CHAPTER 13

Writable CDs Chapter 13
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that does a simulated burn of the CD before the actual creation. After the simulation, you’re
warned of any problems before the actual process begins. This is not always foolproof, but it
can help.
■ Small files are harder to use in mastering a CD than large ones because of the excessive drive tracking
necessary to find them and load them. You might want to use the packet writing mode instead if
your drive and software support it.
■ Keep your drives clean and free from dust. Use a cleaning CD if necessary. Dirty drives cause dataread
errors or data-write errors if your recording drive is the dirty one.
■ Don’t multitask. If you run another program during the mastering process, the computer is
forced to perform time-slicing, which causes it to start a process, switch away from it to start the
next process, switch back to the first process, and so forth. This switching process could cause
the recording drive to run out of data because it isn’t receiving data in a steady stream. Forget
about surfing the Internet, playing Solitaire, or creating a label for your new CD during the
burning process if you want reliable mastering on a drive that doesn’t feature buffer underrun
protection.
If you’re still having buffer underrun problems despite taking all the precautions listed here, try dropping
down a speed. Go to the next lower speed and see how you do. Using a lower speed than the
drive is rated for can be frustrating, but it’s preferable to wasting time creating unusable discs.
Recording Software
Another difficulty with CD-R/RW devices is that they require special software to write them. Although
most cartridge drives and other removable media mount as standard devices in the system and can be
accessed exactly like a hard drive, the CD-R/RW drive uses special CD-ROM burning software to write
to the disc. This software handles the differences between how data is stored on a CD and how it is
stored on a hard drive. As you learned earlier, there are several CD-ROM standards for storing information.
The CD-ROM–burning software arranges the data into one of these formats so a CD-ROM
reader can read the CD later.
At one time, CD recording technology required that you have what amounted to a replica of the CD
on a local hard drive. In fact, some software packages even required a separate, dedicated disk partition
for this purpose. You would copy all the files to the appropriate place on the hard drive, creating
the directory structure for the CD, and then the software would create an exact replica of every sector
for the proposed CD-ROM—including every file, all the directory information, and the volume
information—and copy it to the CD-R drive. The result was that you had to have about 1.5GB of storage
to burn a single CD (650MB/CD × 2 = 1.3GB + overhead = 1.5GB). This is no longer a requirement
because most software supports virtual images. You select the files and directories you want to write to
the CD from your hard drive and create a virtual directory structure for the CD-ROM in the software.
This means you can select files from different directories on different hard drives, or even files from
network or other CD-ROM drives, and combine them any way you want on the CD-R. This works
well provided the drives have adequate speed and your drive has a large buffer or features buffer
underrun protection. If you have problems, follow the advice given earlier to overcome slow data
sources.
The software assembles the directory information, burns it onto the CD, opens each file on the CD,
and copies the data directly from the original source. This generally works well, but you must be
aware of the access times for the media you select as data sources. If, for example, you select directories
from a slow hard drive or from a busy network, the software might not be capable of reading the
data quickly enough to maintain a consistent stream to the recorder. This causes the write to fail,
resulting in a wasted disc.