34 Saturday 14.09.13 theibcdaily An immersive experience
After the 3D debacle: is 4k a big hit, overkill or a placeholder for 8k? The view of Dr Hans Hoffmann, Head Media Fundamentals & Production Technologies, EBU
3D enthusiasts may be saddened by the bitter reality that ‘stereoscopic 3D to the home’ has moved out of the headlines. But it’s no surprise that the industry quickly found a replacement to generate new revenues from displays, by selling an even more immersive television system for the home. For a few years now Ultra High Definition TV has been under debate in standards bodies and the subject of highly impressive demonstrations. And now the debate has moved into the living room with the commercial availability of UHD-1 (‘4k’ – 3840x2160) displays. The early adopters are almost on the starting blocks for UHD-1. But if the race is to run smoothly there are a few essential steps to be taken before the starter’s pistol fires. Profiles for the various UHD parameters set out in the ITU-R BT.2020 recommendation are needed, to reflect what’s possible in silicon both in the short and longer term. And these profiles are needed before UHD reaches the mainstream. Research done by the EBU’s Beyond HD and Broadcast Technology Futures groups has proved that to provide a clearly perceptible improvement over HDTV requires a lot more than
just four or 16 times HD resolution. There are questions around high frame rates (HFR), higher dynamic range (HDR), increased colour space and more. Each of these parameters contributes in its own
characteristic way to an overall improvement in image quality. As an example, one could say that increasing only the resolution and leaving all other parameters untouched, the improvement over HDTV is lost as soon as the viewing distance is increased. However with a higher frame rate, the use of more colours, or making objects in dark areas of the image more visible (via HDR), even at viewing distances of four to five times the picture height we have what can be described as ‘perceptibly better than HD’. So, in summary, a highly immersive experience will come with several wisely chosen technical options for video and audio; but these also have to be measured against hard business figures in a period when many broadcasters are still implementing HDTV.
Performance parameters The EBU’s Broadcast Technology Futures (BTF) group consists of the R&D centres of
Hans
Hoffmann: The early adopters are almost on the starting blocks for UHD-1
The added value for the viewer, crucial to success of a new service,
may be achievable
already with UHD-1 for the home environment
BBC, IRT, RAI and NHK. The group has identified in subjective testing that frame rates beyond 60p can provide a much better viewing
experience. In addition, at a joint EBU/DVB workshop last May and in an ad hoc group of the EBU’s Beyond HD strategic programme, the issue of HEVC performance has been examined. The indications are that 10-bit should become the standard bit depth for UHD-1 (2160p50); and for UHD-1 with HEVC, bit rates equivalent to the ones used in HDTV programme distribution via satellite may be feasible in the coming years. Broadcasters and content
providers launching services in the next few years will, however, not be able to explore the full range of UHD parameters defined in the ITU and SMPTE standards. For more than 8-bits/sample, we’re told that frame rates beyond 60p will not be realisable in chips for infrastructures, encoding and decoding. The interface between home devices – HDMI – will hopefully soon support UHD-1 resolutions at
conventional frame rates, but it may still fall short on HFR, HDR and extended colour. To ensure a certain level of
interoperability and protect consumers’ investments in UHD-1 displays, DIGITALEUROPE is working on a labelling scheme for UHD-1
displays and has established close cooperation with the EBU in this regard. In addition, serious development is required on the infrastructure side for production, in particular to move UHD through the facilities, in distribution and in the home. Higher or extended dynamic range is the technical parameter that has arrived most recently on the agenda for discussion. Done properly it can deliver a further perceptible improvement over HDTV images. What ‘properly’ means is currently under subjective investigation behind the scenes; reports are expected at the autumn meetings of the ITU-R Study Group 6. Open is still how a higher or extended dynamic range broadcast chain would look.
UHD, not 3D So, why is it that broadcasters are showing more enthusiasm for UHD-1 than they did for 3D? The digital workflow for UHD content production is similar to what has been established for HDTV: single camera systems and a single video stream travelling through the production systems to the home.
Specialised skills will be needed to ensure good UHDTV grammar, but not to the same extent as for more costly 3D stereoscopic productions. Additionally, we’re also hearing broadcasters say that using UHD-1 cameras for HDTV productions serves to, via oversampling, deliver very good HD images and to already start filling the archives with content that can be used when UHD-1 becomes feasible in distribution and display.
And what about the future and the prospects for UHD-2 (4320p)? While the industry is focused on UHD-1, the ultimate goal of UHD-2 should not be forgotten. It all depends on the applications and the intended presentation environment. The added value for the
viewer, crucial to the success of a new service, may be achievable already with UHD-1 for the home environment. But other applications – cinema, public viewing, home video walls, etc – will clearly benefit from a full UHD-2 service. The development of display technologies in the coming years will give direction to the UHD-2 trend.
In the final analysis, what will mark success or otherwise for UHD will be determined not by the best possible technology or the compromises made; rather it will be by whether immersive TV experiences that add clear value for the viewer can be generated to enable a valid business case.
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