12.2 DVD Writable and Rewritable
In addition to DVD-ROM, there are
three writable DVD formats—DVD-R(A) for authoring, DVD-R(G) for
general recording, and DVD+R—and three rewritable DVD formats,
DVD-RW, DVD-RAM, and DVD+RW. All DVD writers and rewriters can read
DVD-ROM discs, but each records to its own type of disc, none of
which is fully compatible with any other or with existing standard
DVD-ROM drives and players.
Incompatibility between the various standards has hindered the market
acceptance of all of them, a problem that manufacturers have begun to
address by introducing hybrid devices that read and write more than
one format. For example, Pioneer produces a combination DVD-R and
DVD-RW drive that also writes CD-R and CD-RW, and next-generation
DVD-RAM drives will read and write DVD-RAM, DVD-RW, and CD-R/RW. As
time passes, we expect this trend to continue.
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The DVD Forum has introduced a DVD Multi logo that certifies
compatibility with DVD-R, DVD-RW, and DVD-RAM. (Although
not with DVD+RW—the DVD Forum and the
DVD+RW Alliance don't much like each other.) A DVD
Multi drive or player can play all three formats, and a DVD Multi
writer can write all three formats.
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Here are the competing writable/rewritable DVD formats:
- DVD-R
-
DVD-R (Recordable) was the first recordable DVD standard. DVD-R uses
organic dye technology, and is similar conceptually to CD-R. DVD-R
discs can be read by most DVD-ROM drives and DVD players. DVD-R 1.0
drives shipped in late 1997, cost $17,000 and stored 3.95 GB on a
write-once DVD-R 1.0 disc, which at the time cost $80 each. The
DVD-R1.0 standard is specified by ECMA-279 (http://www.ecma.ch/ecma1/STAND/ECMA-279.HTM).DVD-R
1.9 drives shipped in mid-1999, cost $5,000, stored 4.7 GB on a
write-once DVD-R 1.9 disc (which at the time cost $50 each), and
could also write 3.95 GB 1.0 discs. DVD-R 2.0 drives shipped in late
2000, store 4.7 GB on write-once 2.0 discs (which are copy
protected), and can also write 1.0 and 1.9 discs. DVD-R branched into
two sub-formats in early 2000:
- DVD-R(A)
-
DVD-R(A) (DVD-R Authoring) drives are for professional use, and use a
635 nanometer (nm) laser that can write DVD-R(A) discs but not
DVD-R(G) discs. DVD-R(A) drives can read either type of DVD-R disc,
as can most DVD drives and DVD players. DVD-R(A) drives sell for
$1,500 to $5,000, and DVD-R(A) discs cost roughly twice what DVD-R(G)
discs cost.
- DVD-R(G)
-
DVD-R(G) (DVD-R General) drives are for home use, are particularly
suited to video recording, and use a 650 nm laser that can also write
DVD-RAM discs, although as of June 2002 the only combination
DVD-R(G)/DVD-RAM drive actually shipping is the Panasonic LF-D311.
DVD-R(G) drives can use double-sided discs and incorporate CPRM
(Content Protection for Removable Media) copy protection, which means
that DVD-R(G) drives cannot be used legally to duplicate DVD-Video
discs.
- DVD-RW
-
DVD-RW
(Rewritable) is a newer Pioneer technology, based on DVD-R but using
phase-change erasable media similar conceptually to CD-RW. DVD-RW was
formerly called DVD-ER and DVD-R/W before Pioneer settled on the
DVD-RW designation. Like DVD-R, DVD-RW stores 4.7 GB per disc and
produces discs readable by many DVD-ROM drives and players, although
the lower reflectivity of DVD-RW discs fools some DVD-ROM players
into thinking they're reading a dual-layer disc.
Recent DVD-ROM drives or players that have difficulty with DVD-RW
discs can often be upgraded to support DVD-RW simply by installing
updated firmware.
