You can use a text editor to modify an announcement and make use of the following advanced features:
You can add a <REF> tag to the announcement file in order to specify a rollover URL. The rollover URL identifies alternate Windows Media servers that are streaming the same content. In the following example announcement file, if the client cannot successfully connect to Server1, it automatically connects to Server2 without reentering the URL.
<asx version = "3.0"> <entry> <ref href = "mms://server1/filename.wmv"/> <ref href = "mms://server2/filename.wmv"/> </entry> </asx>
You can add a <REF> tag to the announcement file to specify the content to be played before and after the multicast stream. If a client attempts to connect to a multicast stream using the following example announcement file, the client will connect first to a unicast server to view an introductory file, then will connect to the multicast stream. After the multicast stream has ended, the client will be directed to a concluding file at the end of the broadcast.
<asx version = "3.0"> <entry> <ref href = "mms://server1/introduction.wmv"/> </entry> <entry> <ref href = "http://web_server_name/multicast_information_file_name.nsc"/> </entry> <entry> <ref href = "mms://server1/conclusion.wmv"/> </entry> </asx>
To send forward error correction (FEC) data to clients, you must modify the announcement file so that the client connection URL requests the data. The following example announcement file uses the URL modifier WMFecSpan to define how many data packets the forward error correction data will encompass and the modifier WMFecPktsPerSpan to define how many error correction packets are sent with the data packets. In this example, the parameters specify that the server will send one FEC packed for every four data packets.
<asx version = "3.0"> <entry> <ref href = "mms://server1/filename.wmv?WMFecSpan=4&WMFecPktsPerSpan=1"/> </entry> </asx>