Desktop virtualization is a critical component of today’s enterprise computing environment. The technology behind it is commonly known as VDI – Virtual Desktop Infrastructure. VDI provides a number of benefits including the use of inexpensive workstations as end user desktops, tight security with protection from storing data locally on desktops, centralized management of desktop environments, better support for mobile workforce with users connecting to their virtual desktops from any device, etc.

For the most recent information on this topic, please download our new Video Optimization Pack for Citrix Datasheet and our free whitepaper titled Qumu + Citrix: Optimizing the Video Experience.


Citrix VDI technology is widely used in the enterprise. XenDesktop and XenApp products provide both standard and advanced virtualization features for desktops and apps. In Citrix VDI communication between the client workstation and its server-hosted virtual environment is maintained over an ICA channel. ICA is a proprietary remoting protocol for sending screen images and control data from a VDI server to the client and back. While it works perfectly fine in most applications, some graphically intensive applications with complex rapidly changing images present challenges to the pure VDI architecture. Streaming video is one of such applications. When videos are rendered on the client using strict VDI methods the ICA channel becomes overloaded with the amount of data containing constantly changing frames resulting in the client receiver not keeping up with its VDI-hosted video player. During live webcasts the host server gets overloaded with many virtual desktops processing video and all of them pulling the stream over the server’s network connection. The result is inadequate user experience.

To deal with high load and low quality of video playback Citrix provides a feature called HDX MediaStream with client-side fetching. The idea behind this feature is to let the client render video. When client-side fetching is enabled the video player runs on the client and the stream goes directly to the client not affecting the server. While it is a great concept for improving the end user experience it is not without some limitations:

–          Only Windows Media and Flash formats are supported. Windows Media and Flash are legacy formats.  The streaming media industry has widely adopted Adaptive Bitrate formats such as HTTP Live Streaming (HLS) for serving multiple stream renditions of chunked video to ensure a higher quality user experience. This technology is not currently supported with XenDesktop redirection.

–          Citrix native client-side fetching requires the client workstation to have a Flash player installed. This is not always possible as some thin client images do not have Flash and do not allow its addition

–          Support for video streaming over multicast is limited to Windows Media streaming, again an outdated technology not supported by Windows Servers anymore. A preferred option is to support standard-based RTP multicast with H.264 video codec.

Client-side receiving and playing back video streams will resolve the video quality issues related to VDI, but it may introduce a different problem. Now, instead of receiving “screen-scrapes” over an ICA channel the client will receive it from its LAN. With a streaming source being outside the LAN and multiple clients simultaneously pulling the stream over unicast the load on the WAN connection to the source can be substantial. If the WAN network bandwidth is a concern then the LAN has to be equipped with a proxy-cache device capable of caching and splitting video streams.

Qumu is working on a comprehensive solution–a Video Optimization Pack for Citrix–that will improve both the quality of playback and will reduce the load on the branch network. At the heart of the solution is the intelligent player control running on the VDI side that works in conjunction with video processing libraries that are already present on the client device or can be installed there. The Qumu solution will not have a dependency on a Flash player and will work with most common streaming protocols and formats. Several ways of reducing the network bandwidth utilization will be available with this solution. The client-side player will be capable of receiving RTP multicast. It will also be able to receive a unicast or HTTP-based stream from the closest to the client Qumu VideoNet Edge (VNE) acting as a proxy-cache for live and VOD videos.

Qumu has been working with Citrix for many years helping our mutual customers enhance video experience. We are excited about our upcoming roll out of the new optimization solution for video on VDI endpoints. Stay tuned!

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