DVD recordable and DVD rewritable are a collection of optical disc formats that can be written to by a DVD recorder and by computers using a DVD writer. The "recordable" discs are write-once read-many (WORM) media, whereas "rewritable" discs are able to be erased and rewritten. Data is written ("burned") to the disc by a laser, rather than the data being "pressed" onto the disc during manufacture, like a DVD-ROM. Pressing is used in mass production, primarily for the distribution of home video.
DVD±R (also DVD+/-R, or "DVD plus/dash R") is a shorthand term for both DVD+R and DVD-R formats. Likewise, the term DVD±RW refers to both rewritable disc types, the DVD+RW and the DVD-RW. DVD±R/W (also written as, DVD±R/RW, DVD±R/±RW, DVD+/-RW, DVD±R(W) and other arbitrary ways) handles all common writable disc types, but not DVD-RAM.. A drive that supports writing to all these disc types including DVD-RAM (but not necessarily including cartridges or 8cm diameter discs) is referred to as a "Multi" recorder.Understanding DVD - Physical Compatibility - Optical Storage Technology Association
Like CD-Rs, DVD recordable uses dye to store the data. During the burning of a single bit, the laser's intensity affects the reflective properties of the burned dye. By varying the laser intensity quickly, high density data is written in precise tracks. Since written tracks are made of darkened dye, the data side of a recordable DVD has a distinct color. Burned DVDs have a higher failure-to-read rate than pressed DVDs, due to differences in the reflective properties of dye compared to the aluminum substrate of pressed discs.
Comparing recordable CDs and DVDs The larger storage capacity of a DVD-R compared to a CD-R is achieved by focusing the laser to a smaller point, creating smaller 'pits' as well as a finer track pitch of the groove spiral which guides the laser beam. These two changes allow more pits to be written in the same physical disc area, giving higher data density. The smaller focus is possible with a shorter wavelength 'red' laser of 650 nm, compared to CD-R's wavelength of 780 nm. This is used in conjunction with a higher numerical aperture lens. The dyes used in each case are different as they are optimized for different wavelengths.
R and RW formats
"R" format DVDs can be written once and read arbitrarily many times, whereas "RW" formats can be written to repeatedly. Thus, "R" format discs are only suited to non-volatile data storage, such as audio or video. This can cause confusion because the 'DVD+RW Alliance' logo is a stylized 'RW'. Thus, many discs have the RW logo, but are not rewritable.
According to Pioneer, DVD-RW discs may be written to about 1,000 times before needing replacement. RW discs are used to store volatile data, such as when creating backups or collections of files which are subject to change and re-writes. They are also ideal for home DVD video recorders, where it is advantageous to have a rewritable format capable of digital video data speeds, while being removable, small, and relatively inexpensive. Another benefit to using a rewritable disc is if the burning process produces errors or corrupted data, it can simply be written over again to correct the error, or the corrupted data can be erased. This is also useful for testing optical disc authoring software.
DVD-R and DVD-RW (DVD "dash")
The DVD-R format was developed by Pioneer in 1997. It is supported by most normal DVD players and is approved by the DVD Forum. It has broader playback compatibility than DVD+R, especially with much older players. The dash format uses a "land pre-pit" method to provide sector address information.
DVD "minus" R is not correct, according to DVD-R consortium recommendations; it is, in fact, a dash (i.e. DVD "dash" R). DVD-R and DVD+R technologies are not directly compatible, which created a format war in the DVD technology industry. To reconcile the two competing formats, manufacturers created hybrid drives that could read both—most hybrid drives that handle both formats are labeled DVD±R and Super Multi (which includes DVD-RAM support) and are very popular.
DVD-RW versions A DVD-RW disc is a rewritable optical disc with equal storage capacity to a DVD-R, typically 4.7 GB (4,700,000,000 bytes). The format was developed by Pioneer in November 1999 and has been approved by the DVD Forum. The smaller Mini DVD-RW holds 1.46 GB, with a diameter of 8 cm.
The primary advantage of DVD-RW over DVD-R is the ability to erase and rewrite to a DVD-RW disc. According to Pioneer, DVD-RW discs may be written to about 1,000 times before needing replacement.
There are three revisions of DVD-RW known as Version 1.0 (1999), Version 1.1 (2000) and Version 1.2 (November 2003).
The writing of DVD-RW Version 1.2 is not backwards-compatible with earlier optical drives that have only been adapted to Version 1.1 and Version 1.0.Pioneer computer drive archive
DVD-RW media exists in the recording speed variants of 1× (discontinued), 2×, 4× and 6×. Higher speed variants, although compatible with lower writing speeds, are written to with the lowest error rate at the rated speed, similarly to CD-RW.Archive of TSSTcorp optical drive manualsPioneer computer drive archive
DVD+R and DVD+RW (DVD "plus") History The DVD+R format was developed by a coalition of corporations—now known as the DVD+RW Alliance—in mid-2002, stemming from a research project at Hewlett-Packard Laboratories (a.k.a. HP Labs) that originated in 1996. The project was the brainchild of Josh Hogan, who represented HP and was involved in the negotiations that resulted in the compromise format for DVD-ROM (prerecorded media) between the DVD Forum and the Sony and Philips teams. HP chose to partner with Sony and Philips, who were initially lukewarm to a fully rewritable format. The success of the HP Labs project in proving out the technology convinced Sony and Philips to go ahead with the move.
