|Topic:||Ultra HD TV – real quality|
|Title:||Senior Director of Emerging Technology and Strategy|
Ian Trow is the Senior Director for Emerging Technology & Strategy at Harmonic; he has over 20 years of systems and design experience in High Definition and MPEG video products. Prior to Harmonic, Mr Tow’s worked at Thomson as Director of Compression Technology and at Envivio (VP of Technology & Marketing). Mr Trow also served at Tandberg Television as Engineering Group Manager and, later, as its Segment and Product Manager for satellite, terrestrial and IP delivery of compressed material. Before Tandberg, he was a design engineer at Snell & Wilcox and Sony Broadcast.
Ian Trow obtained a B.Sc in Electronic Engineering from the University of Sussex and is Cisco CCNP & CCDA qualified.
Ultra HD is an important opportunity for the broadcast television industry. There are significant hurdles concerning interfacing, format standardization, and bandwidth requirements, but solutions exist. Cost-effective deployment of services at lower resolutions is needed for services such as OTT HD, since costs are a major problem for broadcasters in a multi-screen world. Repurposing HD and cinema derived content is crucial to providing an exciting Ultra HD experience in the home environment and offer applications like movie download at resolutions beyond HD.
Since the introduction of television in 1925, the user experience has dramatically changed. Aside from the resolution increasing, television has evolved in such a way that consumers can now watch high-quality video content on a wide range of devices, including TVs, PCs, tablets, and smartphones. Some second-screen devices, like tablets, feature Retina® displays with a high enough pixel density that the human eye is unable to discern pixelation at a typical viewing distance.
As consumer demand for a superior video quality increases, a new resolution format called Ultra High Definition Television (Ultra HD) promises to further optimize the television viewing experience, bringing cinema like clarity to the home television viewer. This article provides a detailed overview of the Ultra HD format, including the broadcast workflow, compression techniques, and other necessary steps that need to be accomplished in order to achieve widespread consumer adoption.
What is Ultra HD?
Ultra HD is a new digital video format proposed by NHK Science & Technology Research Laboratories and defined and approved by the International Telecommunication Union (ITU). The Ultra HD format presents native video at two resolutions (See Figure 1.). In this article we shall limit discussion to the lower resolution of 3840 x 2160 pixels. This is a massive improvement in quality over the current HD format (1920 x 1080) and just a step below what is currently being offered by digital cinema 4K (4096 x 2160).
The Ultra HD Workflow
The Ultra HD workflow is extremely complex. This is due to three main factors. Broadcast involves high-bandwidth real-time transfer throughout the chain. Content is derived from a variety of ingest sources as well as consisting of both national and regional feeds. Lastly, even though the highlighted workflow relates to Ultra HD, television provision has to increasingly cater for an ever expanding number of multiscreen options.
It is likely that in the interest of time broadcasters will provision their production environment for Ultra HD in the same way that most production facilities currently do for HD. To cater for resolutions lower than Ultra HD, transcoding the original broadcast content in a cost-effective manner is critical for broadcasters to maintain a healthy margin. While this article discusses the impact of Ultra HD and advocates the use of HEVC, such a compression scheme is equally applicable to the need for compression efficiency in multiscreen all the way up to OTT delivery. Many of the challenges a broadcaster faces when trying to establish an Ultra HD channel are easier to solve in a multiscreen environment. This is because there is often little legacy STB or PVR provision associated with multiscreen. Multiscreen playback relies on software running on standard platforms that can be quickly repurposed for new compression strategies like HEVC.
HEVC: Enabling Broadcasters to Support Ultra HD
A major concern for broadcasters and content providers is how to deliver high-bandwidth services like Ultra HD, specifically for catch-up TV. A new video compression standard called High Efficiency Video Coding (HEVC) provides the answer. HEVC significantly improves upon the current compression standard H.264 also known as MPEG-4 AVC (Advanced Video Coding) by reducing the data rate needed for high-quality video coding by approximately 50 percent. This enables broadcasters to deliver higher-quality services like Ultra HD using the same amount of bandwidth. (See Figures 2, 3, and 4.)
HEVC uses larger block sizes, enabling more efficient coding of large images, especially of regions with few changes in the picture content. This is extremely beneficial for applications like Ultra HD. Improved Intra-frame prediction allows better prediction of pixels by exploiting redundancy within the current frame. By offering more prediction directions than AVC, HEVC allows for a more sophisticated way of predicting and coding the intra mode selected.
HEVC also addresses other issues, such as banding, which won’t be discussed in great detail in this article. However, it is important to note that HEVC may include support for multi-view video coding or stereo 3D video in the future. This, combined with scalable video coding, allows a video stream, sequence, or image to be represented in multiple ways and formats. In other words, content can be prepared in different resolutions, screen characteristics, frame or bit rates, for viewing on multiscreen devices, all while retaining a high level of coding efficiency. With consumer demand for multiscreen services rapidly increasing, this will be important feature of HEVC.
