Ultra HD Alliance, HDR and 4K Blu-ray at CES 2016
Now that the dust has settled, what did we learn at CES 2016?
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85We may look back on this year’s CES as a turning point for the television industry.A game-changing technology arrived, the consumer electronics companies made the sensible but decidedly unusual decision to work together and what will probably be the last physical disc format was finally launched. So let’s start with the game-changing technology. High dynamic range (HDR) is something you’ll be hearing a lot about this year as it not only revolutionises TV technology but fundamentally changes the way film and television is made.
The film community and the consumer electronics industry quickly realised that just increasing the resolution of an image wasn't going to provide enough of a difference to convince people to move from Full HD to Ultra HD. However, if they could widen the dynamic range that would provide the kind of visual difference that might convince consumers to upgrade, as well as allow content creators to take advantage of improvements in display technology. The idea behind HDR is simple, by increasing the difference between the darkest and the brightest parts of the image - the dynamic range - you create an experience that is more lifelike and has greater impact. HDR also gives filmmakers increased latitude when mastering content, allowing them to reveal more detail in both the darker parts of the image and the brighter parts, often within the same scene.
What HDR isn't about is just making the image brighter. Although it's an easy mistake to make, with manufacturers talking about 1,000 nits of peak brightness on their new TVs and HDR content being mastered at 4,000 nits and moving to 10,000 nits in the future. What those numbers actually refer to are the specular highlights, that is the small parts of the image that shine brighter - think of sunlight reflecting off metal for example. No one is suggesting people look at a full screen image that has 4,000 nits of brightness that would simply be uncomfortable, to say the least. The other aspect that is often overlooked about HDR is that it's the difference between absolute black and peak white so, the deeper your blacks, the better your dynamic range. This is why OLED TVs can deliver a fantastic HDR experience despite not being as bright as LED LCD TVs because their black levels produce contrast ratios that LED TVs can only dream about despite their higher peak brightness.
Of course manufacturers continue to develop LED LCD technology to deliver deeper blacks to go with those brighter highlights and at CES we saw some impressive examples of these new capabilities. Panasonic's new DX902 flagship Ultra HD 4K LED TV uses over 500 local dimming zones, with each inside a specially constructed honeycomb structure designed to reduce light leakage. There's also a diffuser filter that is designed to prevent the LEDs themselves being visible behind the panel, despite the DX902 delivering peak brightness in excess of 1,000 nits. The results were impressive with almost no light leakage, deep blacks and bright specular highlights. When watching HDR content there was detail in both dark parts of the image and the brighter parts, whilst highlights such as reflections and sunlight hitting objects had a greater sense of reality.A peak brightness of 1,000 nits is the current limit for consumer displays, although the professional monitors used in HDR mastering can deliver over 4,000 nits of peak brightness. However it probably won't be long before consumer displays catch-up and Sony, despite not commenting on the peak brightness of their 2016 TV models, were demonstrating their Backlight Master Drive. This new technology uses over 1,000 local dimming zones to deliver 4,000 nits of peak brightness and the results were stunning, with images that delivered a highly realistic dynamic range. An aerial shot of the Las Vegas Strip at night, a sight we have become quite familiar with over the years, looked utterly realistic with details in the darker parts of the image and the neon lights popping off the screen. There's no doubt that as display technology evolves, we're going to see better images than we ever thought possible.
As a result of these developments, the creative community is finding that they are able to do much more when shooting and mastering content. We met with Vanja Cernjul, the director of photography of the Netflix series Marco Polo, and he said that he was able to light the second season in ways that he never had before and for the first time could shoot interiors using natural light. He was amazed at the detail he could get in shadows, whilst also picking out the highlights in a fire or the moonlight. He described it as like having all his restrictions removed and now he wanted to discover ways of using this freedom in a creative manner. We heard that some directors of photography are so impressed that they only oversee the HDR master, delegating the SDR master because they don't want to see how restricted it is in comparison.
However it isn't just new content that benefits, older films shot on 35mm or 65mm can also have a lot of latitude, allowing HDR to take full advantage of it. That doesn't mean every film will benefit, some were only lit for 50 or 100 nits and thus offer no real opportunity for an HDR master but many older films will be mastered in HDR. The studios are keen to stress that no HDR master will be created without the consent of the filmmakers or their estates and in fact some directors have simply refused to have their films remastered in HDR because the original version is exactly what they wanted. However other directors, such as Francis Ford Coppola, have embraced the possibilities and we saw HDR remastered clips of both The Cotton Club and Apocalypse Now on an LG OLED TVs. To say the results were spectacular would be an understatement and Apocalypse Now looked like it was made yesterday, rather than in 1976. In fact when looking at HDR masters, directors often comment that the last time they saw some details was on the set with their own eyes. As long as the technology is used in a creative way and as long as remasters are done carefully, then HDR has enormous potential.
