The current state of recordable DVD media formats.

CD-R and -RW continue to be the most widely used removable storage technology because of the extremely low cost of drives, players, and media. However, with prices for DVD hardware and media dropping, the DVD recordable formats are rapidly gaining acceptance for use in document, video, audio, and personal/professional storage.

The prime selling points of DVD are its inherent reliability and massive data storage capabilities--ultimately up to 9.4GB of removable storage with a double-sided disc.

According to Wolfgang Schlichting, IDC's Research Manager, Removable Storage, 2002 will be the year when many consumers will discover the benefits of DVD recording. IDC projects that worldwide DVD media sales will climb from 50 million discs in 2002 to nearly 150 million in 2004.

There are basically two markets for recordable DVD: computer storage and A/V recording. While all of the format developers have focused on providing a single format that will work for both video and computer applications, each DVD format has its strengths and weaknesses

Applications

All DVD media formats share common parameters for use in a wide range of personal and professional applications. The discs look very similar; however, they do not all work in every DVD drive, DVD-Video player, or DVD recorder.

While the DVD formats have important technical differences, Tables 1 and 2 have been developed to help content developers and users determine which media is best for them.

General Format Discussion

DVD-R, a recordable version of DVD-ROM--The DVD Forum has developed specifications for two write-once DVD-R categories--Authoring and General use. Although both types of DVD-R media can be read by nearly all DVD drives and players, technical differences make it impossible to write to DVD-R Authoring media using a consumer DVD-R General system and vice versa. DVD-R General recorders use a 650 nm recording laser wavelength while DVD-R Authoring uses a 635 nm laser. In addition, the General Use media contains content protection technology to prevent users from making bit-for-bit copies of CSS- encrypted entertainment titles (Table 3).

DVD-R for Authoring was designed to meet the needs of professional content developers and software producers. The media is primarily used to create master discs that will be mass produced by software houses, multimedia/video post-production facilities, and archiving.

DVD-R for General Use was developed for business and consumer applications--data archiving and one-time video recording. Delivering 2X write performance, which is equivalent to an 18x CD write speed, the media provides secure recording for volumes of information that cannot be accidentally or intentionally altered. The low storage cost, 100-year data life, and broad compatibility also make DVD-R General media ideal for small-scale distribution of DVD content. DVD-R general discs can be played back by the vast majority of the DVD-ROM drives and video players in use today. Available with street prices as low as $5, the media can be used by DVD-R General drives from Pioneer, Apple, Compaq, Sony, Panasonic, and other leading manufacturers.

DVD+R--The write-once DVD+R specification is an extension of the DVD+RW format supported by the DVD+RW alliance: HP, Philips, Ricoh, Sony, Yamaha, Verbatim/ Mitsubishi Chemical, Dell, and Thomson. Similar in functionality and compatibility to DVD-R General, DVD+R was designed to provide widespread playback on DVD-ROM drives and DVD video players. DVD+R/+RW drives write at 2.4x speed, recording a full DVD disc about 5 minutes faster than 2x writers. DVD+R drives and media provide a reliable, low-cost storage solution for archiving home videos, photos, mixed media presentations, and data that require protection from alteration or erasure. Low-cost DVD+R media will be used withDVD+R/+RW drives and video recorders announced by HP, Dell, Philips, Ricoh, and Sony.

DVD-RW--DVD-RW is officially referred to as a "re-recordable" format by the DVD Forum, but is commonly known as a rewriteable format. Available with a capacity of 4.7GB, DVD-RW media is recorded sequentially, making it ideal for streaming video applications. DVD-RW media contains protection technology that prevents copying of copy-righted content. Users can write to the disc in multiple sessions as long as the disc has not been finalized, but DVD drives and players can only read DVD-RW media after the disc has been finalized. Currently offering 1x write performance, DVD-RW discs can be overwritten 1,000 times. Most legacy DVD-ROM drives and DVD players, especially those produced in the past two years, will read DVD-RW media. Available at street pricing approaching $10, DVD-RW discs are used by drives and video recorders from Pioneer, Compaq, Sony, and other manufacturers.

