The Broadcast Knowledge

Video: IP Fundamentals For Broadcast Seminar Part III

Posted on 24th March 2020 by Russell Trafford-Jones

‘IP’ is such a frequently used term, that is real meaning and context easily gets lost. As we saw from Wayne’s first and seminars, IP stands on top of ethernet and the cabling needed to support the whole network stack. But as we see from the subtitle, this where we get to virtual addressing which, as an abstraction layer, offers us a lot of flexibility. IP, the Internet Protocol, is where much of what we refer to as ‘networking’ happens, so it’s important to understand.

Wayne Pecena, long-standing staff member at Texas A&M University, goes straight into to IPV4 packet types. In the world of SMPTE ST-2110 and SMPTE ST-2022, this is important as much media traffic is sent multicast which is different to unicast and broadcast traffic. These three methods of sending data each have pros and cons. Unicast is the most well-known whereby packets are sent directly from the sender to a specific receiving device. Broadcast is, as the term suggests, a way of sending from one computer to all computers. This is great when you’re shouting out to another device to find out some key information about the network, but it can lead to disaster if all senders are doing this. For media use, multicast is where it’s at, allowing a sender to send to a group of receiving devices each of which opt in to this stream, just like you can opt in to a newsletter.

Wayne digs in to how an IPv4 packet is constructed looking at all parts of the header including the source and destination IP addresses. This leads us into looking at how an IP address is constructed. The trick with IP addresses and moving data from one network to another, we learn is in understanding which machines are on your local network (in which case you can use layer 2 Ethernet to send them data) and those that aren’t (in which case you need to use IP to pass on your message to the other network). This is done using subnets which is explained along with classes of addresses and class-less notation.

Once you know how to tell which network an address is in, this leads to the need to pass information from one to another opening up the topic of Network Address Translation (NAT). The typical example of NAT is that a message might come in to a public IP address on port 3000 which would then be sent to the internal network to a defined internal address on port 80. Wayne explains how this works and runs through examples.

For a network to keep track of which physical interfaces are where and have which IP address requires an ARP table which has been mentioned in previous seminars because it bridges both layer 2 and layer 3. Now we’re at layer 3, it’s time to go in for another look ahead of examining how DHCP workshop it assigns DNS addresses and how DNS itself works.

The next section steps into the world of diagnosis with ping and the ICMP protocol on which it is based. This leads in to explaining how trace route works, based on changing the TTL of the packet. The TTL is the Time To Live, which one way that a network knows it can drop a packet. This exists to protect networks from having packets which live forever and are constantly circling the network. However the TTL, in this situation, can be used to probe information about the network. Wayne explains the pros and the cons of ping and traceroute.

The seminar finishes by a look at routers, routing tables, routing protocols like IGP, EGP, OSPF, EIGRP and their peers.

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Speaker

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

Video: Codecs, standards and UHD formats – where is the industry headed?

Posted on 23rd March 2020 by Russell Trafford-Jones

Now Available On Demand
UHD transmissions have been available for many years now and form a growing, albeit slow-growing, percentage of channels available. The fact that major players such as Sky and BT Sports in the UK, NBCUniversal and the ailing DirecTV in the US, see fit to broadcast sports in UHD shows that the technology is trusted and mature. But given the prevalence of 4K in films from Netflix, Apple TV+ streaming is actually the largest delivery mechanism for 4K/UHD video into the home.

Following on from last week’s DVB webinar, now available on demand, this webinar from the DVB Project replaces what would have been part of the DVB World 2020 conference and looks at the work that’s gone into getting UHD to were it is now in terms of developing HEVC (also known as H.265), integrating it into broadcast standards plus getting manufacturer support. It then finishes by looking at the successor to HEVC – VVC (Versatile Video Codec)

The host, Ben Swchwarz from the Ultra HD Forum, first introduces Ralf Schaefer who explores the work that was done in order to make UHD for distribution a reality. He’ll do this by looking at the specifications and standards that were created in order to get us where we are today before looking ahead to see what may come next.

Yvonne Thomas from the UK’s Digital TV Group is next and will follow on from Ben by looking at codecs for video and audio. HEVC is seen as the go-to codec for UHD distribution. As the uncompressed bitrate for UHD is often 12Gbps, HEVC’s higher compression ratio compared to AVC and relatively wide adoption makes it a good choice for wide dissemination of a signal. But UHD is more than just video. With UHD and 4K services usually carrying sports or films, ‘next generation audio‘ is really important. Yvonne looks at the video and audio aspects of delivering HEVC and the devices that need to receive it.

