Wes Simpson Archives – The Broadcast Knowledge

Video: IP Systems – The Big Picture

Posted on 6th July 2021 by Russell Trafford-Jones

Early adopters of IP are benefiting from at least one of density, flexibility and scalability which are some of the promises of the technology. For OB vans, the ability to switch hundreds of feeds within only a couple rack units is incredibly useful, for others being able to quickly reconfigure a room is very valuable. So whilst IP isn’t yet right for everyone, those that have adopted it are getting from it benefits which SDI can’t deliver. Unfortunately, there are aspects of IP which are more complex than older technology. A playback machine plugged into an SDI router needed no configuration. However, the router and control system would need to be updated manually to say that a certain input was now a VT machine. In the IP world, the control system can discover the new device itself reducing manual intervention. In this situation, the machine also needs an IP configuration which can be done manually or automatically. If manual, this is more work than before. If automatic, this is another service that needs to be maintained and understood.

Just like the IT world is built on layers of protocols, standards and specifications, so is a modern broadcast workflow. And like the OSI model which helps break down networking into easy to understand, independent layers such as cabling (layer 1), point to point data links (layer 2), the network layer (3) etc. It’s useful to understand IP systems in a similar way as this helps reduce complexity. The ‘Networked Media System Big Picture’ is aimed at helping show how a professional IP media system is put together and how the different parts of it are linked – and how they are not linked. It allows a high-level view to help explain the concepts and enables you to add detail to explain how each and every protocol, standard and specification are used and their scope. The hope is that this diagram will aid everyone in your organisation to speak in a common language and support conversations with vendors and other partners to avoid misunderstandings.

Brad Gilmer takes us through the JT-NM’s diagram which shows that security is the bottom layer for the whole system meaning that security is all-encompassing and important to everything. Above the security layer is the monitoring layer. Naturally, if you can’t measure how the rest of your system is behaving, it’s very hard to understand what’s wrong. For lager systems, you’ll be wanting to aggregate the data and look for trends that may point to worsening performance. Brad explains that next are the control layer and the media & infrastructure layer. The media and infrastructure layer contains tools and infrastructure needed to create and transport professional media.

Towards the end of this video, Brad shows how the diagram can be filled in and highlighted to show, for instance, the work that AMWA has done with NMOS including work in progress. He also shows the parts of the system that are within the scope of the JT-NM TR 1001 document. These are just two examples of how to use the diagram to frame and focus discussions demonstrating the value of the work undertaken.

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Speaker

	Brad Gilmer Executive Director, Video Services Forum Executive Director, Advanced Media Workflow Association (AMWA)
	Moderator: Wes Simpson LearnIPVideo.com

Video: NMOS Technology: A User’s Perspective

Posted on 9th December 2020 by Russell Trafford-Jones

Bringing you discovery, registration, control, audio remapping, security and more, the open NMOS specifications from AMWA make using SMPTE’s ST 2110 practical. Most importantly, it makes using 2110 open meaning that different equipment can co-exist in the same ecosystem without being many different drivers being written to translate between each vendor.

Led by Wes Simpson this video talks about implementing NMOS from the perspective of a user, not a vendor with Willem Vermost> from Belgium’s public broadcaster, VRT. One drawback of IP-based solutions, they say early on, is that there are so many options on how to deploy. This potential choice paralysis goes hand in hand with trying to adapt to the new possibilities which come with the technologies. For instance, identifies Willem, says engineers need to adapt their thinking just to design differently knowing that, now, multiple signals can now flow in both directions down a cable. It’s not like SDI’s point to point, unidirectional nature.

Any large plant can get busy with thousands of signals. The question is how to control this massive number of streams; not forgetting that in 2110, an SDI video stream is split up into at least 4 streams. To help put this into perspective, Willem looks back to the original telephone exchange and considers the different workflows there, They work, certainly, but having people present plugging in each individual call doesn’t scale well. In our IP world, we want to get beyond the need to ‘type in an address’ as we want to capture the ease at which cameras are connected

The telephone exchanges worked well but in the early days, there were many exchange manufacturers which, when calling from Berlin to New York all had to work. Willem suggests this is why telecoms acted upon what the broadcast industry is now learning. The last point in this analogy is the need to stop your links between exchanges from becoming over-subscribed. This task is one which NMOS can also be used to deal with, using IS-05.

