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5k edid dummy adapter for looking glass

Hello Looking Glass users,

I got 2 questions which I hope can be answered here…

  1. Is it correct that I need a dongle for looking glass when my display only got 1 dp input? (so I can’t just leave it connected)

  2. Does anybody know of a 5k dongle? I got an LG 5k display with only one DP port. (I know - an early adopters problem)

Thanks in advance

Unless you have a second display with an open input. Also, if you are passing through a quadro, they can have an edid file specified without a display connected.

I don’t, however you could try setting a resolution above what the edid reports.

I’ve got a RTX 2080 for the win10 vm, so i need the dongle or another active connection. Tnx for clarification.

I already tried with a real HDMI connection (display got 2x HDMI but only 1 DP) and didnt managed to get past 5k @ 30Hz. Maybe deactivating VSYNC in games and using a frame limiter to 60Hz would do the trick. Anybody tried this?

Hz has nothing to do with vsync or a frame limiter. Hz is the refresh rate of the display, and FPS can go either under or over the refresh rate. Also a frame limiter only limits the FPS at the top end, and doesn’t do anything to the low-end.
[email protected] is probably the bandwidth limit of whatever HDMI output your GPU has (or the input your monitor has), though I’m too lazy to calculate. Remember that [email protected] is near the limit of most current consumer GPUs, and 5k is almost twice the amount of pixels.

Thank you for the explanation. I was aware of the difference between physical refresh rate and the amount of frames the application renders. Therefore id intented to have 30hz physical and 60hz via frame limiter. The real display connection (from linux vm) got a display port connection and therefore real 60hz. This way i could use HDMI as physical output of my win 10 vm with 30hz while enjoying 60hz on the client side.

Exactly this my problem with HDMI - 30hz in 5k. Therefore i played with the thought of a 5k DP dummy device. Hope there will be one soon.

I’m not sure I’m following…

How would this help with the HDMI bandwidth limit? If you get a dummy device you might be able to set the a higher resolution and refresh rate, but the output will still go to that dummy device (i.e. nowhere), and doesn’t help you with displaying over HDMI.

So I hope I got this right…
“Linux VM” is hopefully typo and you mean the Linux Host, because otherwise none of this makes sense to me.
So the Host has 60 Hz, so far so good.

So your Windows VM would have a physical Display attached with 30 Hz, but you would use 60 Hz via Looking Glass?
AFAIK to do this you’d have 2 options:

  1. Output actual 60 Hz, i.e. overriding what the EDID reports and hope the display just drops every second frame. Which it probably won’t because the HDMI bandwidth limit means that there’s not even 60 FPS going out.
  2. Use the Display and a dummy plug at the same time. But then you’d have mixed refresh rates and I don’t think Windows allows that when mirroring a display.

But what I don’t get: Assuming you get your hands on a working dummy plug, why don’t you just drop the physical Display connection? That way you have only one “Display”, and can use Looking Glass to display the 60 FPS/60 Hz on the Host (i.e. Looking Glass Client).

But at that point you might run into bandwidth limitations in Looking Glass. IIRC there were some issues with [email protected] already. @gnif would know more about that, since I haven’t kept up with Looking Glass.

LG will capture as best it can at the render rate which is usually limited by vsync which in turn is limited by your monitor’s specs. So if your dummy plug advertises 60Hz and you turn off vsync (note a frame rate limiter will still be needed), and your game runs at 144FPS, LG will capture at 144FPS and feed this back to the host to render.

The 1k barrier was broken with the B1 release, 4k 60Hz is viable but depends on your hardware and workload.

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