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Does GSYNC work with video players? [edit: yes, sometimes]

Talk about NVIDIA G-SYNC, a variable refresh rate (VRR) technology. G-SYNC eliminates stutters, tearing, and reduces input lag. List of G-SYNC Monitors.

Re: Does GSYNC work with video players?

Postby masterotaku » 24 Jan 2014, 13:15

The problem is when judder happens inside the video. Example: the Doctor Who Specials (last episodes of David Tennant) in Blu Ray run at 60 interlaced fps (easily noticed at the credits, with the monitor at 60Hz), but some of the episodes per se run at 25fps (like the TV and DVD version). So, it's 25fps inside of 60fps. It has its own internal judder. That should be impossible to synchronize unless you edit the video and discard repeated frames with an algorithm or frame by frame.
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Re: Does GSYNC work with video players?

Postby RealNC » 24 Jan 2014, 13:46

Valyrian wrote:No, actually I haven't been strobing this monitor recently, however now that you mention it I do think most of the content I watch is actually 23.976fps, so I guess that explains it. Also, I am not on Linux, but how is it that you can create a 47.952Hz mode? I thought refresh rates were limited to what the monitor is programmed to support natively (unless you get GSYNC of course). Furthermore, without GSYNC is it not likely that the refresh rate and video frame rate would still be out of sync even if they are exactly the same? Kinda like how you can still get terrible tearing if you frame cap a game to the monitor's refresh rate but don't use v-sync.

Monitors can be driven at any refresh rate. Some monitors will start dropping frames though, but usually they work fine with all refresh rates that lie inside their official specs. So a 120Hz monitor can be usually driven at any rate starting from around 50Hz (and somewhat lower, as in my case) and ending at 120Hz.

The video frames will not be out of sync, since video players always V-Sync (some video APIs don't even allow non-V-Synced video). Also, they usually decode many frames in advance, so they never run out of frames to display.

You can setup these custom modes yourself even if not in Linux. Just create a mode in the NVidia Control panel and enter your own refresh rate. You can then activate that refresh rate prior to starting the video player. The player should then be able to detect the refresh rate and therefore not introduce any weird pull-down mode (at least the one I use, mplayer, works that way.)
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Re: Does GSYNC work with video players?

Postby nimbulan » 24 Jan 2014, 16:08

One of the main reasons I keep my monitor at 120 Hz rather than 144 Hz is due to 30 fps video not being able to play smoothly at 144 Hz (and the same for 30 and 60 fps locked games.)

I can confirm it is possible to use G-sync with a video player. I started using PotPlayer recently, made by a Korean company but you can find an English version. If you enable exclusive fullscreen mode, G-sync activates and does appear to play 24, 25, and 30 fps video all smoothly.
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Re: Does GSYNC work with video players?

Postby Valyrian » 24 Jan 2014, 18:48

So if I'm understanding this correctly, this "judder" or " 3:2 pulldown" effect (if these two terms actually refer to the same thing), is caused by the conflict between a 24fps frame rate and a 60Hz refresh rate. As in, the v-sync coded into the video file or player forces one frame to be displayed for 3 refresh cycles, and the next frame for 2 refresh cycles, and so on, thereby fitting 12 of these 5-refreshes-long 3:2 patterns into every second, which causes shaky motion (judder) because each frame is displayed for a different amount of time than the one before and after it.

So by that logic, a 120Hz or 144Hz refresh rate should work perfectly with a 24fps video because each frame would be displayed for exactly 5 or 6 v-synced refresh cycles. However, since the effect I'm seeing is worse at 144Hz than at 60Hz, and also at higher "Trace Free" settings, this must somehow be caused by the videos which are actually 23.976fps or 25fps instead of 24fps, right? This would explain why some of my video files seem to work fine, while others look like garbage. Unfortunately, I have yet to find a way to determine the exact frame rate of a video because both FRAPS and the Windows "Properties" tab, if it includes it at all, round off to the nearest whole number.

RealNC wrote:You can setup these custom modes yourself even if not in Linux. Just create a mode in the NVidia Control panel and enter your own refresh rate. You can then activate that refresh rate prior to starting the video player. The player should then be able to detect the refresh rate and therefore not introduce any weird pull-down mode (at least the one I use, mplayer, works that way.)


