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Glossary:Variable refresh rate (VRR)

From PCGamingWiki, the wiki about fixing PC games

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Variable refresh rate (VRR), sometimes also called dynamic refresh rate (DRR), refers to technologies that enables dynamic refresh rates for monitors, where the refresh rate of the monitor is continuously synced to the output rate of the content being displayed. This avoids any screen tearing, at least in the supported range, while also lowers power consumption[1] as the monitor does not need to refresh at its highest supported rate while displaying content below that rate.

Variable refresh rate range (VRR range) refers to the range supported by a monitor where a dynamic refresh rate synced to the content is possible. This range usually starts at around 30 Hz and typically covers the full range upwards to the maximum refresh rate supported by the monitor.

Key points

Allows tearing-free gameplay and low input delay on variable frame rates within the supported VRR range of the monitor without resorting to Vertical sync (Vsync).
In laptops with switchable graphics (or generally, any system with more than one GPU) only the last one physically connected to the display matters for support.[2][3]
NOT to be confused with Adaptive V-Sync (aka late V-Sync) which dynamically toggles V-Sync[4] depending on whether the frame rate reaches the refresh rate or not.

Technologies

VESA DisplayPort Adaptive-Sync - An optional feature of both the Embedded DisplayPort[Note 1] and DisplayPort 1.2a standards.
HDMI 2.1 Variable Refresh Rate - An optional[9][10] feature of the HDMI 2.1 standard.
AMD FreeSync - AMD's variable refresh rate technology that makes use of the two aforementioned standards.
Nvidia G-Sync - Nvidia's variable refresh rate technology that makes use of a mix of open standards as well as proprietary hardware.

General information

Dissecting G-Sync and FreeSync - How the Technologies Differ on PC Perspective

Official DP/HDMI extensions

Monitors are generally cheaper compared to certified Nvidia G-Sync monitors, as manufacturers do not have to pay additional licensing fees[Note 2] for adoption, nor implement expensive or proprietary hardware modules.
The open standard makes it possible for the for the feature to be hacked in some "normal" monitors, although your mileage may vary.[11]
On the other hand, no other certification (see below) means advanced gaming features cannot be taken for granted either.

VESA DisplayPort Adaptive-Sync and HDMI 2.1 Variable Refresh Rate are vastly different standards, but just about every practical considerations for variable refresh rate apply to both. The display must support the feature, an applicable cable must be used, and the output/source device (the GPU) must also support the feature and have it enabled. For the time being, the only GPUs with the capability of supporting the DisplayPort standard are AMD's GCN 2nd generation (e.g. Radeon HD 7790), Nvidia's GeForce GTX 10-series, or newer cards, while for the HDMI standard an AMD's Radeon RX graphics card or newer is needed.[12]

Intel 10th generation and newer graphics units support Adaptive sync through Display Port.[13]

AMD FreeSync

Allows VRR to work on HDMI <2.1 hardware.
AMD Radeon Software Crimson 15.11 driver added support for Low Framerate Compensation (LFC).
Linux users must be using Kernel 5.0 or higher with Mesa 19 or newer for AMD graphics.
Freesync Monitor FAQ on AMD.

FreeSync (or Radeon FreeSync as it is sometimes marketed as) is AMD's proprietary variable refresh rate technology and unique hardware/software solution built on top of the industry standards above, that it pushed itself to official specification in the first place. For example, FreeSync utilizes the VESA DisplayPort Adaptive-Sync protocols to allow dynamic refresh rates over a DisplayPort connection, and will also support the Variable Refresh Rate technology adopted in the HDMI 2.1 specification for HDMI connections.[14] To enable the use of variable refresh rate technology over HDMI connections in monitors released 2016, almost two years before VRR became a part of the, at the time, future HDMI 2.1 specification, AMD and technology partners used vendor-specific HDMI extensions to implement AMD FreeSync over HDMI, thereby keeping the technology fully interoperable with HDMI standards.[15]

While certified monitors also provide some really basic flickering guarantee,[16] LFC (low framerate compensation) is only officially supported on monitors whose max/min refresh rates ratio is ≥2.5, [17] although it should work with anything just above 2x.[18][19]

FreeSync 2 is a whole additional set of quality criteria[20] that monitors needs to be certified and validated as supporting, ranging from mandatory LFC support to optimizations of HDR tone mapping process by allowing FreeSync to tone map the original HDR content of the game to the appropriate range of the display directly.

