CD-RW Recording FAQ
posted: June, 2 2003
By Jeff Sauer & Matt McMakin
We know you've got questions about CD-RW, especially about how it compares to regular CD recording, and its compatibility with various players. CD-RW is one of the hottest topics newsletter readers ask about. So we've collected all the answers for you in this handy guide. Read on to become a CD-RW expert!
What is CD-RW?
Once informally dubbed "CD-Erasable," CD-RW is the official acronym for CD-ReWritable. CD-RW uses a phase-change technology that allows a drive's laser to change the state of the recording layer and thus the physical properties of a disc in order to write and rewrite data to the same disc. CD+RW is a slightly different physical recording format supported by certain drive hardware, but the discussion here applies to both CD-RW and CD+RW.
What does the phase change change?
To the casual eye, CD-RW discs look much the same as CD-ROM or CD-R discs, but they are made of an alloy base and a polycrystalline recording layer. That polycrystalline layer can exist in either an amorphous or crystalline state, similar to how water can exist as either liquid or solid ice. When recording data, a CD-RW drive's laser literally heats the polycrystalline and changes it to an amorphous state. At lower power levels, the laser "erases" the disc, returning the polycrystalline to its crystalline phase. At its lowest power level, the laser simply reads data, much like a CD-ROM drive.
How does CD-RW compare with CD-R?
While CD-R, or CD-Recordable, is a "Write-Once, Read-Many" format, CD-RW discs have the potential to be written, then erased, then written to again. CD-RW media is generally more expensive than that of CD-R (from 50 to 200 percent more, although CD-Rs are often extremely inexpensive when on sale), but are reusable. Burning CD-R discs is faster, though how much depends on the specific drive.
Which CD type is best to use when burning computer backups, CD-R or CD-RW?
For permanent archiving, CD-R is preferable. Discs are less expensive and cannot be erased accidentally. However, CD-RWs are excellent for frequent rewriting of your newest data over previous backups, in addition to intermittent full archives. If speed is an issue, CD-Rs are faster.
Can I use a CD-RW disc to make audio CDs?
Relatively few audio CD players, especially those manufactured prior to 2000, can read CD-RW discs. Some newer players, particularly DVD/AudioCD players, carry a CD-RW compatibility label and can play audio CDs recorded onto CD-RW media. However, CD-RW drives can also burn CD-R discs for creating audio CDs. So it's best to use CD-R for audio unless you know your player supports CD-RW, and you expect to want to rewrite the disc in the future.
Where can you play back CD-RWs?
Generally, CD-RW discs can only be played back in CD-RW drives, "MultiRead" CD-ROM drives, and specific DVD players carrying the CD-RW compatibility logo. CD-RW drives, on the other hand, can read and write CD-Rs and read CD-ROMs and Audio CDs.
Do you need to "format" a CD-RW first? How?
If you are writing standard ISO 9660 data to a CD-RW using Easy CD & DVD Creator, there is rarely a need to format a disc prior to use. A small percentage of new discs, however, come pre-formatted for UDF and these would need to be erased prior to use in Creator. Indeed, the more common usage of CD-RW discs is as UDF-formatted discs that appear in the Windows Explorer as typical disc volumes, supporting drag-and-drop and deleting individual files. Easy CD & DVD Creator 6.0 includes a packet-writing application called Drag-to-Disc that is available from the Creator home window, and from the taskbar or Start menu. Drag-to-Disc allows users to record information to a CD or DVD simply by dragging and dropping files to the Drag-to-Disc application icon, or to the drive letter of your recorder. Drag-to-Disc will automatically format a CD when you first copy information to it.
What is the difference between recording a CD-RW within Toast on an Apple computer and use on a Windows-based system?
CD-RW discs were designed to be erasable: to burn a disc, but then have the opportunity to erase and reuse the same disc again. Toast and Roxio's Easy CD Creator for Windows support that use. In Windows, Roxio's DirectCD (a UDF formatting utility included within Easy CD Creator), can format CD-RW discs as UDF volumes which appear in the Windows Explorer as if they were a floppy or hard disk drive, supporting drag-and-drop functionality and the ability to delete individual files. At this time there is no DirectCD for the Mac OS, but Roxio is always is always working to improve Toast to meet customers' CD and DVD burning needs.
What is UDF?
Universal Data Format is an ISO-compliant file system, endorsed by the OSTA (Optical Storage Technology Association), and used by packet-writing and other optical recordable disc technologies, like DVD. Drag-to-Disc uses UDF 1.5 and packet writing to give CD-R and CD-RW drives the effective usability of a large floppy disk. Computers require UDF reading software in order to read UDF-formatted discs.
What is packet writing?
Packet writing is a method of writing data in small increments surrounded by run-in and run-out blocks, rather than in a single large block as was the case with early CD burning. Packets can be a variable or fixed size depending on the application. The small increments are what allow the CD recorder to be used like a floppy drive.
What is the difference between Format, Erase, and Quick Erase?
For Mac OS users, formatting and erasing are much the same thing for CD-RW and generally refer to the process of erasing a CD-RW and returning the entire disc to its native crystalline phase, thus removing all data. Quick Erase erases only the directory information on a disc, leaving other data sectors alone. By erasing that directory, however, all data becomes inaccessible. (For Windows users, "formatting" often refers to formatting a CD-RW disc as a UDF volume.)
Can I erase/replace individual files on a CD-RW in Toast or the Mac Finder?
No. While this functionality is available on Windows using Roxio's DirectCD, there is currently no Mac OS equivalent.
Do I have to "finish" a CD-RW disc?
Any finishing is done automatically in Toast.
In general, what are the things to note about using CD-RWs within Toast, instead of CD-Rs?
Using CD-RWs in Toast is very much the same as using CD-Rs, with the exception of being able to erase discs and start over. Most confusion comes from the two formatting methods for CD-RW that are available on Windows: treating them as "CD-R-like" ISO 9660 volumes in Easy CD Creator or formatting them for UDF with DirectCD and working with them in the Windows Explorer. UDF discs created in Windows can be read by a Mac OS computer with UDF Volume Reader software available for free download from Roxio's online support pages. Go to http://www.roxio.com/en/support/index.jhtml, follow the link for Software Updates, and see the section at the bottom of the screen..