Hardware Reference
In-Depth Information
being semi-transparent to permit recording on the second layer. Because of the lower re-
flectivity of the top layer, some DVD-ROM drives cannot read DVD-R DL media.
Note
If you are unable to read DVD-R DL media with a DVD drive, try using the Layer Jump Re-
cording (LJR) recording method in your DVD mastering software if your drive and software
support it. LJR alternates between recording layers during the writing process, rather than
filling one layer before writing to the other layer. This permits a disc to support multisession
recording and is intended to make it easier for DVD drives to read dual-layer media.
DVD-R DL media is currently available in 4x speed from a relatively small number of
suppliers, although some rewritable DVD drives support faster write speeds.
DVD-RW
The DVD Forum introduced DVD-RW in November 1999. Created and endorsed origin-
allybyPioneer,DVD-RWisbasicallyanextensiontoDVD-R,justasCD-RWisanexten-
sion to CD-R. DVD-RW uses a phase-change technology and is somewhat more compat-
ible with standard DVD drives than DVD-RAM. Drives based on this technology began
shipping in late 1999, but early models achieved only moderate popularity because Pion-
eer was the only source for the drives and because of limitations in their performance.
ThemostcommontypesofDVD-RWmediasupport2xspeeds,although4xand6xmedia
is also available. Drives supporting 2x/4x and faster media have several advantages over
original 1x/2x DVD-RW drives, including these:
•
Quick formatting
—1x/2x drives require that the entire DVD-RW disc be formatted
before the media can be used, a process that can take about an hour. 2x/4x and faster
drives can use DVD-RW media in a few seconds after insertion, formatting the media
in the background as necessary. This is similar to the way in which DVD+RW drives
work.
•
Quick finalizing
—2x/4x DVD-RW drives close media containing small amounts of
data (under 1GB) more quickly than 1x/2x drives.
•
Quick grow
—Instead of erasing the media to add files, as with 1x/2x DVD-RW
drives, 2x/4x and faster DVD-RW drives can unfinalize the media and add more files
without deleting existing files.
However, most DVD-RW drives still don't support lossless linking, Mount Rainier, or se-
lective deletion of files—all of which are major features of DVD+RW.