NMOS is fully available on GitHub and whilst you can take that software and modify it to your needs, Willem says it’s important to maintain interoperability between vendor implementations which is why the JT-NM Tested programme exists to ensure that it’s easy to buy on the market solutions which say they support NMOS and when they do, that it works. Getting an NMOS test system is easy with open projects from Siny and NVIDIA which are ready for deployment.

Willem ends his talk by saying that ST 2110 is easier now than it was, including a recent experience when the en/decoder worked ‘out of the box’. He then answers the question “How do I start out?” Saying you should try something small first, perhaps even an island project. Once you have done that, gained the experience and the concepts, you can take it from there.

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Speakers

	Willem Vermost Design & Engineering Manager, VRT
	Wes Simpson Owner, LearnIPVideo.com

Video: Case Study: Dropbox HQ ST 2110

Posted on 18th November 2020 by Russell Trafford-Jones

Dropbox is embedded in many production workflows – official and otherwise – so it’s a beautiful symmetry that they’re using Broadcast’s latest technology, SMPTE ST 2110, within their own headquarters. Dropbox have AV throughout their building and a desire to create professional video from anywhere. This desire was a driving factor in an IP-based production facility as, to allow mobile production platforms to move from room to room with only a single cable needed to connect to the wall and into the production infrastructure.

David Carroll’s integration company delivered this project and joins Wes Simpson to discuss this case-study with colleague Kevin Gross. David explains that they delivered fibre to seventy locations throughout the building making most places into potential production locations.

Being an IT company at heart, the ST 2110 network was built to perform in the traditional way, but with connections into the corporate network which many broadcasters wouldn’t allow. ST 2110 works best with two separate networks, often called Red and Blue, both delivering the same video. This uses ST 2022-7 to seamlessly failover if one network loses a packet or even if it stops working all together. This is the technique used with dropbox, although there these networks are connected together so are not one hundred per cent isolated. This link, however, has the benefit of allowing PTP traffic between the two networks.

PTP topology typically sees two grandmasters in the facility. It makes sense to connect one to the red network, the other to the blue. In order to have proper redundancy, though, there should really be a path from both grandmasters to both networks. This is usually done with a specially-configured ‘PTP only’ link between the two. In this case, there are other reasons for a wider link between networks which also serves as the PTP link. Another element of PTP topology is acknowledging the need for two PTP domains. A PTP domain allows two PTP systems to operate on the same network but without interfering with one another. Dante requires PTP version 1 whereas 2110, and most other things, require v2. Although this is in the process of improving, the typical way to solve this now is to run the two separately and block v1 from areas of the network in which it’s not needed.

PTP disruptions can also happen with multicast packet loss. If packets are lost at the wrong time, a grandmaster election can happen. Finally, on PTP, they also saw the benefits of using boundary clock switches to isolate the grandmasters. These grandmasters have to send out the time eight times a second. Each end-device then replies to ascertain the propagation delay. Dealing with every single device can overwhelm grandmasters, so boundary clock switches can be very helpful. On a four-core Arista, David and Kevin found that one core would be used dealing with the PTP requests.

A more extensive write-up of the project can be found here from David Carroll

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Speakers

	Kevin Gross Media Network Consultant AVA Networks
	David Carroll President, David Carroll Associates, Inc.
	Wes Simpson Owner, LearnIPVideo.com

Video: IP-based Networks for UHD and HDR Video

Posted on 9th November 2020 by Russell Trafford-Jones

If you get given a video signal, would you know what type it was? Life used to be simple, an SD signal would decode in a waveform monitor and you’d see which type it was. Now, with UHD and HDR, this isn’t all the information you need. Arguably this gets easier with IP and is possibly one of the few things that does. This video from AIMS helps to clear up why IP’s the best choice for UHD and HDR.

John Mailhot from Imagine Communications joins Wes Simpson from LearnIPVideo.com to introduce us to the difficulties wrangling with UHD and HDR video. Reflecting on the continued improvement of in-home displays’ ability to show brighter and better pictures as well as the broadcast cameras’ ability to capture much more dynamic range, John’s work at Imagine is focussed on helping broadcasters ensure their infrastructure can enable these high dynamic range experiences. Streaming services have a slightly easier time delivering HDR to end-users as they are in complete control of the distribution chain whereas often in broadcast, particularly with affiliates, there are many points in the chain which need to be HDR/UHD capable.

