HDX Graphics Modes – Which Policies Apply to DCR/Thinwire/H.264

Description

Legacy graphics

Legacy graphics is a host (computer) policy and its use should be treated as an always on or always off. Behavior will differ between Workstation OS VDA and Server OS VDA. You should only ever be using legacy mode for OSs for which it is designed i.e. Windows 7, Windows 2008 R2 and earlier (that s, Legacy OSs). Legacy graphics is highly optimised for legacy OSs and should be regarded as the first choice for those operating systems unless other factors are involved.

NOTE: Legacy graphics mode is not supported in combination with modern operating systems: Windows Desktop OS: 8, 8.1, 10 or Windows Server 2012, 2012 R2 & Windows Server 2016.

Thinwire plus (aka: TW+ orcompatibility mode) should be used and is the replacement for legacy mode.
Documentation Thinwire Compatibility Mode
Blog post: "To use or not to use?"

Policy templates

We recommend users configure policies for XD/XA 7.6 FP3 via the built in templates available in studio. Further information on policy templates can be found here:

Policy template documentation
Simplify HDX Policy Administration to Amplify the User Experience
HDX Policy Templates - Whitepaper
Additional online templates (including Cloudbridge, HTML5, Framehawk use cases): - Group Policy Management Template Updates for XenApp/XenDesktop

XenDesktop/XenApp 7.6 FP3 Installation

With XD/XA 7.6 FP3, you don’t have to disable DCR as it is now disabled by default.
Because the FP3 release is a VDA-only update, to be able to use the new policies with FP3 you will also need to apply a small update your DDC. If you have stand-alone installations of Citrix Studio on other systems, those should also have the update applied in order to be able to see the new policies.
The file to install on your DDC is “CitrixGroupPolicyManagement_x64.msi”

After installing the update, your “Citrix Group Policy Management” version 2.5.0.0 will appear in Control Panel > Add Remove Programs. Note that on a 7.6 Delivery Controller with no updates this component, while available, does not appear in the Add Remove programs list.

How to check which graphics modes are you using

The graphics mode used will be determined by the policies set and the hierarchy in which those policies apply (see policy precedence table below).

A useful tool is available (here) that allows you to survey all the receivers and sessions on a site and check what graphics mode they are using.
You can also follow the advice in this blog on how to check which graphics mode you are using. (If you are ever submitting an HDX bug – you can use the xml export feature of HDX monitor or the output of the wmic commands to provide information on the graphics mode).
This information can be accessed via the Director console.

When you are using “Thinwire Compatibility” mode you will see the encoder used to be the CompatibilityEncoder. This is a bit confusing, as earlier versions have a compatibility mode, which is completely different code and performance footprint (we generally don’t recommend the old one for general use as usually better performance available via other modes).

Graphics policies available in XenDesktop / XenApp 7.6 FP3

Here is a table of all graphics policies available and which graphics modes they apply to (note how most policies only apply to legacy mode – policies that apply only to legacy mode are in grey cells):

Policy	User/Computer	Framehawk	DCR	H.264	Thinwire Compatibility mode (ECM)	Legacy Graphics Mode	Comment
Desktop Composition graphics quality	User		X
Desktop Composition Redirection	User		X				See graphics display precedence table
Display memory limit	Computer			X	X	X	See CTX201696 – Citrix XenDesktop and XenApp – Support for Monitors Including 4K Resolution and Multi-monitors
Display mode degrade preference	Computer					X	For legacy graphics only. If the Display Memory limit was exceeded, prefer to degrade Color depth or resolution
Dynamic window preview	Computer	X		X	X	X	Enables the windows contents to update even when not displayed on screen, this is so the thumbnails in taskbar, Alt-Tab, etc. keep updated, thus enhancing a rich user experience. This can lead to higher bandwidth and server CPU utilization
Extra color compression	User				X	X	Extra Color Compression is an optimization that can save up to 20% (of size) when compressing graphical screen areas at the expense of quality. Turning it off makes some images, like text over a complex background appear sharper. Savings are most notable in Legacy graphics and less in ECM
Extra color compression threshold	User					X	See: CTX201802 – FAQ: HDX Extra Color Compression (ECC) Policy in XenApp and XenDesktop
Framehawk display channel		X					See graphics display precedence table
Framehawk display channel port range		X					Use this setting in a base (Computer) policy if you desire to change the default UDP ports used. Not necessary if the default ports are used
Heavyweight compression	User					X
Image caching	Computer					X
Legacy graphics mode	Computer					X	See graphics display precedence table
Lossy compression level	User					X
Lossy compression level threshold value	User					X
Minimum image quality	User					X	Valid for Legacy Adaptive Display ONLY : it sets the minimum acceptable quality for transient (moving) images. This setting has been replaced by the ‘Visual Quality’ setting for modern display encoding methods
Moving image compression	User				X	X	Enables or disables Adaptive Display, allowing for automatic graphics quality degradation to maintain frame rate over bandwidth constrained environments. Recommended to be disabled on double hop scenarios, for the connection between the application and the desktop/access session.
Maximum allowed color depth	Computer					X	On legacy graphics, we could request applications to render graphics at lower color depth. A similar setting has been implemented in ECM to allow the reduction color depth when encoding. Currently accepting 16bpp and 24bpp values
Notify user when experience is degrade	Computer					X	For legacy graphics only. NOTIFY If the Display Memory limit was exceeded, prefer to degrade Color depth or resolution
Persistent cache threshold	Computer					X
Preferred color depth for simple graphics	User				X		Allow encoding at 16bpp. Default value 24bpp. Some experimental values available at the time of writing
Progressive compression level	User					X	If enabled, adaptive display is disabled and switch to progressive display
Progressive compression threshold value	User					X
Queuing and tossing	Computer					X
Target frame rate	User			X	X	X	Maximum allowed/desired frame rate.
Target minimum framerate	User			X	X	X	Value at which the image quality should be degraded in favor of maintaining the desired frame rate value. Please note this value is not guaranteed, actual FPS depends also on the ‘Visual Quality’ setting and could be lower if the bandwidth does not allow it
Visual quality	User			X	X

