Streaming Media Supplement sa2150 and sa2250

Chapter 4 Understanding Media-IXT and WMT

• usually has a scheme of mms. MMS is a media-control protocol for opening, setting up, controlling, and

logging of streaming media sessions. The Windows Media media streaming format includes headers

(information about streams) and payloads (the actual media data).

The figure below shows the components of a sample media content URL:

The profusion of WMT file suffixes exists because new formats are introduced as WMT evolves.

Here is a mini-guide to WMT file suffixes, which shows what the suffixes mean and how they are related.

Remember that the format of a file is not the same thing as its suffix.Formats are expressed in capital letters,

while suffixes are expressed in lower case. The formats here are ASX for WMT metafiles, and ASF for WMT

streaming media content files. There are three suffixes associated with each of the two formats, as shown in the

chart: .asx, .wax or .wvx for the ASX format; and .asf, .wmv or .wmau for the ASF format.

WMT streaming with no proxy cache present

WMT streaming with no proxy cache present can be based on these three nodes:

• a web (

HTTP

) server, where .html files reside that contain hyperlinks to the WMT metafiles (.asx,

.wax or .wvx files)

• a Windows Media server, where content resides in the form of files in WMT streaming formats:

.asf,

.wma or .wmv files

• a Media-IXT

For our example, we assume that the user of a web browser equipped with Windows Media Player is viewing

an HTML page containing links to movies. Our story begins when the user clicks on a link to a movie. The URL

invoked by the link is that of a WMT metafile.

1. The web browser passes the URL to Windows Media Player and instructs Windows Media Player to open

the metafile.

2. Windows Media Player sends a request for the WMT metafile to the HTTP server.

3. The HTTP server serves the WMT metafile to Windows Media Player.

o In the metafile script, Windows Media Player finds a pointer to the URL of the actual streaming media

content, the media content URL.

4. The Windows Media Player contacts the Windows Media server at the media content URL.

5. The Windows Media server streams content to the Windows Media Player.

Figure 4-1. Media content URL example

WMT Metafile Associated media file Contents Generation

.asx .asf video and audio (interleaved) older

.wax .wma audio current

.wvx .wmv video and audio (interleaved) current

mms://208.184.229.63/v2/onair/BBC/BBCworld_100k.asf

streaming media filenamescheme