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Compact Discs

Posted by Big Boo on September 5th, 2008

The Compact Disc.  What an invention!  It’s amazing really how a small round piece of plastic and some metallic foil has revolutionised the way we listen to music, play video games and watch movies.  It it wasn’t for the invention of this shiny media format we might still be using lengths of magnetic tape to do all of the above.

In 1979 electronics companies Philips and Sony got together to come up with a new way of storing audio in a digital form.  Prior to this music had come on pressed Vinyl Discs, a format that had been around for decades but was prone to damage and was a bit on the large side.

The biggest difference though between vinyl and compact discs was the way in which the music information was stored.  On Vinyl the musical data was stored in an analogue form, which means at any point on the disc the depth of the groove could be made at any depth to produce the varying volumes of a piece of music.

Compact Discs work in a digital manner, meaning that at any point on the disc only two different states are possible, a binary system.  Music was therefore stored as a long series of 1’s and 0’s.  By grouping a number of these 1’s and 0’s together the volume of a sound at any particular instant could be stored.  By playing back enough of these volume changes, or samples, fast enough the original piece of music could be reproduced.

In order to squeeze enough information onto a disc it was necessary to turn to lasers in order to both create and read the information.  A laser is a highly focussed beam of light, which could be used to burn microscopic grooves into a foil layer on the disc.  To read back the disc a lower intensity laser is used, and the way it is reflected off the surface could determine what the stored data was.

By 1982 this technology was available to the public, and over the years that followed most people have gradually replaced their old vinyl singles and albums with compact discs.  Films first appeared around this time on Laserdiscs, a similar technology using much larger discs to store the image and sound.  These were expensive however, so the cheaper videotape cornered this area of the market.  Movies later appeared on CD, as Video CDs, but the image quality wasn’t particularly good, especially when capturing fast motions.  In the end it wasn’t until the invention of the Digital Versatile Disc, or DVD, that this technology finally replaced the old video cassette.

So what next for the compact disc?  Well, I think it will be around for a while yet, but with the advent of iPods and digital downloads over the Internet for movies and video games it seems likely that they won’t manage to stick around for quite as long as Vinyl.  Most recently we have seen the development of new, higher capacity forms such as Blu-Ray and HD-DVD, the latter of which has already been consigned to the techology dustbin.  However, I believe most people will not want to replace their existing collections of music and films again, so chances are the players will be around for some time, even if new releases stop coming out on shiny plastic discs in the years to come.