The issue was drop-in compatibility of a rewritable format with the existing DVD-ROM players. Rewritable media (such as magnetic hard disk drives or rewritable CDs) have edit gaps between sectors, to provide a buffer so that any timing inaccuracies in the write clock would not result in new data accidentally overwriting any of the other sectors. DVD-ROM disks, being mastered with a continuous stream of data, had no need for edit gaps. In fact, makers of pre-recorded DVD media were quite cool to the idea of users being able to use this format for their own recordings. HP saw this as an opportunity to enter the business, but solving the lack of edit gaps was the key problem. In early 1996, HP exited the hard disk drive business, and two HPL engineers, Daniel (Danny) Abramovitch and Terril Hurst, were moved onto the rewritable DVD project. Abramovitch was (and is) a servo engineer with an interest in timing loops (a.k.a. phase-locked loops). Reading about the wobble grooves on older optical disk formats, Abramovitch proposed that a wobble frequency at roughly the same frequency as the data frequency would provide enough timing accuracy (i.e. allow us to lock a phase-locked loop with small enough jitter) so as to provide sub-bit accuracy on the timing. In a servo systems parlance, this was a high frequency, high-fidelity reference signal for the timing servo loop to follow. Essentially, it would be possible to turn a tracking loop sideways and use all the tools of control theory to improve the timing. The issue was that it was not clear that such a signal would not affect the data itself. It was an insight by David (Dave) Towner, an optical engineer attached to the project, that the detection modes for the wobble and the data (how they added or differenced the regions on the optical detector), would themselves provide enough common mode rejection to separate the signals. At this point, the notion of high frequency wobbles was born. Much of the team's effort after that was to prove out this concept, which led to the fundamental patent for the format by Abramovitch and Towner (US Patent # 6046968, filed July 24, 1997, issued April 4, 2000), entitled Re-Writable Optical Disk Having Reference Clock Information Permanently Formed on the Disk. By late 1998, through the monthly meetings led by project leader Carl Taussig and often accompanied by Josh Hogan, Sony and Philips had warmed to the idea of the format.
In 1999, the team had argued to then HP CEO Lew Platt that HP needed to produce products in the set-top market, the computer market, and the camcorder market to truly exploit the invention. Platt, who had a reputation of being risk averse, chose to stick with only the computer drive product scheduled for development at the Boise facility. In 2000, HP was under the direction of new CEO Carly Fiorina, and the division, under new cost constraints, chose to abandon the manufacture of any new optical drives. However, since HP owned the fundamental patent above, they could receive licensing fees for the patent itself and pursued several expansions of the patent in US Patent # 7701836 (Issued April 20, 2010). There was also US Patent # RE41881 (Reissued October 26, 2010), a reissue of US Patent # 6046968 with expanded claims. Finally, there was US Patent # RE43788 (Issued November 6, 2012), a second reissue of Patent # 6046968 with more claims.
With the timing issue solved by high frequency wobbles, the other key issue solved by the HPL team (through the efforts of Terril Hurst and Craig Perlov) was writing bits in a way that would not result in a bleeding of one bit into the next one. Because DVD+RW used phase-change media, this was solved by high speed modulation of short laser pulses to take advantage of the nonlinear heating and cooling properties of the material and control the pulse shapes. Several papers describing these efforts can be found at:
The DVD Forum initially did not approve of the DVD+R format and claimed that the DVD+R format was not an official DVD format until January 25, 2008.
On 25 January 2008, DVD6C officially accepted DVD+R and DVD+RW by adding them to its list of licensable DVD products.
Features
DVD+RW supports a method of writing called "lossless linking", which makes it suitable for random access and improves compatibility with DVD players. The rewritable DVD+RW standard was formalized earlier than the non-rewritable DVD+R (the opposite was true with the DVD- formats). Although credit for developing the standard is often attributed to Philips, the fundamental work was done by a team at Hewlett-Packard Labs (HPL). It was "finalized" in 1997 by the DVD+RW Alliance once the fundamental patent (US Patent # 6046968) had been filed by the HPL team. It was then abandoned until 2001, when it was heavily revised (in particular, the capacity increased from 2.8 GB to 4.7 GB).
The simulated recording mode feature is no longer an official part of the standard like it was for CD-R, CD-RW, DVD-R and DVD-RW, although supported by Plextor optical drives.
Another distinction in comparison to DVD-R/RW/R DL is that the recorder information (optical drive model) is not written automatically to DVD+ discs by the drive. Nero DiscSpeed allows proprietarily adding such information for later retrieval.
Other changes include the removal of a dedicated SCSI erase command in optical drives, which is done by the software instead that overwrites data with null characters. This means that the standard does not allow reverting the disc to a blank (unwritten) state after the first write.
DVD+RW DL was once developed and announced by JVC but it was never sold due to issues with its low reflectivity (Dual layer).