What Is DVD?
by Jeff Shannon
By the time DVD ("Digital Video Disc" or
"Digital Versatile Disc") was introduced to the American public
in March 1997, years of research and development had preceded its arrival
as the "next generation" format of home entertainment. Consumer
electronics manufacturers and movie studios established an industry-wide
DVD-video standard in 1996; and by the end of 1997, DVD players had set
sales records and well over 500 DVD movie titles had been released, with
the rate of new releases rapidly increasing from that point forward.
A DVD is identical in thickness (1.2 millimeters)
and diameter (120 millimeters or 4.7 inches) to a standard Compact Disc,
but that's where the similarities end. The DVD's storage capacity is seven
times that of a CD, with a 4.7-gigabyte capacity on a
single-side/single-layer DVD. That's the data-storage equivalent of a
133-minute movie, thus allowing 95 percent of all movies to fit
comfortably on a single-layer DVD, eliminating the need for
"flipping" the disc and leaving extra room for multiple audio,
language, and subtitle tracks; bonus materials; menu screens; and other
features unique to DVD. This capacity is nearly doubled (8.5 GB) on a
single-side/dual-layer DVD, and quadrupled (17 GB) on a
double-side/dual-layer DVD, allowing DVD to flourish not only as a
movie-lover's format, but as an amazingly flexible medium (DVD-ROM) for
high-definition computer games and multimedia applications. In short, this
makes DVD the home entertainment and multimedia format of the new
millennium.
Why should I bother with DVD?
Don't worry--you won't have to trash your VCR if
you don't want to. But the vastly improved audio and video quality of DVD,
along with its durability and flexibility (no rewinding, instant scene
access, etc.) makes VHS pale in comparison. You don't need an upgraded
home-theater system (unless DVD makes you want one!); and affordable DVD
players are compatible with CDs, while some "combo" models allow
the playback of DVDs, CDs, and laserdiscs. With all major movie studios
now supporting the format, the selection of current and classic movies on
DVD (along with music videos, opera, documentaries ... you name it!) is
rapidly expanding, along with outlets for DVD sales and rentals.
From big screen to little disc (a basic primer)
Videophiles and laserdisc loyalists will debate
the pros and cons of DVD for years, but one thing is certain: the process
of transferring a movie to DVD is highly advanced and designed to deliver
the highest quality of audio and video available. For every video format
(VHS, laserdisc, and DVD), the process begins with "telecine"
(TEL-a-sin-ee), but the procedures for DVD adhere to much higher
standards. The telecine process begins when light is passed through the
film (frame by frame, with exacting precision) and strikes an array of
semiconductors that convert the light into electrical signals. That
information is then digitally transferred to High Definition video (HD),
which is capable of picture resolution nearly equal to that of the
original film.
The HD master can be color-corrected and further
checked to match the original film (a process often involving the film's
director and cinematographer). Then its massive data capacity must be
compressed via MPEG-2 encoding (developed by the Motion Picture Experts
Group, or MPEG), which produces a varying rate of transferred data to
exploit similarities from one film frame to the next. Less data is
required for redundant details while more data is reserved for complex
details such as rain, smoke, crowd scenes, etc. (This process leads to
image-quality debates between laserdisc and DVD fanatics, due to the
idiosyncrasies of MPEG-2 compression, but DVD maintains a definite edge in
picture resolution.)
The MPEG-2 digital video transfer is later
synchronized with all the audio elements (soundtracks and language or
commentary tracks) and then combined on a specialized computer called a
"multiplexer," along with all the potential elements of DVD,
including subtitles, menu files, chapter stops, closed-captioning,
parental-control information, regional encoding, and copy-protection. This
digitally combined information is then recorded onto a tape drive, which
is then checked for signal integrity, further inspected for quality
control, and finally used as the data source from which a master DVD can
be made for unlimited duplication.
What does it all mean?
Don't let the techno-babble fool you--find a local
consumer outlet and test-drive DVD for yourself, and remember how readily
the public traded in their vinyl records for music CDs. The same
phenomenon appears to be happening with DVD, although VHS videotapes are
far too entrenched in the market to disappear anytime soon. However, as it
becomes clear that DVD will avoid the niche-market fate of laserdiscs to
become the accepted format for home entertainment, DVD--with its
convenience, affordable cost, and superior performance--speaks for itself.
Jeff Shannon is a Seattle-based
freelance writer focusing primarily on films and filmmakers. |
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