DVD recordable

There have been three revisions of DVD-RW known as Version 1.0 (1999), Version 1.1 (2000) and Version 1.2 (November 2003).[4]

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.[5][6]

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.[7][8][9][5]

The DVD+R format was developed by a coalition of corporations—now known as the DVD+RW Alliance—in mid-2002 (though most of the initial advocacy was from Sony). 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.[10]

On 25 January 2008, DVD6C officially accepted DVD+R and DVD+RW by adding them to its list of licensable DVD products.[10]

Developed by Philips and Sony with their DVD+RW Alliance, the "plus" format uses a more reliable bi-phase modulation technique[11] to provide 'sector' address information. It was introduced after the "-" format.

The wobble frequency has been increased from 140.6 kHz to 817.4 kHz.[12]

Like DVD-R (single-layer), DVD+R (single-layer) media officially exists with rated recording speeds of up to 16× (constant angular velocity). However, on both +R and -R types, some models of half-height (desktop) optical drives allow bypassing the rating and recording at speeds beyond 16× on selected recordable media by vendors considered of high quality, including Verbatim and Taiyo Yuden.

On dual-layer media, half-height optical drives released towards 2010, such as the 2007 TSSTcorp TS-H653B,[13] have adapted recording speeds of up to 16× on DVD+R DL media by selected vendors, compared to up to 12× on DVD-R DL. More recent optical drives have reduced their maximum allowable recording speed on both +R DL and -R DL media to 8×, usually P-CAV.[5][8][14]

DVD+RW media exists with the writing speed ratings of 1×-4× and 2.4×-8×.[15][16]

Reading speeds (constant angular velocity) on most half-height optical drives released since the mid-2000s decade are up to 16× on DVD±R (single-layer) and 12× on DVD±R DL and DVD±RW.[8][14][5]

All constant linear velocity transfer rates (read and write) of 2.0× on DVD-R/RW have been replaced with 2.4× in the specification for DVD+R/RW. Thus, specification sheets of optical drives list "2.4× CLV" instead of "2× CLV" as the base transfer rate level for DVD+R/RW. Earlier optical drives also have a 1.0× transfer rate level for both DVD-R/RW and DVD+R/RW.[5][17][18]

DVD+RW supports a method of writing called "lossless linking", which makes it suitable for random access and improves compatibility with DVD players.[19] 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, it was "finalized" in 1997 by the DVD+RW Alliance. It was then abandoned until 2001, when it was heavily revised (in particular, the capacity increased from 2.8 GB to 4.7GB).

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.[20][21]

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.[22]

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.[23]

DVD+RW DL was once developed and announced by JVC but it was never sold due to issues with its low reflectivity (Dual layer).[24][25][26][27]

As of 2006, the market for recordable DVD technology showed little sign of settling down in favour of either the "plus" or "dash" formats, which is mostly the result of the increasing numbers of dual-format devices that can record to both formats, known as DVD Multi Recorders.[28] It has become very difficult to find new computer drives that can only record to one of the formats. By contrast, DVD Video recorders still favour one format over the other, often providing restrictions on what the unfavoured format will do.[29] However, because the DVD-R format has been in use since 1997, it has had a five-year lead on DVD+R. As such, older or cheaper DVD players (up to 2004 vintage) are more likely to favour the DVD-R standard exclusively.[30]

DVD+R discs must be formatted before being recorded by a compatible DVD video recorder. DVD-R do not have to be formatted before being recorded by a compatible DVD video recorder,because the two variants of the discs are written in different formats (see DVD+VR and DVD-VR respectively).

There are a number of significant technical differences between the "dash" and the "plus" format, although most users would not notice the difference. One example is that the DVD+R style address in pregroove (ADIP) system of tracking and speed control is less susceptible to interference and error, which makes the ADIP system more accurate at higher speeds than the land pre pit (LPP) system used by DVD-R. In addition, DVD+R(W) has a more robust error-management system than DVD-R(W), allowing for more accurate burning to media, independent of the quality of the media. The practical upshot is that a DVD+R writer is able to locate data on the disc to byte accuracy whereas DVD-R is incapable of such precision.

DVD+R also has a larger Power Calibration Area (PCA). The PCA in DVD+R has a length of 32768 sectors, compared to the 7088 of DVD-R. In the PCA, which is located close to the inner edge of the disc, a 15-step procedure is carried out to calibrate (vary the power of) the disc drive's laser before every and during writing, to allow for small differences between discs and drives. This process is known as a power test. Calibration during writing allows for small changes in quality between different sections of the disc, such as slightly different optical properties, impurities or dye layer thickness in either the plastic or dye. The results of the power tests are stored in a Recording Management Area (RMA), which can hold up to 7,088 calibrations (in DVD-R). The disc can not be written to after the RMA becomes full, although it may be emptied in RW discs. CD-R, CD-RW, DVD-R, DVD+R, DVD-R DL, DVD+R DL, DVD+RW and DVD-R all have a PCA. CDs (and possibly DVDs) may also have two PCAs: one on the inner edge of the disc, for low speed testing, and another on the outer edge for high speed testing. [31][32][33][34][35][36][37][38]

Additional session linking methods are more accurate with DVD+R(W) versus DVD-R(W), resulting in fewer damaged or unusable discs due to buffer under-run and multi-session discs with fewer PI/PO errors.[39]

Like other "plus" media, it is possible to change the book type to increase the compatibility of DVD+R media (though unlike DVD+RW, it is a one way process). This is also known as bitsetting.[40]

Some half-height DVD Multi Recorder drives released since 2007, such as the TSSTcorp SH-S203/TS-H653B (2007) have officially adapted support for writing speeds of up to 12× on DVD-R DL and 16× on DVD+R DL (on recordable media by selected vendors only), while more recent DVD writers such as the SH-224DB (2013) and Blu-Ray writers such as the LG BE16NU50 (2016) have restricted the supported DVD±R DL writing speed to 8×.[7][8]

DVD-R discs are composed of two 0.6 mm acrylic discs, bonded with an adhesive to each other. One contains the laser guiding groove and is coated with the recording dye and a silver alloy or gold reflector. The other one (for single-sided discs) is an ungrooved 'dummy' disc to assure mechanical stability of the sandwich structure, and compatibility with the compact disc standard geometry which requires a total disc thickness of about 1.2 mm. The sandwich structure also helps protect the layer containing data from scratches with a thick "dummy" disc, a problem with CDs, which lack that structure. Double-sided discs have two grooved, recordable disc sides, and require the user to flip the disc to access the other side. Compared to a CD's 1.2 mm thickness, a DVD's laser beam only has to penetrate 0.6 mm of plastic in order to reach the dye recording layer, which allows the lens to focus the beam to a smaller spot size to write smaller pits.

In a DVD-R, the addressing (the determination of location of the laser beam on the disc) is done with additional pits and lands (called land pre-pits) in the areas between the grooves. The groove on a DVD-R disc has a constant wobble frequency of 140.6 kHz used for motor control, etc.

In 2011, JVC announced an archival DVD recording medium manufactured with quality control and inspection frequencies techniques greater than is traditionally used in media manufacturing, and using specially developed silver alloy as a reflective layer and organic dye with in-house developed additives to secure long-term data retention.[47]

The recording layer in DVD-RW and DVD+RW is not an organic dye, but a special phase change metal alloy, often GeSbTe. The alloy can be switched back and forth between a crystalline phase and an amorphous phase, changing the reflectivity, depending on the power of the laser beam. Data can thus be written, erased and re-written.[48]