Video: NMOS and ST 2110 Pro AV Roadmap

Posted on by Russell Trafford-Jones

ProAV and Broadcast should be best buddies, but only a relatively few companies sell into both. This is because there are legitimate differences in what we need. That being said, interoperability is a helpful end goal for any industry. Whilst proprietary solutions can help kickstart new technologies and be a positive disruptive force, standardisation is almost always beneficial to the industry in the medium to long term.

Whilst broadcast is happy to live with 4:2:2 colour subsampling in much of its workflow, then deliver in 4:2:0, this is often not an option for ProAV who need to take full 4:4:4 4K at 60fps and throw it on a monitor. Whilst 4:4:4 has, technically been possible over SDI for a while, adoption even in the broadcast market has been small.

There are many opportunities for both industries to learn from each other, but it’s hard to overstate the difference in approach of the SMPTE 2110 and NMOS approach to the problem of media over IP compared to the SDVoE model. The former relies on detailed documentation published publicly for anyone who is willing to buy the standard to implement in any way they see fit be that in software or hardware. The latter specifies a chip which has a documented API that does all of the heavy lifting with no option for self-implementation. The fact that the same chip is used everywhere provides the guarantee of interoperability.

One technology which has bridged the gap between ProAV and broadcast is NDI from Vizrt’s Newtek which uses the same binary software application wherever it’s implemented thus providing, like in SDVoE, the interoperability required. The same is true for SRT although they have just released their first draft for IETF standardisation.

In this talk, PESA CTO Scott Barella examines the many existing standards within ProAV and examines their needs such as HDCP. Whilst HDCP, the High-bandwidth Digital Content Protection mechanism, has often been grappled with by broadcasters, it is at least a standard. And it’s a standard that any vendor will have to deal with if they want their equipment to be widely used in the industry. Similarly the requirement for full-frame rate, full-colour UHD is not simply done within many boxes.

The use of PTP within SMPTE’s ST 2110 suite works perfectly in the studio, is arguably not necessary in much of ‘the cloud’ and is widely considered too complex for a ProAV environment. Scott explains that he has thoughts on how to simplify it to make it more practical and taking into account the different use cases.

Secondary interfaces are crucial in much ProAV whereby USB, RS 232 serial and GPI/GPO need to be transported along with the media. And whilst security and encryption are increasingly important for the broadcast industry as it comes to grips with the fact that all broadcasters are vulnerable to hacking attempts, their requirements are not as stringent as the military’s which drives a notable part of the ProAV market. All of these aspects are being considered as part of the ongoing work the Scott is involved with.

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Speaker

Scott Barella Scott Barella
CTO, PESA
AIMS co-chair.

Video: IP Fundamentals For Broadcast Part II

Posted on by Russell Trafford-Jones


After last week’s talk explaining networking from the real basics, Wayne Pecena is back to look at “where the good stuff is” in the next two layers of the OSI model.

Much of what live production needs happens in layers 2 and 3. At layer 2 we have Ethernet which defines how data is passed from switch to switch. Then at layer 3 we have the IP protocols, UDP and TCP which do nearly all of the heavy lifting getting our data from one place to another.

Wayne Pecena from Texas A&M University builds this talk around layer 2 specifically and starts by looking at the underlying protocols of Ethernet including collision detection. Given that the cabling is bi-directional, it’s possible for both ends to be sending data at the same time. This needs to be avoided, so the sending devices need to sense what’s happening on the wire and allow time for the other interface to finish.

Famously Ethernet has MAC addresses which is the way that this Layer 2 protocol deals with addressing the correct end point. Wayne shows the format these addresses follows and looks at the makeup of the frame which houses the data payload. The length of each segment of data is set with a maximum, but there is a high-throughput option called Jumbo Frames which increases efficiency for high bit rate applications by reducing the number of frames needing to be sent and therefore reducing the amount of header data sent.

A switch is an Ethernet device for connecting together multiple devices to communicate over Layer 2 and has a number of functions like learning MAC addresses, filtering frames and forwarding frames from one interface to another one. Switches can provide not only data but power to avoid having to run more than one cable. Usefully, Wayne walks us through the steps taken for one computer to send to another. Stepping through this mixture of ethernet and IP address is very useful to understand how to fault find, but also to see how layer 2 and 3 work so closely together.

