VESA Creates Logo Program for Gaming and Video Display Response
VESA has just announced a new logo program for gaming displays and video displays to make life much better for gamers, content creators, consumers, and set makers. In the longer term, we think it could be beneficial for the development of 8K.
In 8K, Frame Rates Matter
First, with huge screens and 8K content, many think that issues of judder and motion can be more apparent. At the SID Display Week last week, there were 8K 120Hz panels and even an 8K 288Hz panel, so panel makers are looking for variable frame rates to improve the experience. At the beginning of the SID 2022 Display Week, Paul Gray, an analyst from Omdia, pointed out the vast potential for cloud gaming on TVs in the future, including those with 8K sets, so let’s look at what VESA has done.
Over recent years, gaming systems have been able to produce a broader and broader range of different frame rates. From the early days of flat panel displays, when every panel ran internally at 60fps, panel makers can now support a wide range of refresh rates at 360Hz or more. VESA has a way for systems to talk to the display to communicate the optimum rate – VESA Adaptive Sync, but that is just related to the interface. After the success of the VESA DisplayHDR certification program that looked at the actual display performance, VESA has created two new logos to help buyers recognize that displays are doing what they claim to be!
The two logos are for the Adaptive Gaming specification, which is comprehensive. A ‘Media Sync’ logo covers a subset of the specification and is intended to solve some video issues.
The key points that are certified are that the video frame rate can support a minimum of 48 to 60 fps for the Media Sync logo and 60-144 for the Adaptive Sync logo. This latter logo also allows the maker to state the maximum frame rate that the display can go to (and still meet the detailed specification of the test). The Adaptive Sync logo also mandates a minimum response time for the display of 5ms. More importantly, it demands very stringent and detailed tests for that number that might bring some reality to the claimed specifications.
Frame Rates
Anybody interested in gaming will understand why you would want a range of frame rates, but it may be less obvious why you would want this for video and media consumption. The big reason is that you can exploit the technology developed for gaming to make the video look better.
Video content can arrive in 24fps, 30 fps, 50 fps (in Europe), and 60fps (and others such as Ang Lee use even wider frame rates, but that is a real niche), as well as fractional frame rates. Typically panels run at 60fps, so there is often a mismatch. The most well-known solution is the famous 3:2 pulldown scheme for 24fps content. As illustrated below, you repeat the first frame for three of the 60 fps periods, then repeat the next frame for two subsequent 60Hz frames. That gets you to exact multiples but can cause visible artifacts. Something similar happens in a 50 to 60 frame conversion.
Figure 1Source: Wikimedia Commons with modified labels
The Meda Sync logo is tested to ensure that the display can run at an integer multiple of the precise frame rate by covering the critical 48-60fps range. So, for example, a 24 fps movie could run at 48fps, which means no need for 3:2 pulldown and no artifacts from that process.
However, there are ways of doing this that can cause flicker, so to avoid that, VESA has stipulated a stringent limit for flicker, and the display has to work at all the frame rates in the specified range. Even more tricky, because in gaming, the frame rate can vary depending on the GPU load, the display has to be able to cope with any frame rate within the range within one frame. The test involves wholly random and arbitrary frame rates being sent to the display in successive frames and ‘ramps’ up and down the range.
Response Times
There is the old saying that there are lies, damned lies, and statistics. In the display industry, a similar expression can apply to ‘ANSI lumens ratings for projectors’, but it equally could be ‘response time ratings for LCDs’. For example, different types of LCD do better or worse in their speed of response to a request from a system to change their brightness. Some go fast on full black to white and slowly on greyscale, while others can change grayscale quickly but can’t do the extremes very well. Makers, of course, pick what they want to tell you in the response time. Further, if makers tell you grey-to-grey time, they rarely tell you ‘for all greys’, so it has been possible for makers to find which two levels change quickest and quote that. It’s a truth, but not the whole truth.
Many displays also use ‘overdrive’ to change grey levels. To make the transition faster, they try to get the display to respond quicker by boosting or cutting the signal by more than the desired level. VESA decided that there was nothing wrong with that. However, some are using overdrive of up to 200% of the desired level and causing artifacts. The tests mandate a maximum of +20% and -15% undershoot.
Just to add fuel to this particular fire, Roland Wooster of Intel, who has been working on this project, told me at Display Week that a difference of 10 degrees Fahrenheit in the temperature of some liquid crystals could halve the response time. So to get ‘an even playing field’, the VESA test protocol includes the following:
- Mandated room temperature of 22.5 deg to 24.5 deg C and mandatory warm-up times
- Separate test procedures for SDR and HDR as higher brightness usually means more backlight temperature
- The use of a very high-speed probe to measure pixel switching speeds (within the range of 10% – 90% brightness – going beyond that can lead to measurements being compromised by noise)
- Testing of 20 different greyscale changes with multiple samples of each. The average of those samples has to be less than 5ms to achieve the logo.
The certification only applies to the DisplayPort interface, including USB-C and Thunderbolt physical connectors. In theory, if you use an external HDMI-to-DisplayPort dongle that supports variable frame rates, you should be able to make that work, or makers could build in the converter and, in that way, offer the same performance over HDMI. Still, the VESA logo mandates at least DisplayPort.
All products have to be certified by an independent VESA-qualified testing lab.
There’s a table of requirements here. VESA also keeps a list of products on its site. At the time of writing, there were eight monitors from LG and one from Dell on the list, but more will be arriving. Older models could be eligible for the logo, but Wooster told us that some would need firmware upgrades to meet the criteria.
The entire 71-page test process was available for download here when we went to press.
