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4.4 Playlist Streaming

The following sequence occurs between a client and server during playliststreaming using predictive stream selection. The sequencing applies to both the pipelined mode and non-pipelined mode of the protocol:

  1. The client sends a Describe request to retrieve the ASF header.

  2. The server responds with a $H (Header) packet.

  3. The client sends a Play request for the file, selecting one or more streams.

  4. The server responds with a $H (Header) packet and $D (Data) packets of the first playlist element.

  5. After all data packets of the first playlist element have been sent to the client, the server sends an $E (End-of-Stream Notification) packet, and the server sends a $C (Stream Change Notification) packet.

  6. The client sends a Log request for the first element of the playlist.

    Note  When the non-pipelined mode of the protocol is used, the client uses a separate TCP connection to send the Log request to the server; therefore, the server can respond to the Log request while still sending stream data through the previously opened connection.

    Note  When the pipelined mode of the protocol is used, the client sends requests to the server on the same TCP connection. The response to the client is not returned until the previous request is terminated by the server.

  7. The server sends $H (Header) and $D (Data) packets of the next element in the playlist.

  8. The client notifies the server that it is rendering the second element of the playlist by sending a SelectStream request. The client might select other streams than those predictably selected by the server. For information about predictive stream selection, see section 4.5.2.

    Note  When the non-pipelined mode of the protocol is used, the client uses a separate TCP connection for the SelectStream request. The server responds immediately to this request while still sending stream data through the previously opened connection.

    Note  When the pipelined mode of the protocol is used, the client uses the same TCP connection; therefore, the server does not respond to the SelectStream request until the previous request is terminated by the server.

  9. The server responds to the Log and SelectStream requests.

  10. The server continues looping playlist element data packets (step 5) until the end of the playlist is reached.

The following figure shows the sequence described.

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Figure 4: Sequencing during normal playlist streaming

 
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