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Under the Desktop:
CD-R Right or Rong?
Industry hype notwithstanding, CD-R and CD-RW discs won't
always work in DVD-ROM drives. David Morgenstern explores why,
and looks at ways around the problem.
By David Morgenstern
Thursday, March 29, 2001
A generation has grown up with CDs. Today, desktop systems and
notebooks come standard with a CD-Recordable (CD-R), CD-Rewritable
(CD-RW), or DVD-ROM drive (ignoring for the moment the writable
DVD drive now shipping on Apple's fastest machines). It may come
as a shock to content creators that our very familiarity with
these optical technologies may pose a stumbling block when delivering
work to clients. One disc does not fit all.
Here's the back story: I recently added a Power Macintosh G4 400/DVD to my hardware collection. (With Apple's new series of desktop machines finally reaching retail shelves, the resulting price drop for last year's model was just too good of a deal to pass up.) As I packed the new hard drive with necessary software and copious image files from my previous systems, I discovered an apparently bad CD-R disc -- the one holding the drivers and software for my old-but-trusty SCSI-based scanner.
My annoyance at discovering the bad CD-R disc was heightened by the lack of feedback from the DVD-ROM drive in my new G4. After I inserted the disc, the drive came up to speed, whirred for a while, and then stopped. That's all, folks. No "Unknown format, please eject..." message, only silence. The drive obviously had identified it held a disc, but it either couldn't interpret the data or didn't like what it saw.
After much head scratching, I moved the unreadable disc from the DVD drive to my CD-R burner. Voila, the disc was mounted and I was back in the installation business! What a happy turnaround. But the mystery remained: Was the problem with the CD-R disc, or with the DVD drive? Or both?
CD-R: What Me Worry?
Certainly, the nerve-wracking event of a disc that can't be read
has been experienced by countless CD-R and CD-RW users, whether
on Mac or Windows platforms: We all have our share of bad discs.
Yet this disc wasn't completely unreliable, since it choked only
the DVD-ROM drive.
To get some insight, I quizzed Mike Mihalik, an expert in optical storage technologies and former vice president of engineering at LaCie Ltd., about the problem. He said the biggest trouble with the writable CD technology is its similarity to mass-produced CD-ROM and CD-Audio.
"Consumers see a 120mm disc with a hole in it and just expect that it will be usable when it's played," Mihalik said. Our long, successful experience with mass-produced CD-ROM and CD-Audio discs has engendered an unreal expectation of compatibility and usability for writable CDs, he added. "You can't tell from the outside [about any particular disc's format or compatibility]," Mihalik said.
Is the compatibility picture for writable CD technology solid enough that CD-R and CD-RW drives should be considered true consumer products? A safe bet would be yes, counting the votes of most readers and vendors in the storage industry. But Mihalik suggests that expectations of universal compatibility are not yet realistic.
According to Mihalik, here
are just a few of the reasons why my DVD-ROM drive might ignore
a CD-R disc:
- DVD-ROM drives are fundamentally different than their CD-ROM cousins. For example, DVDs are read by a visible red 635- to 650-nanometer (nm) laser; CD-R uses a 780-nm infrared laser. Almost all DVD drives use some type of dual-laser mechanism to solve this problem, but there's no guarantee of 100-percent compatibility.
- The disc may be dirty or slightly
damaged. The optical specifications for CD-ROM and DVDs are based
on playback of manufactured discs, whereas CD-R technology uses
a variety of dyes that emulate the reflective qualities of manufactured
media. A buildup of schmutz on the disc's surface, such as oils
from your hand, can change or lessen the optical characteristics
enough to make the disc unreadable.
In addition, Mihalik noted that anything that contacts the outside edge of the disc -- certain types of hard plastic CD holders, for example -- is potentially damaging. The edge is the very place where a disc's directory information is written, the worst spot for wear and tear.
Even worse are paper cuts. As our fingers occasionally discover, the edges of paper can be very sharp. Placing a disc on papers scattered on your desk -- a common habit -- can bring tiny, mostly unnoticeable scratches that over time will degrade its optical performance.
- Some discs burned on the latest, sexier, faster CD-R burners may give trouble during playback, Mihalik warned. To achieve the widest compatibility, authoring software should force the burner to write at slower speed, such as 2x or 4x.
- The built-in CD-ROM and DVD
drives in Macs prefer "closed" discs, rather than those
left open for continued, multisession recording. The sessions
utilize link blocks between tracks and sometimes a different
formatting for the directory at the end of the disc that may
confuse some drives.
Of course, drivers installed for CD-R and CD-RW mechanisms understand multisession discs, and Mihalik said this may have been the reason why my "unreadable" disc proved suddenly readable when inserted in my CD-R burner. To improve compatibility with CD-ROM and DVD-ROM drives, use the disc-at-once setting in the burning software, Mihalik recommended. Depending on your workflow, this may mean writing more discs. But think about it: Media is cheap nowadays, while your data and its compatibility is priceless.
My continuing list of grievances with writable CDs will be aired in another column. Readers eager for more detailed information should check out Media Science's CD-R FAQ.
Knowledge is Power
It may sound as if I'm on a jihad against writable CD technology,
but nothing is further from the truth. I'm a fan and club member!
However, content professionals must understand any conditions
to its use. For connecting my home office scanner, the CD-R vs.
DVD incompatibility was a brief inconvenience. But what if I
had stumbled on this incompatibility when presenting or delivering
work to a client?
Some readers may say "the heck with old-fashioned discs" and suggest that Internet delivery is the only way to go. I beg to differ. Although broadband's reach is increasing, it's not everywhere, or even to my house. And in many cases, it's just inappropriate. The idea of sending a presentation with embedded video clips to the CEO waiting impatiently on the tradeshow floor via wireless transfer to a Palm Pilot sure sounds sexy, but we're talking about hundreds of megabytes here, folks.
There's still a very strong place for sneakernet as the transfer mechanism for huge creative content files such as digital video or complete layouts with high-resolution images. My definition for sneakernet is broad, encompassing far more than just carrying a file across the office. Sneakernet to me can involve any delivery on any media, near and far, even through the use of third parties such as FedEx. It's a far more reliable method than trying to download files to a foreign hotel room with slow, slow dial-up access.
Anticipate the Worst
Content creators must be cognizant of all client-side
preferences and needs when both planning and delivering a job.
It's second nature to focus on the design itself; perhaps less
obvious to explore the receiving platform. Smart content professionals
check CD-R discs on clients' machines before handing over the
job.
Checking compatibility is doubly critical for presentations, which are often run on the road and in remote locations. Take a burned disc along to any early client-side meetings and test it on the client's notebook(s).
And, alright already, use the Internet as a backup, too. Have a copy of the presentation available for easy download in case of catastrophe. In addition, as I mentioned in my last column, check the notebook's LCD and display capabilities to bring about the best outcome for the job and the client.
Ensuring CD-R compatibility rests on the content creator's shoulders, insofar as it's possible. As the medieval sage Abraham ben Samuel HaLevi commented: "A faultless person is possible only in a faultless world." The same holds true for the current state of writable CD technology.
Read more by David Morgenstern.