IEEE BTS

Video: VVC – The new Versatile Video Coding standard

Posted on by Russell Trafford-Jones

The Codec landscape is a more nuanced place than 5 years ago, but there will always be a place for a traditional Codec that cuts file sizes in half while harnessing recent increases in computation. Enter VVC (Versatile Video Codec) the successor to HEVC, created by MPEG and the ITU by JVET (Joint Video Experts Team), which delivers up to 50% compression improvement by evolving the HEVC toolset and adding new features.

In this video Virginie Drugeon from Panasonic takes us through VVC’s advances, its applications and performance in this IEEE BTS webinar. VVC aims not only to deliver better compression but has an emphasis on delivering at higher resolutions with HDR and as 10-bit video. It also acknowledges that natural video isn’t the only video used nowadays with much more content now including computer games and other computer-generated imagery. To achieve this, VVC has had to up its toolset.

 

 

Any codec is comprised of a whole set of tools that carry out different tasks. The amount that each of these tools is used to encode the video is controllable, to some extent, and is what gives rise to the different ‘profiles’, ‘levels’ and ‘tiers’ that are mentioned when dealing with MPEG codecs. These are necessary to allow for lower-powered decoding to be possible. Artificially constraining the capabilities of the encoder gives maximum performance guarantees for both the encoder and decoder which gives manufacturers control over the cost of their software and hardware products. Virginie walks us through many of these tools explaining what’s been improved.

Most codecs split the image up into blocks, not only MPEG codecs but the Chinese AVS codecs and AV1 also do. The more ways you have to do this, the better compression you can achieve but this adds more complexity to the encoding so each generation adds more options to balance compression against the extra computing power now available since the last codec. VVC allows rectangles rather than just squares to be used and the size of sections can now be 128×128 pixels, also covered in this Bitmovin video. This can be done separately for the chroma and luma channels.

Virginie explains that the encoding is done through predicting the next frame and sending the corrections on top of that. This means that the encoder needs to have a decoder within it so it can see what is decoded and understand the differences. Virginie explains there are three types of prediction. Intra prediction uses the current frame to predict the content of a block, inter prediction which uses other frames to predict video data and also a hybrid mode which uses both, new to VVC. There are now 93 directional intra prediction angles and the introduction of matrix-based intra prediction. This is an example of the beginning of the move to AI for codecs, a move which is seen as inevitable by The Broadcast Knowledge as we see more examples of how traditional mathematical algorithms are improved upon by AI, Machine Learning and/or Deep Learning. A good example of this is super-resolution. In this case, Virginie says that they used machine learning to generate some matrices which are used for the transform meaning that there’s no neural network within the codec, but that the matrices were created based on real-world data. It seems clear that as processing power increases, a neural network will be implemented in future codecs (whether MPEG or otherwise).

For screen encoding, we see that intra block copying (IBC) is still present from HEVC, explained here from 17:30 IBC allows part of a frame to be copied to another which is a great technique for computer-generated content. Whilst this was in HEVC it was not in the basic package of tools in HEVC meaning it was much less accessible as support in the decoders was often lacking. Two new tools are block differential pulse code modulation & transform skip with adapted residual coding each discussed, along with IBC in this free paper.

Virginie moves on to Coding performance explaining that the JVET reference software called VTM has been used to compare against HEVC’s HM reference and has shown, using PSNR, an average 41% improvement on luminance with screen content at 48%. Fraunhofer HHI’s VVenc software has been shown to be 49%.

Along with the ability to be applied to screen content and 360-degree video, the versatility in the title of the codec also refers to the different layers and tiers it has which stretch from 4:2:0 10 bit video all the way up to 4:4:4 video including spatial scalability. The main tier is intended for delivery applications and the high for contribution applications with framerates up to 960 fps, up from 300 in HEVC. There are levels defined all the way up to 8K. Virginie spends some time explaining NAL units which are in common with HEVC and AVC, explained here from slide 22 along with the VCL (Video Coding Layer) which Virginie also covers.

Random access has long been essential for linear broadcast video but now also streaming video. This is done with IDR (Instantaneous Decoding Refresh), CRA (Clean Random Access) and GDR (Gradual Decoding Refresh). IDR is well known already, but GDR is a new addition which seeks to smooth out the bitrate. With a traditional IBBPBBPBBI GOP structure, there will be a periodic peak in bitrate because the I frames are much larger than the B and, indeed, P frames. The idea with GDR is to have the I frame gradually transmitted over a number of frames spreading out the peak. This disadvantage is you need to wait longer until you have your full I frame available.

