ST 2110 Archives – Page 8 of 34 – The Broadcast Knowledge

Video: Keeping Time with PTP

Posted on 23rd October 2020 by Russell Trafford-Jones

The audio world has been using PTP for years, but now there is renewed interest thanks to its inclusion in SMPTE ST 2110. Replacing the black and burst timing signal (and for those that used it, TLS), PTP changes the way we distribute time. B&B was a waterfall distribution, PTP is a bi-directional conversation which, as a system, needs to be monitored and should be actively maintained.

Michael Waidson from Telestream (who now own Tektronix) brings us the foundational basics of PTP as well as tips and tricks to troubleshoot your PTP system. He starts by explaining. the types of messages which are exchanged between the clock and the device as well as why all these different messages are necessary. We see that we can set the frequency at which the announce, sync and follow-up messages. The sync and follow-up messages actually contain the time. When a device receives one of these messages, it needs to respond with a ‘delay request’ in order to work out how much of a delay there is between it and the grand master clock. This will result in it receiving a delay response. On top of these basic messages, there is a periodic management message which can contain further information such as daylight savings time or drop-frame information.

Michael moves on to looking at troubleshooting highlighting the four main numbers to check: The domain value, grandmaster ID, message rates and the communication mode. PTP is a global standard used in many industries. To make PTP most useful to the broadcast industry, SMPTE ST 2059 defines values to use for message repetition (4 per second for announce messages, 8 for sync, delay request and delay response). ST 2059 also defines how devices can determine the phase of any broadcast signal for any given time which is the fundamental link needed to ensure all devices keep synchronicity.

Another good tip from Michael is if you see the grandmaster MAC changing between the grandmasters on the system, this indicates it’s no receiving any announce messages so is initiating the Best Master Clock Algorithm (BMCA) and trying the next grandmaster. Some PTP monitoring equipment including from Meinberg and from Telestream can show the phase lag of the PTP timing as well as the delay between the primary and secondary grandmaster – the lower the better.

A talk on PTP can’t avoid mentioning boundary clocks and transparent switches. Boundary clocks take on much of the two-way traffic in PTP protecting the grandmasters from having to speak directly to all the, potentially, thousands of devices. Transparent switches, simply update the time announcements with the delay for the message to move through the switch. Whilst this is useful in keeping the timing accurate, it provides no protection for the grandmasters. He finishes video ends with a look at how to check PTP messages on the switch.

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Speakers

Michael Waidson
Application Engineer
Telestream (formerly Tektronix)

Video: IP Media Networks for Live Production

Posted on 20th October 2020 by Russell Trafford-Jones

Building and controlling a network for SMPTE ST 2110 go hand in hand when it comes to planning an installation. As ST 2110 delivers all media essences separately, networks can easily end up carrying tens of thousands of flows emphasising the need for efficient network design and having a full understanding of the paths your media are using.

This video is co-presented by Nevion and Arista and starts by observing that the traditional difference between a LAN and WAN is being eroded leading as WANs get faster and better, we find that we can now deliver multi-location broadcast facilities which act similarly to if everything was co-located. Moreover, introduces Martin Walbum Media Function virtualisation which is enabled by network-connected equipment allowing for shared processing and shared control. For instance, it’s now possible to house all equipment in a datacentre and allow this to be used remotely maximising the utilisation of the equipment allowing a broadcaster to maximise the value of its purchases and minimise costs.

Arista’s Gerard Phillips takes a look at SDI systems to understand how we expect IP systems to behave and what we expect them to do. The system needs to deliver high throughput, instantaneous switching with low latency and no tolerance for failure. In order to do this, not only do we need to get the right software but to deliver the resilience we need, the network needs the correct architecture. Gerard takes us through the different options starting with a typical, flat, layer 2 networks and working up to leaf and spine along with a treatment of red, blue and purple networks.

Gerard recently did a deep dive on network design for live production for the IET. Take a look for much more detail on how to architect a network for uncompressed media.

Martin then looks at the need for orchestration. Broadcasters expect to deliver systems with, preferably, no downtime. As such, we’ve seen that network elements are typically duplicated as is the traffic which is delivered over two paths and SMPTE ST 2022-7. If you want to take something out of use for planned maintenance, it’s best to do that in a planned, ordered, way meaning you migrate flows away from it until it’s no longer in-circuit. Software-Defined Networks (SDNs), do exactly that. Martin walks us through the pros and cons of managing your network with IGMP and SDN. Gerard’s previous talk also looks at this in detail.

The video finishes with a look at which Arista switches can be used for media and a look at how Arista and Nevion implemented an ST 2110 network at Swiss broadcaster, tpc. This case study is presented in longer form in this video from the IP Showcase.

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Speakers

	Gerard Phillips Systems Engineer, Arista
	Martin Walbum Senior Vice President of Solution Strategy, Nevion

Video: Is IP Really Better than SDI?

Posted on 29th September 2020 by Russell Trafford-Jones

Is SDI so bad? With the industry as a whole avidly discussing and developing IP technology, all the talk of the benefits of IP can seem like a dismissal of SDI. SDI served the broadcast industry very well for decades, so what’s suddenly so wrong with it? Of course, SDI still has a place and even some benefits over IP. Whilst IP is definitely a great technology to take the industry forward, there’s nothing wrong with using SDI in the right place.

