To the teens . . . More on DVD-RAM standards. Sorry Nikita, no shoe pounding............
japanbiztech.com
DVD-RAMs Confused by Divided Standard
November 17, 1997 (TOKYO) -- Although the DVD Forum
stipulated a standard for DVD-RAMs at the end of the summer of
1997, competitive specifications for rewritable optical disks for mass
storage continue to be released, causing market confusion.
Sony Corp., which introduced in September its Phase-Change
ReWritable (Phase-Change RW) standard to counter the DVD-RAM,
is preparing to release the DVD+ReWritable (DVD+RW) disk drive
that conforms to the new standard in the spring of 1998.
Following Sony, Pioneer Electronic Corp. announced its own
DVD-R/W standard at the International Symposium held in late
October.
In light of these developments, a group promoting the DVD-RAM that
includes Toshiba Corp., Hitachi Ltd. and Matsushita Electric Industrial
Co., Ltd., has begun to emphasize development of a next-generation
4.7GB disk drive even before it begins marketing the current 2.6GB
disk drive.
As a result, four different kinds of rewritable optical disk drives, all of
which can read DVD-ROM disks, will go on the market from late
1997 through 1998. They are: DVD-RAM, Phase-Change
ReWritable, DVD-R/W and AS-MO (advanced storage
magneto-optical disk).
Different Technological Concepts in the Background
All of the disk drives built using DVD-RAM, Phase-Change
ReWritable and DVD-R/W are designed to read DVD-ROM disks.
This is because all the makers share the same view that DVD-ROMs
will become the software distribution media that replace CD-ROMs in
the future.
In fact, the basic specifications, such as the disk appearance and laser
wavelength, are common to the DVD-RAM and Phase-Change
RW(See table). A big difference is found in the data writing technique,
including the recording method and the address signal method, and the
resultant ease-of-use of the disks.
As a recording method, the DVD-RAM uses a land-groove method
and the Phase-Change RW a groove method. The groove method is
compatible with the DVD-ROM drive, but it can't get a higher density
than the land-groove method.
Sony said the storage capacity of the Phase-Change RW can be
extended from the existing 3GB to 4.7GB. It will, however, be difficult
to make the capacity larger than that. And there's a strong possibility
that the laser wavelength will have to be changed from the existing
650nm to 635nm when the capacity is expanded to 4.7GB.
The Phase-Change RW has a disadvantage in storage capacity, but it's
strong point is the address signal method and disk handling. The
Phase-Change RW uses a groove of wobble to record the address
information in the same fashion as the CD-R/RW developed by Sony
and other makers.
By contrast, the land-groove method for the DVD-RAM uses a
dedicated sector, because in principle it cannot use the wobble to
record the address information.
The DVD-RAM disk is made entirely unusable by a defect caused on
an address sector, and therefore, requires all the disks to be inspected
for the surface in production, which makes the disk production cost
higher by about 5 percent to 10 percent. The DVD-RAM disk has to
be used basically in the condition in which it is packed in a cartridge,
but the Phase-Change RW disk is easier to use because it can be used
always on an as-is basis.
Phase-Change RW Supported by HP
Historically, competitive standards have often appeared in the recording
media field, the DVD-RAMs are no exception. What is noteworthy in
this case is that Sony, which took part in the work to determine the
universal specification standard as a member of the DVD-RAM
working group, has announced its own new standard (See chart).
The DVD-RAM working group was organized in January 1996, when
two plans were discussed: the land-groove method led by Matsushita
Electric and the track wobbling method led by Sony.
Finally Hitachi, which chaired the working group, proposed the
wobble-land-groove method as a compromise of the two plans. The
compromise plan was approved with three nos at the vote carried out
in autumn 1996, and was determined at the general conference of the
DVD Forum held in the spring 1997, when two votes were reserved.
The compromise plan was far different from Sony's, although the
wobble was applied. The cartridge shape is like the PD, Matsushita's
rewritable optical disk, which means that Matsushita's proposal was
given strong consideration.
In addition, the presence of U.S.-based Hewlett-Packard Co. (HP)
played an important role in the background when Sony decided to
commercialize the Phase-Change RW product. HP, which had
supported Sony's plan, continued discussions independently with Sony.
In March 1997, three companies, including Sony, proposed the
Phase-Change RW specifications to the European Computer
Manufacturers Association (ECMA).
Makers supporting the Phase-Change RW are members of the
Yokohama Group, which is promoting the CD-R/RW. Notably,
Yamaha Corp. is active in the promotion, and plans to release its drive
before the end of 1998.
DVD-RAM Group Emphasizes Next-Phase Product
With the movements of the Phase-Change RW group, the DVD-RAM
group is in a hurry to establish necessary countermeasures.
In August it aired a 4.7GB product, the same storage capacity as the
DVD-ROM, and the DVD Forum announced a plan to commercialize
it by the end of 1999.
Hitachi made a technology announcement of the 4.7GB DVD-RAM
independently in September, which appears to show its advantage of
having a clear road map of the DVD-RAM.
However, a disk drive with a storage capacity larger than the 2.6GB
DVD-RAM drive is now slated to ship within two years. This may
make users hesitate to purchase 2.6GB products.
DVD-R/W Specifications Akin to DVD-R
Amid an atmosphere of two opposing groups, Pioneer offered its own
DVD-R/W proposal as a third rewritable optical disk option. The
specifications are akin to the DVD-R (See Table). Pioneer chairs the
DVD-R working group and has experience commercializing the
DVD-R product.
Because the DVD-R can be read by existing DVD-ROM drives, there
also is a possibility that DVD-R/W disks will be modified to be read by
first-generation DVD-ROM drives, although the details are unknown.
Data will be recorded in the groove, and address information in the
land. In this case, however, a 635nm wavelength laser will be used to
write data, which will increase the cost and consequently may be
accepted by the market as a business-purpose product.
Table: Part of rewritable optical disk specifications
Click on the link to see the charts. |