Virginie introduces subpictures which are a major development in VVC allowing separately encoded pictures within the same stream. Effectively creating a multiplexed stream, sections of the picture can be swapped out for other videos. For instance, if you wanted a picture in picture, you could swap the thumbnail video stream before the decoder meaning you only need one decoder for the whole picture. To do the same without VVC, you would need two decoders. Subpictures have found use in 360 video allowing reduced bitrate where only the part which is being watched is shown in high quality. By manipulating the bitstream at the sender end.

Before finishing by explaining that VVC can be carried by both MPEG’s ISO BMFF and MPEG2 Transport Streams, Virginie covers Reference Picture Resampling, also covered in this video from Seattle Video Tech allows reference frames of one resolution to be an I frame for another resolution stream. This has applications in adaptive streaming and spatial scalability. Virginie also covers the enhanced timing available with HRD

Watch now!
Video is free to watch
Speaker

Virginie Drugeon Virginie Drugeon
Senior Engineer Digital TV Standardisation,
Panasonic

Video: Hacking ATSC 3.0

Posted on by Russell Trafford-Jones

ATSC’s effort to bring IP into over-the-air broadcast has been long in the making and its deployment in South Korea along with the ITU’s inclusion of it in it’s list of recommended digital broadcast standards is a testament to it gaining acceptance. But as US broadcasters continue with test broadcasts and roll-outs in 2020, what security problems arise when IP’s included in the mix?

Acting is a great network security primer, this talk from Texas A&M’s Wayne Pecena, explains the premise and implications of creating and maintaining security in your broadcast plant. Starting by documenting the high profile attacks on broadcasters over the years, Wayne hones in on the reasons they should care from the obvious, omnipresent threat of ‘dead air’ to ‘loss of trust’ which is particularly motivating in recent years as we have seen state actors move to influence, not disrupt the normal course of life, in low-key, long-burn persistent attacks.

The talk hinges around the ‘AIC’ triad, comprising confidentiality, integrity and availability which are the three core aspects of data to protect. Integrity involves ensuring that the data are not altered either in transit or, indeed, in storage. Confidentiality revolves around ensuring that access control is maintained at all levels including physical, network-level and application live. Finally availability encompasses the fact that if the data isn’t available to the people who need it, the whole thing is pointless. Therefore supporting the availability side of the triangle includes thinking about redundancy and disaster recovery procedures.

Wayne, who is also the president of the Society of Broadcast Engineers, explains some of the attributes of a secure system which starts with security policies. These are the outer layer of any secure environment detailing how the many other layers of security will be managed and applied. Other aspects of a secure environment are appropriately layered and segmented network design, to limit what is available to anyone who does penetrate part of a system, access controls and logging.

After looking at the IETF and IEEE standards bodies, we see how the standard network models overlay neatly on the ATSC layered model with networking in the centre of them all. This leads in to a brief introduction to ‘IP’ in the sense of the the IP protocol on which are based TCP/IP and UDP/IP, between them central to most network communications around the world.

As we see how a small hole in defences can be slowly changed and enlarged allowing the attacker to move forward and create another hole in the next layer, Wayne talks about the types of security threats such malware, denial of service attacks and, of course, inside threats such as your employees themselves being complicit.

As the talk draws to a close we look at how this plays out in the real world talking through diagrams of broadcasters’ systems and how mitigations might play out on premise before talking cloud security. As the threat model in the cloud is different, Wayne explains the best practices to ensure safety and how these and the other security technologies used on the internet keep ATSC 3.0 secure including TLS secure certificate and the use of DNSSEC

The talk finishes with a look at security in the home whether that be with the myriad of consumer media consumption devices or items from the ‘internet of things’.

Watch now!
Speaker

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

Webinar: An Overview of the ATSC 3.0 Interactive Environment

Posted on by Russell Trafford-Jones

Allowing viewers to interact with television services is an obvious next step for the IP-delivered ATSC service. Taking cues from the European HbbTV standard, the aim here is to make available as many ways as practical for viewers to direct their viewing in order to open up new avenues for television channels and programme creators.

Mark Corl is chair of the TG3/S38: Specialist Group on Interactive Environment. Its aim is to support interactive applications and their companion devices. It has produced the A/344 standard which is based on W3C technologies with APIs which support the needs of broadcast television. It describes the Interactive Environment Content Display model allowing video to be mixed with app graphics as a composite display. Mark is also part of the ATSC group TG3-9 which looks at how the different layers of ATSC 3.0 can communicate with each other where necessary.

