DVD Demystified

232
Figure 5.6
DVD cartridges
DVD+RW
Chapter 5
DVD+RW is an erasable format based on CD-RW technology. It is not
supported by the DVD Forum, even though the companies backing it (primarily
Hewlett Packard, Philips, and Sony) are members of the DVD
Forum.
The DVD+RW format uses phase-change media with a high-frequency
wobbled groove that provides highly accurate sector alignment during
recording, thus eliminating linking sectors. Marks are written in the
groove only. Unlike the other writable formats, there is no embossed
addressing information. The groove wobble is frequency modulated to
carry addressing information called address in pregroove (ADIP).
DVD+RW discs can be recorded in either CLV format for sequential video
access (read at CAV speeds by the drive) or CAV format for random access.
CAV-formatted discs are not compatible with most standard DVD readers.
CLV-formatted discs hold 4.7 billion bytes (4.37 gigabytes). CLV formatting
is used for audio and video recording, whereas CAV formatting is
designed for computer data storage. DVD+RW media can be rewritten
about 1000 times. Most DVD+RW drives also will write to CD-R and CD-
RW media.
The lack of linking sectors, the option of no defect management, and CLV
formatting make DVD+RW discs compatible with many existing DVD read-