DVD recordable
Since written tracks are made of darkened dye, the data side of a recordable DVD has a distinct color.
These two changes allow more pits to be written in the same physical disc area, giving higher data density.
[3] 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.
[citation needed] The dash format uses a "land pre-pit" method [5] to provide sector address information.
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 & Philips teams.
The success of the HP Labs project in proving out the technology convinced Sony and Philips to go ahead with the move.
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.
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.
Essentially, it would be possible to turn a tracking loop sideways and use all the tools of control theory to improve the timing.
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.
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.
[16] DVD+RW supports a method of writing called "lossless linking", which makes it suitable for random access and improves compatibility with DVD players.
Although credit for developing the standard is often attributed to Philips, the fundamental work was done by a team at Hewlett-Packard Labs (HPL).
[citation needed] 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] 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.
[21] DVD+RW DL was once developed and announced by JVC but it was never sold due to issues with its low reflectivity (Dual layer).
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.
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).
[38] Developed by HP in collaboration with Philips and Sony and their DVD+RW Alliance, the "plus" format uses a more reliable[citation needed] bi-phase modulation technique[39] to provide "sector" address information.
[42][43] 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.
If a packet writing-enabled Universal Disk Format (UDF) is mounted, the operating system may perform a "background formatting" while the disc is not in use (meaning not being read or written to), which sequentially fills never-written parts of the disc with blank data to make them able to be written to randomly.
It uses physical dedicated sector markers (visible as rectangles on the read side of the disc) instead of the pre-pits or wobbles used in other types of recordable and rewritable media.
[47] Notes: The following table describes the maximal speed of DVD-R and the relative typical write time for a full disc according to the reviews from cdrinfo.com and cdfreaks.com.
Many reviews of multiple brand names on varying conditions of hardware and DVD give much lower and wider measurements than the optimal numbers below.
[51] A series of follow-up studies conducted by the Canadian Conservation Institute in 2019 revealed that CD-R with phthalocyanine-dye and a gold-metal layer had the greatest longevity at over 100 years when stored at ideal temperature and humidity-levels.
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.
[54] The recording layer in DVD-RW and DVD+RW is not an organic dye, but a special phase change metal alloy, often GeSbTe.
A specification for dual-layer DVD-RW discs with a capacity of 8.5 GB (8,500,000,000 bytes) was approved by the DVD Forum,[56] and JVC announced their development of the first media in the format in 2005.
[58] However, manufacturing support for these rewritable dual-layer discs did not materialize due to costs and expected competition from newer and higher-capacity formats like Blu-ray and HD DVD.
