Thanks to DVD, the future of home video has never seemed brighter. Or sharper.
Touted as the greatest breakthrough in entertainment gadgetry since the compact disc, DVD (which, depending on whom you ask, stands for either Digital Video Disc or Digital Versatile Disc) makes VHS tapes or laser discs look positively antiquated. DVD delivers a crisper, more detailed picture than either of them. Moreover, DVD can fit an entire film on a disc the size of a CD, while offering features beyond anything offered on previous generations of video players.
Want to hear "Terminator 2" dubbed in French? Push the "audio" button on your remote, and you can switch from English to French, or Spanish. Need subtitles? Use the "subtitle on/off" feature to turn them on, and the "subtitle change" button to choose which language you want. Viewers can also choose to watch "T2" with the wide-screen picture people saw in theaters, or in the "pan-and-scan" version used for TV broadcast.
Nor are those the only features available with DVD. There's a parental control option that can allow parents to set the machine so it will check a film's MPAA rating and not play NC-17 or R-rated films (parents can choose the cut-off point) without a password. Some DVD discs even offer a multiple-angle option, so the viewer can change the camera angle while watching. DVD players may also be used to play music CDs, but not CD-ROMs.
Most amazing of all is that this technology has arrived on the market at a surprisingly affordable price. DVD players are available for as little as $500 -- much less than first-generation CD players or VCRs -- while most discs are priced between $20 and $25.
Discs may also be rented, though not everywhere. Blockbuster has introduced DVD rentals in about 100 stores nationally, including four in the Baltimore suburbs. There are also a few independently owned shops, such as Cranbrook Video in Timonium, that rent the discs.
DVD, which was developed by an industry consortium, has the support of all the major home electronics manufacturers. Sony and Toshiba have been the most aggressive in marketing the machines, and since DVD's launch in March, more than 100,000 players have been sold in the United States, a figure manufacturers predict will have doubled by spring. There are more than 400 movies and music videos available on DVD, and the number continues to grow.
Still, for all its promise, DVD is likely to leave consumers with a few questions. For instance, how does it work? What are its drawbacks? And how can we be sure DVD won't end up like Beta and quad, forgotten in the scrapheap of entertainment technology?
How it works
Looking at a digital video disc, it's hard to believe it can hold so much information. After all, a CD can barely handle more than 74 minutes of music. But even though it's exactly the same size, a DVD can hold a full-length feature film and still have room for extras. How can that be?
The answer has to do with the way the information on the discs is stored and read. As with CDs, a laser is used to scan the surface of the DVD for microscopic pits. By reading the pits and smooth surfaces as ones and zeros, the laser generates a digital bitstream, which is then decoded into audio and video signals.
One way DVD squeezes more data onto the disc is by using smaller pits and placing them closer together. This is possible because DVD players use a different kind of laser -- the shorter wave-length "red" laser -- than CD players.
Another advantage DVD has is a video compression system called MPEG-2. Basically, what video compression does is sift through the visual information in each frame and delete unnecessary information.
To understand how that works, imagine a movie that shows someone walking through a door into a room. The only parts of the image that actually "move" are the door and the person coming through it; everything else in the room -- the walls, the furniture, the decorations -- remain unchanged.
Now, a piece of film "redraws" the whole image -- both moving and non-moving parts -- 30 times per second. It makes for a vivid visual, but it contains a lot of repetition, something digital engineers consider "redundant data." So what MPEG-2 does is carry over the background information, so the player doesn't have to redraw the entire scene with each new frame. It just draws the changes, saving storage space. Meanwhile, the viewer gets virtually the same effect.
Another difference between DVD and CD is that CDs are one-sided, whereas DVDs can use two sides to store data. All told, DVDs can store up to 13 times the amount of information a CD holds. Whether a movie uses one or two sides of a DVD depends on the amount of features included in the package; most fit on a single side.
Pros and cons
Of all the advantages DVD has over other video players, the most obvious is picture quality. Not only does DVD offer a higher line resolution (more lines per screen) than VHS or laser disc, it also offers greater color separation.