Understanding Advanced Fast Start

Advanced Fast Start is designed to minimize startup latency in Windows Media Player 10. Startup latency is the period of time starting when a viewer requests a stream by using the Player, and ending when the content begins playing. A number of factors can introduce latency, such as the speed of the client computer, the state of the network, the available bandwidth, and the Windows Media server configuration. However, the primary reason for startup latency is the delay caused by buffering on the client.

An adequate buffer size is essential for providing a good user experience. The client buffer stores streaming media data in memory so that the Player can maintain smooth playback of a stream. With inadequate buffer size, presentation playback can be uneven. The buffer is also used by codecs that decode a stream. When more buffer memory is available to codecs, the audio and video quality is improved.

The buffer size affects the amount of startup latency because a client cannot begin playing a stream until the buffer is full. The Fast Start feature in Windows Media Services 9 Series reduces latency significantly by streaming the data at an accelerated rate until the buffer is full. However, the stream still cannot be played until that point.

Advanced Fast Start enables Windows Media Player to begin playing a stream before its buffer is full. As soon as the Player receives a minimum amount of data, it can begin playing a stream while its buffer continues to fill at an accelerated rate—a rate that is faster than the encoded bit rate of the content. When the buffer is full, acceleration stops and the Player begins receiving data at the encoded bit rate.

You can configure the Advanced Fast Start settings for your server on the Properties tab of your publishing point. For more information on these settings, see Enable Advanced Fast Start.

This section contains the following topics:

• How Advanced Fast Start works
• Encoding content for Advanced Fast Start

Notes

• Advanced Fast Start is only used by clients that connect to a unicast stream. For the broadcast publishing points on your Windows Media server, you may choose to allow unicast rollover, which ensures that clients that cannot access the multicast stream can still receive the content by switching to an available unicast stream. You can configure Advanced Fast Start for unicast rollover connections on the Properties tab of your broadcast publishing points. Enabling this property does not enable Advanced Fast Start for multicast client connections.
• On the client side, Advanced Fast Start is supported by Windows Media Player 10 or later running on the Windows XP operating system, or by Windows CE version 5.0 or later (using the HTTP protocol).
• On the server side, Advanced Fast Start is available only if Windows Media Services 9 Series is running on the following editions of the operating system: Windows Server 2003, Enterprise Edition, or Windows Server 2003, Datacenter Edition. If you are running Windows Server 2003, Standard Edition, this feature is not supported.

Related topics

• Enable Advanced Fast Start
• Controlling Advanced Fast Start behavior with URL modifiers
• Understanding Fast Streaming

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