Product Documentation

Graphics policy settings

Sep 25, 2017

The Graphics section contains policy settings for controlling how images are handled in user sessions. 

Allow visually lossless compression

This setting allows visually lossless compression to be used instead of true lossless compression for graphics. Visually lossless improves performance over true lossless, but has minor loss that is unnoticeable by sight. This setting changes the way the values of the Visual quality setting are used.

By default this setting is disabled.

Display memory limit

This setting specifies the maximum video buffer size in kilobytes for the session.

By default, the display memory limit is 65536 kilobytes.

Specifies the maximum video buffer size in kilobytes for the session. Specify an amount in kilobytes from 128 to 4,194,303. The maximum value of 4,194,303 does not limit the display memory. By default, the display memory is 65536 kilobytes. Using more color depth and higher resolution for connections requires more memory. In legacy graphics mode, if the memory limit is reached, the display degrades according to the "Display mode degrade preference" setting.

For connections requiring more color depth and higher resolution, increase the limit. Calculate the maximum memory required using the equation:

Memory depth in bytes = (color-depth-in-bits-per-pixel) / 8) * (vertical-resolution-in-pixels) * (horizontal-resolution-in-pixels).

For example, with a color depth of 32, vertical resolution of 600, and a horizontal resolution of 800, the maximum memory required is (32 / 8) * (600) * (800) = 1920000 bytes, which yields a display memory limit of 1920 KB.

Color depths other than 32-bit are available only if the Legacy graphics mode policy setting is enabled.

HDX allocates only the amount of display memory needed for each session. So, if only some users require more than the default, there is no negative impact on scalability by increasing the display memory limit.

Display mode degrade preference

Note: For the Virtual Delivery Agent 7.x, this policy setting applies only when the Legacy graphics mode policy setting is enabled.

This setting specifies whether color depth or resolution degrades first when the session display memory limit is reached.

By default, color depth is degraded first.

When the session memory limit is reached, you can reduce the quality of displayed images by choosing whether color depth or resolution is degraded first. When color depth is degraded first, displayed images use fewer colors. When resolution is degraded first, displayed images use fewer pixels per inch.

To notify users when either color depth or resolution are degraded, configure the Notify user when display mode is degraded setting.

Dynamic windows preview

This setting enables or disables the display of seamless windows in Flip, Flip 3D, Taskbar Preview, and Peek window preview modes.
Windows Aero preview option Description
Taskbar Preview When the user hovers over a window's taskbar icon, an image of that window appears above the taskbar.
Windows Peek When the user hovers over a taskbar preview image, a full-sized image of the window appears on the screen.
Flip When the user presses ALT+TAB, small preview icons are shown for each open window.
Flip 3D When the user presses TAB+Windows logo key, large images of the open windows cascade across the screen.

By default, this setting is enabled.

Image caching

Note: For the Virtual Delivery Agent 7.x, this policy setting applies only when the Legacy graphics mode policy setting is enabled.

This setting enables or disables the caching and retrieving of sections of images in sessions. Caching images in sections and retrieving these sections when needed makes scrolling smoother, reduces the amount of data transmitted over the network, and reduces the processing required on the user device.

By default, the image caching setting is enabled.

Note: The image caching setting controls how images are cached and retrieved; it does not control whether images are cached. Images are cached if the Legacy graphics mode setting is enabled.

Legacy graphics mode

This setting disables the rich graphics experience, providing fallback to the legacy graphics experience to improve scalability over a WAN or mobile connection.

By default, this setting is disabled and users are provided with the rich graphics experience.

Legacy graphics mode is supported with Windows 7 and Windows Server 2008 R2 VDAs. 

Legacy graphics mode is not supported on  Windows 8.x, 10 or Windows Server 2012, 2012 R2, and 2016.

See CTX202687 for more on optimizing graphics modes and policies in XenApp and XenDesktop 7.6 FP3 or higher.

Maximum allowed color depth

Note: For the Virtual Delivery Agent 7.x, this policy setting applies only when the Legacy graphics mode policy setting is enabled.

This setting specifies the maximum color depth allowed for a session.

By default, the maximum allowed color depth is 32 bits per pixel.

This setting applies only to ThinWire drivers and connections. It does not apply to VDAs that have a non-ThinWire driver as the primary display driver, such as VDAs that use a Windows Display Driver Model (WDDM) driver as the primary display driver. For Desktop OS VDAs using a WDDM driver as the primary display driver, such as Windows 8, this setting has no effect.  For Windows Server OS VDAs using a WDDM driver, such as Windows Server 2012 R2, this setting might prevent users from connecting to the VDA. 

Setting a high color depth requires more memory. To degrade color depth when the memory limit is reached, configure the Display mode degrade preference setting. When color depth is degraded, displayed images use fewer colors.

Notify user when display mode is degraded

Note: For the Virtual Delivery Agent 7.x, this policy setting applies only when the Legacy graphics mode policy setting is enabled.

This setting displays a brief explanation to the user when the color depth or resolution is degraded.

By default, notifying users is disabled.

Queuing and tossing

Note: For the Virtual Delivery Agent 7.x, this policy setting applies only when the Legacy graphics mode policy setting is enabled.

This setting discards queued images that are replaced by another image.

By default, queuing and tossing is enabled.

This improves response when graphics are sent to the user device. Configuring this setting can cause animations to become choppy because of dropped frames.

Use video codec for compression

Allows use of a video codec (H.264) to compress graphics when video decoding is available on the endpoint. When For the entire screen is chosen the video codec will be applied as the default codec for all. When For actively changing regions is selected the video codec will be used for areas where there is constant change on the screen, other data will use still image compression and bitmap caching. When video decoding is not available on the endpoint, or when you specify Do not use, a combination of still image compression and bitmap caching is used. When Use video codec when preferred is selected, the system chooses, based on various factors. The results may vary between versions as the selection method is enhanced.

Select Use video codec when preferred to allow the system to make its best effort to choose appropriate settings for the current scenario.

Select For the entire screen to optimize for improved user experience and bandwidth, especially in cases with heavy use of server-rendered video and 3D graphics.

Select For actively changing regions to optimize for improved video performance, especially in low bandwidth, while maintaining scalability for static and slowly changing content. This setting is supported in multi-monitor deployments.

Select Do not use video codec to optimize for server CPU load and for cases that do not have a lot of server-rendered video or other graphically intense applications.

The default is Use video codec when preferred.

Use hardware encoding for video

Allows use of hardware encoding for H.264 encoding (where available). If such hardware is not available, the VDA will fall back to CPU-based encoding using the software video codec.

This policy setting requires a VDA configured for HDX 3D Pro with an NVIDIA GPU that supports NVENC hardware encoding. See NVIDIA video codec SDK for a list of supported GPUs.

Any Citrix Receiver that supports H.264 decoding can be used with NVENC hardware encoding.  

NVIDIA GRID requires driver version 3.1 or higher. NVIDIA Quadro requires driver version 362.56 or higher. Citrix recommends drivers from the NVIDIA Release R361 branch.

Lossless text, a feature of the VDA when configured in standard mode (not HDX 3D Pro), is not compatible with NVENC hardware encoding. If it has been enabled in HDX 3D Pro mode, lossless text takes priority over NVENC hardware encoding.

NVENC hardware encoding supports both lossy (4:2:0) and visually lossless (4:4:4) compression. Visually lossless (graphics policy setting, Allow visually lossless compression) requires Receiver for Windows 4.5.

This feature performs full-screen H.264 encoding. Multiple monitors are supported. Selective use of the H.264 hardware codec for actively changing regions is not supported.

The default option for this policy setting is Enabled.