Ed Calverley from Q3Media takes an honest look at the pros and cons of SDI. Not afraid to explain where SDI fits better than IP, this is a very valuable video for anyone who has to choose technology for a small or medium project. Whilst many large projects, nowadays, are best done in IP, Ed looks at why that is and, perhaps more importantly, what’s tricky about making it work, highlighting the differences doing the same project in SDI.

This video is the next in IET Media’s series of educational videos and follows on nicely from Gerard Phillips’ talk on Network Design for uncompressed media. Here, Ed recaps the reasons SDI has been so successful and universally accepted in the broadcast industry as well as looking at SDI routing. This is essential to understand the differences when we move to IP in terms of benefits and compromises.

SDI is a unidirectional technology, something which makes it pleasantly simple, but at scale makes life difficult in terms of cabling. Not only is it unidirectional, but it can only really carry one video at a time. Before IP, this didn’t seem to be much of a restriction, but as densities have increased, cabling was often one limiting factor on the size of equipment – not unlike the reason 3.5mm audio jacks have started to disappear from some phones. Moreover, anyone who’s had to plan an expansion of an SDI router, adding a second one, has come across the vast complexity of doing so. Physically it can be very challenging, it will involve using tie-lines which come with a whole management overhead in and of themselves as well as taking up much valuable I/O which could have been used for new inputs and outputs, but are required for tying the routers together. Ed uses a number of animations to show how IP significantly improves media routing,

In the second part of the video, we start to look at the pros and cons of key topics including latency, routing behaviour, virtual routing, bandwidth management, UHD and PTP. With all this said, Ed concludes that IP is definitely the future for the industry, but on a project-by-project basis, we shouldn’t dismiss the advantages that do exist of SDI as it could well be the right option.

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Speakers

	Ed Calverley Trainer & Consultant Q3Media.co.uk
	Moderator: Russell Trafford-Jones Exec Member, IET Media Technical Network Editor, The Broadcast Knowledge Manager, Services & Support, Techex

Video: Progress Update for the ST 2110 WAN VSF Activity Group

Posted on 25th September 2020 by Russell Trafford-Jones

Is SMPTE ST 2110 suitable for inter-site connectivity over the WAN? ST 2110 is moving past the early adopter phase with more and more installations and OB vans bringing 2110 into daily use but today, each site works independently. What if we could maintain a 2110 environment between sites. There are a number of challenges still to be overcome and moving a large number of essence flows long distances and between PTP time domains is one of them.

Nevion’s Andy Rayner is chair of the VSF Activity Group looking into transporting SMPTE ST 2110 over WAN and is here to give an update on the work in progress which started 18 months ago. The presentation looks at how to move media between locations which has been the primary focus to date. It then discusses how control over which media are shared will be handled as this is a new aspect to the work. Andy starts by outlining the protection offered in the scheme which supports both 2022-7 and FEC then explains that though FEC is valuable for single links where 2022-7 isn’t viable, only some of the possible ST 2022-5 FEC configurations are supported, in part, to keep latency low.

The headline to carrying 2110 over the WAN is that it will be done over a trunk. GRE is a widely used Cisco trunking technology. Trunking, also known as tunnelling, is a technique of carrying ‘private’ traffic over a network such that a device sending into the trunk doesn’t see any of the infrastructures between the entrance and the exit. It allows, for instance, IPv6 traffic to be carried over IPv4 equipment where the v4 equipment has no idea about the v6 data since it’s been wrapped in a v4 envelope. Similarly, the ipv6 equipment has no idea that the ipv6 data is being wrapped and carried by routers which don’t understand ipv6 since the wrapping and unwrapping of the data is done transparently at the handoff.

In the context of SMPTE ST 2110, a trunk allows one port to be used to create a single connection to the destination, yet carry many individual media streams within. This has the big benefit of simplifying the inter-site connectivity at the IT level, but importantly also means that the single connection is quite high bandwidth. When FEC is applied to a connection, the latency introduced increases as the bit rate reduces. Since ST 2110 carries audio and metadata separately, an FEC-protected stream would have variable latency depending on the type of the of traffic. Bundling them in to one large data stream allows FEC to be applied once and all traffic then suffers the same latency increase. The third reason is to ensure all essences take the same network path. If each connection was separate, it would be possible for some to be routed on a physically different route and therefore be subject to a different latency.

Entering the last part of the talk, Andy switches gears to talk about how site A can control streams in site B. The answer is that it doesn’t ‘control’, rather there is the concept of requesting streams. Site A will declare what is available and site B can state what it would like to connect to and when. In response, site A can accept and promise to have those sources available to the WAN interface at the right time. When the time is right, they are released over the WAN. This protects the WAN connectivity from being filled with media which isn’t actually being used. These exchanges are mediated and carried out with NMOS IS-04 an IS-05.

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Speakers

	Andy Rayner Chief Technologist, Nevion, Chair, WAN IP Activity Group, VSF
	Moderator: Wes Simpson Founder, LearnIPVideo.com Co-chair RIST Activity Group, VSF

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