20 TVBEurope
News & Analysis Guest Opinion
I’m UHDTV, get me out of here
After the agreement on UHDTV in ITU BT. 2020, David Wood, chairman of the DVB Commercial Module for Ultra High Definition Television, examines what follows
WAS IT raining when Noah built his ark? No. Wise men start ahead of the curve. Both DVB and the EBU are doing so for UHDTV. ‘Disruptive technology’ like UHDTV takes many years to mature to the point of being ‘on-air’. The ITU UHDTV Recommendation is there, yes. The first Ultra High Definition Television sets are already on sale in some countries. But there are still a lot of electrons to flow under the Wheatstone bridge before broadcasting happens. ITU BT.2020 specifies two UHDTV levels, UHD-1 and UHD-2. They are successively four times the spatial resolution of 1080p and 16 times its resolution — 8Mpixels and 32Mpixels. There are other features which will bring higher quality to UHDTV; new colour primaries that will embrace even those in tomorrow’s OLED displays, 10 or 12 bits/sample, and an old wish-list item, ‘constant luminance coding’. The ‘big one’ is the inclusion of a frame rate of 120Hz — twice the highest used today for any media — movie or TV. This should really benefit sports. At a DVB-EBU fact-finding
The enabler Coming at the same time as ITU UHDTV Recommendation is the enabler of UHDTV broadcasting — HEVC compression. Perceived quality does not increase linearly with spatial or temporal resolution, rather with their
We also examined whether
there are limitations due to programme production technology. Here again the answer seems to be, at least in principle, no. We are about to enter the age of fibre optic interconnection, which means that essentially anything we reasonably ask for can be moved about the studio.
David Wood: The DVB answer is that we just have to take things as they come, and start with UHD-1. Do you agree?
workshop we estimated that the initial commercial demand for UHD-1 broadcast services would materialise in 2014/2015. Even by that time, its lesser cousin HDTV will still not be universal. But today the ‘development cycle’ is faster than the ‘implementation cycle’ for new media. So work is now underway in the DVB Project to specify a ‘broadcast profile’, UHD-1. Set makers have clear plans to market
UHD-1 displays. UHD-2, on the other hand, should wait until there are commercial plans for UHD-2 displays. It is the conundrum of UHDTV
that UHD-2 will come along ‘X’ years after UHD-1, and X may be shorter that the ‘roll out’ cycle for UHD-1. Is it better to go with UHD-1 or wait for UHD-2? The DVB answer is that we just have to take things as they come, and start with UHD-1. Do you agree?
Coupled with the improved content-adaptive HEVC, this means that UHD-1 will be very broadcastable by satellite, cable or a terrestrial system like DVB-T2
square roots. Happily, compressed bit rate probably does the same. Coupled with the improved content-adaptive HEVC, this means that UHD-1 will be very broadcastable by satellite, cable, or a terrestrial system like DVB-T2. The broadcasting standard need not constrain the parameters of UHD-1. UHD-1 trials in Korea with DVB-T2 have used bit rates of 20-25Mbps.
However, it is not all plain sailing. Although the HEVC specification allows pretty much anything from BT.2020, at the DVB/EBU workshop it seemed that UHD-1 receivers — essentially the ICs — would not be available running at up to 120Hz frame rate by 2014/15. So, the discussion today is
about two generations of UHD-1 receivers. The first, UHD-1C would allow up to 60Hz frame rate, and be available in 2014/15. The second, UHD-1H would be available later in the decade, and allow up to 120Hz. How can the system be
arranged so that UHD-1C sets can still watch UHD-1 content at 120Hz when available? An answer may be to broadcast the UHD-1 120Hz signal as a spatially scalable signal with a 1080p/120Hz base layer, and to include in UHD-1C sets the capability to decode 1080p/120Hz. This should be within the capability of the UHD-1C chip sets. The discussion today is also
about whether to request the ITU to add 100Hz to the UHDTV frame rates, or even 150Hz, as this would allow higher quality and lower cost conversion to and from 25Hz/50Hz HDTV. The UHD-1C scenario is a
practical one to get the show on the road, and movie content will not be troubled by the limitation on frame rate. When available, 120Hz will have serious benefits for critical sports content, but we may have to wait a while. But probably Noah had to be
pragmatic too, when he was building the Ark.
www.tvbeurope.com September2013
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