From Analog To Digital

Most audio or video content you want to serve-- whether it's a video tape from a conference, a live video feed from a performance, or tape from a standard video camera-- originates from an analog format. An analog signal is continuous: it represents an infinite number of smooth gradations between given levels of signal strength.

Equipment for recording analog translates these gradations into electrical signals, whose voltage changes with the strength of the signal. Traditional devices for playing back or copying analog audio (such as speakers) recreate these levels by electrical or mechanical means. However, doing so introduces "noise" or distortion and degrades the signal.

Computers operate in a numerical world, so content that's in analog format needs to be converted to digital format before it can be "understood" by a computer. This conversion process, called "capturing", is done using hardware and software designed to take the original signal strength levels and assign values to them that are then saved in a file. The computer can then manipulate and play the file. The more data the computer generates about the original levels and stores in the file, the more accurate the digital representation will be. The process is similar to plotting points on a curve- the more point that are plotted, the closer the resulting graph will look to a smooth curve. Or, consider a digital clock that shows hours and minutes. It's not quite as inclusive as one that shows hours, minutes, and seconds. And an analog clock with a sweep second hand actually shows all the possible instances of time (even though they're probably not physically marked on the clock face).

However, the more data, the more storage space and processor power is required. High-quality captured audio files can require up to 10MB of disk space/minute, while video can consume 20MB of disk space/second!

On the plus side, digital audio or video files can be copied infinite number of times with no loss of quality.