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Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

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Re: Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

#111

Post by tjoff »

mritun wrote: post #74

PSA: Many 4K Dell monitors (like my Dell UltraSharp U3219Q ) have a built-in KVM switch and they support full DDC commands for switching the input as well (over HDMI, DP and USBC). I can control them from Mac and Linux with hot keys that trigger the appropriate ddc commands.

Well, 4K is not exactly a requirement. And while most older don't have the ability to swithc USB my U2415 displays (released in 2014) supports switching input over DDC. And honestly, I'd expect any half-decent display sold in the last decade to support it as well. But I could be very wrong. The samsung and AOC display I have connected at work also supports them and the samsung is quite old. For USB though I have to press a button. Or use the excellent virtualhere software for connecting USB over the network (that I could easily script to switch over usb as well).

I have a short script that will allow me to change input on a specific display. Very handy. However please note, that while this does work for HDMI, DVI and Displayport only DVI/HDMI seems to have an active connection when another input has been selected.

That means that while I can switch to another input I can not switch back from the same computer but must install something on the other machine to give it back. This is of course exactly what the linked article is doing, but with HDMI/DVI I don't have to have that requirement. And on top of that, operating systems in general seem to believe that, when using displayport, switching to another input is equivalent to disconnecting the display altogether and thus remove it and rearrange windows etc. Insanely frustrating.

Again, no problem with HDMI/DVI. So although Displayport is a much better interface and I've been a strong advocate for it, these issues makes me hate it with passion.

DDC can also be used to change display brightness, which in my opinion is way too cumbersome to do manually (especially if you have more than one display).

Re: Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

#112

Post by MegaDeKay »

mritun wrote: post #74

PSA: Many 4K Dell monitors (like my Dell UltraSharp U3219Q ) have a built-in KVM switch and they support full DDC commands for switching the input as well (over HDMI, DP and USBC). I can control them from Mac and Linux with hot keys that trigger the appropriate ddc commands.

I have a shortcut on my Linux desktop to switch my Dell U3818DW display to its HDMI input where a second graphics card passed through to Windows is running on as a KVM guest.

  #!/bin/bash
  ddcutil setvcp 60 0x11
On my Windows guest desktop, I set up a shortcut for Dell Display manager to switch back to my Linux host and primary graphics card on my display's DisplayPort input

  "C:\Program Files (x86)\Dell\Dell Display Manager\ddm.exe" SetActiveInput DP
Trivial to set up and works great.

Re: Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

#113

Post by gbraad »

crtasm wrote: post #109
cowtongue wrote: post #75

Earlier quoted context omitted.

I don't notice it when using it for work. I barely notice it when using it for console games. Probably wouldn't want to use it for competitive shooters, but non-issue for most other games. Few more notes: - I use PCIE rather than USB for the capture card - Can be costly if you need 4k + multiple inputs (for multiple "monitors" as different OBS windows) - I had issues getting the capture card to recognize scaled HiDPI…

You can do this without a capture card using https://ndi.tv/tools/ - other clients on your LAN can view in OBS or with the included program. I'm yet to try it with 4k. No help with consoles of course, and perhaps not an option for a work machine. edit: feature list also mentions "KVM remote control of any workstation running Scan Converter from NDI Studio Monitor"

I use NDI a lot, but with a phone as webcam, or from obs to obs, scan converter, audio stream between devices like ipad/iphone/Android to desktop... But it is demanding to encode this way. HDMI capture does only use bandwidth over the USB or pcie bus, while ndi uses cpu or gpu.

Re: Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

#114

Post by gbraad »

crtasm wrote: post #109
cowtongue wrote: post #75

Earlier quoted context omitted.

