Wait before you buy DVD optical drives-prices are a bit steep

Then the developers realized DVD was a digital storage medium. Perhaps someone reminded
them that consumers long ago opted for the fuzzy but recordable videocassette instead of
the superior but play-only laser disk. DVD then became the acronym for digital versatile
disk.


DVD drives will be backward-compatible with CD-ROMs, so their lowest disk capacity will
be 550M or 600M. But that's only the beginning.


The initial DVD standard will start with a single-sided, 4.7G disk. The 8.5G capacity
you've heard about refers to a disk recorded on both sides. Since you have to flip it over
physically, this is a somewhat misleading capacity increase.


Another way to reach 8.5G capacity is much more sophisticated. It will actually double
the basic DVD storage by recording data in two layers, one on top of the other. The top
layer will be semitransparent, the lower completely reflective, and data will be read by a
dual-power laser beam.


This gives 8.5G capacity without turning the disk over, or as much as 17G on a
dual-layer, double-sided disk. That's about 28 times the capacity of a CD-ROM.


Although double-sided disks are practical for storing videos, I don't see much future
for them in database storage. They wouldn't make any more sense than double-sided CDs that
you remove and turn over. Such an operation isn't actually possible with a CD-ROM disk,
because of the thickness of its recording layer, but the idea is the same.


For single, multigigabyte databases, users are going to demand DVD changers or, once
the price has come down, multiple DVD drives. Double-sided DVD makes even less sense if
you have totally different databases on each side of a disk.


The reason DVD installation won't be as simple as adding a CD-ROM drive is that part of
DVD's appeal is its video and audio capability.


For now, vendors seem ready to market bare DVD drives along with a separate Motion
Picture Experts Group-2 video compression decoder board, which will support the new
six-channel, Dolby AC3 audio. Video quality should equal that of new DSS satellite disks
using MPEG-2 compression.


To install a DVD drive, you'll have to get the drive itself to work with the computer
through the AT attachment packet interface, then bring the video and audio signals from
the combined interface and decoder card to the PC's graphics card and audio card.


My bet is that a lot of conflicts will pop up-both physical conflicts and software
conflicts. Preinstalled DVD will add about $800 to the price of a new system, and I doubt
all manufacturers will get everything preinstalled right at first.


Data playback from a DVD initially will be about as fast as on current 8X and 10X CD
drives. Seek times should be very fast, because the data will be stored in the same
physical space as current CDs, but DVD packs in much more data. Its solid-state blue laser
operates at a short wavelength and can resolve smaller objects, so data can be packed more
closely.


Read-write DVD already is in the works for 1998. Its capacity will only be half that of
mass-produced DVD disks, due to the difficulty of making cheap, short-wavelength write
lasers.


Incidentally, DVD disks, like mass-produced CD-ROM disks and laser disks, are pressed
much like vinyl records. They aren't recorded one by one with a laser recorder.


For training videos, DVD won't be any big paradigm shift. Quality will be similar to
that of laser disks, and only physical size and capacity will change. This will make it
possible to put wide-screen and TV-format full-length videos on the same disk, or to store
more training sessions on a single disk. But there will be little change in the way these
products are used.


Fast CD changers cost less than a third as much as new DVD players, multiple CD-ROM
drives only cost about $60 each, and CDs already can handle multidisk telephone number and
map databases. DVD can accommodate more of these, as well as full-screen, full-motion,
feature-length video, but it won't bring any radical changes to the desktop.


Bottom line? DVD is great, but don't rush to be the first in your office to get it-at
least not at current prices.


John McCormick, a free-lance writer and computer consultant, has been working with
computers since the early 1960s. E-mail him at jmccormick@penn.com.


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