Variable refresh rate (VRR) refers to a dynamic
display that can continuously and seamlessly change its refresh rate without user input. A display supporting a variable refresh rate usually supports a specific range of refresh rates (e.g. 30 Hertz through 144 Hertz). This is called the VRR range. The refresh rate can continuously vary seamlessly anywhere within this range.
Purpose
On displays with a fixed refresh rate, a frame can only be shown on the screen at specific intervals, evenly spaced apart. If a new frame is not ready when that interval arrives, then the old frame is held on screen until the next interval (stutter) or a mixture of the old frame and the completed part of the new frame is shown (
tearing). Conversely, if the frame is ready before the interval arrives, then it won't be shown until that interval arrives.
Variable refresh rates eliminate these issues by matching the refresh rates of a display to be in sync with the
frame rate
Frame rate, most commonly expressed in frame/s, or FPS, is typically the frequency (rate) at which consecutive images (Film frame, frames) are captured or displayed. This definition applies to film and video cameras, computer animation, and moti ...
from a video input, making the display motion more smooth. Although VRR is strongly associated with
video games
A video game or computer game is an electronic game that involves interaction with a user interface or input device (such as a joystick, game controller, controller, computer keyboard, keyboard, or motion sensing device) to generate visual fe ...
due to such content having unpredictable, discontinuous frame rates that would benefit from the technology, it is also useful for media whose frame rate is fixed and known in advance, such as film and video. Being able to sync the refresh rate with industry standard framerates (24, 30, and 60 FPS), it again helps to eliminate screen tearing.
VRR also has use in
power management
Power management is a feature of some electrical appliances, especially copiers, computers, computer CPUs, computer GPUs and computer peripherals such as monitors and printers, that turns off the power or switches the system to a low-power ...
, by temporarily lowering the refresh rate of a display during instances when there is little movement on the screen to save power.
History
Vector displays had a variable refresh rate on their
cathode-ray tube
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a ...
(CRT), depending on the number of vectors on the screen, since more vectors took more time to draw on their screen.
Since the 2010s,
raster displays gained several industry standards for variable refresh rates. Historically, there was only a limited selection of fixed refresh rates for
common display modes.
Implementations
Variable refresh rate display technologies include several industry standards and proprietary standards:
*
AMD FreeSync
*
Nvidia G-Sync
*
DisplayPort 1.2a's optional ''Adaptive-Sync'' feature
*
HDMI 2.1 Variable Refresh Rate (VRR)
References
External links
TestUFO Animation: Variable Refresh Rate Simulation
Graphics hardware
Temporal rates
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