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Hotfix for Citrix XenApp 6.5 enhances Video, SlideShow, Windows Media direction and more

Citrix have released an important hotfix for Citrix XenApp 6.5 that enhance the user experience dramatical that previously was available in XenDesktop 5.5 is now available in XenApp 6.5 with Hotfix XA650W2K8R2X64002.

I highly recommend that you implement this hotfix if you are running Citrix XenApp 6.5

!! Please be aware that some of the policies can “ONLY” be configured using Microsoft Group Policy and “NOT” AppCenter policy

This release provides the following features and enhancements to servers running XenApp 6.5:

Support for Additional Communications Software:

In addition to Microsoft Office Communicator and Lync, XenApp now supports the use of Web cams in conjunction with the following communication software published on XenApp 6.5 servers:

  • Citrix GoToMeeting with HD Faces
  • Skype
  • Adobe Connect

Enhanced Audio Virtual Channels:

Enhancements have been made to the audio virtual channels to help reduce latency. This results in improved performance of softphones and the voice chat feature of Unified Communications applications.

Adaptive Display Settings for Smooth-running Videos and Slide Shows:

Previously available in XenDesktop 5.5, Adaptive Display is now enabled by default in XenApp 6.5. Adaptive Display dynamically adjusts image quality and frame rates to deliver the best possible user experience when viewing graphics or server-rendered video content over a limited bandwidth network connection. Adaptive Display is the successor to Citrix’s highly successful Progressive Display technology. Adaptive Display is self-tuning and generally does not require configuration. However, Adaptive Display policies are available should you wish to adjust the behavior of this feature. To configure Adaptive Display on XenApp 6.5, use Windows Group Policy Editor (gpedit.msc)* and follow the procedures outlined in eDocs, the Citrix Documentation Library.

* Note: At this time, Adaptive Display policies cannot be configured using AppCenter. Use Windows Group Policy Editor (gpedit.msc) instead.

Windows Media Redirection Enhanced Flow Control:

Enhancements to Windows Media Enhanced Flow Control provide improved results for streamed HD videos delivered over WAN connections.


Flow control is an integral part of multimedia redirection that is responsible for choosing and adjusting the rate at which multimedia data is transmitted to the client and defining a strategy to reduce the bit rate when network conditions are unfavorable. The effectiveness of the flow control implementation has a fairly large impact on the overall end user experience.

The enhancements

  • End-to-End Flow Control. Video samples are no longer queued in the host-side virtual channel and instead force data to back up in the DirectShow/MediaFoundation interception filters. The major benefit here is reliability; video controls remain responsive even when network conditions are unfavorable.
  • Frame Dropping. Sometimes the available bandwidth is less than the bit rate of the video being played. Frame dropping enables flow control to preserve the audio and playback synchronization at the expense of the video. It is important to note that key frames will never be dropped because these frames are often used as reference frames from which other frames will be constructed. In addition to key frames, decoders also use the last decompressed non-key frame as a reference frame. For this reason, once a non-key frame is dropped, all subsequent non-key frames are dropped (until the next key frame is found). Otherwise, the video becomes progressively noisier.


Frame dropping has some limitations. It is not always known ahead of time how many frames will be dropped for a given media type. Frame dropping does not typically occur until the effective network bandwidth approaches or drops below the bit rate of the media file. Users should have reasonable expectations for the user experience. In most cases, frame dropping will provide a benefit but the amount of video that is dropped can vary from media file to media file.

Note: Adaptive Display generally provides a better user experience than frame dropping when the available bandwidth is less than the bit rate of the video. For this reason, customers who need to deliver HD videos with bit rates of 6 or 7 Mbps are advised to set the SmartRendering Bandwidth Threshold to 8 Mbps to ensure that Windows Media Redirection is used only when there is sufficient bandwidth. For more information about setting the SmartRendering Bandwidth Threshold, see Knowledge Center article CTX124777.

Supported media formats

WMA, WMV, ASF, MP3, Divx, Xvid, and MPEG-4. Other formats, such as MPEG-1 and MPEG-2, continue to use the old flow control.

 Download Citrix hotfix  XA650W2K8R2X64002 for XenApp 6.5 here


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