2.2.1.4.27 stream-switch-entry

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This token specifies one or more stream-switch entries. For information about how to specify the number of stream-switch-entries, see stream-switch-count (section 2.2.1.4.26).

This token MUST appear on a separate Pragma header; that is, no other tokens are allowed to be included on the same Pragma header as the stream-switch-entry token.

This token is defined for use only in requests sent to a server.

Each stream-switch-entry consists of three 16-bit hexadecimal numbers separated by colons:

  • The first number is the source ASF stream number to switch from.

  • The second number is the destination ASF stream number to switch to.

  • The third number is the stream thinning level to apply to the destination ASF stream number.

    • Thinning level 0: The ASF packets in the stream are not filtered (no thinning is applied).

    • Thinning level 1: The ASF packets in the stream are filtered such that they contain only key frame media objects.

    • Thinning level 2: The ASF packets in the stream are filtered such that all media objects belonging to the stream are removed.

      The source ASF stream number can be set to a special value of "ffff" to indicate that no stream is specified. Stream numbers are located in the ASF file header delivered by the server prior to streaming the file. For details about ASF headers, ASF packets, and media objects, see the ASF specification as described in [ASF]. For more information about stream thinning in the Windows Media Services 9.0 Series SDK, see [WMSSDK].

The syntax of the stream-switch-entry token is defined as follows.

 stream-switch-entry = "stream-switch-entry=" 
                       1*4HEXDIG ":" 1*4HEXDIG ":" 
                       ("0" / "1" / "2")
 

The following is an example for "turning on" streams one and two. 

 Pragma: switch-stream-entry=ffff:1:0 ffff:2:0

The following is an example for "turning off" stream two. 

 Pragma: switch-stream-entry=ffff:2:2

The following is an example for thinning stream one.

 Pragma: switch-stream-entry=1:1:1