Finally we look at VVC, also known as H.266, the successor to HEVC, also known as H.265. ATEME’s Sassan Pejhan gives us a look into why VVC was created, where it currently is within MPEG standardisation and what it aims to achieve in terms of compression. VVC has been covered previously on The Broadcast Knowledge in dedicated talks such as ‘VVC, EVC, LCEVC, WTF?’, ‘VVC Standard on the Final Stretch’, and AV1/VVC Update.

No Registration Necessary!

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Speakers

	Ben Schwarz Communication Working Group Chair, Ultra HD Forum
	Ralf Schaefer VP Standards R&I InterDigital Inc.
	Yvonne Thomas Strategic Technologist DTG (Digital TV Group)
	Sassan Pejhan VP Technology, ATEME

Video: Buffer Sizing and Video QoE Measurements at Netflix

Posted on 20th March 2020 by Russell Trafford-Jones

At a time when Netflix is cutting streaming quality to reduce bandwidth, we take a look at the work that’s gone into optimising latency within the switch at ISPs which was surprisingly high.

Bruce Spang interned at Netflix and studied the phenomenon of unexpected latency variation within the netflix caches they deploy at ISPs to reduce latency and bandwidth usage. He starts by introducing us to the TCP buffering models looking at how they work and what they are trying to achieve with the aim of identifying how big it is supposed to be. The reason this is important is that if it’s a big buffer, you may find that data takes a long time to leave the buffer when it gets full, thus adding latency to the packets as they travel through. Too small, of course, and packets have to be dropped. This creates more rebuffing which impacts the ABR choice leading to lower quality.

Bruce was part of an experiment that studied whether the buffer model in use behaved as expected and whist he found that it did most of the time, he did find that video performance varied which was undesirable. To explain this, he details the testing they did and the finding that congestion, as you would expect, increases latency more during a congested time. Moreover, he showed that a 500MB had more latency than 50MB.

To explain the unexplained behaviour such as long-tail content having lower latency than popular content, Bruce explains how he looked under the hood of the router to see how VOQs are used to create queues of traffic and how they work. Seeing the relatively simply logic behind the system, Bruce talks about the results they’ve achieved working with the vendor to improve the buffering logic.

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Speakers

Bruce Spang
PhD Student, Stanford

Video: Harness SSAI’s Superpowers

Posted on 19th March 2020 by Russell Trafford-Jones

Server-side Ad Insertion (SSAI) is a great option for streaming services delivering video to a wide variety of devices and for those who need to avoid ad blockers. Whilst ad insertion can happen in the player, this mechanism can be interfered with allowing users to avoid ads. Whilst client-side ad insertion can much more easily create a unique stream for each client, dynamic SSAI can now do the same with a better user experience.

This panel from the OTT Leadership Summit at Streaming Media West 2019 brings together Disney, WarnerMerdia and Crunchyroll to share their experiences with SSAI. They discuss beaconing, ad standards, scaling, SCTE and more.

Beaconing goes hand in hand with ad playback providing metrics on what happened. When you perform certain actions, the player will reach out to a URL. This can be used to indicate such things as users skipping or pausing a video. The beacon information can then be used to verify how much of which ads were seen by whom and charge advertisers accordingly.

The panel moves on to discussing scaling using live sports as an example and cover questions to ask vendors to ensure you and they are ready for maximum scale. Bandwidth, is declared the biggest challenge, but a less obvious problem is that your upstream ad providers can’t always scale well. If you rely on calls from your server to others, then it’s vital to understand their scaling capacity and strategy. They discuss issues with losing beacons when operating at scale and the need for detailed logging and debugging in order to spot errors and reconcile the results.

Some time is next spent on VPAID and VAST 4 which are both messaging specifications to allow ad servers to tell applications which ads to play. The panel discusses the pros and cons in their use for SSAI where the stitcher needs to reach out to and ad server in real time to find out which ads to play.

At the end of the discussion, the panel takes questions from the floor but not before discussing SCTE Markers and ‘content conditioning’ which surrounds taking care of your source videos and encoder such that the two assets fit together properly at I-frame boundaries.

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Speakers

	Robert Jameson Technical Director, Media Enablement Turner \| WarnerMedia
	Stephen Gray Director, Ad Tech Systems Walt Disney Direct-to-Consumer & International
	Michael Dale VP Engineering, Crunchyroll
	Nadine Krefetz Consultant, Reality Software Contributing Editor, Streaming Media

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