what you need to know about 4k video

 WHAT YOU NEED TO KNOW ABOUT 4K VIDEO
by Greg Stidsen, NAD Director of Technology and Product Planning www.NADElectronics.com WHAT YOU NEED TO KNOW ABOUT 4K VIDEO
by Greg Stidsen, NAD Director of Technology and Product Planning
WHY 4K VIDEO NOW?
We live in an era when people feel compelled to have the absolute latest technology available for fear that
they may be buying a product that is already obsolete. As Canada’s eminent philosopher and technology guru,
Marshall McLuhan, famously quipped, “If it works, it is obsolete.” Commenting on the ever-increasing pace of
technology development, McLuhan meant to be tongue-in-cheek, but it seems our industry has embraced the
idea of releasing products before they are finished just to get the marketing bump ahead of their competitors.
Clearly, large TV brands are pushing for 4K as they hunger for new technology to drive sales.
WHAT’S THE BIG DEAL?
The switch from HDTV to UHDTV is just as big as the switch was from analogue 480i (576i) to 1080 digital
progressive TV a decade ago. This requires new HDMI transmission specifications, new HDCP copy
protection, a new colour gamut, new video compression, and the requirement for a whole new generation of
high-speed digital video parts to handle the huge bandwidth of UHDTV.
Because so many different stakeholders—licensors, patent holders, manufacturers and government
agencies—are needed to coordinate and agree on all the details, we expect a prolonged stage of confusion
and uncertainty in the market as these elements begin to mesh. We also expect to see some serious
compatibility problems before all the bugs get worked out. Remember the early days of HDMI? Expect to see
similar inexplicable problems as different generations of 4K parts interact in complex systems.
WHAT CAN I WATCH IN 4K?
The infrastructure required to film, produce, store and transmit 4K content is also in its infancy. The industry
will wobble and lurch through the ‘the egg and the hen’ phase where there is ‘nothing to watch’ on the new
UHDTVs, because content producers won’t release 4k media until there are enough 4K TVs to make the
release commercially viable.
In addition to Sony’s reportedly buggy HDD Player with the specially encrypted link only to Sony TVs, Netflix,
Amazon and YouTube are planning to stream 4K content to subscribers over the Internet. It appears there will
also be a new optical disc format, an upgraded Blu-ray in late 2015, for secondary movie distribution.
WHAT’S WRONG WITH 4K VIDEO?
Beyond the obvious lack of any 4K content, the next generation of the semiconductors required for UHD are
still in development. Currently, older 3GHz parts are being used, resulting in severe limitations to video quality,
especially when compared to what the standards allow. In order to get 60fps video cadence, for example, the
colour resolution must be severely reduced to stay within the 3GHz bandwidth limitation. The colour (chroma)
is only present in every other horizontal pixel, and these alternate every other line (4.2.0). This is like having
progressive scan for Luminance and a low resolution interlaced display for Chroma. This leads to some
familiar, but unpleasant picture artefacts, especially during fast motion. Now you know why the 4K TVs at
exhibitions and shows are always displaying a fixed image or a slow motion pan of stationary objects.
Unfortunately, it looks like it will be 2016 before the necessary 6GHz parts will be in full production. These will
allow the full capability of the UHD specification including 4.4.4 colour and yes, 8K video. At that time we
should also have a good idea about program sources and availability, and the bugs should be ironed out of the
copy protection system.
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MAY INTELLIGENCE PREVAIL
NAD takes a more rational approach to technology evolution – we call it Modular Design Construction (MDC) –
that allows products to be upgraded to the latest technology without throwing away the elements that are not
obsolete. Upgrading the HDMI to the latest version, adding surround sound features, and even adding
streaming wireless music services is all made possible with MDC. This also allows us to take the time required
to perfect new technology and make sure the standards are well established before subjecting our customers
to the possibility premature obsolescence. A prime example is 4K Video where many of the details regarding
this new format are not fully settled and where testing and compatibility between different models has not
begun.
Why buy a half-baked solution now? With MDC you can add exactly what you need when you have the need
for it.
NAD is working closely with leading semiconductor providers to develop intelligent solutions for our customers.
Working with the latest parts is challenging as the documentation for implementing the parts is often lacking in
the early stages of development. We often find bugs that can only be resolved by the chip vendor. Often the
full spec and capabilities are not yet implemented or proven. This is particularly true with a new and complex
technology like UHD.
With MDC, you can wait until the dust settles. Then we know exactly what the download, streaming, and Bluray options will be, plus what mix of technology will be required to fully exploit these ultra-high definition
programs. Right now, 1080p is all you need because there isn’t much of anything else to watch. As 4K native
programming becomes commonplace, all the open questions about encryption, compression, and colour
space will be answered, and the complete video chain will be reliable from start to finish. That will be the right
time to upgrade.
