Understanding intelligent streaming

Intelligent streaming refers to the method by which your Windows Media server works with Windows Media Player to detect network conditions and adjust the properties of a stream automatically to maximize playback quality. With intelligent streaming, users receive a continuous flow of content tailored to their specific connection speeds.

For the server to provide the full advantage of intelligent streaming, you should encode your content using multiple bit rates. Multiple-bit-rate (MBR) content contains several streams encoded at different bit rates, each of which usually corresponds to a common connection rate. When a distribution server is used to deliver multiple-bit-rate content, all of the streams are sent by the origin server to the distribution server. When multiple-bit-rate content is sent to a Player, either from the origin server or a distribution server, only the bit rate that is the most appropriate for current bandwidth conditions is streamed. Windows Media Player determines which bit rate stream to use and communicates this information to the Windows Media server, which then transmits the appropriate stream to the Player. The bit rate evaluation and selection process is completely invisible to the user. Windows Media Services can distribute both multiple-bit-rate streams from an encoder and multiple-bit-rate files.

With intelligent streaming enabled, the Player responds to insufficient bandwidth by requesting that the server reduce the bit rate by using one of the following techniques. If one technique does not solve the problem, the Player will try the next one:

• If the file is encoded using MBR, the first step the Player takes to rectify insufficient bandwidth is to request a lower bit rate version of the stream.
• If a video file is not MBR, or if using a lower bit rate stream does not reduce the bandwidth requirements enough, the Player requests that the server thin the video stream. This means that the server reduces the frame rate of the video being streamed.
• If thinning the video stream does not reduce the bandwidth requirements enough, the Player requests that the server stop sending the video stream.

Intelligent streaming is controlled by adding the WMThinning URL modifier to the path of the source. If intelligent streaming is not desired, you can set the value for WMThinning to 0 to disable intelligent streaming, and then manually control the bit rate at which clients receive the stream by specifying values for the WMBitrate and WMContentBitrate URL modifiers. For more information, see Controlling Fast Streaming behavior with URL modifiers.

Note

• MP3 files cannot use the intelligent streaming feature in Windows Media Services.

Related topics

• Controlling Fast Streaming behavior with URL modifiers
• Understanding content delivery