What is Vsync (or Vertical Sync) and how does it affect gaming?

Xiaobai Software  2022-08-22 17: 49  read 67 views

Modern video games have a dizzying array of graphics settings.Most of these settings provide better performance or graphics quality.However, vertical synchronization, so-called VSync, is more complicated.

By itself, VSync has no effect on graphics quality, but enabling it can eliminate unsightly screen tearing.While this may seem like a no-brainer, it also reduces your framerate and increases input lag -- both of which are the bane of competitive gaming.

Confused about what to do with this mysterious graphics setting?Let's figure out how VSync works.

 

What Is VSync?

VSync is a method of synchronizing the frame rate of a video game with the refresh rate of the monitor displaying the game.Graphics card manufacturers have developed vertical sync technology to remove a visual artifact known as screen tearing.It appears as a horizontal split of the display frame, so half of the frame lags behind the other.

 

While this may look like a tearing of the space-time continuum, it's just that your GPU is sending out frames faster than your monitor's maximum refresh rate.Depending on how much your GPU frame rate exceeds the monitor refresh rate, you can see two or more GPU frames being stitched horizontally during a single monitor refresh.

VSync eliminates screen tearing by limiting the GPU frame rate to the monitor's refresh rate.However, that alone isn't enough to prevent screen tearing.This setting also forces GPU-rendered frames to be displayed along with the display's refresh cycle.

Preventing parts of multiple frames from being displayed at the same time is the key to eliminating screen tearing.Whereas VSync does this by preventing the GPU from pushing new frames during the monitor refresh cycle.

VSync creates more problems than it solves

While VSync is guaranteed to fix screen tearing, it comes at the expense of performance and responsiveness.To see why, let's look at the two main functions of VSync.First, it reduces the frame rate of the GPU to match the refresh rate of the monitor.Second, it can also synchronize the frame rate of the GPU to match the refresh rate of the display.

Did you notice that both VSync mechanisms involve slowing down the GPU output to match the static monitor refresh rate?This is an important detail.When the display is refreshed at specific intervals, the GPU outputs frames at a rate inversely proportional to the complexity of the game scene being rendered.

 

Forcing the GPU to synchronize the cadence of its frames with the monitor's refresh rate prevents it from forwarding the latest frame to the monitor.Players describe this as input lag, believing that what is displayed on the monitor lags behind their actual controller input.This input lag is especially noticeable in fast-paced FPS games, where the crosshair lags noticeably behind your actual mouse input.

If the lag wasn't bad enough, VSync can even cripple the overall GPU performance by significantly reducing frame rates.This has to do with its tendency to limit GPU frame rates to monitor refresh rates.While that's fine when your GPU frame rate is higher than your monitor's refresh rate, when the frame rate drops below the refresh rate threshold, you're in trouble.

例如,一个复杂的场景,如果强迫GPU的最大帧率为59帧,那么在刷新率为60Hz的显示器上就不能以59帧显示。VSync对60Hz显示器要求的16.67毫秒的同步间隔将迫使实际显示的帧率从59帧下降到45帧。

To make matters worse, the performance of the GPU (and thus the frame rate) varies widely during video games.In this case, VSync caused some frames to stay on screen longer than others.This is perceived by viewers as stuttering or inconsistent frame rhythms.

What is Adaptive VSync and Fast Sync?

Fortunately, the inherent problems of VSync have not been ignored by AMD and NVIDIA.Both GPU manufacturers have released their own advanced versions of VSync to alleviate the aforementioned issues.These options are available through in-game settings, or more commonly enforced through the GPU driver control suite.

Adaptive VSync

Adaptive VSync, developed by NVIDIA, eliminates all the ugly input lag and performance issues that come with the GPU not keeping up with the monitor's refresh rate.This implementation of VSync is only effective if the GPU can meet the refresh rate requirements of the display.The adaptive sync system shuts down VSync immediately if it cannot be satisfied.This provides a healthy balance between video game performance and mitigation of screen tearing.

fast sync

Quick Sync, also developed by NVIDIA, adds the magic of triple buffering to adaptive VSync.In its simplest form, triple buffering involves the GPU rendering an extra frame.This allows it to select the latest of two rendered frames to send to the display while waiting for the display refresh cycle.The idea is to reduce input lag by displaying the most recent frame, but this also requires a lot of GPU power.

enhanced synchronization

Just like NVIDIA's Adaptive VSync offering, AMD-specific Enhanced Sync turns off VSync when the GPU lags behind the monitor's refresh rate.Like NVIDIA's Quick Sync, it employs multiple buffering to reduce input lag by passing the most recent frame to the monitor.

Beyond VSync

We've looked at how VSync can eliminate screen tearing and the downsides of implementing it.While Nvidia and AMD have released more sophisticated versions of VSync to alleviate these issues, there is a whole new way to address them with G-Sync and FreeSync technology.

However, this requires a compatible monitor, cable and graphics card.For those lacking fancy hardware, turning VSync on or off is a matter of deciding your priorities.If your GPU is powerful enough to match your monitor's refresh rate, VSync will work just fine.However, if you don't like input lag, you'd better not use it.

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