About stream formats

Applies To: Windows Server 2008, Windows Server 2008 R2

A Player uses stream format information to decode a stream. A stream format includes information about the stream, including codecs, bit rates, and frame sizes.

Stream format information is transmitted to Players when they first connect to a publishing point on your server. However, if you are delivering your content as a multicast stream, Players do not connect directly to your server to receive the stream. In this situation, the multicast information file incorporates the stream format information instead. The multicast information file is created when you run the Multicast Announcement Wizard.

When you use the Multicast Announcement Wizard to announce content that is delivered as a multicast stream, you must list the stream formats used by the content. If you are combining multiple pieces of content into one multicast stream and the content uses different codecs, bit rates, or frame sizes, you must specify the stream format for each piece of content. For example, if you have set up a playlist to stream two files that use different codecs, you must specify the stream format for each file. The method used to specify stream formats for a multicast stream differs depending on the type of content you are streaming, as follows.

Content type Location of stream format information


Stream format information is obtained from the header portion of the file. To include the stream format information for the file, you must specify a Universal Naming Convention (UNC) path or a local path to the file in the Multicast Announcement Wizard.

Stream from an encoder

Stream format information is stored in a stream format that is generated by an encoder. For Microsoft Expression Encoder, this file has an .asf extension. To include the stream format information for the encoder stream, you must specify a UNC path or a local path to the stream format file. Expression Encoder automatically transmits the stream format information to the server when it connects.

If stream format information is missing or incorrect for a piece of content, the Player cannot render that content.


Multicast information files must include all the stream formats used by your content. If the stream formats are not listed in the multicast information file, clients cannot access the multicast stream.
Multicast streaming is not available if Windows Media Services is installed on some Windows Server 2008 and Windows Server 2008 R2 operating systems. For more information, see Decide which version of Windows Server is right for you.