From the TG3 group, too, is the Companion Device Concepts A/338 standards document which details discovery of second devices such as smartphones and enabling them to communicate with the ATSC 3.0 receiver.

In this webinar from the IEEE BTS, Mark marries an understanding of these documents with the practical aspects of deploying interactive broadcaster applications to receivers including some of the motivations to do this, such as improving revenue through the introduction of Dynamic Ad Insertion and personalisation.

Register now!
Speakers

Mark Corl Mark Corl
Chair, TG3/S38 Specialist Group on Interactive Environment
Co-chair, TG3-9 AHG on Interlayer Communications in the ATSC 3.0 Ecosystem
Senior Vice President, Emergent Technology Development, Triveni Digital

Webinar: ATSC 3.0 Physical Layer and Data Link Layer Overview

Posted on by Russell Trafford-Jones

ATSC 3.0 brings IP delivery to over-the-air TV marking a major change in delivery to the home. For the first time video, audio and other data is all delivered as network streams allowing services available to TV viewers at home to modernise and merge with online streaming services better matching the viewing habits of today. ATSC 3.0 deployments are starting in the USA and it has already been rolled out in South Korea for the XXIII Olympic Winter Games in 2018.

Whilst the move to IP is transformational, ATSC 3.0 delivers a whole slew of improvements to the ATSC standard for RF, bandwidth, Codecs and more. In this, the first of three webinars from the IEEE BTS focussing in on ATSC 3.0, we look at the physical layer with Luke Fay, Chair of the ATSC 3.0 group and also a Senior Manager of Technical Standards at Sony.

Click to register: Wednesday, 15th January, 2020. 11am ET / 16:00 GMT

What is the Physical Layer?
The physical layer refers to the method data gets from one place to another. In this case, we’re talking about transmission by air, RF. Whilst this isn’t, in some ways, as physical as a copper cable, we have to remember that, at a basic level, communication is about making a high voltage in place A change the voltage in place B. The message physically moves from A to B and the medium it uses and the way it manipulates that medium are what we refer to as the physical layer.

In this webinar, Luke will talk about System Discovery and Signalling, defined by document A/321 and the Physical Layer Protocol defined by A/322. Both freely available from the ATSC website. The webinar will finish with a Q&A. Let’s take a deeper look at some of the topics which will be covered.

Choice of modulation

ATSC 3.0 has chosen the COFDM modulation scheme over the previous 8VSB, currently used for first-generation ATSC broadcasts, to deliver data over the air from the transmitter. COFDM, stands for Coded Orthogonal Frequency Devision Multiplexing and has become the go-to modulation method for digital transmissions including for DAB, DAB+ and the DVB terrestrial, satellite and cable standards.

One of the reasons for its wide adoption is that COFDM has guard bands; times when the transmitter is guaranteed not to send any data. This allows the receiver some time to receive any data which comes in late due to multi-path reflections or any other reason. This means that for COFDM, you get better performance if you run a network of nearby transmitters on the same frequency – known as a Single Frequency Network (SFN). A transmitters signal from further away will arrive later, and if in the guard interval, will be used to re-inforce the directly received signal. This means that, counter-intuitively from analogue days, running an SFN actually helps improve reception.

Multiple operating points to match the business case
Another important feature of ATSC 3.0 at the physical layer is the ability to be able to choose the robustness of the signal and have multiple transmissions simultaneously using different levels of robustness. These multiple transmissions are called pipes. As many of us will be familiar with, when transmitting a high bandwidth, the signal can be fragile and easily corrupted by interference. Putting resilience into the signal uses up bandwidth either due using some of the capacity to put error checking and error recovery data in or just by slowing down the rate the signal is sent which, of course, means not as many bits can be sent in the same time window.

Because bandwidth and resilience are a balancing act with each one fighting against the other, it’s important for stations to be able to choose what’s right for them and their business case. Having a high robustness signalm for penetration indoors can be very useful for targeting reception on mobile devices and ATSC 3.0 can actually achieve reception when the signal is below the noise, i.e. a negative signal to noise ratio. A higher bandwidth service delivering UHD at around 20Mbps can be achieved, however, by using 64 instead of 16 QAM.

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Speaker

Luke Fay
Chairman, ATSC Technology Group 3,
Senior Manager Technical Standards, Sony Home Entertainment & Sound Products – America