There are three distinct types of DVD-RW discs, all of which store
4.7 GB and can be rewritten about 1,000 times. DVD-RW 1.0 discs were
used with the first DVD-RW drives shipped in Japan, are seldom seen
outside Japan, and have compatibility problems with some drives.
DVD-RW 1.1 discs do not support CPRM and so cannot be used for
copying any CPRM-protected original DVDs. DVD-RW 1.1B discs support
CPRM, and can be used to copy CPRM-protected original DVDs (but only
if the producer of the original DVD has encoded the disc to permit
copying, and only then by adhering to the restrictions enforced by
the CPRM encoding on the original disc). In effect, this means that
commercial DVD movies cannot be copied on a DVD-RW drive other than
by using special software—the use or even possession of which
is illegal in some jurisdictions—to bypass the copy protection.
In April 2001, Pioneer began shipping the sub-$1,000 DVR-A03 drive,
which despite its name writes DVD-R(G) discs rather than DVD-R(A)
discs. In addition to DVD-R(G) discs, the DVD-A03 writes DVD-RW,
CD-R, and CD-RW, and by June 2002 had dropped to a street price of
about $500. This is the same drive that Apple and Compaq bundle with
their own model designations with some Mac and Presario models.
Because there is nothing inherently more expensive about DVD-RW
technology, it is possible that this broad-based support will reduce
the price of drives and media dramatically, making DVD-R (and
particularly DVD-RW) a viable competitor with other recordable DVD
standards. As of June 2002, DVD-R(G) disks sold for $5 to $15 each,
and DVD-RW discs for $15 to $20 each.
DVD-R and DVD-RW remain the almost exclusive preserve of Pioneer,
although repackagers such as QPS sell DVD-RW drives under their own
labels. Although Ricoh, Sony, and Yamaha announced in 2000 that they
planned to ship DVD-RW drives in 2001, as far as we can determine
none had actually shipped such drives by mid-2002 (although Sony has
installed DVD-R drives in some Vaio models).
- DVD-RAM
-
The DVD-RAM standard is backed by Hitachi, Matsushita (Panasonic),
and Toshiba, which until late 2001 had the writable DVD market all to
themselves. Although DVD-RW and DVD+RW drives became widely available
from several vendors by late 2001, relative to those writable DVD
standards, DVD-RAM has several advantages for use in computers,
including superior defect management, use of zoned CLV (PCAV) for
faster access, and greater media protection via a cartridge. A
DVD-RAM disc can be rewritten at least 100,000 times.
First-generation (DVD-RAM Book 1.0)
DVD-RAM drives began shipping in mid-1998, and used a mix of
phase-change and magneto-optical technology to record 2.58 billion
bytes per side on rewritable media. These discs are not readable by
older DVD players and drives, although some recent DVD-ROM drives
will read them. Second-generation (DVD-RAM Book 2.1) DVD-RAM drives,
which began shipping in late 2000, read and write both original
2.6/5.2 GB DVD-RAM discs and 4.7/9.4 GB DVD-RAM discs.
Several DVD-RAM media types are available. Single-sided 2.6 GB discs
are available in Type 1 (sealed) or Type 2 (removable) cartridges.
Single-sided 4.7 GB discs are available only in Type 2 cartridges.
Double-sided 5.2 GB and 9.4 GB discs were originally available only
in Type 1 cartridges, but are now available in Type 2 cartridges as
well. Although using a cartridge has advantages for computer use, a
cartridge raises two issues. First, because standard DVD players and
drives cannot physically accommodate a cartridge, DVD-RAM discs
enclosed in cartridges cannot be read on these devices. Second, once
removed from their cartridges, single-sided DVD-RAM discs in Type 2
cartridges may no longer be reliably recorded in some drives,
particularly older models, so removing discs from their cartridges
may effectively turn them into write-once media. Most DVD-RAM drives
will not write reliably (if at all) to a bare disc, but recent
DVD-RAM drives will generally write reliably to a disc that has been
removed from and then reinstalled in its cartridge.
