The advantages of 4K displays over 1080 full HD

Displays with 4K UHD resolution are more common and set to become the standard format for professional LCD displays in the future. Rob Moodey, of Matrox Graphics outlines the advantages they offer for the professional display industry and the issues associated with their use in large, multi-segment videowalls.

What are the advantages of 4K displays over 1080 full HD? Don’t we have enough pixels and resolution already?
4K Ultra High Definition (UHD) displays offer a pixel format of 3840 x 2106 pixels in 16:9 aspect ratio. This is four times as many pixels as full HD (at 1920 x 1080 pixels). On a screen of 32” the pixels are smaller and an unscaled image will appear slightly sharper. Below that, it is difficult to see the individual pixels and there will only be marginal differences in discernible images between the two types of screen.

The real advantage of 4K is for larger screens and when you get to 50” plus, the difference really begins to show up. Because of the increased resolution and our ability to resolve narrow angles 4K screens can display much more usable content. That means we can portray greater levels of information on a given screen size. This advantage escalates as the screen size increases, so it becomes possible to show the same amount on a single 65” screen as four, 32” screens for example.

Why does this matter, what are the benefits?
Mounting a single 65” screen is nearly always simpler than four 32” screens, with the 3-dimensional alignment and access issues it presents, as well as the attendant power supply, signal wiring and reliability and ventilation considerations.

There are no bezels across the single display and you do not need to worry about creating and managing the image in an off-board controller.

Any other advantages?
An interesting point that some AV people seem to have missed is in relation to events that are recorded, televised or even simply relayed to screens in the auditorium. Professional AV specialists always think about pixel pitch in relation to the distance of viewers from the wall. However, the distance that most viewers are from the displays is not related to the disposition of seats in the auditorium! There is a second, much larger, audience at a ‘viewing distance’ dictated by the zoom of the camera. When cameras focus, as they do, on the speaker standing in front of the wall, that distance is quite small. Many large ‘event’ walls would benefit from much closer pitched pixels than has historically been used to avoid strange aliasing patterns in the wall behind the ‘star turn’.

Eliminating that aliasing will expose the limits of lower spec scalers that have been historically built into the displays.

What implication does this have on the videowall market?

From the display point of view the installation will be simplified, particularly in applications of high density; control rooms, surveillance etc because you can display four times as much viewable content in a given area with a 4K display compared with four HD ones. So there are fewer screens overall, with fewer seams and a cleaner image across the wall. There is, potentially, less output processing for the videowall controller to do which simplifies the process.

However, the digital signal processing (DSP) requirement for 4K is significantly higher than for HD, and higher bandwidths are involved. Manufacturers of display processors and graphics devices are beginning to catch up with events and products are emerging. Future video processing kit must be able to handle higher resolutions at the appropriate quality. This starts at the cards rendering the images, like the new Matrox Cseries, and reaches onwards through all the routing equipment. Frame rates and latency will be challenges for many manufacturers here.

What problems will UHD inflict on installations, in distributing signals for example?
We are all familiar with the tiny distances that HDMI-based signals can be distributed and even the limitations with compressed HD over CatX and fibre cabling. With 4K at a much higher bandwidth this situation is compounded. Distance is roughly half that of HD: it is possible to achieve 50 – 70 metres or so before the signal disappears.
It is currently possible to transmit 4K, 30 fps with 4:2:2 chroma encoding or 4K, 60fps with 4:2:0 encoding on single link transmission, within the HDMI specification (latest 1.4) as they run at around 9 Gbit/s within the allowable 10.2 Gbit/s data rate of HDMI. Higher subsampling rates, longer distances and 8K resolution will require more, which means that realistically only fibre can suffice.

Matrox Avio KVM extenders with multi- or single-mode fibre connection operate at up to 400 metres and 10Km respectively for DVI) Dual Link capability. This makes them ideal in mission-critical environments that require stable, reliable I/O extension technology and where data security, heat, noise and space are prevalent issues. In situations such as utility control rooms, surveillance, command and control etc.

A final word on 4K?
Combining Avio KVM extenders together, for example, will enable 4K video at 60 fps 4:4:4 to be transmitted uncompressed with no latency over a single fibre. It is also possible to combine extenders with a 10Gbps network switch to create a high-bandwidth KVM extension and switching solution.

Display video resolution is on an inevitable march upwards, the video processing industry needs to keep up. Solutions will evolve and there will be ways to achieve what users and integrators demand.

Useful links

NEC Display Solutions – 4K UHD portfolio
NEC Display Solutions UK
Matrox Graphics

Published on: 30/09/2014