Windows Media Services starts up like all other Win 2K services. To configure streaming, three parameters have to be taken into account: source, protocol and the publishing method. The first tells you the type of data to be streamed, the second one is the choice of protocol that will carry this stream, and the third involves how you would present the data to a user. This could be as an HTM file, e-mail, or any other publishing method. These three configuration parameters will vary, depending on whether you choose unicast or multicast streaming.

All these setting are finally saved as ASX files. These files connect clients to the correct IP address for receiving streamed content. Links can be made to these files from a Web page, or it can directly be sent to clients through e-mail. Alternatively, if the client has the exact reference URL to the data (MP3, ASF, etc.) being streamed, he can directly connect to the stream through his media player. This is talked about in detail later.

Unicast streaming

In unicast streaming you have two options: on-demand publishing or broadcast publishing. While the former allows a user to actively control playback content, the latter is a passive data stream for the user. It is like a radio, where you can tune into it, but can’t control it. However, being unicast, a separate stream will flow to each user who demands it.

For on-demand streaming, the source can be an ASF, WMA or MP3 file. You can place the ASF files in a default home directory (usually ASFRoot) or any other local folder. The source can also be specified as a network folder, or a shared folder on any other machine. There’s a configuration wizard for this, which takes you through a series of steps for publishing your content. Once you’ve specified the data source, you have to choose the protocol to carry it. The choice is between MMS (Microsoft Media Server), UDP (User ..........)TCP. HTTP can also be used for streaming, but could involve resolving some port conflicts. After this, give the source a reference URL, specify the mode of publishing, and you’re ready to go.

At the client end, files can be accessed using Windows Media player. Here, you have to specify the path for the streaming file in a specific format. So click the File menu, and select Open. In the path box, specify the path of the ASF to be accessed, for example, mms://Server_name/file_name.asf, where Server_name is the name of the server (or the IP address) running your media services and the filename is the name of the file to be accessed. The Media player will connect to the server and on-demand streaming will start. Choosing MMS as the protocol is advisable because it automatically rolls over to other protocols (MMS-UDP or MMS-TCP) if required.

In broadcast publishing, the procedure is similar except for source specifications. Here, the data source can be a Windows Media encoder (local or remote); a remote broadcast station or a remote publishing point. The first option involves using the Netshow encoder, which we’ve talked about earlier. Here, you’ll need to use the MSBD protocol, and specify the name of the machine running the encoder with the connecting port (which is usually 7007 by default). This is the case where encoding and transmission is done on the fly. The encoder does the encoding and sends the data to the output port from where the Win 2K server accesses it for further publishing.

Interestingly, the broadcast station - your server - can also serve as a transmission station, by using a remote broadcast station (which already uses MSBD or HTTP), or a remote publishing point (using MMS) as the source. Here again, you need to specify the protocol and the publishing option as in case of on-demand unicast publishing.

At the client end, access is through the MSBD protocol. The syntax is msbd://Server_name/station_name where station name is the name you’ve specified for the particular broadcast stream.

Multicast streaming

In this, a single stream is constantly broadcast over the network and anyone can tune into it. Configuring a multicast stream is quite similar to unicast. A wizard guides you through the steps of specifying the source, which can be an ASF file, a remote publishing point, or a Windows Media encoder. The method of setting the paths of the source is also the same as in unicast streaming.

After this, you need to give the station name (the reference to your stream), program name (which stores and organizes the content to be broadcast) and stream names (the actual content), and you’re ready to publish. You can program the multicast station to play once or loop forever. This is again a passive stream to which users connect with the syntax mms://Server_name/station_name.

MM Vijay Sargunar and M Syed Masood, Department of Computer Science, Engineering and Applications, Crescent Engineering College, Chennai
Next Month: Streaming Media with Apple Quicktime