http://www.tvtechnology.com/opinions/0004/uhd-is-about-more-than-just-pixels/278889
UHD is About More Than Just Pixels
High dynamic range, high frame rate, wide color gamut and deeper sample bit
depth are important too
June 22, 2016
By Matthew Goldman
BOSTON-I had the pleasure of being part of the 2016 NAB Show Super Session "4K,
UHD, HDR and More: The Future of Video." In a very large conference room
completely full of attendees, my co-panelists and I-under the astute direction
of TV Technology's Deborah McAdams-talked about a variety of Ultra High
Definition (UHD) related topics, describing the state of the industry with
regard to UHD as well as opining about what we thought were the important
issues to tackle and where we thought the industry was heading.
"Ultra HD," of course, means much more than just higher spatial resolution (4K
and 8K), even though that is to what many in the industry and consumers equate
it. It includes four other image as well as immersive audio technologies. The
four other image technologies are high dynamic range (HDR), wide color gamut
(WCG), deeper sample bit depth (higher number of coefficient bits for the
digital samples), and high frame rate (HFR). All of these technologies combined
create a much more realistic and immersive TV viewing experience than today's
conventional HDTV, without requiring any special head gear (such as that
required for the near-totally immersive virtual reality techniques that are
also a new exciting area of discussion).
BANDWIDTH CONSTRAINTS
As is typical, pre-produced content is ahead of live TV broadcasting for
delivering UHD, with Ultra HD Blu-ray discs and some on-demand or over-the-top
services already providing both 4K and HDR. This should not be a surprise: it's
much easier to implement new services when one controls both ends of the
ecosystem, with only a passive delivery pipe in between. All post-production is
done in advance, with the receiver/player/rendering/etc. acting on the content,
unchanged by the delivery mechanism, whether via wire, wireless or "sneaker
net." With live TV broadcasting, there is no advanced post-production; all is
done in real-time. Live changes (such as logo insertion, lower thirds, graphic
overlays, picture-in-graphics, squeeze & tease, cross-fades for interstitials,
or country-specific format conversions, etc.) could occur at each "node" along
the live broadcast chain. Another major factor is available bandwidth; there
simply may not be sufficient bandwidth to delivery UHD services, especially for
the technologies that require a lot more bandwidth than today's conventional HD
services do. Lastly, there may be regulatory restrictions impacting new
services over certain networks, such as over-the-air broadcasting, that prevent
economically-viable transmission of UHD services.
As previously mentioned, all of the five image technologies combine to give a
much more compelling visual user experience than today's conventional HDTV, so
if a content/service provider is able to offer a UHD service that includes all
five, then fantastic. Definitely offer this compelling, much more realistic TV
viewing experience. Consumers will be thrilled.
However, what if bandwidth constraints prevent the content/service provider
from offering "full UHD," so to speak? Should the provider just resign itself
to continue with today's conventional HD service? Absolutely not. The
combination of HDR + WCG + 10-bit sample depth (which many of us refer to as
"HDR+") has been shown in numerous demonstrations to have fantastic "wow"
factor for consumers. And the good news is, depending upon the HDR+ scheme
chosen, the bandwidth increase over conventional TV (what's now referred to as
standard dynamic range + narrow color gamut + 8-bit depth) is minimal, in the
general range of zero-20 percent when using the new HEVC video compression at
direct-to-consumer bitrates... most definitely the Best Bang for the Bit.
Compare this to 4K resolution: Even with the best video compression available
today (HEVC), 4K resolution still requires somewhere around 250 percent the
bandwidth of conventional HD (also coded using HEVC, for apples-apples
comparison). And since the "bread and butter" of revenue still will be the
conventional HD service, this bandwidth requirement most likely will be in
addition to the existing service (that is, simulcast will be required).
IS 4K NEEDED? WHY NOT 1080P?
So in the case of bandwidth constraints, why not transmit in 1080p HDR+ and
achieve the "wow" factor of HDR+? All 4K TVs upconvert 1080p to 2160p (4K) and
the newer UHDTVs (4K + HDR+) will display an HDR+ image if the incoming stream
has HDR+ coded, regardless of the spatial resolution. Many consumers may not
even realize that the image was upconverted to 4K: An oft under-discussed issue
is that the proper viewing distance for the human visual system to resolve 4K
resolution is approximately 1.5x the picture height of a 16:9 display, whereas
HD resolution can be resolved in full as far back as 3x the picture height. In
most TV viewing environments today, consumers are sitting back from the display
about 2.5-3.5x the picture height, therefore not really "seeing" much
difference between HD and 4K.
Ericsson has done "unscientific" experiments at trade shows over the past two
years, with two equal size flat screens side-by-side and we asked attendees
which image they preferred (without telling them what they were looking at).
Almost 100 percent would select the 1080p HDR display over the 2160p SDR
display (and this was done at the proper viewing distance). This unscientific
experiment is just one of many that have shown the "wow" factor of HDR+ to
consumers, regardless of screen resolution.
So what about HFR? Like 4K resolution, HFR requires lots of changes in the
studio and post production facilities. Its impact is also related to how fast
or complex the scene motion is, so it's extremely useful for high motion sports
and nature documentaries, but doesn't do anything much at all for "talking
heads" and other low motion content. While there are examples of specialty
content being shot at HFR-for video, this is defined as anything higher than 50
or 60 fps (country TV-standard specific), but it typically refers to 100 or 120
fps today-wider use of HFR likely will not occur for several more years to
come, so it is not so big an issue for today.
In summary, if a provider is able to offer a UHD service that contains all of
the five image technologies than definitely do it. This is just so much better
than today's conventional HD. However, if bandwidth constraints prevent "full
UHD" from being delivered, the Best Bang for the Bit is definitely 1080p
HDR+... with much of the "wow" factor and a far superior user experience over
today's conventional HD.
Matthew Goldman is the senior vice president of Technology, TV & Media Strategy
for Ericsson
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