In short, less than 8 years ago, VESA introduced its Adaptive-Sync specification for DisplayPort monitors. Based on the earlier variable refresh rate technology designed for embedded DisplayPort (eDP), Adaptive-Sync has extended this technology to allow it to operate fully with the variable refresh rate as we know it from PC and laptop displays ever since.
And while the introduction of Adaptive-Sync has significantly increased the number of variable refresh rate monitors on the market, it was not completely smooth operation. AMD was an early promoter of this technology with its Freesync initiative, which essentially backed its own promotion and certification program beyond Adaptive-Sync, but also mixed up some things with the Freesync HDMI standard and poor basic certification. Meanwhile, NVIDIA was late with the game, although it finally adopted VESA support in 2019 – adding Adaptive-Sync support along with the existing proprietary G-Sync standard. But even after that, AMD and NVIDIA are dueling to some extent with different standards and certification processes (and Intel considers itself a weirdo).
At all times, displays that support Adaptive-Sync have been hit and miss, with a great variety of refresh rate ranges supported and a great deal of inconsistency in how well variable refresh performed. Even today, there are still displays that can handle variable refresh rates but provide a worse experience at the same time. All of this hurt VESA’s efforts to promote the adoption of Adaptive-Sync technology and ultimately the proliferation of variable refresh displays and use them to troubleshoot issues such as frame jitter.
To that end, VESA is stepping in today and will play a much more active role in the standardization and marketing of Adaptive-Sync monitors. Recognizing that support for Adaptive-Sync alone is not enough, and that a good VFD monitor experience also requires boundaries and a minimum in performance, the group has created two new logo creator programs to certify the performance of Adaptive -Display Synchronization. Or, as the group likes to put it, these new programs are setting the standard for “front-screen performance.”
The main purpose of these new logo programs is to help buyers identify monitors that implement Adaptive-Sync efficiently. There is also an additional goal of helping VESA member companies to clearly communicate to these buyers that their variable refresh rate monitors are, politely speaking, legally good, as implementing Adaptive-Sync does not come with any quality guarantees. This is obviously an area where both NVIDIA and AMD have a hand, with the G-Sync and Freesync certification programs respectively, with a mixed performance history thanks to multiple standards and the use of proprietary technologies. As such, VESA wants to do what none of them have done yet by creating a set of open standards that are not vendor tied and rely solely on DisplayPort Adaptive-Sync technology.
VESA, on the other hand, will essentially cover the subject at both ends of the spectrum. There will be something new in the high-end VESA AdaptiveSync certification display standard to be the compliance standard for high-end gaming displays and has very strict requirements. At the other end of the spectrum, it is VESA MediaSync certification, which is a much simpler specification aimed at marking displays that offer basic and efficient support for variable refresh rates for multimedia consumption purposes – and with no emphasis on gaming. In practice, AdaptiveSync is a superset of MediaSync, so while both standards exist in the market, you won’t see logo displays for both; if the display meets the AdaptiveSync standards, it is good enough to meet media playback needs as well.
AdaptiveSync: LFC, Flicker Free and Shenanigans Free
We’ll start by looking at the high-end AdaptiveSync display standard. Designed with gaming displays in mind (more specifically, “game frame rates”), AdaptiveSync is a compatibility test that takes many factors into account. The standards define not only basic functions such as refresh rates, but also standards for flicker (or lack thereof), dropped frames, jitter, pixel response times (G2G) and ghosting / overshoots / shortcomings. Beyond the HDR functionality (which for many reasons is a completely different boiler), AdaptiveSync meets all the essential requirements for a high-end gaming display.
It all came as a surprise to me. When VESA first informed me that it was working on a quality standard for variable refresh displays, I must admit that I was skeptical. The group’s consensus-based nature means that VESA’s performance standards have sometimes been held back by the need to satisfy hardware manufacturers who want many (if not all) of their products to meet the new standard. Apparently this is about DisplayHDR certification, which while technically the correct program at the higher tiers is detrimental to the existence of the DisplayHDR 400 tier, making DisplayHDR certification itself pointless.
This is clearly something VESA has taken to heart because, to my surprise, AdaptiveSync makes no such compromises. Instead, the group went all out, developing a high-end spec that isn’t watered down to cover or qualify more basic displays. As a result, most Adaptive-Sync-enabled displays on the market today do not meet the AdaptiveSync display standards, and even most gambling the displays will also fail. VESA has set out to create a high-end standard and is clearly sticking to the gun right through to the end.
And of course, the AdaptiveSync display standard is merely a performance standard – it does not define any new technology. Thus, the standard can be used to test and certify existing PC monitors, integrated displays (AIO computers) and laptop displays as long as these devices are connected via the DisplayPort / eDP standard. Note that technically this means that AdaptiveSync only applies to the DisplayPort input on the device, not the HDMI inputs. But, since 99% of the hard work providing a good variable refresh rate is done under the hood with components like TCON and backlighting, I’d be surprised to see that this is a problem.
Refresh rate: minimum 60-144, LFC required
Delving into the AdaptiveSync display standard itself, VESA started things off with significant refresh rate requirements. A compatible display must support a variable refresh rate range of at least 60Hz to 144Hz – the minimum magic range of 2.4x required to support Low Frame Rate Compensation (LFC). Displays can go below this minimum (e.g. 48Hz) and above the maximum (see 360Hz displays), but 60-144 is the smallest range that qualifies. And it has to be out of the box; Displays that need to be “tweaked” in any way to meet the minimum requirements will not be of high quality. In fact, this applies to all tests, as AdaptiveSync certification tests are run with monitors running at their native resolution and set to a default, ready-made configuration.
As such, VESA also tests for dropped frames as apparently some monitors are accepting more frames than they are able to display. As a result, the compatibility test looks for skipped frames at both constant and variable refresh rates to make sure that each frame is displayed.
Flickering: testing from min. to the max and everything in between
The second main area of concern for the AdaptiveSync Compatibility Test is screen flickering, which essentially covers the entire set of display and backlight anomalies that can occur with displays with variable refresh rates. Using a dedicated probe (possibly a photodiode), the VESA test system looks for evidence of visible flicker, with a technical requirement of no more than -50 dB flicker regardless of the refresh rate. In this case, VESA relies on the existing Japan Electronic Information Technology Association (JEITA) perception method to calculate flicker, which is weighted to look at the frequencies to which human eyes are most sensitive.
The test, in turn, breaks things down into looking for flicker at typical frame rates / refresh rates for multimedia (23.976 fps / 71.928 Hz etc.) and at a minimum panel refresh rate, as well as running a few flicker tests with full variable refresh rate scenarios, in whose refresh rate varies from frame to frame.
The Variable Refresh Mode Compatibility Test relies on four refresh rate patterns to make sure your displays can properly handle both slow and fast changing refresh rates. These patterns are sine wave, zigzag pattern, square wave and finally full random test. According to VESA, the square wave test is especially brutal as it requires you to quickly switch between the minimum and maximum refresh rates. Random Test is also quite capable of turning off monitors as it can display switching to significantly different refresh rates at once, rather than smoothly increasing or decreasing.
And while the AdaptiveSync Display Compatibility Test does not have a clear test for backlight or gamma flicker (a fairly common problem with early Adaptive-Sync displays), according to the group, they believe their flicker test should be sensitive enough to detect these specific phenomena.