ABA Archives – The Broadcast Knowledge

Video: ATSC 3.0 Seminar Part III

Posted on 19th May 2020 by Russell Trafford-Jones

ATSC 3.0 is the US-developed set of transmission standards which is fully embracing IP technology both over the air and for internet-delivered content. This talk follows on from the previous two talks which looked at the physical and transmission layers. Here we’re seeing how IP throughout has benefits in terms of broadening choice and seamlessly moving from on-demand to live channels.

Richard Chernock is back as our Explainer in Chief for this session. He starts by explaining the driver for the all-IP adoption which focusses on the internet being the source of much media and data. The traditional ATSC 1.0 MPEG Transport Stream island worked well for digital broadcasting but has proven tricky to integrate, though not without some success if you consider HbbTV. Realistically, though, ATSC see that as a stepping stone to the inevitable use of IP everywhere and if we look at DVB-I from DVB Project, we see that the other side of the Atlantic also sees the advantages.

But seamlessly mixing together a broadcaster’s on-demand services with their linear channels is only benefit. Richard highlights multilingual markets where the two main languages can be transmitted (for the US, usually English and Spanish) but other languages can be made available via the internet. This is a win in both directions. With the lower popularity, the internet delivery costs are not overburdening and for the same reason they wouldn’t warrant being included on the main Tx.

Richard introduces ISO BMFF and MPEG DASH which are the foundational technologies for delivering video and audio over ATSC 3.0 and, to Richard’s point, any internet streaming services.

We get an overview of the protocol stack to see where they fit together. Richard explains both MPEG DASH and the ROUTE protocol which allows delivery of data using IP on uni-directional links based on FLUTE.

The use of MPEG DASH allows advertising to become more targeted for the broadcaster. Cable companies, Richard points out, have long been able to swap out an advert in a local area for another and increase their revenue. In recent years companies like Sky in the UK (now part of Comcast) have developed technologies like Adsmart which, even with MPEG TS satellite transmissions can receive internet-delivered targeted ads and play them over the top of the transmitted ads – even when the programme is replayed off disk. Any adopter of ATSC 3.0 can achieve the same which could be part of a business case to make the move.

Another part of the business case is that ATSC not only supports 4K, unlike ATSC 1.0, but also ‘better pixels’. ‘Better pixels’ has long been the way to remind people that TV isn’t just about resolution. ‘Better pixels’ includes ‘next generation audio’ (NGA), HDR, Wide Colour Gamut (WCG) and even higher frame rates. The choice of HEVC Main 10 Profile should allow all of these technologies to be used. Richard makes the point that if you balance the additional bitrate requirement against the likely impact to the viewers, UHD doesn’t make sense compared to, say, enabling HDR.

Richard moves his focus to audio next unpacking the term NGA talking about surround sound and object oriented sound. He notes that renderers are very advanced now and can analyse a room to deliver a surround sound experience without having to place speakers in the exact spot you would normally need. Options are important for sound, not just one 5.1 surround sound track is very important in terms of personalisation which isn’t just choosing language but also covers commentary, audio description etc. Richard says that audio could be delivered in a separate pipe (PLP – discussed previously) such that even after the
video has cut out due to bad reception, the audio continues.

The talk finishes looking at accessibility such as picture-in-picture signing, SMPTE Timed Text captions (IMSC1), security and the ATSC 3.0 standards stack.

Watch now!
Speaker

Richard Chernock
Former CSO,
Triveni Digital

Video: ATSC 3.0 Part II – Cutting Edge OFDM with IP

Posted on 30th April 2020 by Russell Trafford-Jones

RF, modulation, Single Frequency Networks (SFNs) – there’s a lot to love about this talk which is the second in a series of ATSC seminars however much is transferable to DVB. Today we’re focussed on transmission showing how ATSC 3.0 improves on DVB-T, how it simultaneously delivers feeds with different levels of robustness, the benefits of SFNs and much more.

In the second in this series of ATSC 3.0 talks, GatesAir’s Joe Seccia leads the proceedings starting by explaining why ATSC 3.0 didn’t simply adopt DVB-T2’s modulation scheme. The answer, explained in detail by Joe, is that by putting in further work, they got closer to the Shannon limit than DVB-T2 does. He continues to highlight the relevant standards which comprise the ATSC 3.0 standard which define the RF physical layer.

After showing how the different processes such as convolutional encoding and multiplexing fit together in the transmission chain, Joe focuses in on Layered Division Multiplexing (LDM) where a high robustness signal can be carefully combined with a lower robustness signal such that where one interferes with the other, there is enough separation to allow it to be decoded.

