Durable Endurance of DVD; Expected to Weather Tech Advances
Byline: Christian Toto, THE WASHINGTON TIMES
A seemingly endless series of plastic pits and indentations has brought plenty of joy to movie lovers everywhere.
DVD technology hit the market hard in 1997, and in only six years, it has become an entrenched part of any true movie fan's library.
The term DVD originally stood for "digital video disc," according to Memorex, but later the acronym stood for "digital versatile disc." Neither name is bandied about with much regularity anymore. It's simply DVD, much as compact discs are called CDs.
Like CDs before them, DVDs are made out of optical-grade polycarbonate plastic, says Terence O'Kelly, a Boston-based technical marketing manager with Memorex.
The discs go through a mold, say for the new-to-DVD film "2 Fast 2 Furious," that leaves millions of tiny impressions in the plastic.
Those pits, created along one long spiral track teeming with data, will later be read by a DVD player's laser. When the laser hits an impression, it bounces back to an optical reader in the player. That reader analyzes which light beams bounce back or scatter, depending on whether it hits a pit or a flat portion of the disc.
The player registers the difference in much the same way a computer reads basic digital information as either a one or a zero.
The discs are made in numerous plants across the country, including sites in Michigan and California, plus factories outside the United States.
DVD should "outlast the format that it's been made for," Mr. O'Kelly says.
"Plastic is relatively stable," he says, estimating the life span of a movie DVD at anywhere from 100 to 200 years.
Erasable DVD formats - such as DVD-RAM, DVD-RW and DVD+RW - should last from 25 to 100 years. The "R" in "RW" stands for readable, while the "W" denotes a disc that can be written over repeatedly to store new information.
Other factors can prevent that healthy shelf life. Scratches, the most common form of damage, can affect how the laser sees the various indentations.
Typically, the scratches are created on the upper surface of the disk. "The laser is focusing beyond them," he says. "They can be scratched significantly enough if they're mishandled so that the light is scattering through them."
DVDs were preceded on the market by another disc format, laser disc technology. These larger discs captured analog, not digital, data - a format that stores less information and is incompatible with the increasingly digital times.
The DVD was created when researchers tinkered with the standard CD and found ways to reduce the size of the pits and increase the number of tracks, or grooves, in each disc.
Brian Burgess, a senior editor with Vox-Cam Associates, a video production company in Silver Spring, says the average CD holds 700 megabytes of information, while a DVD packs in 4.7 gigabytes, nearly seven times the amount of information.
Newer double-sided DVDs can pack in even more information, Mr. Burgess says, which could help movie studios unwilling to put epics such as "Apocalypse Now" on two discs. DVDs also can carry up to four layers of information, two on each side in the recently developed double-sided discs. …