In Broadcast - In Show Guide 2016 - 10


10

www.inbroadcast.com | IBC2016 InShow Guide | 9-13 September

HDR - A Stride Toward
a Truly Immersive
Video Experience
By Bernard Riera, Director of New Technologies and Innovation

H

igh Dynamic Range is an
increasingly hot topic for the
industry as a whole, especially when you
consider its potential to give audiences
the type of immersive experience that
they increasingly demand.
The 4Ever consortium - of which
Globecast is an active participant - was
recognised for its work on UHD-TV
phase 2 with the 2016 NAB Technology
Innovation Award. The award is
given in recognition of significant
contribution to broadcasting and is
given to companies or organisations
that bring advanced technology
exhibits and demonstrations to
the show. The 4EVER-2 consortium
received this year's award for
'Demonstrating Important Benefits
and Features of Ultra High Definition
Television over Different Types of
Networks'.
At NAB, 4Ever presented its UHD-TV
HDR (High Dynamic Range) and HFR
(High Frame Rate) demonstrations
during the show, illustrating three
UHD-TV aspects: spatial definition
(4K); contrast and detail levels (HDR);
and motion rendering (HFR). The
new ATSC3.0 standard was used to
deliver the HDR version, while HFR
4Ever-2 Open Innovation Camp presentation.
Photo Caroline Ablain

was encoded real-time with HEVC
technology on an end-to-end live chain
over IPTV.
Operational Partners
Following on from the successful
4EVER project (June 2012 to June
2015), 4EVER-2 began in June
2015 with nine partners (Orange,
AMPVisualTV,
ATEME,
France
Televisions, Globecast, Highlands
Technologies
Solutions,
INSA,
TeamCast, and Telecom ParisTech).
Following on from its initial
successful work in High Frame Rate
evaluations and High Dynamic Range
live production, the group will continue
collaborating with major industrial
manufacturers to evaluate their
technologies and demonstrate live
operations during premium sports and
cultural events. They will also continue
contributing to standardisation bodies
and international forums working on
Ultra High Definition, and will share
their visual assessment results and live
trial results with these communities.
Dynamic Displays
HDR was also one of CES 2016's buzz
words and the ITU has recently issued

a standard for the format, which is a
big step towards HDR adoption and will
help to drive the availability of HDR TV
sets in the market.
On the subject of HDR, the ITU
says in its recent ITU-R BT.2100-0
recommendation, "HDR TV provides
viewers with an enhanced visual
experience by providing images that
have been produced to look correct on
brighter displays; that provide much
brighter highlights; and that provide
improved detail in dark areas."
In order to discuss HDR, and
consequently brightness, we need to
introduce the concept of a Nit. A Nit
is a non-SI unit with 1 Nit equalling
1 candela per square metre. HDR
provides detail in content where
SDR (Standard Dynamic Range)
cannot, with fine rendering in both
the brightest and darkest areas of a
picture. That means expanding the
quantity of Nits in bright content while
decreasing them to the minimum in
the darkest content.
But there's a limit to increasing
the rendering of the darkest content
and that's down to the light-handling
capabilities of a display. Any external
light source - natural or artificial
- will dramatically impact
the rendering of the darkest
content. Consequently, display
manufacturers
prioritise
rendering of the brightest
content with the highest value of
Nits on HDR displays.
EOTF is the Electro-Optical
Transfer Function and it defines
the way to extract light from
digital
information.
EOTF
definition is necessary to view
content properly as the EOTF
must match the reference
display used by the artist to
create the original content.
Ideally, the EOTF curve has to
match human eye performance
that's defined by the Barten
Ramp; below the Barten Ramp

the human eye is unable to perceive
contrast steps. OETF is the inverted
EOTF function that defines the way to
encode the light captured both by the
camera sensor and also the artist's
intention.
Legacy SDR EOTF is based on CRT
response capacity with the physical
characteristics of LCD/Plasma displays
allowing extension of that range.
Typically, SDR legacy displays had
a brightness of 100 Nits; more recent
displays are able to reach 300 to
400 Nits, while the most recent HDR
displays reach a brightness of more
than 1000 Nits.
HDR Technologies
Backwards compatibility ensures that
HDR signals can be understood by any
device and interpreted as a SDR signal
if the device is not HDR compatible.
For this, associated metadata are
key in order to guarantee that the
receiving device will be able to
interpret the information carried by
the signal.
At the encoder level, HEVC codecs
are fully compatible with HDR signals,
with the bitrate increase due to HDR
estimated to be between 15 and 20
percent of the SDR signal.
In conclusion, HDR is here
and here to stay. The recent ITU
standardisation offers confirmation
of the work done. HDR dramatically
improves the viewer experience.
Even at 2K or 4K video resolution,
subjective tests demonstrate that
HDR technology impacts on using the
experience much more significantly
than spatial resolution improvement.
HDR technology is suitable for both
post-produced content as well as
live content and benefits drama,
documentary and sports content.
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