什么是G-SYNC

关于G-SYNC，我们首先要知道到底什么是“刷新率”。刷新率就是屏幕每秒钟会展示的画面。每秒展示60张画面就是60Hz刷新率，每秒144张画面就是144Hz刷新率.

刷新率究竟有什么用呢？根据The Effects of Screen Refresh Rate on Editing OperationsUsing a Computer Mouse Pointing Device中实验得出的数据，根据在不同刷新率下捕获目标的时间，得出结论：捕获目标时间随着刷新率的提高而降低.

There was a significant effectof refresh rate in the time to capture the target, F(2, 36) = 5.56, p =0.008, with a pattern of means very similar to that found in Experiment 1(50 Hz: M = 2153 msec; 75 Hz: M = 1777 msec; 100 Hz: M = 1946 msec).

In contrast to the apparent de-couplingof eye and cursor during the initial phases of the movement, inspection ofreal-time plots of eye and cursor trajectories and the data reported hereconfirm the obvious conclusion that to perform the final phase of thetask, subjects directly inspect the cursor. At this point, performance isquite markedly worse at the relatively low refresh rate of 50 Hz. Insummary, rapid movements of the eyes across a pulsating surface appear tolead to a global degradation in performance, which increases at higherrefresh rates and is unrelated to perceived flicker.

更高的刷新率意味着你将拥有跟多的反应时间，这对于FPS类游戏具有极大地优势作用.

但是，明明有了更高的刷新率，为什么有时还是感觉画面会发生卡顿. 我们来看看NVIDIA给出了什么解释：不幸的是，显示设备的刷新率通常与渲染速率无关。例如，目前视频被设计为以24 Hz、60 Hz等固定速率播放. 也就是说，无论渲染速率是什么，视频都是以固定的速率显示的，这是可变的。这导致引入了限制的方案，试图补偿不同的呈现和显示刷新率之间的任何差异.

Unfortunately, the refresh rate of adisplay device has generally been independent of the rendering rate. Forexample, currently video is designed to playback at fixed rates of 24 Hz, 60Hz, etc. That is, video is displayed at a fixed rate no matter the renderingrate, which is variable. This has resulted in limited schemes being introducedthat attempt to compensate for any discrepancies between the differingrendering and display refresh rates.

也就是说，当显卡（GPU）渲染帧率大于显示器刷新率时，由于显卡向显示器短时间内传输了过多的画面，显示器无法快速完成画面衔接处理，导致了画面出现撕裂感. 即画面会以一条甚至更多条分界线为界，上下显示的为显卡不同时刻输出的画面.

而NVIDIA G-SYNC有效解决了这个问题. 这项技术是由显卡来主导显示器，当显卡绘制完成当前帧后会立即通知显示来输出画面，这样丢帧、撕裂、延迟都得到了解决.

由此以来解决了传统垂直同步技术由显示器主导显卡，产生画面延迟的问题. 为PC用户带来了更流畅的体验的同时减少了延迟输入带来的弊端.

文献参考

[1] KENNEDY A,BACCINO T. The Effects of Screen Refresh Rate on Editing Operations Using aComputer Mouse Pointing Device[J/OL]. The Quarterly Journal of ExperimentalPsychology Section A, 1995: 55-71. http://dx.doi.org/10.1080/14640749508401375.DOI:10.1080/14640749508401375.

[2] NVIDIA CORP.VARIABLEREFRESH RATE VIDEO CAPTURE AND PLAYBACK: US2018061364[P]. 2018.03.01