Ultra HD and Multiscreen
While Ultra HD brings prestige to the television screen, the real challenge is cost effective delivery in multiple playout and delivery scenarios, enabling increased opportunities for targeted advertising. The MPEG DASH standard will allow content delivery operators to deliver Internet services, including Ultra HD, while containing the CAPEX and OPEX associated with multiscreen delivery.
DASH provides operators with a universal HTTP delivery format to cost-effectively scale adaptive streams to any connected device using a common encryption technology with one master key. Utilizing a single encryption standard, content is encrypted once and streamed to clients that support various digital rights management (DRM) systems. Each client receives a set of decryption keys and other necessary information using its specific DRM system, which is signaled in the DASH protocol, and then has the capability to stream the commonly encrypted content from the same server.
DASH can be implemented across all content delivery vehicles – broadcast, mobile, interactive television, and the Internet – while providing interoperability between all DASH profiles and connected devices. As Ultra HD content makes its way onto multiple consumer devices, DASH will be a critical enabling technology.
Applications and Consumer Adoption
HD took nearly a decade to mature; therefore, Ultra HD will likely be a gradual process before becoming a worldwide broadcast format. When HD was first introduced, there was relatively little content. A lot of content was upconverted from SD. A move to Ultra HD requires an even greater stretch to allow HD content to be repurposed.
It’s expected that Ultra HD will first take off in the production environment for applications like sports, where there’s a huge drive to achieve higher quality for major events like the World Cup. Ultra HD allows the use of advanced slow-motion and pan and scan techniques to capture high-quality live and replay content, which will greatly enhance sporting event coverage. Ultra HD also has massive appeal in the download market, where industry giants like Netflix and YouTube are already encoding their files using HEVC to support Ultra HD for cinematic 4K releases.
Before Ultra HD achieves mass adoption, work needs to be done on the consumer front. Current HDMI interfaces only support resolutions up to 1080p at 50Hz and 60Hz. Without a further iteration of the HDMI standard any move toward Ultra HD will be temporally hindered, unless the user is prepared to use dual synchronized HDMI connection into televisions. This approach is unlikely to appear on consumer equipment, although it is interesting to note that this approach has been adopted on 4K cameras where four HDMI synchronized connections are used to sustain the bandwidth required for baseband 4K video.
HDMI does have competition, namely HDBaseT, an Ethernet-based standard using Cat 5e connectors with major manufacturer backing from the likes of Sony, Samsung, and LG as well as Thunderbolt, commonly available on Apple devices. For Ultra HD to be a genuine successor to HD, consumer interface standards will need to evolve to support the data rates needed for Ultra HD at a minimum of 50 Hz and 60 Hz for broadcast and 100 Hz and 120 Hz for premium download applications.
SES ASTRA: An Ultra HD Real-World Case Study
While work remains to be done on the consumer front, the satellite industry has already been successful at transmitting Ultra HD content. SES recently partnered with Harmonic and Broadcom Corporation to pioneer the first Ultra HD transmission in the new HEVC standard live from an ASTRA satellite at 19.2 degrees East.
The end-to-end demonstration was powered by advanced HEVC transcoding (ProMedia Express) from Harmonic and an HEVC decoder from Broadcom for receiving HEVC encoded Ultra-HD television transmissions. The signal was broadcast in DVB-S2 using a data rate of 20 Mbit/s, proving that the HEVC format is able to support Ultra HD content at manageable bitrates.
This demonstration marked the first time that a full 3840 x 2160 pixel Ultra HD picture was broadcast live using HEVC compression. Previous demonstrations were broadcast in H.264 often using four HD encoders in parallel which introduces motion estimation and synchronization issues in the final decoded and reassembled picture. While Ultra HD delivery to consumer homes may still be a bit in the future, the demonstration iilustrates to broadcasters the potential for Ultra HD services.
Ultra HD is an exciting opportunity for the broadcast television industry. While there exist significant hurdles concerning interfacing, format standardization, and bandwidth requirements, solutions exist that will allow such services to launch within the next few years.
Understanding the likely workflow associated with Ultra HD will aid the cost-effective deployment of services at lower resolutions, for example OTT HD delivery. This is vital for broadcasters to improve their margins. CAPEX and OPEX have been an increasing problem for broadcasters in a multiscreen world.
Native Ultra HD content is the ideal for a broadcast service, but this expectation will be seldom met with initial service launches. Understanding how to repurpose HD and cinema derived content will be crucial if Ultra HD sets are to deliver the wow factor in the home environment and open up parallel applications like movie download at resolutions beyond HD.
The prospect of Ultra HD will further narrow the perception of a scene portrayed by television being indistinguishable from the live event, further immersing the viewer and enhancing the perception of broadcast television.