What's V-Sync?



You might have asked yourself this question many times if you are a gamer. The toggle to turn on Vsync on or off is prevalent in almost every game, the technology has been there since the development of polychromatic televisions (color televisions) in the 1950's.




In order to define vertical sync, we need to look at another term called vertical blank interval. The term vertical blank interval defines the duration of time between the final line of a frame and the beginning of another frame. I am sure that most of you are aware of Cathode ray tubes or CRT's for short, CRT's are vacuum tubes with electron guns at the back of them and phosphorescent screen at the front. The electron gun shoots charges at phosphorescent screen and excites the phosphor dots on the screen giving them a glow which creates the image that you enjoy on a television, the dots are excited consecutively from top to bottom and when the last phosphor dot on the screen is excited (this forms one frame of an image) the gun then needs to zip back to the original position and start over, the duration this takes is called the vertical blank interval. The gun zips back up and starts all over again because the phosphor dots lose energy and stop glowing if the gun doesn't supply them with continuous energy.



Therefore, we need to refresh the phosphor dots and how many times we refresh them per unit time is called the 'refresh rate' which is another term you might have heard or read about if you are into PC gaming. The duration or the Vertical blank interval allowed the computer or the CRT to prepare for the next frame to be displayed on the screen. LCD's or liquid crystal displays do not need to refresh their pixels. When the crystals in an LCD are electrically excited, they twist and allow the light to pass through and how much light they allow to pass through determines the image displayed on the screen. The crystals remain in the twisted position until they are told otherwise.  The vertical blank synchronization is still there, however because the screens need to remain backwards compatible with the graphics cards of the day and age. This is why many professionals in the technology sector say that display technology is miles ahead of the graphics game. So now that we know what vertical sync is, we can now appreciate its importance in the gaming world.



For a PC gamer, a graphics card is an integral part of his gaming machine, a display is another integral part of his gaming machine and how those to interact to form the picture of the games on your screen is where Vertical sync is concerned. When your GPU (be it integrated or discreet) is processing a game in order to produce an output on your screen it stores the image formed temporarily in what we call framebuffers, when the GPU finishes forming the image on the framebuffer it can then transfer the image to a certain part of the GPU called the display circuitry. After the frame has been transferred to the display circuitry it then travels via your HDMI cables, display cables, VGA or even DVI cables to your screen to produce an image you can perceive. Vertical Sync is a technology that matches the framerate of your game to the refresh rate of your monitor. So, if you have a 60HZ monitor, Vsync will lock your frame rate to 60fps which translates to 60 images shown on your screen per second.




Why is this important?
Sometimes GPUs are very fast and can form images faster than the conventional 60HZ and therefore can output images faster than 60HZ, but since your monitor can only display 60HZ the other frames are only wasted and serve no purpose in most cases (there are exceptions of course). So, when the GPU is transferring those images and since the GPU is transferring said images at a much faster rate than what can be displayed on a monitor the image can sometimes get distorted and screen tearing will occur. But there is also another case where your GPU is not fast enough to transfer the images to the screen. So, if your monitor has a refresh rate of 60HZ and your GPU is only capable of 30fps on a certain game, then the GPU will lag when compared to the refresh rate of your monitor.
The graphics card will have more than one framebuffer of course, in most cases it will have a primary and a secondary buffer, this is done because when the display circuitry reads the image formed in the buffer the GPU can’t work in that buffer and therefore offloads the processed image onto another buffer called the secondary buffer. When the display circuitry is done with reading the image in the primary buffer, it will move to the secondary buffer, and so forth. But in the case where the GPU is slow and can’t form the image in time, the display circuitry is forced to send the image again to the screen; this is what gamers experience as stuttering on their screens.


So how does Vsync rectify this issue? Vsync tries to limit the framerate you are getting to get a more stable gameplay experience and that is important for most gamers, but you won’t get any higher fps than what Vsync limits the framerate to which is another hindrance in the gameplay experience. Vsync has many advantages, but it also carries disadvantages.
Pros:
• It allows for a more fluid experience while gaming, by avoiding screen tearing and artifacting.
• It reduces the temperature of your GPU, because it lowers the speed at which the GPU operates.
Cons:
• It introduces a lag in the gameplay for inputs like keyboard and mouse inputs, usually noticed in competitive scenarios.
• It is inapplicable in cases where your GPU cannot produce a framerate correspondent to your screen’s refresh rate in which case it creates stutters and this renders the entire purpose of the technology mute.
Verdict
I am a PC gamer and I play mostly competitive games like Call of Duty, Battlefield and other shooters where even a millisecond of lag can get you killed. I have a monitor with a 75HZ refresh rate and I never use Vsync because it hinders my ability in the game. If you are like me and play shooters for the most part, I do not recommend you use Vsync. But for people who play single player games, RPG’s or any other game where a tiny amount of lag makes no difference and you have a graphics card capable of matching your screen’s refresh rate, Vsync can be a God send. I will be writing reviews on Gsync, adaptive Vsync, Fast Sync and Free Sync and I will be comparing and contrasting them to each other. So, stay tuned!


This is Kerod with ICT, signing off.