You probably are a gamer or new to gaming or maybe you just brought a new graphics card and encountered an unheard feature called "Vsync" that you are not aware of. You need not worry because in this article we will learn about the basics of Vsync and why do we need it. But to understand Vsync, we need to understand some basic terms like Frame rate and Refresh Rate.
Frame Rate: Frame Rate refers to the number of frames projected by the game on the display in a second. Since it is the frequency of frames projected hence it is measured in hertz and is commonly referred to as fps(frames per second). Every dynamic graphic file like Animation, Video, Game, etc. is a collection of images or frames changing at higher rates and due to their continuous change at higher rates(more than 10-12 Hz per second) human eye sees it as a continuously moving clip.
Refresh Rate: Refresh rate is a phenomenon similar to the Frame rate. It is the rate(number of times) at which the device refreshes the display with a new image in a second. Since it is also the frequency of fresh images projected on the display in a second so that's why it is also measured in hertz. Nowadays monitors come with a standard refresh rate of 60 Hz. Monitors of Higher refresh rates like 144 Hz, 180 Hz, etc. are also available in the market.
Screen Tearing: When two different frames appear on screen at the same time then the screen appears torn or distorted which is referred to as screen tearing.
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What is Vsync ?
Vsync stands for Vertical Sync. It is a graphic technology that makes sure that the frame rate of the game and the refresh rate of the Monitor remain synchronized or the same for a smooth experience. Most of the modern games are coming with high frame rates(fps) up to 100 Hz and more which requires high refresh rate monitors for a smooth gaming experience, but if we use a low refresh rate monitor then a major problem called Screen Tearing comes into play. You might be wondering that what Screen Tearing is ? Understand this with an easy example that you are playing a game having a frame rate of 120 Hz and the monitor you are using is having a refresh rate of 60 Hz. In this condition, your GPU or the graphics card would be pushing frames higher than the refresh rates of the monitor, due to which two different frames will be visible together on the same screen and this mismatch of the frames will look like the screen is torn off, which is referred to as Screen tearing. So to conclude, we can say that Screen tearing is displaying two different frames at the same time which were supposed to be shown at different intervals of time.
Here comes the role of Vsync which synchronizes the frames of the game with the refresh rate of the monitor to give us a smooth experience.
What does actually Vsync do ?
Vsync limits the graphic card or GPU to not deliver frames higher than the refresh rate of the monitor. When we are playing a game on a 60 Hz monitor and our graphics card is delivering frames more than the refresh rate of the monitor(60 Hz) then if the Vsync feature will be turned on, it will make the graphics card hold the upcoming frame in the secondary buffer(back buffer) or freeze the game engine till the monitor sends a signal to send a new frame. But what if we turn on the Vsync when our graphics card is delivering less frames than the refresh rate of the monitor? If we are using a graphics card that is delivering slightly fewer frames than the refresh rate of the monitor then turning on Vsync will lower down the frame rate. The graphics card delivering lesser frames will be taking more time to deliver a frame while the monitor will send signals to the graphics card for newer frames(because it has a higher refresh rate) but due to the unavailability of a newer frame, the frame in the primary buffer(current frame) which was already displayed will still be displayed till the graphics card delivers a new frame. The mismatch in the timing of the frames will lead to an increase in the waiting time of both the equipment which will finally drop the frame rate to a much lower value(almost half).
Why do we need this Technology ?
Let's suppose that you are playing a first-person shooting game that requires fast reflexes, but due to the screen tearing the enemy is not visible to you then you will miss the shot and will end up losing the game. Apart from this, if we want our experience to be smooth and the life of our graphics card to be long then we will be needing this feature. Unnecessary frame rate delivery by the graphics card can cause stress to its internal circuitry but since Vsync limits the frames so it also makes our graphics card healthy and long-lasting. But Apart from advantages, Vsync also has some flaws.
Since frame rates fluctuate up and down depending on what's going on in a game, it can be difficult to know when to turn it on and when to turn it off. For instance, you may get a consistent 60+ fps while you're playing at an indoor level, but the second you enter the game's open-world area your fps drops to 50.
One feature that can be used to help deal with this problem is Triple Buffering. With VSync enabled, both the Primary or Front Buffer(buffer where the current frame is stored) and Secondary or Back Buffer(where the upcoming frame is stored) buffers can often fill and then have to stop working until the graphics card receive a signal from the monitor that it's ready for a new refresh. Triple Buffering introduces a third buffer to the scene, which can help to control the drop in fps by giving the graphics card another place to generate an image.
If we have the solution then why not always enable Triple Buffering? The answer is that not all games support it, and even if they do, Triple Buffering requires more VRAM to be dedicated to the Frame Buffer. With the lower end graphic cards that don't have a lot of spare VRAM(Video RAM) and games that require a good amount of it, additional performance issues can result since the card now has to balance its use of VRAM with the added demand of the extra buffer. Apart from this, Vsync causes high latency due to the holding of frames in buffer and backpressure which means that everything like buffer, GPU, etc. gets filled up due to which the game slows down to the system.
Adaptive Vsync: Nvidia has come up with a smart solution to tackle the problem of fluctuating frame rate. As Adaptive Vsync is a smart feature that turns on the Vsync when the graphics card is sending more frames than the refresh rate of the monitor and turns off the Vsync when the graphics card is delivering lesser frames than the refresh rate of the monitor.
Fast Sync: Vsync limits the frames but this causes the problem of Backpressure, so Nvidia introduced the feature of fast sync which reduces screen tearing without building backpressure. In this feature, the buffer uses decoupled render and display technique where the buffer is divided into 3 parts Front Buffer, Back Buffer, and last rendered buffer where these three keep changing their positions so that there is always a free buffer available for GPU to process the next frame.
This technology reduces the problem of Backpressure. This technology is different from Tripple buffering or third buffering because here we keep changing positions and there is always a place for a new frame.
Enhanced Sync: It also reduces the latency and screen tearing without creating Backpressure and works on technology same as Fast Sync, the only difference is that Fast sync is made by Nvidia while Enhanced sync is made by AMD.
Pros:
- If your GPU is producing more frames than the refresh rate of the monitor then it synchronizes them and gives a smooth output by solving the problem of screen tearing.
- Since Vsync limits the output frames of GPU so there will be less stress on it and less heat will be produced which will keep the GPU in a healthy state and increase its life.
- Due to the limiting of frame delivery till the next signal by the monitor, backpressure develops and latency increases up to 100 ms and also increases the response time for the mouse and keyboard which can be a major issue in gaming.
- If the Vsync is used while the graphics card is delivering frames lesser than the refresh rate of the monitor then it will reduce the frame rates to a very low value, so that's why it can not be used to boost lower frame rates.
If you are using a high-end graphics card or if it is delivering more frames than the refresh rate of the monitor then only the use of Vsync is favorable, but if the frame rates delivered by GPU are less than the refresh rate of the monitor then it is not recommended to turn on Vsync.
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