R the HDR data. SDR is encoded using a tradition-
al gamma curve compatible with SDR displays,
while the HDR data is encoded using a logarith-
mic curve that lets compatible HDR displays
stretch the signal over the additional brightness
and contrast in the display. This allows one bit
stream to serve both SDR and HDR sets, and
you can see how the name was derived from
the italicized words in the paragraph. Later in
this feature, you’ll read more about the creative
challenges this technique imposes.
Beyond metadata, Dolby Vision can process
at up to 12 bits, which may help avoid color banding and similar issues over the two other systems
that process at 10 bits. Although the contrast of
most current HDR displays peak at around 1,000
nits, you can master Dolby Vision at up to 4,000
nits, which should make it more future-proof for
more capable TVs in the future. Finally, as part of
the license, Dolby Vision-equipped displays use
a consistent color mapping engine that should
ensure that Dolby Vision-mastered content provides better color and tone accuracy.
As stated above, backward compatibility
with older 4K sets without HDR was a major
driver for HLG. Dolby Vision can support backward compatibility via a dual-layer system, in
which the base layer contains a legacy SDR
bitstream and an optional enhancement layer
carries a supplementary signal and the Dolby
Vision metadata. For delivery to known Dolby
Vision-enabled systems, you can also produce a
single layer that contains both video and metadata, which is the approach most producers use.
HDR10 does not have a configuration that supports SDR devices.
At press time, Samsung and Amazon announced HDR10+, which is essentially HDR10
with dynamic tone mapping. This takes HDR
from static mapping on the left in Figure 2 to
dynamic mapping on the right; a very significant
improvement. This feature will be available on
2017 TVs and on older HDR10-compatible TVs
via a firmware update.
Figure 3 shows pre-NAB support for the various manufacturers and publishers for the technologies discussed above. For complete coverage, you’re going to have to select two or possibly
three technologies and create the bitstreams
necessary to support them. Hopefully, the list
won’t keep growing.
Beyond the features table analysis above,
several considerations will likely dictate which
standards you decide to support. For example,
Dolby Vision is also deployed in movie theaters,
so if you’re using the technology there, you have
a substantial investment in expertise and equip-
ment, and the Dolby workflow easily supports
distribution to all display points. This makes
Dolby support a natural.
On the other hand, if you’re looking for live
HDR technology, Dolby doesn’t yet have an offering, while both HDR10 and HLG systems are
available. Finally, geographical considerations
are also important, and the technology selected
by the BBC and NHK will likely dominate the
U.K. and Japan. One U.K. broadcasting executive I spoke with said they adapted HLG because
they knew it would likely dominate in the U.K.
In this regard, when choosing which HDR technology or technologies to support, it’s not only
about supporting the highest-quality technology
available; it’s about supporting the technologies
used by your target viewers.
6. Your workflow and toolset will
be dictated by your format choice.
Your workflow will almost certainly be dictated by your HDR technology choice, particularly if you elect to produce Dolby Vision. You
can see this in Figure 4 on the next page, which
details the Dolby Vision workflow that incorporates key development partners at every step.
This graphic is from an informative overview
presentation available on Vimeo at vimeo.com/
The Dolby Vision workflow is very structured, and includes grading and output provisions for screens ranging from digital theaters
to old Rec. 709 TVs. Martin Zeichner, Colorist
at Deluxe’s Encore Post in New York, who mastered the second season of Netflix’ Marco Polo
for Dolby Vision, describes the process: “What
HDR support by
Ultra HD 4K News)