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Samsung Q series TVs

Talk about AMD's FreeSync and VESA AdaptiveSync, which are variable refresh rate technologies. They also eliminate stutters, and eliminate tearing. List of FreeSync Monitors.

Re: Samsung Q series TVs

Postby RealNC » 06 Oct 2018, 10:45

lossofmercy wrote:https://www.youtube.com/watch?v=oHtXx1JOUpo

Just excited to get this a bit more exposure.

Why are they still having issues with the VRR range? 48-60 is really not good at all for consoles. Why not 0-60 through LFC? If you want it to work well on the XBox X, you really need that, IMO.
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Re: Samsung Q series TVs

Postby Chief Blur Buster » 16 Oct 2018, 11:45

RealNC wrote:Why are they still having issues with the VRR range? 48-60 is really not good at all for consoles. Why not 0-60 through LFC? If you want it to work well on the XBox X, you really need that, IMO.

LFC requires predictive logic to pre-emptively start early re-refresh scanouts without colliding with the timing of the next frame presentation.

This gets extremely challenging when framerates fluctuate very well. LFC works perfectly if frametimes are consistent, since it can reliably simply pre-emptively trigger LCD duplicate-refresh-cycle scanouts exactly between the real frames (non-duplicate refresh cycles).

However, if a new frame arrives while the monitor is still in the middle of a refresh cycle (whether a new refresh cycle, or simply a re-refreshing scanout), that new frame has to wait. That wait creates a bit of lag & a bit of stutter.

So good LFC logic requires:

1. Very fast scanouts (e.g. 240Hz monitors means re-refreshes are only 1/240sec 4.2ms, and less likely to collide with frame presentation timing)
AND
2. Smart logic to pre-emptively time the re-refreshing pass exactly between previous frame and the predicted time of presentation of next frame.

This gets really challenging with slower-scanning panels (e.g. 60Hz panels which will block for 16.7ms during a repeat-refresh pass) combined with wildly fluctuating frametimes. There are rather severe limitations of doing LFC on both G-SYNC and FreeSync that are predicated by laws of physics.

Engineering Point of View: If you are familiar with anti-collision logic (Ethernet, WiFi in the light of bursty internet traffic) the same collision math problem occurs with LFC in the light of bursty frametimes. It cannot be solved perfectly, just improved -- via (1) and (2) as aggressively as possible. Or you decide that the artifacts of doing true low-Hz native refreshing is the lesser-of-evils than doing LFC (and its frame-vs-refresh collision math problem). That is often finely tuned at ~30Hz or ~48Hz, because flicker artifacts (e.g. low-frequency LCD inversion artifacts) can start to become really bothersome, and actually create visible flickering as LCD decay (pixel fade; loss of the static voltage over time of an unrefreshed pixel) starts becoming visible at lower Hz.
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