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DVD Formats - Get a clear Picture?
(By Mok Heng Ngee, Computer Times September 18, 2002)

With prices already below the $1,000 mark, have you considered getting a DVD burner for your PC? If so, do some research first, because a DVD created by certain burners may not run on some DVD players.

Distributing your data or amateur home videos on DVDs seems like a cool idea, especially since home DVD players are getting common. A single DVD, or digital versatile disc, can store between 4.7 GB and 17 GB of data, or seven times more than a 650 MB CD-ROM.

The DVD movies which you buy are encoded in a format called DVD Video, which can be read by all home DVD players and PC DVD drives. Some software makers are also starting to distribute their applications on a single DVD-ROM instead of multiple CD-ROMs.

While the two read-only DVD formats -- DVD Video and DVD-ROM -- are mature today, there is a technology war being fought over the DVD recordable formats.

Shop around for a DVD burner and you will come across models supporting different recording formats: DVD-RAM, DVD-R, DVD-RW, DVD+R and DVD+RW. And yes, the plus sign is not a typo mistake.

Check the facts about compatibility before you settle for a DVD burner or player.

DVD Burners: How they compare:
Read-only Formats
DVD Video Used to commercially distribute movies which can be played on home DVD players Capacity is 17 GB (if two layers on both sides are used), huge capacity is big advantage over CD-ROM as more movie details can be stored.
DVD-ROM Used to store/ distribute data in the same way CD-ROMs are used. Similar to DVD Video, but with computer-friendly file formats.
Recordable formats
DVD-R and DVD+R Used for storing data or movies. Write-once only; non rewritable Two versions of DVD-R: DVD-R(G) and DVD-R(A). (DVD+R is relatively new in the market)
DVD-RW Used for storing data or movies. Rewritable up to 1,000 times. Supports only CLV* rotation method; constant bit rate; native Mac support; may be able to read DVD-RAM disc.
DVD+RW Same as above Defect management; supports both CLV and CAV** rotation methods; variable bit rate; will be supported by Mount Rainier file system in Windows Longhorn.
DVD-RAM Used as a virtual hard disk/ shared storage on PCs. Rewritable up to 100,000 times. Features random read-write access; capacity is 2.6 GB to 4.7 GB per side.
* CLV or Constant Linear Velocity: The disc is read/ write at a constant speed regardless of which part of the disc is being accessed.
** CAV or Constant Angular Velocity: The disc is read/ write at different speeds depending on which part of the disc is being accessed.


Two camps

From the names, it is obvious that DVD-R and DVD+R are write-once formats.

Like their CD-R counterparts, DVD-R/+R discs can only be recorded upon once.

On the other hand, DVD-RW and DVD+RW are rewritable formats, which support up to 1,000 rewrites.

The fact is that the DVD-R/-RW and DVD+R/+RW specifications originated from different camps, and are backed by equally influential industrial bodies.

With members including Hitachi, Matsushita (Panasonic), Toshiba and Pioneer, the DVD Forum ( and the Recordable DVD Council are behind the DVD-R/-RW (and DVD-RAM) specifications.

Supporting the DVD+R/ +RW standards is the DVD+RW Alliance ( with leading companies such as Sony, Ricoh, Hewlett-Packard, Philips, Mitsubishi, Yamaha and Thomson Multimedia under the flag.

If you get a DVD-R/-RW burner, make sure you get the corresponding DVD-R or DVD-RW discs only. All five types of recordable media are easily available in Singapore from $8 (for a 4.7 GB DVD-R) to $39 (for a 4.7 GB DVD-RAM).

While both standards record to a 4.7 GB disc, DVD-RW and DVD+RW differ in several aspects. Most DVD-RW burners provide native Macintosh support and can also read DVD-RAM discs.

To make matters more complex, the DVD-R format are sub-categorised into two groups: DVD-R(A), and DVD-R(G) -- the A and G representing "Authoring" and

"General" respectively. The difference is significant since a DVD-R(A) burner may not record to a DVD-R(G) disc and vice-versa.

Virtual hard disk

While you may want to burn your home videos on a DVD-R/-RW or DVD+R/ +RW disc, the DVD-RAM format, which is also supported by the DVD Forum, is geared more towards data storage.

Unlike the other media types, DVD-RAM discs are usually sold in cartridges and feature real random read-write access. You can rewrite data to a DVD-RAM disc for up to 100,000 times. On PCs and Macintoshes, a DVD-RAM drive is very much like a hard drive of a capacity of between 2.6 GB and 9.4 GB.

Compatibility issues

Now comes the tricky part: compatibility. If you are one of those gizmo-geeks who had purchased your home DVD player when it first appeared in the shops, the bad news is that it is unlikely that your player can play movies recorded on DVD-RW/+RW discs, although most DVD-R/+R discs should work.

On the other hand, the newer DVD players and DVD-ROM drives should be able to access data and movies stored on DVD-R/-RW/+R/+RW discs with the exception of DVD-RAM discs. DVD-RAM discs are really only good for data back-up and storage.

Most DVD+RW burners will also be able to write to DVD+R discs. Similarly, most DVD-RW burners will be able to write to DVD-R discs. And almost all DVD-R/-RW/+R/+RW burners will be able to read from any of the recordable media types (except DVD-RAM discs). Most of these (except DVD-RAM burners) should also be able to read from and write to CD-R and CD-RW discs.

The above rules only act as a rough guideline; be sure to ask your dealer about compatibility with the various DVD recording formats.

So, which standard should you invest your dollars in if you really want a DVD burner now?

For data back-up or shared network storage, DVD-RAM is fine, if you ignore the compatibility issues.

For recording home videos, check if the target DVD player supports your chosen format.

Many have likened the rivalry between the two DVD recordable camps to the Sony Betamax versus VHS showdown a couple of decades ago, or the competition between the Iomega Zip disk and the LS-120 SuperDisk.

Nevertheless, in February this year, several major electronic makers agreed on greater cooperation for setting standards when the next generation of blue laser DVDs appear.

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