John starts by looking at how UHD was implemented in the early stages. UHD, being twice the horizontal and twice the vertical resolution of HD is usually seen as 4xHD, but, importantly, John points out that this is true for resolution but, as most HD is 1080i, it also represents a move to 1080p, 3Gbps signals. John’s point is that this is a strain on the infrastructure which was not necessarily tested for initially. Given the UHD signal, initially, was carried by four cables, there is now 4 times the chance of a signal impairment due to cabling.

Square Division Multiplexing (SQD) is the ‘most obvious’ way to carry UHD signals with existing HD infrastructure. The picture is simply cut into four quarters and each quarter is sent down one cable. The benefit here is that it’s easy to see which order the cables need to be connected to the equipment. The downsides included a frame-buffer delay (half a frame) each time the signal was received, difficulties preventing drift of quadrants if they were treated differently by the infrastructure (i.e. there was a non-synced hand-off). One important problem is that there is no way to know an HD feed is from a UHD set or just a lone 3G signal.

2SI, two-sample interleave, was another method of splitting up the signal which was standardised by SMPTE. This worked by taking a pair of samples and sending them down cable 1, then the next pair down cable 2, the pair of samples under the first pair went down cable 3 then the pair under 2 went down 4. This had the happy benefit that each cable held a complete picture, albeit very crudely downsampled. However, for monitoring applications, this is a benefit as you can DA one feed and send this to a monitor. Well, that would have been possible except for the problem that each signal had to maintain 400ns timing with the others which meant DAs often broke the timing budget if they reclocked. It did, however, remove the half-field latency burden which SQD carries. The main confounding factor in this mechanism is that looking at the video from any cable on a monitor isn’t enough to understand which of the four feeds you are looking at. Mis-cabling equipment leads to subtle visual errors which are hard to spot and hard to correct.

Enter the VPID, the Video Payload ID. SD SDI didn’t require this, HD often had it, but for UHD it became essential. SMPTE ST 425-5:2019 is the latest document explaining payload ID for UHD. As it’s version five, you should be aware that older equipment may not parse the information in the correct way a) as a bug and b) due to using an old standard. The VPID carries information such as interlaced/progressive, aspect ratio, transfer characteristics (HLG, SDR etc.), frame rate etc. John talks through some of the common mismatches in interpretation and implementation of VPID.

12G is the obvious baseband solution to the four-wires problem of UHD. Nowadays the cost of a 12G transceiver is only slightly more than 3G ones, therefore 12G is a very reasonable solution for many. It does require careful cabling to ensure the cable is in good condition and not too long. For OB trucks and small projects, 12G can work well. For larger installations, optical connections are needed, one signal per fibre.

The move to IP initially went to SMPTE ST 2022-6, which is a mapping of SDI onto IP. This meant it was still quite restrictive as we were still living within the SDI-described world. 12G was difficult to do. Getting four IP streams correctly aligned, and all switched on time, was also impractical. For UHD, therefore SMPTE ST 2110 is the natural home. 2110 can support 32K, so UHD fits in well. ST 2110-22 allows use of JPEG XS so if the 9-11Gbps bitrate of UHDp50/60 is too much it can be squeezed down to 1.5Gbps with almost no latency. Being carried as a single video flow removes any switch timing problems and as 2110 doesn’t use VPID, there is much more flexibility to fully describe the signal allowing future growth. We don’t know what’s to come, but if it’s different shapes of video rater, new colour spaces or extensions needed for IPMX, these are possible.

John finishes his conversation with Wes mentioning two big benefits of moving to IT-based infrastructure. One is the ability to use the free Wireshark or EBU List tools to analyse video. Whilst there are still good reasons to buy test equipment, the fact that many checks can be done without expensive equipment like waveform monitors is good news. The second big benefit is that whilst these standards were being made, the available network infrastructure has moved from 25 to 100 to 400Gbps links with 800Gbps coming in the next year or two. None of these changes has required any change in the standards, unlike with SDI where improvements in signal required improvements in baseband. Rather, the industry is able to take advantage of this new infrastructure with no effort on our part to develop it or modify the standards.

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Speakers