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HDMI VRR: that’s behind the display technology


Numerous questions arise around the topic of HDMI VRR (English for “Variable Refresh Rate”): What exactly is HDMI VRR? How does the technology work? What do you need to use them?

For adequate answers we first have to clarify a few terms: Let’s start with “Refresh Rate” – the update rate. This is the number of updates an ad can make per second. Most televisions and mobile devices update at 60 Hertz. This means that 60 individual images can be displayed in one second. Current televisions reach 120 Hertz, while special gaming monitors can now create 144, 240 or even a full 360 Hertz.

The “Frame Rate” (Frames per Second, FPS) – the frame rate – indicates the number of pictures a computer can deliver per second. If the full 60 frames per second are not possible here, a partial image is sent instead. For the display, it doesn’t matter whether it receives a full or partial image. It shows whatever arrives. However, this leads to an unsightly effect, the so-called “screen tearing” (image tearing). Here partial images are superimposed on the previous, fully rendered image. Since the frames are rendered horizontally from top to bottom, the tearing effect manifests itself as a shaky horizontal line that often appears roughly in the middle of the screen.

Screen tearing can be clearly seen in this screenshot. After about a third from the top, the image breaks (circled in red) - this is very annoying.

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Screen tearing can be clearly seen in this screenshot. After about a third from the top, the image breaks (circled in red) – this is very annoying.

Every now and then a small piece of a few partial images is not a big problem in itself. However, if the graphics processor keeps dropping frames due to an excessive render load, the tearing of the screen can significantly affect the experience, especially when gaming. Fortunately, variable refresh rates can help eliminate this problem and make games look better and smoother.

PC gamers have been using a function called V-Sync (vertical synchronization) for years to limit update and frame rates. In order for V-Sync to effectively reduce screen tearing, you must also ensure that the graphics card can keep up with the refresh rate of your monitor. If you’re using a 60 Hz display and the graphics card performance drops below 60 frames per second, you’ll also see tearing with V-Sync. Another downside: you may have to choose between performance and graphics fidelity. In this case, you get a trouble-free gaming experience with a reduced picture quality or a better looking game that does not remain flawless at 60 frames per second.

In the HDMI 2.1 standard, VRR is also part of the party. The variable synchronization technology must be supported by the display and player.

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In the HDMI 2.1 standard, VRR is also part of the party. The variable synchronization technology must be supported by the display and player.

In order to prevent screen tearing, the refresh rate and the frame frequency must be able to be varied flexibly. This only works if the technology is integrated in both the monitor and the player – in other words: You need both a VRR-compatible graphics card and a VRR-compatible screen. Nvidia and AMD each have their own VRR technologies known as G-Sync and Freesync, respectively. Freesync is also used in Microsoft’s Xbox One S and X game consoles, for example. G-Sync is the counterpart for users of Nvidia’s GTX and RTX graphics cards.

But as already mentioned, the screens must also master the techniques. G-Sync requires a special chip in the monitor, while Freesync only needs the correct video connection. However, AMD has divided the function into the three areas Basic, Premium and Premium Pro. The division shows ever finer gradations – from simple synchronization and high frame rates to certified HDR inputs and outputs. HDMI VRR is defined in the latest HDMI 2.1 standard. However, some TV sets with HDMI 2.0b connections are also capable of variable updating. In a few years, HDMI VRR is likely to be found in displays of all price segments. This is not currently the case. The new game consoles Xbox One Series X and Playstation 5 support HDMI 2.1. However, many current high-end TVs are currently still missing HDMI 2.1.

Tip:

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