Slide 2 of 4
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, ChemLab.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.
