| A DVD-RW is a rewritable optical disc with | | | | The DVD+R format is divergent from the DVD-R |
| equal storage capacity to a DVD-R, typically | | | | format. Hybrid drives that can handle both, |
| 4.7 GB. The format was developed by Pioneer | | | | often labeled "DVD±RW", are very popular |
| in November 1999 and has been approved by the | | | | since there is not yet a single standard for |
| DVD Forum. Unlike DVD-RAM, it is playable in | | | | recordable DVDs. There are a number of |
| about 75% of conventional DVD players. | | | | significant technical differences between the |
| | | | "minus" (or often and incorrectly "dash") |
| The primary advantage of DVD-RW over DVD-R is | | | | format and the "plus" format, though most |
| the ability to erase and rewrite to a DVD-RW | | | | consumers would not notice the difference. |
| disc. According to Pioneer, DVD-RW discs may | | | | One example is the ADIP system of tracking |
| be written to about 1,000 times before | | | | and speed control being less susceptible to |
| needing replacement, making them comparable | | | | interference and error than the LPP system |
| with the CD-RW standard. DVD-RW discs are | | | | used by DVD-R, which makes the ADIP system |
| commonly used for volatile data, such as | | | | more accurate at higher speeds. In addition, |
| backups or collections of files. They are | | | | DVD+R(W) has a more robust error management |
| also increasingly used for home DVD video | | | | system than DVD-R(W), allowing for more |
| recorders. One benefit to using a rewritable | | | | accurate burning to media independent of the |
| disc is if there are writing errors when | | | | quality of the media. Additional session |
| recording data, the disc is not ruined and | | | | linking methods are more accurate with |
| can still store data by erasing the faulty | | | | DVD+R(W) versus DVD-R(W), resulting in fewer |
| data. | | | | damaged or unusable discs due to buffer |
| | | | under-run and multi-session disks with fewer |
| One competing rewritable format is DVD+RW. | | | | PI/PO errors.[citation needed] |
| Hybrid drives that can handle both, often | | | | |
| labeled "DVD±RW", are very popular since | | | | Like other "plus" media, it is possible to |
| there is not yet a single standard for | | | | use bitsetting to increase the compatibility |
| recordable DVDs. | | | | of DVD+R media. |
| | | | |
| The recording layer in DVD-RW and DVD+RW is | | | | As of 2006, the market for recordable DVD |
| not an organic dye, but a special phase | | | | technology shows little sign of settling down |
| change metal alloy, often GeSbTe. The alloy | | | | in favor of either the "plus" or "minus" |
| can be switched back and forth between a | | | | formats, which is mostly the result of the |
| crystalline phase and an amorphous phase, | | | | increasing numbers of dual-format devices |
| changing the reflectivity, depending on the | | | | that can record to both formats; it has |
| power of the laser beam. Data can thus be | | | | become very difficult to find new devices |
| written, erased and re-written. | | | | that can only record to one of the formats. |
| | | | However, because the DVD-R format has been in |
| A DVD+R is a once-writable optical disc with | | | | use since 1997, it has had a five-year lead |
| 4.7 GB (4.38 GiB) of storage capacity (more | | | | on DVD+R. As such, older or cheaper DVD |
| precisely, 2295104 sectors of 2048 bytes | | | | players (up to 2004 vintage) are more likely |
| each). The format was developed by a | | | | to favour the DVD-R standard exclusively, and |
| coalition of corporations, known as the | | | | when creating DVDs for distribution (where |
| DVD+RW Alliance, in mid 2002. Since the DVD+R | | | | the playing unit is unknown or older) the |
| format is a competing format to the DVD-R | | | | DVD-R format would normally be preferable. |
| format, which is developed by the DVD Forum, | | | | |
| it has not been approved by the DVD Forum, | | | | DVD+R DL (DL stands for Double Layer), also |
| which claims that the DVD+R format is not an | | | | called DVD+R9, is a derivative of the DVD+R |
| official DVD format. | | | | format created by the DVD+RW Alliance. Its |
| | | | use was first demonstrated in October 2003. |
| In October of 2003, it was demonstrated that | | | | DVD+R DL discs employ two recordable dye |
| double layer technology could be used with a | | | | layers, each capable of storing nearly the |
| DVD+R disc to nearly double the capacity to | | | | 4.7 GB capacity of a single-layer disc, |
| 8.5 GB per disc. Manufacturers have | | | | almost doubling the total disc capacity to |
| incorporated this technology into commercial | | | | 8.55 GB. Discs can be read in many DVD |
| devices since mid-2004 (see DVD+R DL). | | | | devices (older units are less compatible) and |
| | | | can only be created using DVD+R DL and Super |
| Unlike DVD+RW discs, DVD+R discs can only be | | | | Multi drives. DL drives started appearing on |
| written to once. Because of this, DVD+R discs | | | | the market during mid 2004, at prices |
| are suited to applications such as | | | | comparable to those of existing single-layer |
| nonvolatile data storage, audio, or video. | | | | drives. However, the price of DL media ($1 to |
| This can be very confusing because the DVD+RW | | | | $5 USD per disc) is many times that of |
| Alliance logo is a stylized "RW" (See image, | | | | single-layer media. The latest DL drives |
| below). Thus, a DVD+R disc can have the RW | | | | write double layer discs slower (2.4x to 8x) |
| logo, but it is not rewritable. | | | | than current single-layer media (8x-16x). |
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