DVD+RW--Introduced in October 2001, DVD+RW is a rewriteable format developed by the DVD+RW Alliance.Offering 2.4x recording and 1,000 rewrites, the 4.7GB DVD+RW technology is used by consumers for both audio/video and data storage applications. DVD+RW incorporates lossless linking technology, allowing the drive or video recorder to accurately stop and start the writing process, or to replace individual 32kB data blocks. Lossless linking improves compatibility, performance, and ease of use, and permits support of drag-and-drop applications like the Mount Ranier specification (similar to CD-RW functionality). For PC applications, DVD+RW hardware can optionally support CAV (constant angular velocity) recording to enable fast, random-access reading of the disc. With multi-session writing technology, users who have not finalized the disc can quickly add documents, data, and video segments without having to open and close write sessions. By incorporating the +RW specification for defect management, manufacturers ensure that data is accurately written to and read from the disc. DVD+RW media, which is currently available for $10 to $15, is compatible with +RW drives and video recorders from HP, Philips, Sony, Dell Computer, and other leading manufacturers.

DVD-RAM--DVD-RAM (DVD Random Access Memory), the rewriteable format developed by the DVD Forum, provides 100,000 write/rewrite cycles. DVD-RAM features random write/read support, so data, video, and audio can be stored and accessed like a hard drive using standard drag-and-drop techniques. DVD-RAM also offers Defect Sector Management (DSM) to ensure that randomly written data is only placed in usable areas of the media and that data is accurately recovered during the read, write processes. No Finalization is required, so users do not have to open and close write sessions. However, the format specifications that allow these hard-drive like features also renders DVD RAM media incompatible with most DVD-ROM drives and set-top video players. Single-sided (4.7GB) and double-sided (9.4GB) media are available as bare discs or enclosed in a cartridge, with end user pricing ranging from $10 to $35. DVD-RAM discs are used with drives and video recorders from Panasonic, Hitachi, Toshiba, LaCie, QPS, and others.

CLV vs. CAV Recording Methods

When selecting a DVD format, the intended application (computer or AV) and the technology used to carry out the recording process should be considered. Basically, there are two recording methods: Constant Angular Velocity (CAV), which is used in high-speed access applications such as computer storage, and Constant Linear Velocity (CLV), which is used in streaming video applications.

Most magnetic disk drives use CAV storage, where the drive rotates at a constant rpm (revolutions per minute), no matter what section of the disc is being read. With the ability to provide quick random access, CAV is favored for computer and game read/write storage.

The DVD-R and DVD-RW formats use CLV technology, the mode used for the various CD formats and DVD-Video. With CLV, the drive rotates at different rpms, depending on what track of the disc the laser is reading, to maintain a constant data transfer rate. The CLV mode enables higher data transfer rates than CAV, which makes it the preferred recording mode for streaming video, but it slows access when searching for data.

DVD-RAM, DVD+RW, and DVD+R offer a combination of recording solutions that make them suitable for both computer and video storage.

DVD-RAM discs use Zoned CLV (ZCLV), a combination of CLV and CAV that allows data to be transferred at a variable rate while the drive spins at a constant rate, like a hard disk.

The DVD+RW and DVD+R formats utilize sequential CLV recording to provide high data transfer rates and offer CAV as an option when random access is required.

Solving Playback Issues

Pressed media (DVD-Video, DVD-ROM) is most easily read by all DVD drives and players. Write-once media, DVD-R and DVD+R, is the next most easily read. The rewriteable formats--DVD-RW, DVD+RW, and DVD-RAM--are more difficult to read, but -RW and +RW still have good compatibility because their formats closely resemble that of pressed media.

Compatibility problems arise when media does not meet the physical specifications for data format, recording properties, and reflectivity, typically due to poor media manufacturing procedures. When selecting a media brand, users should consider the manufacturer's reputation for quality. Archives of mission-critical information and precious memories deserve the highest quality media.

Other problems occur because the player or drive's capabilities and firmware are marginally designed to meet minimum specifications. As DVD format specifications have been finalized, many drive and player manufacturers have enhanced their read mechanisms to improve compatibility with the various media. By making sure that the media has been qualified by the drive manufacturer, users can avoid having to deal with these types of issues.

Because DVD format specifications have been finalized at various times since 1997, it is difficult for drive, player, or recorder manufacturers to completely eliminate compatibility issues for Recordable DVD media with all legacy DVD-ROM drives and DVD players. Similar problems existed in the early days of CD-R/RW technology development. Compatibility is improving; and eventually, peripheral manufacturers and users won't have to worry about the compatibility of the recordable DVD format they use to store data, videos, and music.

Recognizing that no single format currently offers everything users want, drive manufacturers have introduced combination drives that support both write-once and rewriteable DVD media--DVD-R/-RAM drives, DVD-RW drives, and DVD+R/ +RW drives. By combining a write-once DVD format with a rewriteable DVD format, the drives provide a single solution for sharing and archiving on broadly compatible DVD-R or DVD+R media and the ability to use rewriteable media for files that can be edited and recycled.

Table 1
What Works Where?

