HDX 3D Pro – Toggling between lossy and lossless protocols to sharp CAD lines just got easier!

I’ve blogged before about how H.264 technologies can inherently have artefacts associated with them (read here). Particularly CAD hidden-line/wireframe lines that are near parallel can show a fading in colour or seem “less sharp”

HDX allows users to switch between lossless and lossy graphics modes dynamically but switching to lossless has a high bandwidth overhead. Better strategies can be to use the “Build to visually-lossless” policy which will use the standard H.264 technologies when the screen is transient (moving) e.g. when a user rotating a CAD part or a video is playing. When the moment stops the screen will build to a higher quality (you can read more in my article about using built to visually lossless, here). Or another option can be to use the new thinwire compatibility mode just released with XenDesktop/XenApp 7.6 FP3 (see Thinwire Compatibility Mode), and particularly explore the innovations in buid-to-loss.

Some users however like the ability to snap to true lossless at their discretion (avoiding the lossless bandwidth overhead when moving parts and just using lossless for detailed workflows) and we’ve long provided a hotkey to allow this workflow, popular with many CAD or medical users. (The small lossless icon will tell you if a screen is lossless). The existing hotkey though was fiddly to use (ALT+SHIFT+1) – try it for yourself, you need to have very big hands and a bendy middle finger or use two hands (or be an Octopus!)! So in XD7.6 FP3 we’ve added the ability for the administrator to customise the hotkey


Hotkey to switch between lossy and lossless compression

A hotkey was provided for HDX 3D Pro in 😄 7.x (ALT+SHIFT+1) which allowed users to switch between lossy and lossless compression.


Custom hotkey configuration for lossless compression.

You can find the documentation for this, here: see GPU acceleration for Windows Desktop OS.

With HDX 3D Pro in 😄 7.6 FP3 and up, the administrator can now configure a registry setting to set a custom keyboard shortcut to override the default (ALT+SHIFT+1). Users can instantly switch between lossy and visually lossless compression, or between lossy and lossless compression using a custom hotkey.

In 7.6 FP3, you can override the default shortcut, ALT+SHIFT+1, to select or deselect Lossless within a session. Configure a new registry setting at


Name: HKLM_HotKey,

Type: String

The format to configure a shortcut combination is C=0|1, A=0|1, S=0|1, W=0|1, K=val. Keys must be comma “,” separated. The order of the keys does not matter.

A, C, S, W and K are keys, where C=Control, A=ALT, S=SHIFT, W=Win, and K=a valid key. Allowed values for K are 0-9, a-z, and any virtual key code. For more information on virtual key codes, see Key Codes on MSDN.

For example:

  • For F10, set K=0x79
  • For Ctrl + F10, set C=1, K=0x79
  • For Alt + A, set A=1, K=a or A=1, K=A or K=A, A=1
  • For Ctrl + Alt + 5, set C=1, A=1, K=5 or A=1, K=5, C=1
  • For Ctrl + Shift + F5, set A=1, S=1, K=0x74


Caution: Editing the registry incorrectly can cause serious problems that may require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.

3 thoughts on “HDX 3D Pro – Toggling between lossy and lossless protocols to sharp CAD lines just got easier!”

  1. Very nice feature, both for testing and to be able to switch to one ode or the other, depending on the circumstances. Is there something similar available for clients accessing XenApp ?


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