Playing video or sound files from your computer’s CD-ROM drive is a good starting point because it has some similarities to streaming.
For example, let’s say I have a three minute video file on a CD-ROM disc. It’s in a Windows .avi format and it’s about 15 MBs in size. It will play on my computer because I have special software installed called a video codec which decodes video files in an AVI format. Most computers already have these codecs preinstalled.

In order to play the video in an application, a path is required to find the file on my local computer system. The path begins with the letter E:\ which is my CD-ROM drive. It’s followed by the name of the folder on the CD where the video file resides; and finally it includes the name of the file itself, viewcast.avi.

So, if I click the play button in a PowerPoint application, the program searches the path to find the target video file on the CD disk. The codec software immediately starts decoding the file and begins sending a continuous data stream which flows from the CD disk through the computer processor and eventually to my PowerPoint application. When I click the pause button the video data stream stops as if I turned off a water faucet. The concept behind streaming media on the web is similar except for a few key differences.
In this example, notice I have a media file but it’s no longer in an avi format. Using special software, which I’ll talk about later, I’ve converted the original file into a RealMedia streaming format. This is indicated by the .rm file extension. During the conversion process the file was also compressed or decreased in size to about 1.2 MB’s. I’ll talk more about compression later. Also, I’m using the RealMedia player, which contains it’s own software decoders to decode and play this video file.

Another big difference is that the video file is stored on a remote server. You can see this in the path statement. The path begins with rtsp:// which tells an application that the file is located externally on a streaming sever and is using Real Time Streaming Protocols. Next in the path we have the name of the folder on the streaming server where the video file resides; and finally it includes the name of the target file itself, viewcast.rm.
So now when I click a link on a web page to view this video file, the Web Browser and the RealMedia player communicate with the streaming server. The server then sends a steady and continuous data stream of the file’s contents over the network to my computer. This is happening right now as you listen to me talk. Here are all the components that work together to make streaming media happen on the web.
First, you need a computer connected to the internet over a local area network or a modem. You also need a web browser with the proper player or plug-in installed. Plug-ins can be downloaded on the web for free. A plug-ins works in conjunction with the browser to play streaming encoded files in a particular format.

A web server stores web pages or HTML files. Streaming media files normally reside on a separate dedicated streaming server. So when a media link is clicked on a web page the browser reads the HTML code, and lets the player/plug-in take over. The player negotiates with the streaming server and gets the target media file using a path statement. After a few seconds of buffering the media file begins to stream within the player onto your screen.
So next time you click a streaming media link on a web page try to envision all these components working together.
We’ll look at the different types of content you can stream as well as the streaming technologies that make it all possible.