It is about time operators’ views were taken properly account of in setting priorities for development of standards for Ultra HD infrastructure, but that has now been done by the Ultra HD Forum. While some of the feedback confirms what we already knew or suspected, at least there is some clarity over which of the components or which versions operators are looking to deploy first.
To some extent, consumers’ voices have already been heard by the UHD alliance, the other of two bodies charged with bringing UHD standards to market, although not actually formulating them. The standards themselves come from the long-standing industry bodies such as DVB, SMPTE and the ITU, although the UHD Alliance and Ultra HD Forum wield growing influence over priorities for development and certainly over deployment.
The UHD Alliance is concerned with both the in-home viewing experience and the actual creation of the content. There is a determination to avoid the disappointments and bad publicity associated with the first so called “4K ready” TVs, which turned out to be incapable of exploiting other components of UHD now deemed more critical for the experience – such as HDR (High Dynamic Range) coupled with WCG (Wide Color Gamut) and in future HFR (High Frame Rate) as well as NGA (Next Generation Audio).
The Ultra HD Forum deals with all the infrastructure in between camera and viewing device, with a strong focus on interoperability but also backwards compatibility, which is where it overlaps with the UHD Alliance. We heard at the recent IBC 2017 that the bodies have acknowledged to some extent the absurdity of maintaining separate organizations, given the obvious and increasing synergy as well as overlap in members. They have announced they will be converging over the coming year, although not specifying whether this would be a complete union.
Meanwhile, the Ultra HD Forum has completed its survey of over 80 service providers with representation from all markets and all categories including cable, DTH, IPTV and pure play OTT. While full results will be published over the next few weeks, early findings appear to confirm the view that has taken hold for some time now, that HDR trumps higher resolution, delivering a much greater boost in perceived picture quality at a far smaller gain in bandwidth. 4K or 2160p resolution in principle generates four times as many pixels and therefore bits as 1080p “full HD”, although the bandwidth gain required is actually less after application of video processing and encoding, with more scope for exploiting redundancies within and between frames. By contrast, HDR only increases bandwidth required by about 20%, with slight variations between the different versions.
Various tests and focus groups have shown that 99% of people find a 1080p feed with HDR looks better than a 4K feed without HDR, yet it consumes less than half the bandwidth at most. The former has other advantages as well, being easier to produce and deliver with less change to the infrastructure. For example, 4K requires new cameras for the higher resolution, while existing 1080p cameras can capture enough dynamic range for HDR. The main extra requirement for HDR is some post production work including addition of metadata to ensure the full benefits are delivered.
Admittedly, this post production process is still work in progress and being addressed by the standardization process the Ultra HD Forum is overseeing. There are differences here between the versions, with Dolby Vision, already supported on a number of TV sets, requiring dynamic metadata which can be added to each frame, although often just per scene at present. That enables content to be rendered much more realistically with changes in the color levels and contrast.
The downside with dynamic metadata is that it has to be added to the picture on the fly, which requires a lot of computational power or else it can add delay, making it less appropriate for live content. For that reason, the BBC and NHK opted for a simpler approach called Hybrid Log-Gamma (HLG), based on current broadcast tools and workflow practices, compatible with its existing 10-bit infrastructure. Even so, HDR is simpler to deliver than 4K and less expensive to deploy on the production side. This sentiment was reflected in the Ultra HD Forum’s survey, where 81% of the 80 plus operators involved saw a benefit in not requiring static or dynamic metadata to be carried in production.
The most interesting aspects of the survey results revealed so far concerned two cornerstones of the Ultra HD Forum’s Phase B specifications. Phase A was the Ultra HD Forum’s first tranche of standards covering technologies already available commercially in 2016, including 4K 2160p resolution, the advanced BT.2020 and first versions of HDR, PQ and HLG, but frame rates only up to 60 fps and no NGA (Next Generation Audio).
Phase B embraces technologies that had been conceived by 2016 but were not then available commercially. They are now deemed likely to become available and start being deployed between two and five years from now, which is therefore the period covered by the Ultra HD Forum’s survey.
Apart from fleshing out HDR and ensuring that the best experience possible is delivered to legacy TV sets, phase B is most concerned with HFR and NGA. The findings for HFR were the less surprising of the two, as almost all operators agreed that there would be significant benefits going up to 50 fps or 60 fps, and 42% said that 100 fps or 120 fps would deliver a notably better experience still. Those higher frame rates come into their own for any content involving fast moving action, which includes many sports, especially the likes of golf, squash, cricket and even tennis where balls are moving at much higher speeds than humans can run.
The findings for NGA were interesting in that many saw great benefits from object based audio, not so much to create a more immersive experience through exotic surround sound, but to improve the clarity of on screen dialogue. Apparently more operators than we realize have had complaints from viewers unable to hear conversations above background noise, such as an audience or ambient sounds. Turning up the volume makes those background sounds louder as well.
NGA can ride to the rescue with object based audio, although many acoustic engineers dislike this term for being misleading and prefer “element based audio”. Such elements could include a motorbike passing by or a lion roaring, but could also isolate conversation. As well as separating these sounds out so they can be relayed across speakers to enhance sensations of movement, NGA can also differentially alter volumes of the individual elements, so that dialogue could be turned up while background noise is reducing, which could be very valuable for the hard of hearing.
The Ultra HD forum has acknowledged that such feedback from the field will help tune the standards and steer the Phase B roll out.