When used with Windows Media Player 9 Series or later, Fast Cache provides a way to stream content to clients faster than the data rate specified by the stream format. For example, using Fast Cache, the server can transmit a 128-kilobits-per-second (Kbps) stream at 700 Kbps. The stream is still rendered in Windows Media Player at the specified data rate, but the client is able to buffer a much larger portion of the content before rendering it. This allows the client to handle variable network conditions without a perceptible impact on the playback quality of either on-demand or broadcast content.
This ability is useful in the following situations:
When the available network bandwidth of the client exceeds the required bandwidth of the content; for example, clients that use a cable modem, DSL connection, or corporate intranets.
When the network connectivity is intermittent or has high latency; for example, wireless networks.
When the quality of the content received is of paramount importance; for example, businesses that provide pay-per-view movies.
When Fast Cache is enabled, Windows Media Services cannot use intelligent streaming.
You can control the behavior of individual streams by adding Fast Streaming URL modifiers to the URL that a client uses to connect to the stream. For example, you can use the WMCache URL modifier to enable a client to use Fast Cache. You can also control the maximum bandwidth available for streaming a file or a live stream by using the WMBitrate and WMContentBitrate URL modifiers. For more information, see Controlling Fast Streaming behavior with URL modifiers.