for software and multimedia content distribution.
Mike Weiss, vice president of entertainment and business development at Sirius Publishing, a Scottsdale, AZ-based CD medium producer, says CD-ROMs are so well entrenched that it will be at least five years before they are supplanted by the newer technology. "It will be years before all machines ship out with DVD as standard equipment," Weiss says. "Until DVD can replace a VCR, I don't see widespread consumer acceptance."
It took several years for the industry to make the leap from using CDs at the desktop to also authoring them at the desktop. CD Recordable (CD-R) discs, which appeared in the late 1980s, use a coating of temperature-sensitive dye. To write data, a laser in the drive heats spots on the dye layer, changing its color and therefore its reflective properties. Although scattered cases of incompatibility exist, often due to poor calib
ration of laser power during writing, the read laser of a standard CD-ROM drive can generally read CD-R discs.
The allure of mastering your own discs using CD-R was undeniable, but it was not without its disadvantages. The medium was costly, and a single mistake rendered a disc unusable. CD Rewritable (CD-RW) drives have emerged to address these issues.
CD-RW drives use phase-change technology to alter the reflectivity of spots on the disc surface in a reversible way. The alloy used to coat CD-RW discs can withstand up to 1000 write-erase cycles, making CD-RW a good candidate for backup and data exchange.
But CD-RW is not without its problems. The reflectivity of a CD-RW disc is low -- an unavoidable characteristic of its rewritable coating. As a result, most existing CD-ROM and CD-R drives cannot read CD-RW discs.
A new MultiRead standard specifies higher-gain read circuitry and will allow future CD drives -- expected to include most DVD drives -- to read CD-RW discs. Although CD-RW d
iscs will work primarily in CD-RW drives, the drives will also write to CD-R media, letting CD-RW owners create media compatible with CD-R and CD-ROM devices.
Increasing confusion in the CD market is as simple as introducing an entire new family of standards. DVD-ROM is being promoted as a panacea for both publishers and consumers. Originally envisioned as a unifying standard that would gather previous CD technologies under its wings, DVD standards are now more fractious than CD standards have ever been.
Vadim Brenner, engineering division product manager at Plextor, says the lack of firm standards is enough to delay his company's entry into the DVD market. "Plextor hasn't come out with a DVD drive," Brenner said, "and won't until the hardware requirements stabilize."
In its single-sided form, a DVD can hold 4.7 GB. A two-layer version boosts a DVD's capacity to 8.5 GB, doubling to 17 GB for a double-sided version -- enough to hold 8 hours of feature video on a disc the same size as a standa
rd CD. But some medium producers question the need for such a standard at the desktop.
"I can't see the difference between having
Star Wars
on VHS or DVD," Weiss says. "Promoting DVD's potential higher resolution and better video is setting early adopters up for a big disappointment."
A DVD drive is built around a laser that produces shorter-wavelength light than standard CD drives. The shorter wavelength lets the laser produce smaller spots. This, combined with tighter track spacing, yields the DVD's higher single-sided density. By using both sides of the disc and bonding a semitransparent second layer over the primary layers, DVD capacity can be boosted to an impressive 17 GB.
To take advantage of DVD content, you'll need more than just the drive. Typically, a DVD bundle includes a PCI video card with the specialized hardware needed to decompress the MPEG-2 video signal coming from the disc. The decoded video goes directly to your computer's monitor, bypassing your CPU and regular v
ideo card. High-end systems require decoding of Dolby AC3 audio, which provides sound in six dimensions (five speakers plus a subwoofer).
The rush to market and the shifting nature of DVD technology are making manufacturers edgy and casting consumers as potential victims. Early DVD drives, for example, are unable to read CD-R discs. More recent drives overcome this limitation and claim to read CD-RW discs as well. "If your DVD drive was designed with one pickup and won't read CD-R," says Brenner, "there's not much that can be done."
Like CD-ROM before it, DVD technology is evolving toward a rewritable version -- but at a greatly accelerated pace. Currently, the DVD Forum is attempting to negotiate a standard, but the battle is furious. Nothing less than control of the industry and sizable future royalties are at stake.
DVD Recordable (DVD-R) is a write-once technology with more than passing similarity to CD-R. DVD-R's use of a wavelength-sensitive dye means it will probably suffer incompatib
ility problems with future short-wavelength DVD drives. When you combine that uncertainty with high hardware and medium prices and a reduced capacity of 3.8 GB per side, DVD-R may have a mercifully short marketable life.
A DVD consortium was championing, with some success, a 2.6-GB-capacity rewritable format dubbed DVD-RAM and based on phase-change technology. But recently, Sony and Philips Electronics have broken away and, joined by Hewlett-Packard, Mitsubishi Chemical, Ricoh, and Yamaha, are pursuing an independent DVD rewritable format.
If you're considering buying into this technology, you should proceed carefully. It will be an expensive battle to stay at the edge of current technology.
DVD Remains a Moving Target
