Video: Case Study: Dropbox HQ ST 2110

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

Video: IP-based Networks for UHD and HDR Video

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

John Mailhot John Mailhot
Systems Architect, IP Convergence,
Imagine Communications
Wes Simpson Wes Simpson
RIST AG Co-Chair, VSF
President & Founder, LearnIPvideo.com

Video: IPMX – The Need for a New ProAV Standard

IPMX is an IP specification for interoperating Pro AV equipment. As the broadcast industry is moving towards increasing IP deployments based on SMPTE 2110 and AMWA’s NMOS protocols, there’s been a recognition that the Pro AV market needs to do many of the same things Broadcast wants to do. Moreover, there is not an open standard in Pro AV to achieve this transformation. Whilst there are a number of proprietary alliances, which enable wide-spread use of a single chip or software core, this interoperability comes at a cost and ultimately is underpinned by one, or a group of companies.

Dave Chiappini from Matrox discusses the work of the AIMS Pro AV working group with Wes Simpson from the VSF. Dave underlines the fact that this is a pull to unify the Pro AV industry to help people avoid investing over and over again in reinventing protocols or reworking their products to interoperate. He feels that ‘open standards help propel markets forward’ adding energy and avoiding vendor lock-in. This is one reason for the inclusion of NMOS, allowing any vendor to make a control system by working to the same open specification, opening up the market to both small and large companies.

Dave is the first to acknowledge that the Pro AV market’s needs are different to broadcast’s, and explains that they have calibrated settings, added some and ‘carefully relaxed’ parts of the standards. The aim is to have a specification which allows one piece of equipment, should the vendor wish to design it this way, that can be used in either an IPMX or ST 2110 system. He explains that the idea of relaxing some aspects of the ST 2110 ecosystem helps simplify implementation which therefore reduces cost.

One key relaxation has been in PTP. A lot of time and effort goes into making the PTP infrastructure work properly within SMPTE 2110 infrastructure. Having to do this at an event whilst setting up in a short timespan is not helpful to anyone and, elaborates Dave, a point to point video link simply doesn’t need high precision timing. IPMX, therefore, is lenient in the need for PTP. It will use it when it can, but will gracefully reduce accuracy and, when there is no grandmaster, will still continue to function.

Another difference in the Pro AV market is the need for compression. Whilst there are times when zero compression is needed in both AV and Broadcast, Pro AV needs the ability to throw some preview video out to an iPad or similar. This isn’t going to work with JPEG XS, the preferred ‘minimal compression’ codec for IPMX, so a system for including H264 or H265 is being investigated which could have knock-on benefits for Broadcast.

HDMI is essential for a Pro AV solution and needs its own treatment. Different from SDI, it has lots of resolutions and frame rates. It also has HDCP so AIMS is now working with the DCP on creating a method of carrying HDCP over 2110. It’s thus hoped that this work will help broadcast use cases. TVs are already replacing SDI monitors, such interoperability with HDMI should bring down the costs of monitoring for non-picture critical environments.

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Speakers

David Chiappini David Chiappini
Chair, Pro AV Working Group, AIMS
Executive Vice President, Research & Development,
Matrix Graphics Inc.
Wes Simpson Wes Simpson
RIST AG Co-Chair, VSF
President & Founder, LearnIPvideo.com

Video: The 2020 EBU Pyramid of User Requirements

There’s a lot more to IP-based production than just getting your video and audio streaming between devices. You need configuration tools, you need timing, there’s the management of the devices to consider and, critically, security. the problem is, working in IP is still new and many of the solutions are yet to mature. This means we still don’t have all the tools we need to realise the full promise of live production IP systems.

Back in 2018, the EBU embarked on a project to focus the industry on the gaps: The Technology Pyramid. This pyramid shows that although we, as an industry, had largely succeeded in defining essence transport over IP, this was only the ‘top of the iceberg’, so to speak, in what needed to be done. also known by its full name, “The Technology Pyramid for Media Nodes 2018”, it shows that everything is underpinned by security, upon that is configuration and monitoring, with discovery and registration built on that.

One important aspect of the pyramid is the green – yellow – red colour coding. When initially released, the only green was the transport layer, but this talk looks at the 2020 edition of the pyramid which shows that the time & sync, as well as discovery and connection, have improved.

We’re joined by Willem Vermost and Félix Poulin to discuss the problems the industry has faced to date and the progress made in making the pyramid green. Both previously with the EBU and now both with early-adopter broadcasters who are going live with IP systems, they are perfectly placed to explain the evolution on of the market.

Not only has the colouring of the pyramid changed, but the detail of what each layer constitutes has evolved. The industry has reacted with a number of specifications such as JT-NM TR-1001-1 and AMWA BCP-003. Willem and Félix explain the hidden necessities that have come out of the woodwork as the early adopters have fought to make everything work. PTP is a good example, being able to free-wheel without a PTP clock for 5 minutes and then join back without a glitch has been added to the list of requirements. Time stamping and lip-sync have proven tricky, too. Intermediate processing steps place their timestamps over the original timestamp of when the media was captured. If you are trying to sync audio and video which have gone through processing, you need the original timestamps which have now been lost. This problem is being addressed but until it is, it’s a big gap.

Overall we can see the power of focussing people’s attention in this way. Whilst there is much more detail in the talk itself, just from the extracts in this article, it’s clear progress has been made and with plenty more broadcasters starting their IP projects, there is all the more motivation for the vendors to implement the requirements as laid out than there was before.

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Speakers

Willem Vermost Willem Vermost
Design & Engineering Manager,
VRT
Félix Poulin Félix Poulin
Direcor – Media Transport Architecture & Lab
CBC/Radio-Canada