Digital Trends

Introduction

The ability to hold a movie or several episodes of your favorite television with crystal clear picture and full surround sound has transformed how we enjoy our entertainment centers. Unfortunately, the specifications of this media are not as clear as the picture it provides. There are numerous, non-compatible, often conflicting formats currently in use. One of the problems here is the merger of the home theater with the computer. DVD is the central point between the two and has to accommodate both types of systems. There is also a variety of reasons for DVD drives. While the one that comes to mind first and foremost is viewing movies there is also data storage, music and editing your only multimedia endeavors. At first glance all DVDs might seem the same but they are not all created equally.

Commercial DVDs

This is the familiar DVD that we buy and play on our home theaters or DVD drives in our computers. Like most DVDs it may look like a regular CD, 120mm in diameter, but that is about where the similarity ends. This DVD uses a different laser to read the information. A CD uses 780 nm (infra red light) where the DVD has a laser of 640 nm (red light). This allows for a finer focus and more data on the disc. The pits that the laser reads is also different, 0.834 microns for the CD versus 0.40 microns. All this translates into the greater data density 0.68 GB on the CD and 4.7 GB for the DVD. Add to this the fact that there is only one layer for the CD but 1, 2 or even 4 in use on the DVD. This adds up to about two hours of high quality audio and video per side, up to eight hours on a DVD-18, a disc with two layers on each of the two sides. If you look at the DVD if it is silver in color its one layer, gold for two layers. On many players there is a slight pause when the player moves from one layer to the next.

DVD-ROM

Basically this is a large data drive readable by most DVD drives. On commercial discs it provides video games, web links, scripts and other extras. Many DVD players cannot read this data, it usually requires a computer based DVD player like WinDVD or Interactual. More and more DVDs out on the market have DVD-ROM information embedded on them.

DVD-RAM

This format transforms your DVD drive into a virtual hard disk. It has capacities of 2.6GB or 4.7GB for single sided discs and 5.2GB or 9.4GB for double sided discs. They reportedly can be re-written about 100,000 times. They can not be used in your home theater DVD player and do require a DVD-RAM compatible drive on your computer.