So if HDR is so great, what's the catch? Well there has, up until now, been a lack of coordination when it comes to Ultra HD in general and HDR in particular. The standards relating to television technology are set out by professional bodies like the Society of Motion Picture & Television Engineers (SMPTE), the International Telecommunications Union (ITU) and the European Broadcast Union (EBU). In fact the standards for Ultra HD (both 4K and 8K) have been established for some time and are covered by the ITU-R recommendation BT.2020 (also referred to as Rec.2020) which encompasses display resolution, frame rate, chroma subsampling, bit depth and colour space. Of course setting standards and reaching them are two very different challenges and it has taken a number of years for television technology to reach the point where it can actually deliver much of the new standards. We are now at a point where display technology can handle 4K resolution, 10-bit video depth, a frame rate of at least 60Hz and the DCI-P3 colour space used in the cinema. In the future we will undoubtedly see a move to 8K, 12-bit, 120Hz and a colour space that approaches the full Rec.2020 standard.
To this we can add HDR which is defined by a PQ (perceptual quantiser) transfer function developed by Dolby and which has been adopted by SMPTE as the SMPTE ST 2084 electo-optical transfer function (EOTF) or gamma curve to use a more familiar term. This new approach is a response to the fact that the current transfer function used, which was only standardised by the ITU-R as BT.1886 in 2011, is actually based on CRT technology going back decades. Dolby realised that not only is CRT extinct but display technology has moved far beyond its capabilities, so why not create a gamma curve based upon human perception rather than one derived from the limitations of an old technology. That certainly sounds sensible and Dolby are to be congratulated for developing and championing the idea of high dynamic range; in fact we saw the first demonstrations of Dolby Vision over two years ago.
However Dolby Vision isn't the only version of HDR and that's where things get complicated. During CES things got a little simpler, with Technicolor and Philips combining forces and possibly working with the open source HDR10 adopted by the Consumer Electronic Association (CEA) and currently used by Samsung, Panasonic, Sony Electronics, 20th Century Fox, Youtube and Amazon. HDR10 uses the ST 2084 EOTF and is mastered at 1,000 nits using 10-bit video depth and a colour space that can go up to Rec.2020. Philips/Technicolor take a similar approach but add mapping technology in order to adapt the content to correctly match the capabilities of the display. We actually saw an example of how this technology works and it certainly appeared to retain the original mastered image when mapping to a display that wasn't able to support HDR.
Meanwhile Dolby Vision has gained a degree of traction and is being used by LG for their new OLED TVs, along with Vizio, TCL and probably Hisense. Dolby Vision is also the choice for the majority of the studios so far with Warner Bros., Sony Pictures and Universal all embracing the technology. Dolby Vision's popularity probably stems from the fact that it's an end-to-end solution with a high degree of future proofing. Dolby Vision HDR is currently mastered at 4,000 nits (with plans to move to 10,000 nits in the future), using 12-bit video depth and the Rec.2020 colour space. Dolby Vision is also backwards compatible because it can deliver a base layer at HDR10 and then an additional 2-bit layer that overlays a 1080p mask on the content and adds the specular highlights up to 10,000 nits. As with the Technicolor/Philips solution there is also technology to map the content to the display's native capabilities using metadata.
A year ago the entire industry took the unusual step of joining together as an alliance in order to ensure that TVs could deliver a base level of performance that will allow consumers to get the most from all these new standards. The Ultra HD Alliance includes just about every manufacturer, film studio, internet provider and broadcaster you can think of, along with companies like Technicolor, Arri, Intel and THX. It is probably the most wide-ranging industry body ever assembled and they have spent the last year developing a set of guidelines for Ultra HD 4K. Some people might ask why this wasn't done sooner but it takes a long time to get this many companies with this much vested interest to agree on anything. There was also a need for the technology to evolve to a point where TVs could actually deliver the kind of performance that the content demanded. To the UHD Alliance's credit, the specifications they have drawn up are actually quite demanding and although they will undoubtedly change over time, they'll certainly provide an excellent base level of performance for the next few years.
The Ultra HD Alliance has created three different specifications to cover the next-generation entertainment ecosystem. The first relates to devices and, more specifically TVs, because the UHDA is still discussing how best to specify projectors. For a TV to be certified as Ultra HD Premium it must be capable of a 3840 x 2160 resolution, 10-bit colour depth and a wider colour gamut of at least 90% of DCI-P3. The certified TVs must also be able to accept the ITU’s Rec.2020 signal-input interface, which doesn't mean the TV has to actually meet the much wider Rec.2020 colour space, but it does have to be able to accept the Rec.2020 container which will be used for future 4K content. In terms of HDR the certified TVs have to include the SMPTE ST 2084 EOTF and thus can support either HDR10, Dolby Vision or Philips HDR. LG's new OLED TVs are certified Ultra HD Premium and they support Dolby Vision, whilst Panasonic and Samsung's LED LCD TVs are certified by supporting HDR10. In order to allow for both LED LCD and OLED displays, there are two different requirements for HDR; the TV must either either offer a combination of at least 1,000 nits peak brightness and less than 0.05 nits black level or, alternatively, more than 540 nits peak brightness and 0.0005 nits black level.