DVD-RAM 1.0 (2.6/5.2GB) standards are specified by ECMA-272
(http://www.ecma.ch/ecma1/STAND/ECMA-272.HTM)
and ECMA-273 (http://www.ecma.ch/ecma1/STAND/ECMA-273.HTM),
released in June 1999 and February 1998, respectively. DVD-RAM 2.0
(4.7/9.4GB) standards are specified by ECMA-330 (http://www.ecma.ch/ecma1/STAND/ecma-330.htm)
and ECMA-331 (http://www.ecma.ch/ecma1/STAND/ecma-331.htm),
both released in December 2001.
- DVD+RW
-
Originally called DVD+RW, changed to +RW when
the DVD Forum objected, and later changed back, DVD+RW is backed by
Hewlett-Packard, Mitsubishi Chemical, Philips, Ricoh, Sony, Thomson
Multimedia, and Yamaha. Although all are members of the DVD Forum,
the DVD+RW standard is not recognized by that organization.
First-generation DVD+RW drives were to use phase-change rewritable
technology to store 2.8 GB per side. DVD+RW manufacturers formally
abandoned the 2.8 GB DVD+RW 1.0 standard in late 1999, without ever
having produced drives in commercial numbers. Second-generation
DVD+RW drives, which finally shipped in volume in late 2001, expand
capacity to 4.7 GB per side and support writing CD-R and CD-RW discs.
DVD+RW discs are readable by most recent DVD players and DVD-ROM
drives, although as with DVD-RW the lower reflectivity of DVD+RW
discs causes some devices to mistake them for dual-layer DVD-ROM
discs and therefore refuse to read them. A firmware update solves
that problem in many drives and players that experience it.
DVD+RW backers claim two primary advantages for DVD+RW relative to
DVD-RAM. First, like CDs, DVD+RW discs do not use a cartridge. This
should ultimately translate into lower costs for drives and media,
and allows DVD+RW discs to physically fit standard drives. It also
makes DVD+RW drives a viable alternative for laptop systems, which
the cartridge-based DVD-RAM drives are not. Second, DVD+RW drives use
CLV access for sequential data (like movies) and CAV access for
random data, which allows higher performance. Balanced against this
is the fact that DVD+RW discs can be rewritten only 1,000 times,
versus 100,000 for DVD-RAM.
More information about DVD+RW is available at
http://www.dvdrw.org. The obsolete and
abandoned +RW standard is specified by ECMA-274 (http://www.ecma.ch/ecma1/STAND/ECMA-274.HTM). The
current DVD+RW standards are maintained by the DVD+RW Alliance
(http://www.dvdrw.org).
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DVD+R
-
DVD+R is the write-once version of DVD+RW, which provides the
equivalent of a 4.7 GB CD-R disc. DVD+R discs began shipping in
mid-2002. Although the DVD+RW Alliance and DVD+RW drive makers had
originally announced that DVD+RW drives would require only a firmware
upgrade to support DVD+R discs, in fact it turns out that DVD+RW
drives produced prior to spring 2002 are incapable of supporting
DVD+R discs, and the only way to
"upgrade" them to add DVD+R support
is to replace the drives. Like CD-R and DVD-R before it, DVD+R discs
use organic dye technology, so nothing other than patent royalties
prevents DVD+R (and DVD-R) discs from eventually falling to prices
nearly as low as CD-R discs.
It's clear that the competition to become the
mass-market writable DVD standard is a three-horse race, but it is
uncertain which will ultimately triumph. DVD-RAM has been shipping
since 1998, is now well into its second generation, is an official
standard of the DVD Forum, is backed by Hitachi, Panasonic, and
Toshiba, and has distinct advantages for recording data. DVD+RW is
not recognized by the DVD Forum, but is backed by HP and Sony, and
has advantages for recording video. With only Pioneer backing it,
DVD-R/RW was a dark horse until Apple and Compaq began bundling
DVD-RW drives with some of their systems, making it possible that
DVD-RW will become a mainstream technology.
