Multicast Comes to Silverlight!

Today is a big day for Enterprise media departments who want to migrate to Silverlight. At the Streaming Media East show in New York City this morning, Qumu, Inc., known as an innovator in rich media streaming video solutions for the enterprise, announced a new multicast capability for Silverlight. This new Multicast Plug-in, developed in cooperation with Microsoft, allows enterprises for the first time to deliver live video broadcasts via multicast across the network to thousands of Silverlight-based players simultaneously. In addition to being delivered in Qumu’s commercial products, the plug-in components are also available to third party ISV’s and end-users as open source code on

Key Points for the Silverlight Multicast Plug-in:

  • Leverages the existing Windows Media Services (WMS) multicast infrastructure broadly deployed among Enterprises – no server or network changes required
  • Great example of how Silverlight is “Extensible by Design,” enabling partners to innovate and add value to their Silverlight-based solutions
  • Requires the install of a single ActiveX or NPAPI plug-in to the user’s desktop
  • Integrates transparently with Silverlight applications, no end-user action necessary
  • Works wherever Silverlight works - Mac and Windows, IE, Safari, and Firefox
  • Available as open source on Codeplex enabling other companies to develop their own commercial multicast products for Silverlight

I want to really stress the importance of this new capability for Silverlight. Not much noise is made about the use of Windows Media in the Enterprise these days, but the simple fact is that WMV is still by far the most pervasive format in this space. For nearly a decade, Enterprises have relied on the robust and scalable combination of Windows Media Services & Windows Media Player and have built out multicast across large infrastructures accordingly. And while Enterprises now desire the interactive, data-driven media experiences and standard .NET development available with Silverlight, they prefer not to give up the huge benefits of multicast for live broadcasts.

Why Multicast? Simply because it’s the most cost-efficient and scalable way to stream video on bandwidth-constrained networks.



Unlike Unicast streaming done through traditional streaming servers like WMS and Flash Media Server, multicast functions more like a TV broadcast where viewers “tune in” to a program rather than creating a 1:1 connection to the media server or proxy.


This means that adding more viewers has little effect on the overall bandwidth required throughout a network and doesn’t overburden the media server. The result is a reliable, high-quality media experience.

Unfortunately, for various reasons, multicast is not something ubiquitous on most of the Internet like HTTP caching is. But in the Enterprise, multicast-enabled infrastructure is broadly deployed for media. So while there’s no reason that the new Multicast Plug-in for Silverlight can’t be used on the Internet, its main value is to multicast-enabled Enterprise networks.

(Shameless Plug) For the best quality media experiences on the Internet, Microsoft recommends IIS7 Smooth Streaming for live and on-demand video. Unlike WMS streaming or even Adobe’s new Dynamic Streaming, Smooth Streaming is HTTP-based and leverages the massive existing HTTP caching infrastructure on the Internet. As live and on-demand media is delivered to viewers it is stored at the nearest cache. As additional viewers request the content they do not need to connect directly to the media server. Instead they get the content directly from the nearest cache. In this way, Smooth Streaming offers some of the benefits of multicast. For more in-depth information on Smooth Streaming visit the IIS Product Website or our technical overview whitepaper.

(And now back to our program…) The new Silverlight browser plug-in will be available at no cost via the Codeplex Open Source Community website ( and is consistent with the terms of the Microsoft Public License (MS-PL). Cross-browser plug-ins for Silverlight-compatible versions of IE, Safari, and Firefox for Mac and Windows, allowing users to received multicast broadcasts from Windows Media Services, are available in the release. Both source and binary code will be available on Codeplex, along with code samples to connect the plug-in to the Silverlight runtime, and technical documentation and sample players.

In addition to the ActiveX or Netscape Plug-in API (NPAPI) browser plug-in described above, the software also includes a component which implements demuxing of the ASF video streams and parsing of NSC files, and a component which implements a Media Stream Source interface to Silverlight, using the plug-in and ASF component to provide video to Silverlight. Both of these components are packaged into the deployed Silverlight application XAP and do not require any install or user notification/action.

The new plug-in will be demonstrated at the Streaming Media East (SME) show May 12 & 13 at the Qumu and Microsoft booths. At SME Qumu will also showcase its latest developments with Silverlight, including the new employee generated content interface and new Qumu Capture Studio 2 which includes Microsoft Expression Encoder and Silverlight-based player.

We hope this new multicast capability enables many of our Silverlight partners and customers and look forward to seeing some great new Enterprise media applications in the future.

Tim Harader,
Sr. Product Manager, Silverlight Media

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