Knowing the innards of a switch is vital to a full understanding of network behaviour. Wayne talks through a diagram of the what’s inside a switch showing that each NIC has its own set of buffers, a backplane (also known as ‘switch fabric’) and shared resources like a CPU. We see then how the switch learns the MAC addresses of everything connected to it and we see that, with the CPU and separating MAC address lists, a switch can create virtual lans, known as VLANs which allow a logical separation of interfaces that are on the same switch. It has the effect of creating multiple networks, that can’t speak to each other by default, on the same hardware and then allows the flexibility to add certain interfaces to multiple networks. VLANs are highly utilised in enterprise computing.

The talk finishes with a full description of how VLANs work and interact and 802.1Q VLAN tagging.

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Wayne’s previous talk
Speaker

Wayne Pecena Wayne Pecena
Director of Engineering, KAMU TV/FM at Texas A&M University
President, Society of Broadcast Engineers AKA SBE

Video: Video Compression Basics

Posted on by Russell Trafford-Jones

Video compression is used everywhere we look. So often is it not practical to use uncompressed video, that everything in the consumer space video is delivered compressed so it pays to understand how this works, particularly if part of your job involves using video formats such as AVC, also known as H.264 or HEVC, AKA H.265.

Gisle Sælensminde from Vizrt takes us on this journey of creating compressed video. He starts by explaining why we need uncompressed video and then talks about containers such as MPEG-2 Transport Streams, mp4, MOV and others. He explains that the container’s job is partly to hold metadata such as the framerate, resolution and timestamps among a long list of other things.

Gisle takes some time to look at the past timeline of codecs in order to understand where we’re going from what went before. As many use the same principles, Gisle looks at the different type of frames inside most compressed formats – I, P and B frames which are used in set patterns known as GOPs – Group(s) of Pictures. A GOP defines how long is between I frames. In the talk we learn that I frames are required for a decoder to be able to tune in part way through a feed and still start seeing some pictures. This is because it’s the I frame which holds a whole picture rather than the other types o frame which don’t.

Colours are important, so Gisle looks at the way that colours are represented. Many people know about defining colours by looking at the values of Red, Green and Blue, but fewer about YUV. This is all covered in the talk so we know about conversion between the two types.

Almost synonymous with codecs such as HEVC and AVC are Macroblocks. This is the name given to the parts of the raster which have been spit up into squares, each of which will be analysed independently. We’ll look at who these macro blocks are used, but Gisle also spends some time looking to the future as both HEVC, VP9 and now AV1 use variable-size macro block analysis.

A process which happens throughout broadcast is chroma subsampling. This topic, whereby we keep more of the luminance channel than colours, is explored ahead of looking at DCTs – Discrete Cosine Transforms – which are foundational to most video codecs. We see that by analysing these macro blocks with DCTs. we can express the image in a different way and even cut down on some of the detail we get from DCTs in order to reduce the bitrate.

Before some very useful demos looking at the result of varying quantisation across a picture, the difference signal between the source and encoded picture plus deblocking technology to hide some of the artefacts which can arise from DCT-based codecs when they are pushed for bandwidth.

Gisle finishes this talk at Media City Bergen by taking a number of questions from the floor.

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Speaker

Gisle Sælensminde Gisle Sælensminde
Senior Software Engineer,
Vizrt

Video: Pervasive video deep-links

Posted on by Russell Trafford-Jones

Google have launched a new initiative allowing publishers to highlight key moments in a video so that search results can jump straight to that moment. Whether you have a video that looks at 3 topics, one which poses questions and provides answers or one which has a big reveal and reaction shots, this could help increase engagement.

The plan is the content creators tell Google about these moments so Paul Smith from theMoment.tv takes to the stage at San Francisco Video Tech to explain how. After looking at a live demo, Paul takes a dive into the webpage code that makes it happen. Hidden in the tag, he shows the script which has its type set to application/ld+json. This holds the metadata for the video as a whole such as the thumbnail URL and the content URL. However it also then defines the highlighted ‘parts’ of the video with URLs for those.

Whiles the programme is currently limited to a small set of content publishers, everyone can benefit from these insights on google video search. It will also look at YouTube descriptions in which some people give links to specific times such as different tracks in a music mix, and bring those into the search results.

Paul looks at what this means for website and player writers. On suggestion is the need to scroll the page to the correct video and make the different videos on a page clearly signposted. Paul also looks towards the future at what could be done to better integrate with this feature. For example updating the player UI to see and create moments or improve the ability to seek to sub-second accuracy. Intriguingly he suggests that it may be advantageous to synchronise segment timings with the beginning of moments for popular video. Certainly food for thought.

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Speaker

Paul Smith Paul Smith
Founder,
theMoment.tv