I don't notice it when using it for work. I barely notice it when using it for console games. Probably wouldn't want to use it for competitive shooters, but non-issue for most other games. Few more notes: - I use PCIE rather than USB for the capture card - Can be costly if you need 4k + multiple inputs (for multiple "monitors" as different OBS windows) - I had issues getting the capture card to recognize scaled HiDPI…

You can do this without a capture card using https://ndi.tv/tools/ - other clients on your LAN can view in OBS or with the included program. I'm yet to try it with 4k. No help with consoles of course, and perhaps not an option for a work machine. edit: feature list also mentions "KVM remote control of any workstation running Scan Converter from NDI Studio Monitor"

You have hardware devices for ndi, but they ain't cheap!

Re: Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

#115

Post by 3np »

mmastrac wrote: post #42

I bought a fantastic curved Samsung monitor and it supports reading from the port that tells you the current input but not setting it. It also has the worst possible input switcher that cycles until it finds a valid input. I wish it were easier to hack on monitor firmware. I'd love to improve it.

The least-horrible (but still not great) monitor firmwares I had so far were Eizo, followed by Dell.

I will never buy Samsung or LG again - the displays themselves were great but the UI/UX for switching inputs and brightness etc are simply too excruciating.

Re: Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

#116

Post by 3np »

Damogran6 wrote: post #103
freen wrote: post #80

Earlier quoted context omitted.

I’ll never buy anything from Samsung again. The software on their otherwise delightful hardware is absolute crap.

Or their dryers...or their dishwashers...I hear their phones are okay...It sucks when a multinational conglomerate has a sketchy quality issue.

The phones are terrible too, these days. I bricked a phone and lost access to all data on it by trying to back it up. Every Galaxy generation has gotten worse and worse in terms of preinstalled malware that takes a lot of effort and care to disable (if possible at all).

The only thing I would still buy from Samsung these days is storage devices.

Re: Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

#117

Post by stutteringsteve »

Can anyone concisely explain how this hack works, as if one were to introduce it to a five year old?

I'm having a hard time understanding how a USB switch can manipulate a monitor, directly or indirectly, to behave as an alternative to a KVM switch. The project README fails to provide practical examples and detail this hack in the simplest way possible. I'd love to have this solution working for a personal homelab, as prices for KVM switches are too high to financially bear.

If I get this solution working, I will contribute back to the README to address this issue.

UPDATE: Never mind! I found a relevant thread: https://news.ycombinator.com/item?id=29609573

Re: Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

#118

Post by crtasm »

gbraad wrote: post #113
crtasm wrote: post #109

Earlier quoted context omitted.

You can do this without a capture card using https://ndi.tv/tools/ - other clients on your LAN can view in OBS or with the included program. I'm yet to try it with 4k. No help with consoles of course, and perhaps not an option for a work machine. edit: feature list also mentions "KVM remote control of any workstation running Scan Converter from NDI Studio Monitor"

I use NDI a lot, but with a phone as webcam, or from obs to obs, scan converter, audio stream between devices like ipad/iphone/Android to desktop... But it is demanding to encode this way. HDMI capture does only use bandwidth over the USB or pcie bus, while ndi uses cpu or gpu.

It's not at all demanding on my RTX2060 but I'm only doing 1080p 60fps - don't know how other cards/resolutions/framerates compare.

Re: Display-switch: Turn a $30 USB switch into a full-featured multi-monitor KVM

#119

Post by tekknik »

gbraad wrote: post #113
crtasm wrote: post #109

Earlier quoted context omitted.

You can do this without a capture card using https://ndi.tv/tools/ - other clients on your LAN can view in OBS or with the included program. I'm yet to try it with 4k. No help with consoles of course, and perhaps not an option for a work machine. edit: feature list also mentions "KVM remote control of any workstation running Scan Converter from NDI Studio Monitor"

I use NDI a lot, but with a phone as webcam, or from obs to obs, scan converter, audio stream between devices like ipad/iphone/Android to desktop... But it is demanding to encode this way. HDMI capture does only use bandwidth over the USB or pcie bus, while ndi uses cpu or gpu.

HDMI capture cards can definitely use CPU, and this is the case for most USB capture cards as USB does not have enough bandwidth to send an entire raw stream in realtime.
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