Is it the "Create Custom Resolution" option you can find through the "Change resolution" tab of the NV Control Panel that you are referring to? That was the only thing I could find, but it had some pretty nasty warnings about voiding monitor warranties and not guaranteeing that the utility would even be accurate, reliable, or virus-free. I figured it was probably the usual hyperbolic legal stuff to cover their own asses, but I'd rather check first that this is the option you were talking about.

nimbulan wrote:I can confirm it is possible to use G-sync with a video player. I started using PotPlayer recently, made by a Korean company but you can find an English version. If you enable exclusive fullscreen mode, G-sync activates and does appear to play 24, 25, and 30 fps video all smoothly.


This is great news! Have you by any chance heard of any other players that work with GSYNC?
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Re: Does GSYNC work with video players?

Postby sharknice » 24 Jan 2014, 18:59

I haven't messed around with it, but Media Player Classic has options for changing resolutions when entering full screen mode based on the frame rate of the video. It also has Sync display to video settings and a bunch of rendering output settings I haven't messed with. It might be possible to get it to activate GSYNC somehow.
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Re: Does GSYNC work with video players?

Postby nimbulan » 24 Jan 2014, 19:04

Valyrian wrote:So if I'm understanding this correctly, this "judder" or " 3:2 pulldown" effect (if these two terms actually refer to the same thing), is caused by the conflict between a 24fps frame rate and a 60Hz refresh rate. As in, the v-sync coded into the video file or player forces one frame to be displayed for 3 refresh cycles, and the next frame for 2 refresh cycles, and so on, thereby fitting 12 of these 5-refreshes-long 3:2 patterns into every second, which causes shaky motion (judder) because each frame is displayed for a different amount of time than the one before and after it.

So by that logic, a 120Hz or 144Hz refresh rate should work perfectly with a 24fps video because each frame would be displayed for exactly 5 or 6 v-synced refresh cycles. However, since the effect I'm seeing is worse at 144Hz than at 60Hz, and also at higher "Trace Free" settings, this must somehow be caused by the videos which are actually 23.976fps or 25fps instead of 24fps, right? This would explain why some of my video files seem to work fine, while others look like garbage. Unfortunately, I have yet to find a way to determine the exact frame rate of a video because both FRAPS and the Windows "Properties" tab, if it includes it at all, round off to the nearest whole number.

It's not simply an issue of vsync. I believe the problem occurs when video players or the video encoder do the 3:2 pulldown automatically (especially with an interlaced video source) because they are expecting the video to be played on a 60Hz display so it doesn't sync up properly at 144 Hz. Of course on top of this there are a wide variety of interlacing methods used in different video sources, some of which are impossible to deinterlace properly and will always result in horrible stuttery motion no matter your refresh rate.

Valyrian wrote:This is great news! Have you by any chance heard of any other players that work with GSYNC?

In theory, any player that has the option for a real fullscreen mode rather than the borderless window fake fullscreen mode usually used should be able to utilize G-sync. I was also able to activate G-sync with Media Player Classic Home Cinema by enabling the D3D Fullscreen option.
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Re: Does GSYNC work with video players?

Postby Haste » 25 Jan 2014, 02:29

nimbulan wrote:I was also able to activate G-sync with Media Player Classic Home Cinema by enabling the D3D Fullscreen option.
Would it still work if you use SVP with it?
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Re: Does GSYNC work with video players?

Postby nimbulan » 25 Jan 2014, 03:04

Haste wrote:Would it still work if you use SVP with it?

SVP doesn't make a difference as it's just extra video processing and won't affect the video player's renderer. It may actually be a good idea to use SVP or a simple frame doubler (if anyone knows where to find one?) because 29.97 fps video can trigger G-sync's automatic refresh behavior and cause stutter.
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Re: Does GSYNC work with video players?

Postby Haste » 25 Jan 2014, 03:06

Nice. That's good news!
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Re: Does GSYNC work with video players?

Postby RealNC » 25 Jan 2014, 09:19

Valyrian wrote:Is it the "Create Custom Resolution" option you can find through the "Change resolution" tab of the NV Control Panel that you are referring to? That was the only thing I could find, but it had some pretty nasty warnings about voiding monitor warranties and not guaranteeing that the utility would even be accurate, reliable, or virus-free. I figured it was probably the usual hyperbolic legal stuff to cover their own asses, but I'd rather check first that this is the option you were talking about.

Yes, that's where you create custom modes. I hope you were joking with the "virus-free"...
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