Adaptive streaming

Adaptive streaming is a process that adjusts the quality of a video delivered to a web page based on changing network conditions to ensure the best possible viewer experience. Adaptive streaming is made possible by changes introduced in Microsoft Silverlight 2.

Internet connection speeds vary widely, and the speed of each type of connection also varies depending on a wide variety of conditions. For example, if a user connects to an ISP at 56 Kbps, that does not mean that 56 Kbps of bandwidth is available at all times. Bandwidth can vary, meaning that a 56-Kbps connection may decrease or increase based on current network conditions, causing video quality to fluctuate as well. Adaptive streaming adjusts the bit rate of the video to adapt to changing network conditions.

Adaptive streaming simplifies content creation and management, making streaming video easy to deploy, and does not require any coding. For viewers who use Microsoft Windows Media Player rather than Silverlight 2, Windows Media Multiple Bit Rate encoding is available.

To use adaptive streaming, you need Microsoft Expression Encoder 2 with Service Pack 1, Microsoft Windows Server 2008, Microsoft Internet Information Services (IIS) 7.0, the IIS Smooth Streaming module, and Silverlight 2.

When you encode video for adaptive streaming using Expression Encoder 2, the video is output in IIS Smooth Streaming format. The video files can then be published to IIS by using the WebDAV publishing plug-in available by default in the Publish section of the Output tab. Once the video is published, IIS then delivers it to the Silverlight client for viewing by the user.

To encode video for adaptive streaming

  1. Import the video to be encoded by clicking File, locating the video to be encoded, and then clicking Import.

  2. On the Encode panel, in the Video dropdown list in the Profile category, click Adaptive Streaming.


The Adaptive Streaming profile encodes the video at four different bit rates.

  1. In the Container category, in the Output Mode dropdown, click IIS Smooth Streaming.

  2. On the Output panel, in the Template dropdown list in the Job Output category, click a Silverlight 2 template.

  3. Publish the video to a Windows Server that is running IIS and has the Smooth Streaming module installed. For more information, see Publish a video.