Byte by Bite

Plusses and Minuses of CDs and DVDs

by Marv Dealy

Straight to the mail bag – from reader Charles Cameron: “I enjoy your column and look forward to it every Friday in the Union Democrat. I must be regular listener 33 or 34.”

“Would you do an article about the different types recording discs. CD's, DVD-r, DVD+r etc. What are the differences, which is best for backing up stuff on the computer. What kind of DVD recorder is required.”

“Another question for you is do you or can you recommend someone in the area to tune up my computer. It seems to going slower and slower (like me).”

Well, Charlie, I trust that your computer is feeling better now; when you brought it into my shop we found that 18 of the 32 white mice weren’t running on the treadmill as they were supposed to be, so we injected them all with some quite strong coffee and off they went. Happy to help.

About the questions regarding recording discs – good one, and it comes up a lot. So let’s do a little learnin’.

Let’s start with the CD-R (for CD-Recordable). This is a disc that can be recorded to one time, but can’t be erased; they are called “write once” disks. CD-Rs can be used to make copies of stuff for distribution or for backups of important stuff. The process of recording to a CD is called “burning” even though no open flames or dangerous chemicals are involved. Go figure. Burning a disc requires a CD-R drive, a CD-RW drive or a CD/DVD drive which is a combination drive.

CD-Rs can be read in most types of CD drives, including older units and newer combination drives. If you have a newer drive, it will be rated something like 40x and will take only a few minutes to record a full disc. Originally, discs held 650MB of information (or 74 minutes of music). This was upped in 1998 to 700MB (80 minutes) and in 2002 to 800 MB (90 minutes) for the CD-R. The bigger capacity for storage is possible by a reduction between the tracks on the disc.

CD-ROM (Compact Disc Read Only Memory) is the standard for software distribution. The disc can hold text, graphics and music, but uses a different format than the audio CD (CD-DA) from which it evolved. A music CD player can’t play CD-ROMs but CD-ROM players can play audio discs.

Mini CD-ROM are only 80mm in diameter versus the 120mm for standard discs. Minis also hold less stuff – only 180MB. The mini discs fit into the indent in the center of your CD or combo player. I’ve also seen mini-discs shaped like, among other things, a Buick Rendezvous. It doesn’t look any better as a CD than it does on the road, by the way.

Visually, CD-ROM disks have a silver cast to them, just like your music CDs. CD-Rs have either a green, blue or gold cast. Remember that your CD-Rs can be burned once and will read on almost any CD or combo drive.

Onto CD-RW discs. These discs have a blue cast, and can be burned multiple times, but must be read on newer MultiRead CD and DVD drives.

Early on, CD drives used a “caddy” into which you inserted your CD before poking it into the drive bay in the computer. I still have one around the office somewhere if you’re really dying to see one work.

Today, when someone refers to a “CD drive” in their computer, they’re probably talking about a CD-RW drive that is a combination of a CD-ROM, CD-R and CD-RW drives. The early CD-ROM drives transferred data at a rate of 150KB per second and were rated as 1x. Today, a 40x drive is common; its data transfer rate is 6MB per second, 40 times faster than the original and hence is known as a 40x drive.

CD-RW drives come with a three-speed transmission, so to speak, one for CD-R writing, the second for CD-RW writing, and the third for CD-ROM reading. These numbers are usually written as 00/00/00, and a typical drive might be labeled thusly: 40x/12x/48x.

DVDs (Digital Versatile/Video Disc), too, come in a variety of speeds. They started out 9 times faster than CDs did, which translated to a transfer rate of 1.35MB per second. DVDs have just kept getting faster, first by doubling the spindle speed, or RPMs to create 2x DVD drives (which were, by the way, 18 times faster than a 2x CD drive, as each DVDx is 9 times a CDx). DVD-Rs are recordable once discs, and DVD-RWs are rewriteable discs.

Most DVD drives can play DVD Video (movies) and music CDs as well as DVD-ROMs and CD-ROMs. Still other drives may support some combination of, or even all of, CD-RW, CD-R, DVD-RW or DVD-R discs.

Are we there yet? Nope; drives and discs that use the minus sign (e.g., DVD-RW) are endorsed by the DVD Forum, the industry’s primary association (www.dvdforum.org) for establishing formatting standards. Naturally, there are groups that have risen to challenge publishers’ assertion of absolute control over digital media (OpenLaw: Open DVD at http://cyber.law.harvard.edu/openlaw/DVD/).

A competing technology uses a plus sign, resulting in DVD+R and DVD+RW discs. For information on the Plusees, try www.dvdplusrw.org. Newer DVD-R DL and DVD+R DL discs really up the ante with recordability of about 8GB or four hours of high quality video. Many, but not all, DVD drives support both formats. Dual layered double sided DVD-Rs can hold an incredible 16GB of stuff.

A third competing technology, called DVD-RAM, has less DVD player and CD-ROM player compatibility but better recording features and is used as the storage device in some DVD recorders. For lots more about DVDs, visit www.videohelp.com/dvd

So, back to Charlie’s question: what’s the best disc and device? The answer is, it depends. If you want to make a disc you can send to Auntie what’s her name with pictures of your newest curtain crawler, you might want to consider her older computer might not be able to read your new DVD disc, and send along a CD-R disc instead. Chances are she’ll be able to see the stuff. If you’re transferring stuff to a friend with a new computer, on the other hand, you’ll be safe in recording to just about any media. Just consider how the disc will be used. Will, for example, it be a weekly backup of stuff? Is it a one-time recording of something, whether data or some music or a movie? Remember that DVDs will hold an incredible amount of information – that’s how they can cram a movie and the director’s cuts and a whole bunch of ads on one DVD. Finally, you can assume that technology will continue to be forward- but not necessarily backward-compatible.