Using an Nvidia GPU as a render card

SetGPU is a DLL injector for DirectX 11 64-bit games which tries to force the use of an Nvidia graphics card of a system with the monitors connected to an AMD graphics card. This allows the use of AMD FreeSync with the Nvidia graphics card acting as a render card, while the AMD graphic cards is responsible for enabling and managing FreeSync.

Install SetGPU[21]
  1. Ensure the FreeSync monitor is connected to the AMD graphics card, with no monitors connected to the Nvidia graphics card.
  2. Download the latest version of SetGPU from GitHub.
  3. Navigate to <path-to-game>, or the appropriate subfolder where the executable of the game is located in.
  4. Extract the downloaded archive to the folder.
  5. Launch the game. If everything works as intended the Nvidia graphics card will automatically be used as a render card.

Nvidia G-Sync

G-Sync FAQ on GeForce
G-Sync 101 on Blur Busters
List of G-Sync, G-Sync HDR ("Ultimate") and G-Sync Compatible monitors

G-Sync refers to Nvidia's proprietary variable refresh rate solution, hardware module, and related technologies and features available for use with some monitors with variable refresh rate capabilities when paired with an Nvidia graphics card. The use of G-Sync was restricted to only certified monitors up until 2019 when Nvidia announced an expansion of the G-Sync ecosystem to also allow the use of G-Sync on unlicensed monitors. Monitors with support for use with G-Sync can be categorized in four different groups: G-Sync, G-Sync HDR, G-Sync Compatible, and non-validated monitors.

G-Sync (classic)

Always assures variable overdrive, and the full refresh rate range of the monitor through the use of low frame rate overcorrection.[16]
On dedicated monitors G-Sync can be traded for the alternative Ultra Low Motion Blur (ULMB) blur reduction mode.[22][23]
Requires proprietary hardware and/or licensing fees, increasing the cost of monitors implementing the technology.

G-Sync refers to the classic variant of Nvidia's variable refresh rate solution for certified monitors available in two forms depending on whether an external or integrated display is used. For external displays (sometimes seen as the "full" G-Sync experience) the typical internal scaler of the display is replaced with Nvidia's custom and proprietary G-Sync module. As a consequence an external G-Sync display does not have the built-in scaling support regular external displays typically have, and instead the display relies on the graphics card to scale the video signal as needed before sending the video signal over to the monitor. For integrated monitors (such as laptop monitors) a fundamentally different interface technology[24] sometimes referred to as Mobile G-Sync is used instead. This technology does not require the proprietary G-Sync module, and instead the technology makes use of standardized embedded DisplayPort (eDP) features (e.g. VESA DisplayPort Adaptive-Sync) to enable dynamic refresh rates.[25]

G-Sync HDR

Requires proprietary hardware and/or licensing fees, increasing the cost of monitors implementing the technology.

G-Sync HDR (also known as Ultimate G-Sync) is the HDR compatible G-Sync module, currently only available on a few expensive monitors. According to PC Perspective's findings when disassembling the ASUS ROG Swift PG27UQ monitor, the G-Sync HDR module alone might make up $500 of the final price point of G-Sync HDR compatible monitors.[26]

G-Sync Compatible

Automatically enabled on tested monitors that can deliver a validated experience through G-Sync.
Requires a GeForce GTX 10-series or RTX 20-series graphics card.
List of G-Sync Compatible monitors

G-Sync Compatible refers to VESA DisplayPort Adaptive-Sync compatible monitors that have been tested and validated by Nvidia to deliver a baseline VRR experience without flickering, blanking, or other forms of artifacts in VRR mode.

Non-validated monitors

Untested monitors or monitors failing validation that required manual activation of G-Sync from the end-user.
Requires a GeForce GTX 10-series or RTX 20-series graphics card.