Here's our take on the competition: DVD-RW and
DVD+RW are inherently compatible enough with each other that we think
the two standards will merge. Unless market considerations prevent
it, we think most drive manufacturers will begin producing hybrid
drives that write DVD-RW and DVD+RW interchangeably. One or the other
(or both, as a merged standard) will become the standard for
recording video, but neither is best suited for desktop data storage.
We think DVD-RAM will continue to dominate that market.
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All these technologies are legally useless for
duplicating DVD-Video discs (although very few technical hurdles
exist and many people already do it on a regular basis). Laws like
the Digital Millennium Copyright Act (DMCA) and standards like CPRM
(Content Protection for Removable Media) have effectively eliminated
Fair Use provisions of traditional copyright. You can use these
drives to store data or video that you have produced, but
not as a digital VCR or to back up your
DVD-Video discs, at least without breaking the
law. Movie industry lobbyists are fighting desperately to
make sure you don't have that option.
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12.2.1 Read/Write Compatibility
Table 12-2 lists read/write compatibility between
various types of DVD drives with CD and DVD media. Drives are in the
heading row; media types are in the left column. The first circle
indicates read-compatibility and the second write-compatibility. An
asterisk on either or both sides of the slash means some but not all
drive models of that type read and/or write the media type in
question, possibly with limitations, which may be drive- or
media-specific. For example, only some recent DVD-ROM drives can read
DVD-RAM media, and some DVD-ROM drives cannot read DVD-RW media
because they mistake them for dual-layer DVD-ROM discs.
Compatibility may vary by drive manufacturer. For example, a DVD-ROM
drive made by a member of the DVD-RAM group may read DVD-RAM discs,
but is unlikely to read DVD+RW discs. Conversely, a DVD-ROM drive
made by a member of the DVD+RW group may read DVD+RW discs, but is
unlikely to read DVD-RAM discs.
12.2.2 Choosing a Writable DVD Drive
You take a
risk no matter which of the three competing technologies you choose.
Whichever you buy, there's a chance it will be
orphaned if the market chooses one of the others. So which of these
drives should you buy?
If you need fast, reliable, high-capacity optical storage for data
and CD-RW is too small, get a DVD-RAM drive. It
won't write CD-R or CD-RW, but otherwise does it
all. DVD-RAM is the best choice if the drive and the data it stores
will be used on one computer, or if you will be transferring large
amounts of data between computers that both have a DVD-RAM drive. The
downside to DVD-RAM is that it uses a cartridge. If you need to read
the data in a DVD drive other than a DVD-RAM drive, you must remove
the disc from the cartridge. Even then, most DVD-ROM drives (except
recent models from Hitachi, Toshiba, and other DVD-RAM supporters) do
not read bare DVD-RAM discs reliably, and no DVD player we know of
will read the DVD-RAM disc. And, once you have removed the DVD-RAM
disc from the cartridge, it may not be writable even after you put it
back in the cartridge. In short, DVD-RAM is the best solution for
storing large amounts of data, but only if you will never need to
read that data in any system that does not have a DVD-RAM drive.
If you need a DVD writer that produces discs that can be read by most
recent DVD-ROM drives, get a DVD+RW drive. DVD+RW uses bare discs
rather than cartridges, so it's easy to move discs
between the DVD+RW drive and standard DVD-ROM drives. Some
early-model or inexpensive DVD-ROM drives may have problems reading
discs written by a DVD+RW drive, but general compatibility is much
higher for DVD+RW discs than for DVD-RAM discs. But in exchange for
that convenience and compatibility, you pay a price. DVD+RW has much
less robust error detection and correction than DVD-RAM, which means
that DVD+RW is an inferior choice for storing data.
The only reason we can think of to buy a DVD-R/RW drive is if you
need to be able to write discs that can be read by other DVD-R/RW
drives. We think DVD-R/RW is the poorest of the three choices for
storing data, although it has undeniable advantages for recording
video. Still, this is a book about PC hardware, so on the assumption
that you want a writable DVD drive as a data storage device, we
recommend avoiding DVD-R/RW.
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