Sarasota PC Monitor
Tech Talk (12/01)
Burn, Baby, Burn!
by Brian K. Lewis, Ph.D.*
Member of the Sarasota Personal Computer Users Group, Inc.It seems that just about every computer I've seen lately, has a CD-burner installed. It also seems that although many people would like to burn CD's, they too often end up with a nice shiny coaster. So let's go over some basics on CD writers, writing software and maybe a few tips as well.
First let's take a look at some of the terminology related to CDs and CD writing. Blank CDs are sold as CD-R and CD-RW. The CD-R designation means that the CD can be written to once and then read many times. That assumes that the CD is "closed" at the end of the writing session. If it is not closed, additional data can be written on it, up to the full capacity of the disk. When data is written to a CD-R in several sessions, it is referred to as "multi-session" writing. CD-RW is the designation for a CD that can be written, erased and rewritten multiple times. These are useful for recording information that is of a temporary or changing nature.
Another difference in these two disks is the cost. CD-Rs are now quite cheap when bought in quantity, fifty cents per disk or less. I recently saw some on sale at 50 disks for $4.99, after multiple rebates. The speed of writing to a CD-R is also much faster than writing to a CD-RW. You will for example, see CD burners rated as 20X-16X-40X. The first number (20X) is the speed of writing a CD-R, the second number (16X) is the speed of writing a CD-RW and the last number is the read speed. If you want to translate this to actual data transfer speeds, then multiply the X number by 153.6 KB per second. That means that a 20X drive has a maximum data transfer rate of 3.072 MB per second. That is much slower than most of the new multi-gigabyte hard drives which can transfer data at a sustained rate of 40MB/s.
The data that is written to a CD follows a continuous spiral track starting at the center of the disk and continuing to the outer edge. This is quite different from the pattern used on hard disks. (On a hard disk the data is written to concentric tracks starting at the outer edge.) The spiral track on a CD is 3.59 MILES long and can contain up to 640 MB of data or 74 minutes of music.
Commercial CDs are manufactured by stamping a data image into a polycarbonate plastic base. It is then coated with aluminum to make a reflective surface. This is covered with a thin lacquer coat and the label. The distance from the label to the data layer is far less than the distance from the data layer to the clear polycarbonate surface. Thus damage to the label surface is far more likely to damage the data than would any damage to the clear surface. In addition, there are polishing and cleaning kits that can restore the clear surface. The same is not true of damage to the label surface. So in handling CDs, beware of damaging the label surface. That includes writing on the label with anything containing harsh chemicals.
There is evidence that a CD can retain its data for at least ten years, providing it is not subjected to any temperature extremes. Some of the "experts" expect them to be good for 50-100 years. That remains to be seen. However, the life span of the data does seem to be related to the color of the CD-R media. A gold reflective layer with a green dye layer is rated at a 10-year life span. Those with a silver reflective layer and a green dye layer are rated at 100 years. So select your CD blanks based on how you plan to use them. If you need to keep data intact for the next century, then get the more expensive blanks.
There are three current standards for writing CDs. They are the Red book (audio CD), Orange book (current CD-R & CD-RW formats) and Photo CD. Most CD writing software conforms to the specifications in these three formats. You will frequently note on the blank CD packages a statement that the disks conform to the Orange book or Orange Book II standards.
The Orange book defines single-session, multi-session and packet writing of CDs. The single-session format specifies a lead-in of approximately 9.2MB of data or 1 minute of time. The lead-out at the end of the recording is 1.5 minutes or 13.8MB. The disk is then closed and cannot be recorded further. This also relates to "disk at once" recording. The lead-in, data, lead-out and disk closure occur in a single operation.
A multi-session format allows sequential recording sessions, which can occur at any interval. In other words, today you copy a few files. Tomorrow you copy some more, etc. Each recording session has its own lead-in and lead-out entry. The lead-in entry indicates that it is a multi-session recording and gives the next writeable address. In theory, 48 sessions on a multi-session disk would fill it with lead-in/lead-out entries and no data.
The track-at-once format can be used with a multi-session CD. In this format each track is individually written until the session is closed. Additional sessions can be added to the disk as long as the disk is not closed. In this format tracks are automatically separated by a two second gap. The CD written with this format can't be read in a CD-ROM until the disk is closed.