DVD Format         Typical          Supporting
                   Manufacturers    Organization

DVD-R Authoring    Pioneer          DVD Forum

DVD-R/RW *         Pioneer          DVD Forum
                   LaCie
                   QPS
                   CD Cyclone

DVD-RW/+R *        Ricoh            DVD+RW
                   H-P              Alliance (8C)
                   Philips
                   Sony
                   Thompson

DVD-RAM/R          Panasonic        DVD Forum
                   Hitachi
                   LG Electronics
                   Samsung
                   LaCie
                   QPS

DVD SuperMulti *   Hitachi          DVD Forum
                   Panasonic
                   LG Electronics
                   LaCie
                   QPS

DVD Multi *        LG Electronics   DVD Forum
                                    DVD+RW
                                    Alliance

DVD Format         Primary             Compatible
                   Application         Media

DVD-R Authoring    Content             DVD-R(A)
                   Development

DVD-R/RW *         Video               DVD-R(G)
                   Development,        DVD-RW
                   archiving

DVD-RW/+R *        Computer,           DVD-RW
                   Video               DVD+R

DVD-RAM/R          Computer,           DVD-RAM
                   Video,              DVD-R(G)
                   Optical Libraries

DVD SuperMulti *   Computer,           DVD-RAM
                   Video,              DVD-R(G)
                   Libraries           DVD-RW

DVD Multi *        Computer,           DVD-RAM
                   Video               DVD-R(G)
                                       DVD-RW
                                       DVD+R

* Drives also write all published CD format media


Table 2
DVD Format Feature Comparison

Format    Write   Read         Random        Defect       Rewrites
          Speed   Capability   Write         Mgmt.

DVD-R     2X      Excellent    No            No           -0-

DVD+R     2.4X    Excellent    No            No           -0-

DVD-RW    1X      Good         No            No           1,000

DVD+RW    2.4X    Good         Yes           Yes          1,000
                               (as option)   (by drive)

DVD-RAM   2X      Poor         Yes           Yes          100,000
                                             (on disc)


Table 3
DVD Media Specifications

                    DVD-R              DVD-R          DVD+R
                    Authoring          General 4.7/
                                       9.4GB

Capacity            4.7GB              4.7GR/side     4.7GB

Laser Wavelength    635nm              650nm          650nm

Numerical           0.6                               0.6
Aperture

Recording Layer     Dye                               Dye

Reflectivity        45-85%                            45-85%

Modulation          0.6 min.                          0.6 min.
Amplitude

Data Track Form     Wobbled groove +                  Phase modulated
                    Land pre-pit                      wobbled groove

Track Pitch         0.74[micro]m                      0.74[micro]m

Tracking Method     DPD                               DPD
(reading)

Min. Pit Length     0.40[micro]m                      0.40[micro]m

Data Modulation     8/16, RLL(2,10)                   8/16, RLL(2,10)

Error Correction    RS-PC                             RS-PC

Channel Bit Rate    26.16Mbps                         26.16Mbps

Scanning Velocity   3.49 m/s                          3.49-8.44 m/s

Rewritability       N/A                               N/A

Copy Protection     None               CSS            CSS

                    DVD-RW             DVD+RW            DVD-RAM
                                       4.7/9.4GB         4.7/9.4GB

Capacity            4.7GB              4.7GB/side        4.7GB/side

Laser Wavelength    650nm              650nm             650nm

Numerical           0.6                0.65              0.6
Aperture

Recording Layer     Phase-Change       Phase-Change      Phase-Change

Reflectivity        18-30%             18-30%            15-25%

Modulation          0.6 min.           0.6 min.          0.4 min.
Amplitude

Data Track Form     Wobbled groove +   Phase modulated   Wobbled land &
                    Land pre-pit       wobbled groove    groove +
                                                         Pre-pit

Track Pitch         0.74[micro]m       0.74[micro]m      0.615[micro]m

Tracking Method     DPD                DPD               DPD
(reading)

Min. Pit Length     0.40[micro]m       0.40[micro]m      0.420[micro]m

Data Modulation     8/16, RLL(2,10)    8/16, RLL(2,10)   8/16,
                                                         RLL(2,10)

Error Correction    RS-PC              RS-PC             RS-PC

Channel Bit Rate    26.16Mbps          26.16Mbps         58.36Mbps

Scanning Velocity   3.49 m/s           3.49-8.44m/s      8.16-8.49m/s

Rewritability       1,000              1,000             100,000

Copy Protection     CSS, CPRM          CSS               CSS, CPRM

www.verbatim.com

Tim Clatterbuck is the product manager of Optical Media at Verbatim Corp. (Charlotte, NC).