It has been some time since we posted our market update on UltraHD, and we promised to provide further posts on just what UltraHD is, particularly now in the latter part of 2016. This post covers the key technologies as a primer.
The industry sees UltraHD as a set of four key technology areas:
- High Dynamic Range/Wide Colour Gamut
- Next Generation Audio
- High Frame Rate
It is important though to see these as a menu rather than a recipe for next generation entertainment experiences. What we mean by this is that creating an UltraHD experience, you can pick some items from the menu rather than being required to use all the ingredients in the recipe.
When we published our white paper, the main focus was on 4K resolution, or more precisely 3840×2160 pixels. However in line with the view that better pixels is key rather than number of pixels, it is today accepted by many that 1920×1080 pixels is included in the UltraHD experience as long as it is used alongside High Dynamic Range/Wide Colour Gamut and at a minimum frame rate of 60fps (50fps in other markets like Europe). It also includes 8K, or more precisely 7680×4320 pixels, but this is something that is only really in the labs and demonstrations at this point. It is also important to point out that resolution (as well as the other key technology areas) is very much a property of both content and display, and there is full scope for up and downconversion at the device end to maximise the quality of the experience for the viewer regardless of the content or display resolution.
High Dynamic Range/Wide Colour Gamut
A key area of UltraHD is about making ‘better’ pixels and not just more, and this is where HDR/WCG comes in. HDR and WCG accomplish better pixels by increasing the range of content/display brightness and the range of displayable colour respectively, providing a more realistic image to the viewer.
HDR maps the digitisation of light levels in a useful way that creates a non-linear relationship between the digital representation and actual light levels (also done in Standard Dynamic Range using a different curve) known as a transfer curve. The two leading techniques are Perceptual Quantiser (PQ SCTE ST.2084) and HLG (ITU BT.2100) and focus on improving light level reproductions at low and high light levels as shown on the following charts.
There are other transfer curves in use and development and the selection and use of which curve is something to be saved for a whole lot longer post (or consulting engagement).
WCG in UltraHD uses a new colour space defined by ITU BT.2020, as opposed to the HD ITU BT.709, as represented by the following colour space diagrams with the triangles representing the colour spaces for each respectively, here shown using 10bit sampling levels.
The use of 10bits is not absolutely required but the additional digitisation precision that it brings over 8 bit significantly would remove the banding that would be introduced by increasing the colour gamut range without increasing the number of digitisation points.
Next Generation Audio
Existing video services are provided with multichannel audio ranging from stereo through to 5.1 and 7.1 reproductions, using standards based audio such as PCM, Dolby and DTS. New developments in audio are moving from channel based to object based audio, where separate audio sources are filtered, boosted, mixed and rendered on the client device based on information about the device, speaker and room configuration, as well software control. This space is defined by Dolby and Fraunhofer at this time, with AC-4 and MPEG-H respectively. This is designed to improve the audio experience as for the visual experience through ‘better’ vibrations. These developments are not part of the current generation of services in the main but will be a mainstream part of any 2017/2018 developments.
High Frame Rate
Existing HD services are transmitted using 25/30 frames per second or even 50/60 frames per second in some situations, particular for content where there are large amounts of motion. Much work has gone into the improvements that even higher frame rates can provide and there is significant benefit in picture quality and viewer experience. There is also the need to reduce the negative impacts in spatial bandwidth requirements from objects having to move more pixels for the same physical movement – a property noticeable when objects ‘jump’ or smear across screen more in a 4K image than in a 2K image.
However HFR use is dependent upon having the content made with higher frame rates, but there are some advantages seen from using it as a pure display technology. The lack of content (movies are generally produced in 24fps/48fps/60fps only currently) and technical issues with silicon and display interconnect technology limits its use in the short term. Certainly content organisations like the BBC see definitive improvements with frame rates exceeding 100fps particularly with respect to Sport however we will need to wait for technology to mature further as well as content to be produced. Definitely something that will be progressed in the 2017 to 2020 period with standards ahead of technology in this area.
This has been a very high level view of the four key technology areas of UltraHD and that you now have an appreciation of what it is but without much of the technical detail below the key definitions. If you wish to know more about the technical details and the latest status of these, Fairmile West is working with clients in developing and deploying UltraHD video solutions and devices and we are available to take you deeper into the key technologies and developments of UltraHD on request.
In addition we work with clients on technology strategy and product delivery through three key practices in Consumer Devices, Video Services and Business Development. If you are interested in learning more about what we do, please do get in touch via our website – Contact us.