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Technical Details about UHD and FUHD
It’s Not Really 4K, it is UHD
‘4K’ has become the common name for ultra-high definition television (UHDTV), although its resolution is only
3840 x 2160 (at a 16:9, or 1.78:1 aspect ratio), which is lower than the 4K industry standard of 4096 x 2160 (at
a 19:10 or 1.9:1 aspect ratio). This allows easy upscaling from 1080p and 720p programs, which are likely to
be the majority of programs watched on the new UHDTVs for at least the next few years.
The use of width to characterize the overall resolution marks a switch from the previous generation of high
definition television, which instead categorized media according to the vertical dimension, such as 720p or
1080p. Under the previous convention, a 4K UHDTV would be equivalent to 2160p.
The Ultra HD 4K resolution of 3840 × 2160 simplifies video scaling from the popular high-definition source
formats 720p and 1080p. A 1080p video source can be scaled perfectly by simply doubling each pixel
horizontally and vertically, using 4 pixels on the Ultra HD 4K display to represent each pixel from the 1080p
source. Similarly, a 720p source pixel can be tripled horizontally and vertically, using 9 pixels on the 4K display
for each pixel from the 720p source. The 720p and 1080p resolutions will also evenly divide the 8K resolution
of 7680 × 4320.
Which Compression Algorithm for Streaming?
There isn’t enough bandwidth available today for streaming 4K video without the use of lossy compression.
Unfortunately we don’t have a common standard for video compression, so playback equipment will have to
support multiple codecs.
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YouTube began supporting 4K for video uploads in 2010. Users could view 4K video by selecting "Original"
from the quality settings until December 2013, when the 2160p option appeared in the quality menu. In
November 2013, YouTube started to use the VP9 video compression standard, saying that it was more
suitable for 4K than High Efficiency Video Coding (HEVC); VP9 is being developed by Google, which owns
YouTube.
HVEC - The first version of the standard was completed and published in early 2013. The second version of
the standard was completed in July 2014 (expected to be published in late 2014) and includes range
extensions (supporting enhanced video formats), scalable coding extensions, and multi-view extensions.
Additional extensions remain under active development, which includes 3D video extensions.
In 2014, Netflix began streaming House of Cards, Breaking Bad and "some nature documentaries" at 4K to
compatible televisions with an HEVC decoder. Most 4K televisions sold in 2013 did not natively support HEVC,
with most major manufacturers announcing support in 2014. Amazon Studios began shooting their full-length
original series and new pilots with 4K resolution in 2014.
Full Ultra HD
UHD is a resolution of 3840 pixels × 2160 lines (8.3 megapixels, aspect ratio 16:9) and is one of the two
resolutions of ultra-high definition television targeted towards consumer television, the other being FUHD
which is 7680 pixels × 4320 lines (33.2 megapixels). UHD has twice the horizontal and vertical resolution of
the 1080p HDTV format, with four times as many pixels overall.
What About an Optical Disc Format?
On September 5, 2014, the Blu-ray Disc Association announced that the 4K Blu-ray Disc specification will
support 4K video at 60 fps, High Efficiency Video Coding, the Rec. 2020 colour space, high dynamic range,
and 10-bit colour depth. 4K Blu-ray Disc will have a data rate of at least 50 Mbit/s and may include support for
66/100 GB discs. 4K Blu-ray Disc will be licensed in the spring or summer of 2015 and 4K Blu-ray Disc players
have an expected release date of late 2015.
New Expanded Colour Gamut
This chart shows the full spectrum of colour perceivable by
Humans (outline of colour area). The small black triangle
shows the colours reproducible by HDTV, while the large
black triangle shows the colours reproducible by UHDTV.
Diagram of the CIE 1931 colour space that shows the
Rec. 2020 (UHDTV) colour space in the outer triangle
and Rec. 709 (HDTV) colour space in the inner
triangle. Both Rec. 2020 and Rec. 709 use Illuminant
D65 for the white point.
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Chroma Subsampling
Chroma Subsampling reduces colour resolution to save bandwidth and storage requirements. Since the eye is
less sensitive to colour than to brightness, the colour portion of the signal can be compressed without inflicting
as much damage to the picture compared to reducing the Luminance portion of the signal. It also relies on the
eye’s reduced sensitivity to the extremes of the red and blue spectrum of light. While engineers try to reduce
the ill effects of compression, it would certainly be better to include all the colour information.
The amount of compression is described by how many pixels of Luminance and Chroma are present in the
signal. 4.4.4 means that every pixel has complete colour information.
4:4:4 Y'CbC
Each of the three Y'CbCr components have the same sample rate.
4:2:2
The two chroma components are sampled at half the sample rate of luma:
the horizontal chroma resolution is halved. This reduces the bandwidth of an
uncompressed video signal by one-third with little to no visual difference.
4:2:0
In 4:2:0, the Cb and Cr channels are only sampled on each alternate line in
this scheme, the vertical resolution is halved. The data rate is also halved.
This has only half the vertical chrominance resolution of 4.2.2. 4:2:0 only
stores and transmits one colour channel per line (the other channel being
recovered from the previous line).
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