Non-validated monitors (not an official term) are VESA DisplayPort Adaptive-Sync monitors that either have not been tested and validated by Nvidia to be categorized as "G-Sync Compatible" yet, or was tested but found to not be able to deliver a validated experience. Users can still enable the use of G-Sync with these monitors by manually enabling G-Sync through the Nvidia Control Panel.

Recommended optimal settings

Check out G-Sync 101: Optimal G-SYNC Settings & Conclusion on Blur Busters for more tips and tricks.
Recommended optimal settings[27]

Nvidia Control Panel settings:

  1. Launch the Nvidia Control Panel.
  2. Navigate to Set up G-SYNC and select Enable G-SYNC for full screen mode.
  3. Navigate to Manage 3D settings and select the Global Settings tab.
  4. Change Vertical sync to On as this will allow the G-Sync module to compensate for frame time variances (prevents screen tearing within the VRR range) and allow G-Sync to fall back on V-Sync behavior when the frame rate exceeds the maximum refresh rate range of G-Sync.

In-game settings:

  1. Configure the game to run in Exclusive Fullscreen or Fullscreen mode if available.
  2. Disable all options available related to Vertical sync (Vsync).
  3. Limit the frame rate of the game to 3 FPS below the maximum refresh rate of the monitor (so 141 FPS on a 144 Hz monitor), either through an in-game FPS limiter (if available) or a third-party alternative.

Notes

  1. ↑ Albeit officially only present in eDP specification starting from version 1.4a, functionally[5] MSA_TIMING_PAR_IGNORED could have always been exploited for such functionality since the very first revision (even if no "fast pacing" requirement had to be met back then[6][7][8])
  2. ↑ While on desktops Nvidia should not be technically charging any other cost aside of the hardware module itself, on laptops there is not such thing. And it's really arguable why going at such lengths to embed cookies in the system BIOS otherwise