The least understood format is packet writing. Generally, to use packet writing you must have CD writing software that specifically supports this format. Such software is DirectCD (Roxio), FileCD (NTI), etc. These applications will first format the CD, which can be a CD-R or a CD-RW. The formatting process the Universal Disk Format (UDF) file system. The CD then appears to the computer as a large floppy drive. Consequently, files can be copied to the disk using the copy command, or "drag & drop" in Windows Explorer. Files can also be erased. On a CD-R disk, the space taken by the file cannot be reclaimed, but the file will no longer be available. On a CD-RW, the space taken up by the erased file will be reclaimed and reused. Because of this difference, most packet writing is done using CD-RW disks. You also need to realize that using the packet writing format, the CD can not be read by a CD-ROM drive in a computer that does not have packet writing software. Windows does not support the UDF CD format. Most packet writing software will allow you to convert the CD back to a format that can be read by any CD-ROM. However, it must be reconverted before any further writing or erasing can be done.
Some packet writing software gives you the option of formatting your CD in either ISO 9660 format or the UDF format. If you expect to share your CD with others, then the ISO 9660 format would be the best choice. The reason for this is that ISO 9660 is a standard that can be read by computers using Windows, Unix, Linux or Apple Macintosh operating systems. This format is the International Standard that was developed from the original CD format known as the High Sierra format. It requires that file names be 8+3 characters or less, directories are limited to eight levels and files must be contiguous on the disk. Its main appeal is the ability for the CD to be read by computers that don't have packet-writing software installed.
You may also see references to the Joliet format. This is an extension of the ISO 9660 format that allows long filenames, among other changes.
I have heard a number of members complaining about problems in burning CDs. There are a few tips to keep in mind. I discussed turning on DMA for your hard drives some time ago. The major advantage being that you reduce CPU usage when reading/writing to your hard drive. The same is true for your CD writer. If possible, you should turn on the DMA setting in the device manager for this drive. However, some CD writing software will not run when you turn on the DMA setting. In general, software that will not work with DMA needs to have everything turned off except Explorer and Systray. This is frequently true of the software that is supplied with the CD-RW drives. There is software available that runs with DMA turned on and automatically shuts down your screen saver and/or your power management settings. All you have to do is temporarily turn off your anti-virus software. And sometimes even that isn't necessary. Since this software isn't supplied with the drive, you will have to look for it and buy it separately.
Another program that can interrupt the data stream during CD recording is the Microsoft Office FastFind. That usually loads in your startup folder and should be turned off whenever you are burning CDs. If you are using a cable modem, turn off your automatic mail collection and anything else that might try to access the Internet. The key is, don't try to run any other programs, including Solitaire, while you are burning a CD. Go get a cup of coffee and leave your computer alone during this process. If your CD-ROM and your CD writer are connected to the same IDE cable you should not try to copy a CD directly. Instead, you should copy the CD to a temporary folder on your hard drive and then burn it to the CD from the hard drive. When you try to read/write to two different drives using the same cable, you may have data errors or buffer under-run problems.
Finally, when you buy CD-R or CD-RW blanks, try to match them with the speed of your CD writer. They should be rated to burn at the maximum speed capability of your drive or faster. Otherwise you will have to reduce your writing speed to prevent writing problems.
For more information on CD writers, software and tips try these Websites:
http://www.mrichter.com/cdr/primer/primer.htm
With the proper software, CD burning can be a solid, reliable process. Like everything else related to my computer, I wonder how I managed to get along without it for so many years.:
*Dr. Lewis is a former University and Medical School professor. He has more than 20 years of experience working with personal computer hardware and software. He can be reached via e-mail at brian_klewis@hotmail.com or voice mail at 941-925-3047. :
Copyright 2001. This article is from the December 2001 issue of the Sarasota PC Monitor, the official monthly publication of the Sarasota Personal Computer Users Group, Inc., P.O. Box 15889, Sarasota, FL 34277-1889. Permission to reprint is granted only to other non-profit computer user groups, provided proper credit is given to the author and our publication. We would appreciate receiving a copy of the publication the reprint appears in, please send to above address, Attn: Editor. For further information about our group, email: admin@spcug.org/ Web: http://www.spcug.org/The Sarasota Personal Computer Users Group, Inc. has 1,300+ members and was established in 1982. We are members of the Assoc. of PC User Groups (APCUG), the Florida Assoc. of PC Users Groups, Inc., and we are members of the America Online Ambassador Program.
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