Note: You should only ever be using legacy mode for legacy OSs for which it is designed i.e. Windows 7, Windows 2008 R2 and earlier. Taking the table above and deleting every policy that only relates to legacy graphics mode will leave the only policies in XenDesktop 7.6 FP3 as it was initially released which you need to consider if you are not explicitly setting your deployment to use legacy mode. As shown in the table below:

Policy	User/Computer	Framehawk	DCR	H.264	Thinwire Compatibility mode (ECM)	Comment
Desktop Composition graphics quality	User		X			When using DCR, what quality should graphics be. Low value can cause text over graphics to be fuzzy
Desktop Composition Redirection	User		X			See graphics display precedence table
Display memory limit	Computer			X	X	See CTX201696 – Citrix XenDesktop and XenApp – Support for Monitors Including 4K Resolution and Multi-monitors
Dynamic window preview	Computer			X	X	Enables the windows contents to update even when not displayed on screen, this is so the thumbnails in taskbar, Alt-Tab, etc. keep updated, thus enhancing a rich user experience. This can lead to higher bandwidth and server CPU utilization
Extra color compression	User				X	Extra Color Compression is an optimization that can save up to 20% (of size) when compressing graphical screen areas at the expense of quality. Turning it off makes some images, like text over a complex background appear sharper. Savings are most notable in Legacy graphics and less in ECM See: CTX201802 – FAQ: HDX Extra Color Compression (ECC) Policy in XenApp and XenDesktop
Framehawk display channel		X				See graphics display precedence table
Framehawk display channel port range		X				Use this setting in a base (Computer) policy if you desire to change the default UDP ports used. Not necessary if the default ports are used
Legacy graphics mode	Computer					See graphics display precedence table. Note: If enabled, will override: EVERYTHING in RDS (server OS) Thinwire h.264 and/or ECM for Workstation OS
Moving image compression	User				X	Enables or disables Adaptive Display, allowing for automatic graphics quality degradation to maintain frame rate over bandwidth constrained environments. Recommended to be disabled on double hop scenarios, for the connection between the application and the desktop/access session.
Preferred color depth for simple graphics	User				X	Allow encoding at 16bpp. Default value 24bpp. Some experimental values available at the time of writing
Target frame rate	User			X	X	Maximum allowed/desired frame rate.
Target minimum framerate	User			X	X	Value at which the image quality should be degraded in favor of maintaining the desired frame rate value. Please note this value is not guaranteed, actual FPS depends also on the ‘Visual Quality’ setting and could be lower if the bandwidth does not allow it
Visual quality	User			X	X

IMPORTANT: You must not extrapolate this reduced table to later Feature Packs of XD/XA 7.6, this information related to XenApp/XenDesktop 7.6 FP3 as it was released.

Or presenting it another way, the only policies that apply if you are using non-legacy mode are:

Graphics Mode	Policies that have effect
Framehawk	Framehawk display channel Framehawk display channel port range
DCR	Desktop Composition graphics quality Desktop Composition Redirection
H.264	Display memory limit Dynamic window preview Target frame rate Target minimum framerate Visual quality
Thinwire Compatibility	Display memory limit Dynamic window preview Extra color compression Moving image compression Preferred color depth for simple graphics Target frame rate Target minimum framerate Visual quality

IMPORTANT: You must not extrapolate this reduced table to later Feature Packs of XD/XA 7.6, this information related to XenApp/XenDesktop 7.6 FP3 as it was released.

Graphics display precedence table

Assuming legacy policy and mode are not in use.

Framehawk	Will have precedence if: 1. Enabled 2. Receiver and VDA are compatible (VDA 7.6 FP2 or higher, Receiver for Windows 4.3.100 or higher or IOS 6.x or higher) 3. Connection on the required UDP ports is possible
DCR	Will be used if: 1. Enabled – please note: 7.0 to 7.6 FP2 VDA will be enabled by default 2. Framehawk is NOT IN USE (see above) 3. Receiver and VDA OS are compatible (VDA Windows 7, 8 or 8.1, Receiver for Windows 3.0 or higher or Receiver for Mac 11.9 or higher) 4. Client device has a suitable GPU (most likely yes) 5. VDA 5.x will stop DCR if bandwidth not available
Thinwire H.264	Will be used if: 1. Use Video Codec for compression allowed 2. Higher precedence encoders are NOT IN USE (see above) 3. Receiver is compatible. a. Windows 3.4 or higher b. Mac 11.8 or higher c. Linux 13.0 or higher d. IOS 5.9 or higher e. Android 3.4 or higher f. Chrome/HTML5 1.4 (SF2.1 or higher) 4. No modification to the VDA registry have been made (some registry modifications have been recommended in the past to enable experimental/tech preview features)
Enhanced Thinwire compatibility mode	Will be used if: 1. Use Video codec for compression set to : Do not use 2. Higher precedence encoders NOT IN USE (see above) 3. As noted above, some receivers will not support any of the above encoders. For sake of completion they are listed here: a. Windows receiver earlier than 3.4 b. Mac receiver earlier than 11.8 c. Linux receiver earlier than 13.0 d. Linux receiver with h.264 support disabled (see documentation) e. Dell/Wyse ThinOS with receiver 13.0.0.6685 f. IOS receiver earlier than 5.9 g. Android receiver earlier than 3.4 h. Very old HTML5 i. Any receiver not listed here

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