References

  1. ↑ Adaptive-Sync for mobile devices — Tech Specs
  2. ↑ NVIDIA Launches Mobile G-Sync, Enables Windowed G-Sync, & More
  3. ↑ AMD FreeSync Working With NVIDIA GPUs - Some Strings Attached
  4. ↑ GeForce - Adaptive V-Sync - last accessed on 2019-09-10
  5. ↑ 2nd Generation Intel® Core™ Mobile Processor Datasheet, Vol. 1 - last accessed on 2018-09-15
    "When a Local Flat Panel (LFP) supports multiple refresh rates, the Intel® Display Refresh Rate Switching power conservation feature can be enabled. The higher refresh rate will be used when on plugged in power or when the end user has not selected/enabled this feature. The graphics software will automatically switch to a lower refresh rate for maximum battery life when the notebook is on battery power and when the user has selected/enabled this feature.
    [...] The seamless Intel® Seamless Display Refresh Rate Switching Technology (Intel® SDRRS Technology) method is able to accomplish the refresh rate assignment without a mode change    "
  6. ↑ Dynamic Media Refresh Rate Switching | Intel Embedded Community - last accessed on 2018-09-15
    "DRRS only focus on the static picture."
  7. ↑ The Sync Wars | ahmed sharif - last accessed on 2018-09-15
    "Fast forward approximately 6 months later to CES’14, where AMD clarifies ‘But… we’ve had support for variable refresh rates since the Radeon 5000 series in our GPU hardware. In fact so have Intel (who also make embedded Laptop GPU’s). Have a look at our APU do the exact same thing as G-Sync on a regular laptop because laptops use the VESA-developed eDP standard for display hardware.’"
  8. ↑ SweClockers - Interview: AMD on dynamic frequencies with Project Freesync (English) - last accessed on 2018-09-15
    "Project FreeSync will utilize DisplayPort Adaptive-Sync protocols to enable dynamic refresh rates for video playback, gaming and power-saving scenarios. All AMD Radeon graphics cards in the AMD Radeon HD 7000, HD 8000, R7 or R9 Series will support Project FreeSync for video playback and power-saving purposes. The AMD Radeon R9 295X2, 290X, R9 290, R7 260X and R7 260 additionally feature updated display controllers that will support dynamic refresh rates during gaming."
  9. ↑ HDMI Forum Demonstrates HDMI 2.1 VRR Capabilities on Samsung TV - Anandtech - last accessed on 2018-09-17
    "There is a reason why HDMI Forum wants to use the HDMI 2.1 brand for hardware that will support only one or two new features from the package, even if it comes with certain confusion. [...] things like VRR and ALLM make sense for gamers today, but since they have to be supported by both sinks and sources, proper marking is required so that people who want to have them know to get the right hardware."
  10. ↑ HDMI Forum Releases Part 1 of the HDMI 2.1 CTS - Tech News - Linus Tech Tips - last accessed on 2018-09-17
    "Nothing in HDMI is mandatory other than baseline requirements for interoperability. Features like VRR are optional."
  11. ↑ FreeSync worked on CRT too -- tested by a few! • Blur Busters Forums
  12. ↑ OC3D - HDMI 2.1 VRR support will come to AMD Radeon RX GPUs with a future driver update - last accessed on 2018-09-17
  13. ↑ Does My Intel Graphics Support Intel® Adaptive Sync? - last accessed on 2022-03-11
  14. ↑ HDMI 2.1 Specification Released: Variable Refresh, Dynamic HDR, & More In 2018 - last accessed on 2018-09-15
  15. ↑ FreeSync Over HDMI to Hit Retail In Q1’16 - AMD Discusses 2016 Radeon Visual Technologies Roadmap - last accessed on 2018-09-17
  16. ↑ 16.0 16.1 Nvidia's G-Sync Updates: Windowed Mode, Notebook Implementation, New Displays
  17. ↑ AMD Radeon Software Crimson Improves FreeSync and Frame Pacing Support | PC Perspective
  18. ↑ Why does LFC in Freesync require such a large refresh range? : Amd - Reddit
  19. ↑ Does LFC (Freesync) support still require that the Freesync range is: maximum ≥ 2.5x minimum ? : Amd - Reddit
  20. ↑ FreeSync 2 Explained - TechSpot
  21. ↑ GitHub - pinnumbernumber/SetGPU - last accessed on 2018-10-09
  22. ↑ TFT Central - Variable Refresh Rates, G-sync and FreeSync - last accessed on 2018-09-02
  23. ↑ Blur Busters - Motion Blur Reduction (ULMB, LightBoost, etc) - last accessed on 2018-09-02
  24. ↑ PC Perspective - Mobile G-Sync Confirmed and Tested with Leaked Alpha Driver - last accessed on 2018-09-07
    "While NVIDIA confirmed that G-Sync on mobile is coming in the near future, it wasn't able to discuss timing specifics or technology specifics. But because we were clearly able to get most of the positive experiences of a G-Sync monitor on a notebook that not only is not G-Sync branded, but also does not have a G-Sync module in it, questions are going to fly around the community. Here's the facts: NVIDIA will release G-Sync on mobile devices without the requirement of a G-Sync module, but the company claims that there will be experience differences between desktop and mobile iterations of the technology. When pushed on what differences those might be, NVIDIA emphatically stated they exist but would be holding off on talking specifics until the mobile release of G-Sync when feature support is finalized."
  25. ↑ Anandtech - NVIDIA Launches Mobile G-Sync, Enables Windowed G-Sync, & More - last accessed on 2018-09-14
    "With embedded DisplayPort (eDP) now being a common fixture in high-end notebooks these days, NVIDIA will be able to do away with the G-Sync module entirely and rely just on the variable timing and panel self-refresh functionality built in to current versions of eDP. eDP's variable timing functionality was of course the basis of desktop DisplayPort Adaptive-Sync (along with AMD's Freesync implementation), and while the technology is a bit different in laptops, the end result is quite similar. Which is to say that NVIDIA will be able to drive variable refresh laptops entirely with standardized eDP features, and will not be relying on proprietary features or hardware as they do with desktop G-Sync."
  26. ↑ PC Perspective - ASUS ROG Swift PG27UQ 27" 4K 144Hz G-SYNC Monitor: True HDR Arrives on the Desktop - last accessed on 2018-09-02
  27. ↑ Blur Busters - G-SYNC 101: Optimal G-SYNC Settings & Conclusion - last accessed on 2018-09-02