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. 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). 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. 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. 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,. 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, and DVD+RW 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. 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. 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.
Wobble frequency Developed by
HP in collaboration with
Philips and
Sony and their
DVD+RW Alliance, the "plus" format uses a more reliable
bi-phase modulation technique 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.
Transfer rates 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, 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. 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.
Random writing DVD+RW discs can be written randomly in any location that has been sequentially written to before at least once. 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. == DVD-RAM ==