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[ Go to April 1997 Table of Contents ]
WinLab Reviews
-- by Jonathan Blackwood
Are CD-ROMs and laserdiscs about to go the way of 8-track tapes? Maybe not today, but by the turn of the century they'll give way to DVD. The latest in laser technology, DVD stands for digital versatile disc, digital videodisc or nothing at all, depending on the person you ask-and it's coming to your computer, your office and your living room. DVD reads CD The CD-ROM vs. DVD compatibility problem that everyone worried about initially turns out to be a non-issue. Virtually every major manufacturer and content provider extant is already aboard the DVD standards train. Originally, there were two main players in the DVD game: On one side was a Sony/Philips pairing, which brought the world the original compact disc (CD); on the other was Toshiba/Warner, in a consortium with 17 other manufacturers. Though they started out with competing formats, the two sides joined forces in 1995, fearing a replay of debacles past (think Betamax/VHS or EISA/PCI) DVD originally was planned for market entry by last fall, certainly in time for sale by last Christmas shopping season. We're still waiting. The holdup? Concerns of software publishers and content providers that offering a perfect digital master of a motion picture or other content will likely encourage piracy. As a result, every DVD player will have a copy protection chip to defeat attempts to copy the disc. DVD brings a lot to the party, both for computer users and home-entertainment mavens. Physically, the discs seem like ordinary CDs, being exactly the same diameter (4.7 inches), thickness (0.048 inch) and color (silver) of the standard CD. But while a CD holds some 650MB on a single layer on a single side, the smallest-capacity DVD can hold more than seven times that amount. Up to 17GB of data on one disk A single-layer, single-sided DVD will hold 4.7GB of data, enough for 133 minutes of high-quality MPEG II-encoded video with 5.1-channel digital AC3 sound (better than laserdisc). Compare that to the 5 minutes of video the CDV format offers, using laserdisc technology on a standard compact disc. Movies released in DVD format will also offer a choice of three aspect ratios-full-screen, letterbox or 16:9-three audio languages and four subtitled languages. Another advantage for video reproduction inherent in DVD: It uses component video, as opposed to NTSC composite video. This means the image is free of artifacts such as dot crawl and cross color distortion. Even better, manufacturers will be able to add a second data layer to the same side of the disc, boosting single-sided capacity. And both sides of the disc can be used; a double-sided, double-layer disc can potentially hold 17GB of data. But even the smallest-capacity DVD, 4.7GB, is capable of storing 7 hours and 24 minutes of CD-quality digital audio. How does DVD compress so much additional information into the same dimensions as an ordinary CD? There are two ways. First, DVD uses a much finer wavelength laser beam (780 nanometers for ordinary CD, 650 and 635 for DVD) for both reading and mastering, meaning smaller pits and more tightly spaced track. The result is seven times as much data in a given area as a CD holds. The second answer, at least for video, is the fact that MPEG-II compression results in a data footprint smaller by an effective factor of approximately 3.6 than ordinary laserdisc data. The Toshiba Infinia MMX with DVD in this review is the first machine we've been allowed to examine with a DVD drive installed, but unfortunately, the system's prototype status made it impossible to accurately benchmark the drive. Step up to DVD on your PC We'll review upgrade drives as soon as they become available. DVD players for home-entertainment purposes should be available from a number of manufacturers as you read this. Expect to see the first DVD upgrade kits for your PC this spring. When available, those upgrades should cost around $500, will fit into a standard 5.25-inch drive bay and can replace your CD-ROM drive-they're backward-compatible with CD-ROMs and audio CDs. DVD does have one limitation manufacturers have so far been unable to overcome: The DVD laser cannot read a CD-Recordable, which uses a different color reflective dye in the platter itself. Some manufacturers plan to build DVD drives with dual lasers, so that a single unit can read CDs, DVDs and CD-Rs, but these devices will likely be far more expensive than standard DVD upgrades. If your company uses CD-Rs to archive records or distribute software, you'll probably find that hanging on to your existing CD-ROM and adding a DVD drive in another bay is your most cost-effective upgrade option. You can expect to see recordable DVD units hit the market by the end of 1997, with initial prices for units in the sub-$10,000 range. These double-sided DVD-Rs will hold 7.6GB of data and will be readable in any DVD drive. PC home theater? DVD-RAM rewriteable disc drives should reach the consumer marketplace by 2000. They'll operate more like removable hard drives than the CD-Recordable devices you're used to. You'll simply insert a DVD-RAM disk and use it as you would a hard drive. Only the technology-optical phase change instead of magnetic Winchester drive-will differ. And a DVD-RAM drive will hold 5.2GB of data-not bad for a small silver platter. Don't expect to play full-length movies on your computer right away. Although it's theoretically possible with any existing PC, in practice, slow video throughput will keep the DVD+PC combination a poor substitute for the VCR. It probably will be a year or more before accelerated video playback technologies, including the Accelerated Graphics Port, make PC theater truly practical.
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