Multimonitor

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Stratodesk NoTouch Desktop supports multimonitor operation. In fact, dual-screen operation has become very common in today's offices and so is it a commonly used feature on machines run by NoTouch.

Background

If the system detects multiple monitor ports, by default the system will output the same image on both screens ("cloned" mode in our terminology) which is usually a safe bet and also works if there is only one monitor connected. In an office scenario where you have two monitors next to each other, you most probably want to have both monitors being part of a large logical desktop, this is called "merged" mode.

In "merged" mode, when operating remote desktops such as via Citrix, VMware or RDP, the server-side Windows desktop may or may not know about the actual screen geometry. In the simplest case server-side Windows may believe that there is a single screen that is 3840 pixels wide, for instance, when the client has two monitors connected with 1920 pixels horizontally each. Now if you maximize a program window, it would be maximized over both screens - and most people feel uncomfortably with that. That means it is important that the server side Windows instance gets to know about the actual screen geometry on the client side - and fortunately this is done automatically the way NoTouch is configured by default. Not all protocols support this, but the Citrix Receiver, VMware Horizon View client, and FreeRDP do and you can tune the settings.

The actual support for dual monitor or multi-monitor is hardware- and driver-dependent. If you feel you have found a device where multimonitor doesn't work even though it has two display outputs, please create and send us a support file.

Raspberry Pi

On the Raspberry Pi, there are two options for multi-monitor:

  • For use with Citrix only, the SDA (Secondary Display Adapter)
  • For all other uses, a DisplayLink based USB adapter

Citrix Secondary Display Adapter

Exclusively for use with Citrix there is a type of SDA (Secondary Display Adapter) available through NComputing and ViewSonic. It does not require configuration on the NoTouch end.

This is a very interesting technology. The SDA is used by the Citrix Receiver and receives the compressed ICA/HDX data stream. That means, USB bandwidth limitations do not apply. The SDA hardware decodes the data and displays the content. The SDA is not used by the local operating system, it is not usable by e.g. the local browser or anything else than Citrix. However, once you start a Citrix session, the session will extend automatically to the SDA.

Note: Please make sure the Multimonitor mode parameter is set to "cloned" (do NOT set it to merged mode).

DisplayLink Plugable UGA-165

On Raspberry Pi based devices the DisplayLink based Plugable UGA-165 USB 2.0 to VGA/DVI/HDMI Adapter is supported. To operate it, simply

  1. Plug the adapter in (make sure your Pi device as at least a 2.5A power supply)
  2. Set the Multimonitor mode to merged as described here in this article
  3. Reboot

Limitations: The Raspberry Pi will switch to a 16-bit framebuffer. The second screen will be a bit slower than the first and obviously it can not do H.264 decoding on the second screen.

Multimonitor modes

Enable merged multi-screen (typical office setting)

Merged multiscreen is the setting for typically office settings where a user has two monitors and wants to have one large logical desktop made of two monitors.

To enable merged multi-screen, set the parameter "Multimonitor mode" in the "Display" options to "merged". If you use NoTouch Center, it is part of the "Group Settings" / "Desktop" options. Make sure the change is saved and then reboot the device for the changes to go in effect.

Enable cloned multi-screen (same contents on all screens)

Cloned multiscreen mode is the setting where you want two screens to display the exact same picture, such as when having one monitor as your desktop and the other pointed to a customer with same screen contents or an overhead projector.

To enable cloned multi-screen, set the parameter "Multimonitor mode" in the "Display" options to "cloned". If you use NoTouch Center, it is part of the "Group Settings" / "Desktop" options. Make sure the change is saved and then reboot the device for the changes to go in effect.

Hint: By default, NoTouch selects the best resolution for each monitor individually. If you want to force both displays to have the same resolution in cloned mode, please set the parameter "Cloned display has same resolution" to "on". Again, make sure the value is saved, and reboot the device.

Multimonitor parameters

  • Multimonitor mode. Multimonitor operation master switch:
    • off. Do not consider any second monitor at all.
    • cloned (same picture on all monitors). This will "mirror" or "clone" the same "single-monitor" image on both monitors.
    • merged (all monitors form one desktop). This will create only logical desktop made from both monitors.
    • Matrox G4xx/G5xx (deprecated). This was a special mode for the now EOL-ed Matrox G4xx/G5xx graphics cards. Do not set it on other machines.
  • Position of secondary screen. Defines the position of the second screen, either right or left of the primary monitor.
  • Primary monitor. This allows to define which monitor should be considered the "primary". This parameter makes only sense on systems where there are both an analog (VGA) and digital output (DVI) so that one can distinguish between them. Values can be logically or-ed by the pipe symbol, thus HDMI|DVI means HDMI or DVI. Acceptable values are: CRT, VGA, HDMI, DVI, DP
  • Cloned display has same resolution. If you clone the screen, e.g. to a secondary display or a projector, should the second display forced to the resolution of the primary monitor, yes or no.

FAQs

The resolution is not set correctly

Some devices, especially TV sets or projectors, may fail to provide correct EDID/DDC data. This is their fault, actually, but nevertheless you have to cope with it: Please set the desired resolution manually.

Furthermore KVM switches usually cripple EDID/DDC traffic. If you don't plan on using the KVM switch productively (which is highly unlikely), don't use one for testing/evaluating.

Sometimes it may help to plug the failing monitor into port 1 (depending on hardware/graphics card) and set the resolution manually. The second monitor will still be configured automatically.