Burning & Playing CDs & DVDs
by Paul Rego
(Last updated 1/13/07)

Background
During the M.A.C.S. January meeting, a question was presented as to why his Macintosh could read a CD he had created (on that Macintosh) but his son's Macintosh could not read it.

There were several good suggestions from the other members that night and one confusing statement from me. I had mentioned that he may have burned the CD at a speed higher than his son's Mac was capable of reading. Several members immediately said this wasn't true. Because I have to have my facts straight whenever I talk about something, I said I would look into this.

Research
After reading some Apple articles and several message threads on this subject it turns out that I was "right" and "wrong"…

Burning a CD or DVD at a speed which is faster than another player can burn a CD or DVD doesn't have any affect on that other player's ability to actually read (playback) that information. However, burn speed does matter during the actual "burning" process.

When a CD or DVD is burned a laser makes microscopic marks in the dye. (These discs are manufactured with several layers. One of them contains dye.) These light and dark spots (called "pits" and "lands") represent the "zeros" and "ones" which make up your text, images, video, sound, etc. During playback, a different light is used to detect the pits and lands. When a disc is burned at a fast speed, the pits and lands are not as perfectly-formed.

You may ask…
"If this were true, then my computer would not be able to consistently playback ANY CD or DVD I create on that same computer."
It seems there are several factors which come into play here:
• The calibration and other tolerances within a CD/DVD player can influence consistent playback of optical media — especially the "consistent" playback of optical media which was burned in another optical drive.

• The rated speed of the media. (CDs and DVDs usually have speed ratings or a suggested speed listed on their packaging. Going outside this may cause problems.)

• The technology inside the CD/DVD burner. (This could involve the speeds the burner is capable of using, the angle of the laser used to do the actual burning, etc.)

• Sometimes, when technologies progress, a CD/DVD burner must have a "firmware" update. (Some manufacturers provide software which will modify some of the information within one or more of the burner's silicon chips. This allows it to be "improved" and keep up with some features in newer technology.) On the Macintosh, you would simply pull down the Apple menu (in Mac OS X) and choose "Software Update…". This will tell you if a firmware update is available for your Mac's optical drive. (Most Macs never need such an update.)

• The burn software may be more tolerant of slightly deformed pits and lands. In this case, the burn will verify as "successful", you'll think it will work in any player but the player you use is less tolerant and it won't play.

• The CD/DVD's manufacturing process and quality of materials can determine "consistent" or "inconsistent" reliability. Even the thickness of the dye layer or the thickness of the disc itself can have a dramatic effect on burning and playback.

• Sometimes even the humidity can influence the reliability of a burn.

CD/DVD Trivia
• Burning starts in the center of the disc and spirals out to the edge. If you set the burn speed to a fast setting and you only burn a small amount of information (not even filling half the disc), you will not experience that fast speed because the disc spins at different speeds during the burning process — the burner spins it faster as the burning moves closer to the edge of the disc.

• Because the CD/DVD burning process speeds up the disc's rotation as the burning reaches the edge of the disc, it's possible for some information and video to be reliable and other data to be corrupted or garbled. (When viewing a DVD movie, for example, some of the video may play fine but during a movie random images, garbled sound and other quirks may make viewing the rest of the movie intolerable.

• Each CD and DVD contains information about itself. This is stored, during manufacture, on a part of the disc which is never used when burning. This tells the burner (the optical drive) some important information about that particular disc: suggested speed range, capacity, etc.

• Just before burning your data, a test burn is performed in an area which isn't used for your information.

• Discs are burned in a spiral, so if it becomes necessary to clean a disc, always gently wipe from the center vertically out to the edge and never horizontally in a circle or arc. A vertical scratch across a track may just cause a blip in playback, but a horizontal scratch can interfere with more information in adjacent space horizontally along the track.

• Depending on storage and handling conditions, burned CD-Rs can last 70 to 100-years.

• Some CD-R discs offer over one million "read" passes. This information was found at this FujiFilm page:
http://www.fujifilmusa.com/JSP/fuji/epartners/ServiceSupportProductContent.jsp?dbid=670587&prodcat=235757&sscucatid=664277

• The unrecorded (blank) shelf-life of a CD-R disc is conservatively estimated to be between 5 and 10-years. This information was found at this Optical Storage Technology Association (OSTA) web site:
http://www.osta.org/technology/cdqa13.htm

So, it seems the Pros and Cons are:
• Burning a CD or DVD at a fast speed will save you time — because your Macintosh will be occupied for less time. However, burning at a slower speed will increase the odds of that CD or DVD being read "reliably" in the future.

• You may not have to spend extra money for better blank CDs and DVDs. Although you may get 10 opinions from 10 different people, ask during the M.A.C.S. meetings and check some of the online forums to see what other people are having success with. "Well, I've been using this brand and have had no problems and I'm not going to give my burned CDs and DVDs to anyone else. I won't be using them in any other player." Well, that's fine "for now". However, when you buy another Macintosh in the future, some of your CD/DVD backups may not work in that new computer. So it might be a good idea to find a "consistently" reliable brand of blank media now.

• Burning at a "slower" speed will ensure more reliability. However, if you burn at a speed which is slower than the drive or CD's suggested speed, you may also have problems. When using a Macintosh and burning with Apple's included software (the Finder or Disk Utility), sometimes the speed menu will show one entry with the words "(More Reliable)" next to it. This is Apple's suggested speed for this situation.

Homework
Here are some links which will provide details into this subject…

Apple's web site:
http://docs.info.apple.com/article.html?artnum=301551

Another Apple web page:
http://docs.info.apple.com/article.html?artnum=25402

A short overview of things to keep in mind:
http://www.acoustica.com/mp3-cd-burner/support/cd-playback-support.htm

A forum discussion on this subject:
http://forum.digital-digest.com/showthread.php?t=24233

(Some of the information may be talking about "PCs" (not Macs) but the technologies, problems and most solutions are the same for PCs and Macs.)

A wealth of technical information on CDs from this Optical Storage Technology Association (OSTA) web site:
http://www.osta.org/