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.
Here are the competing writable/rewritable DVD formats:
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 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 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 (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).
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.
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).
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.
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.