Sometimes more can be less in the world of TV standards and there are signs of that being the case for Ultra HD. With the UHD Alliance already established eyebrows were raised when the Ultra HD Forum was launched as a separate body at IBC 2015 in Amsterdam, especially as both had one or two common members, such as Dolby.
Besides, the whole area of UHD had become inflated to embrace everything associated with what might loosely be called next generation TV, which meant that the field was already cluttered with standards bodies such as the ITU, EBU, DVB, SMPTE, MPEG and more recently the Streaming Video Alliance and the Alliance for IP Media Solution. But the point was precisely that another standards body was needed to restore some order and establish clear lines of interaction between the various contributors.
The result was that the UHD Alliance and Ultra HD Forum became closely coupled from the outset and neither defines standards themselves. There was a clear demarcation between the two, with the UHD Alliance charged with ensuring that content production and displays conform with emerging standards across the UHD spectrum, while the Ultra HD Forum focuses on the delivery infrastructure bringing those two components together.
This is reflected to a large extent in their respective memberships, with the Alliance being more compact but representative with around 10 companies, including Disney, Fox and Warner Bros, on the studio side, Samsung, Sony, Panasonic, and Sharp representing CE makers, Dolby and Technicolor on the technical front and then Netflix and DirecTV (now AT&T) as major service providers.
The Ultra HD Forum has at least an equally representative and significantly larger membership, with founder infrastructure players like Harmonic led by the redoubtable Thierry Fautier joined subsequently by silicon makers or designers like Broadcom, Sigma Designs and Marvell. Newer members include DirecTV, TNO, Sky, Unified Streaming, Fox, SkyPerfecTV, and Communicare Digital. This month the addition of Comcast, Fox, Deutsche TV Platform, Sky, Technicolor and MovieLabs representing Hollywood studios collectively brought the membership up to 46.
Meanwhile the Forum is poised to launch its first specifications for UHD infrastructure at NAB next week. But given its close alignment with the Alliance we can be confident they will be fairly close to its specs announced at CES 2016 in January. So it’s worth taking a quick peek back at those, which TVs now have to meet to carry the “Ultra HD Premium” logo.
Naturally the specified image resolution was 3840×2160, which was initially virtually the sole requirement before it became clear that all aspects of picture display quality needed to be scaled up together in some kind of consistent relationship to deliver a more immersive experience. The Alliance specified color depth of 10 bits, which means 1024 shades of each color rather than the 256 currently with 8 bits. Then for color gamut the BT.2020 color representation with a display reproduction comprising more than 90% of DCI-P3 colors is required, essentially adopting the standard developed by the US Film Industry to come closer to the color spectrum perceived by humans with normal vision. There is an argument that the contribution of improved color gamut to UHD has been underappreciated given the obsession with resolution and more latterly HDR (High Dynamic Range) as well as to lesser extent HFR (High Frame Rate).
Then for HDR the Alliance opted for the SMPTE ST2084 EOTF version with a contrast performance of either over 1000 nits peak brightness and less than 0.05 nits black level or over 540 nits peak brightness and less than 0.0005 nits black level. These two different specifications were chosen to allow for the differing display characteristics of LED and OLED displays. LED is capable of reaching higher luminance levels but weaker blacks and so can do better on the former while requiring more latitude for the latter. OLED can go significantly deeper on black levels which is one of its strengths, enabling display of more realistic darker scenes.
The choice of SMPTE’s version of HDR was also a significant development because there were several contending versions including HDR10 adopted for Blu-ray disks and already backed by many studios as well as Samsung and Sony. Then Dolby has its own format for OTT services called HDR, while Hybrid Log-Gamma (HLG) also has traction with the ITU-R as well as having been adopted by the Japanese Association of Radio Industries and Businesses (ARIB).
That is why there has been talk of HDR being the next major format battlefront for video and also why both the Forum and the Alliance are keen to converge on a common version, presumably SMPTE. The outcome is still unclear though with some major content providers such as Netflix and Amazon continuing to back both HDR10 and Dolby Vision HDR, as are some big TV makers such as LG and Vizio.
As expected the Alliance’s choice of parameters precluded most existing TVs from qualifying to carry its logo. Many sets failed to meet the peak luminance levels for example. Clearly then the Alliance and Forum together want to ensure this does not happen again and that both CPE equipment and infrastructure products that meet their specifications now do not become absolute as little as a year or 18 months down the road.
Yet even though most of the CE makers belong to one or both of these two standards groups, mostly the Alliance, some of them have been reluctant to concede to a common version of HDR. They have regraded this as an area for differentiation rather than standardization, but most are now seeing the light in the wake of the Alliance’s specification. Around 15 displays have now been certified as Ultra HD Premium, including all 2016 Samsung SUHD TVs, the Panasonic TX-65DX900 LED-LCD TV, and the LG Signature series of OLED TVs, all of which were also introduced at CES.
This was certainly a major step towards maturation of UHD around a coherent set of standards and technologies and we now await next week’s equivalent from the Forum doing the same for the infrastructure. At any rate Fautier, the Forum’s president as well as VP for Video Strategy at Harmonic, is now optimistic. He conceded that there was little coordination between standards groups in the early days of UHD, by which he means until well into 2015, but significantly he highlights two others on top of the Forum and Alliance that are playing key roles in uniting the field.
These are the Streaming Video Alliance, which develops and publishes open standards for interoperability within video streaming infrastructures; and then the Alliance for IP Media Solutions launched just in December 2015 to promote adoption of standards for the broadcast and media industry as it migrates from SDI to IP. Essentially these two groups are shaping the standards for future IP based infrastructures featuring larger amounts of streaming and naturally the UHD movement needs to be in harmony with that.