The UHD Alliance also have specifications for distribution, such as 4K Ultra HD Blu-ray, 4K streaming and 4K downloads, and although the Ultra HD Alliance is agnostic as to the method used to deliver content it does have certain requirements. The content must support an image resolution of 3840 x 2160, a minimum 10-bit colour depth, Rec.2020 colour representation and high dynamic range using the SMPTE ST2084 EOTF. Of course given the existing specifications for 4K Ultra HD Blu-ray, the new disc format not only meets these requirements, it easily exceeds them. Finally, there are specifications for content mastering with an image resolution of 3840 x 2160 and a minimum of 10-bit colour depth, Rec.2020 colour representation and high dynamic range using the SMPTE ST2084 EOTF. The Ultra HD Alliance also recommends that mastering displays must be capable of a minimum of 100% of DCI-P3 and a peak brightness of 1,000 nits and a black level of less than 0.03 nits.
For both the mastering and distribution channels, the Ultra HD Alliance does not specify a minimum colour gamut or dynamic range, so as not to constrain the artistic intentions of the content creator. However mastering and distribution channels are expected to use the Rec.2020 container even if the actual colour gamut used is less than the potential of the standard. As well as projectors, the UHD Alliance has yet to agree any specifications for 4K broadcast, which is why there is no mention of other EOTFs like the BBC's Hybrid Log Gamma or higher frame rates like 100/120Hz. However it's certainly a step in the right direction and whilst companies like THX provide a professional level of accountability, the UHDA will provide a consumer level of accountability. Naturally the licensing of the logo and certification of Ultra HD Premium TVs are as much about marketing as they are about recommendations but they are an important first step. Annual shipments of Ultra HD 4K TVs are expected to grow from 12 million in 2014 to 96 million in 2019 and the UHDA hopes to ease this transition. What is of particular importance is that consumers are able to enjoy some of the benefits of Ultra HD on their 4K TVs, even if they don't meet all the specifications.
Which brings us on to the final big launch at CES 2016 - 4K Ultra HD Blu-ray. The UHD version of Blu-ray has been a long time coming and although other methods of 4K delivery exist, it represents the highest quality 4K source imaginable. The standards for 4K Blu-ray include a three-layer disc with a resolution of 3840 x 2160, 10-bit video depth, 100Mbps, Rec.2020, HDR up to 10,000 nits, frame rates up to 60Hz and HEVC encoding. The BDA has also taken the sensible decision not to enforce regional coding with Ultra HD Blu-ray, which is certainly good news for enthusiasts. Although there has been a move towards people streaming more content, including 4K, there is still a place for a physical disc format. According to Panasonic only 15% of internet connections globally can deliver 4K and Ultra HD Blu-ray will provide the highest quality video and audio possible. It will also be able to deliver that performance repeatedly and once you've purchased the disc it is yours to watch whenever you want, you're not dependant on a third-party to provide access.
After DVD and Blu-ray, the studios have a well established workflow for producing discs and adding 4K Ultra HD Blu-ray will be relatively straightforward. As a result they will produce multiple masters for different delivery systems and physical disc will remain a viable format. In fact, disc sales remain a major source of profit for the studios, so there is certainly support for Ultra HD Blu-ray from them. The first players have also been announced, with the UBD-K8500 from Samsung and the DMP-UB900 from Panasonic. The Samsung is the cheaper of the two, with the Panasonic offering higher-end audio, but both deliver all the specifications laid down by the BDA. However it should be noted that neither player supports Dolby Vision, which is an option under the specifications, because the necessary chipsets won't be available until the summer. Panasonic feel that whilst HDR10 is the baseline standard, it's also a rich and compatible standard for the consumer to enjoy. At the moment both Sony and LG are holding off producing players of their own, as they wait and see how the format performs this year; and there will undoubtedly also be players from smaller manufacturers like Oppo at some point.
What is important to the studios is that at no point does a consumer put a disc in their player and get a washed out picture due to incompatibility with the 4K TV. The industry has gone to great lengths to ensure that consumers will get the best picture possible and the player will map the content to the native capabilities of the display. If for some reason that proves impossible, then the consumer will be asked to play the other disc included, which will probably be a standard Blu-ray. Amazon has already begun to take pre-orders for 4K Ultra HD Blu-ray discs and although these are quite expensive at the moment, prices will undoubtedly drop as production ramps up and the format becomes more mainstream. There will be some big changes in terms of display technology this year and even AVForums will need to establish new testing procedures for our reviews; whilst calibrators are going to have to develop new test patterns to setup HDR TVs and calibrate for the wider colour spaces. One thing is for sure, 2016 is going to be a brave but exciting new year.
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