all find the best way to get the job done.

Thomas Kernen is a staff architect at Mellanox with plenty of experience under his belt regarding PTP so he’s come to the IP Showcase at IBC 2019 to explain.

The talk starts by discussing what good timing actually is and acknowledging everyone’s enthusiasm going into a project for a well designed, fully functioning system. But, importantly, Thomas then looks at a number of real-world restrictions that come into projects which compromise our ability to deliver a perfect system.

Next Thomas looks at aspects of a timing strategy to be careful of. The timing strategy outlines how the timing of your system is going to work, whether that is message rates or managing hierarchy amongst many other possibilities.

The network design itself, of course, has an important impact on your system. This starts at the basics of whether you build a network which is, itself, PTP aware. In general, Thomas says, it should be PTP aware. However, for smaller networks, it may be practical to use without.

Security gets examined next, talking about using encrypted transports, access control lists, ensuring protect interfaces etc. with the aim of preventing unintended access, removing the ability to access physically – much of this is standard IT security, but it’s so often ignored that it’s important to point it out.

PTP is a system, it’s not a signal like B&B so monitoring is important. How will you know the health of your PTP distribution? You need to monitor on the network side, from the point of view of the deices themselves but also analyse the timing signals themselves, for instance, by comparing the timing signals between the main and reserve.

Finally, Thomas warns about designing redundancy systems since “Redundancy in PTP doesn’t exist.” and then finishes with some notes on properly completing a PTP project.

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Speaker