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
When the quality of the content received is of paramount
importance; for example, businesses that provide pay-per-view
You can configure the Fast Cache settings for your server on the
Properties tab of your publishing point. For more
information on these settings, see Enable Fast Cache and Limit Fast Cache content
delivery rate. Fast cache is supported by both the RTSP
and the HTTP protocols. Clients that connect using the MMS protocol
will not receive the stream using Fast Cache, but will instead
receive the standard bit rate stream.
You can control the behavior of individual
streams by adding Fast Streaming modifiers to the URL that a client
uses to connect to the stream. For example, the WMCache modifier
enables a client to use the Fast Cache feature when it uses the
following URL format to connect to the server:
http://servername/file.wmv?WMCache=1. You can also control
the maximum bandwidth available to stream a file or live stream by
using the modifiers WMBitrate and WMContentBitrate. For more
information, see Controlling streaming behavior
with URL modifiers.
The Fast Cache feature is only used by clients
that connect to a unicast stream.
If you are using Fast Cache with a server-side
playlist, clients that connect to your server must use the RTSP or
the HTTP 1.1 protocol to receive the benefit of the Fast Cache
If you define the src attribute of a
server-side playlist media element as being a publishing
point on the local server using the lpp:// syntax, you must enable
or disable player caching on the source publishing point. Changing
the setting of the Enable Fast Cache property on any
publishing point except the source will not affect the ability of
players to cache content.