Next we are introduced to PLPs – Physical Layer Pipes. These can also be found in DVB-T2 and DVB-S2 and are logical channels carrying one or more services, with a modulation scheme and robustness particular to that individual pipe. Within those lie Frames and Subframes and Joe gives a good breakdown of the difference in meaning of the three, the Frame being at the top of the pile containing the other two. We look at how the bootstrap signal at a known modulation scheme and symbol rate details what’s coming next such which allow this very dynamic working with streams being sent with different modulation settings. The bootstrap is also important as it contains Early Alert System (EAS) signalling.

Layered Division Multiplexing is the next hot topic we hit and this elicits questions from the audience. LDM is important because it allows two streams to be sent at the same time with independent or related broadcasts. For instance this could deliver UHD content with HD underneath with the HD modulated to give much better robustness.

Another way of maintaining robustness is to establish an SFN which is now possible with ATSC 3.0. Joe explains how this is possible and how the RF from different antennae can help with reception. Importantly he also outlines how toward out the maximum separation between antennae and talks through different deployment techniques. He then works through some specific cases to understand the transmission power needed.

As the end of the video nears, Joe talks about MIMO transmission explaining how this, among other benefits, can allow channel bonding where two 6Mhz channels can be treated as a single 12Mhz channel. He talks about how PTP can complement GPS in maintaining timing if diverse systems are linked with ethernet and he then finishes with a walkthrough of configuring a system.

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Speakers

Joe Seccia
Manager, TV Transmission Market and Product Development Strategy
GatesAir

Video: IP Fundamentals For Broadcast Seminar IV

Posted on 3rd April 2020 by Russell Trafford-Jones

“When networking gets real”, perhaps, could have been the title of this last of 4 talks about IP for broadcast. This session wraps up a number of topics from the classic ‘TCP Vs. UDP’ discussion to IPv6 and examines the switches and networks that make up a network as well as the architecture options. Not only that, but we also look at VPNs and firewalls finishing by discussing some aspects of network security. When viewed with the previous three talks, this discusses many of the nuances from the topics already covered bringing in the relevance of ‘real world’ situations.

Wayne Pecena, President of SBE, starts by discussing subnets and collision domains. The issue with any NIC (Network Interface Controller) is that it’s not to know when someone else is talking on the wire (i.e. when another NIC is sending a message by changing the voltage of the wire). It’s important that NICs detect when other NICs are sending messages and seek to avoid sending while this is happening. If this does’t work out well, then two messages on the same wire are seen as a ‘collision’. It’s no surprise that collisions are to be avoided which is the starting point of Wayne’s discussion.

Moving from Layer 2 to Layer 4, Wayne pits TCP against UDP looking at the pros and cons of each protocol. Whilst this is no secret, as part of the previous talks this is just what’s needed to round the topic off ahead of talking about network architecture.

“Building and Securing a Segmented IP Network Infrastructure” is the title of the next talk which starts to deal with real-world problems when an engineer gets back from a training session and starts to actually specify a network herself. How should the routers and switches be interconnected to deliver the functionality required by the business and, as we shall see, which routers/switches are actually needed? Wayne discusses some of the considerations of purchasing switches (layer 2) and routers (layer 3 & 2) including the differing terms used by HP and Cisco before talking about how to assign IP addresses, also called an IP space. Wayne takes us through IP addressing plans, examples of what they would look like in excel along with a lot of the real-world thinking behind it.

Security is next on the list, not just in terms of ‘cybersecurity’ in the general sense but in terms of best practice, firewalls and VPNs. Wayne takes a good segment of time out to discus the different aspects of firewalls – how they work, ACLs (Access-control Lists), and port security amongst other topics before doing the same for VPNs (Virtual Private Networks) before making the point that a VPN and a firewall are not the same. A VPN allows you to extend a network out from a building to be in another – the typical example being from your work’s address into your home. Whilst a VPN is secured so that only certain people can extend the network, a firewall more generally acts to prevent anything coming into a network.

As an addendum to this talk, Wayne explains IPV4 depletion and how IPv6 addressing works. In practice, for broadcasters deploying within their company in the year 2020, IPv6 is unlikely to be a topic needed. However, for people who are distributing to homes and working closer with CDNs and ISPs, there is a chance that this information is more relevant on a day-to-day basis. Whilst IP address depletion is a real thing, since every company has a 10.x.x.x address space to play with, most companies use internal equipment with an IPv4 address plan.
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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: 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