Pioneer has also developed an 8.54 GB dual layer version, DVD-R DL, which appeared on the market in 2005. Data on a DVD-R cannot be changed, whereas a DVD-RW (DVD-rewritable) can be rewritten multiple (1000+) times. DVD-R(W) is one of three competing industry standard DVD recordable formats; the others are DVD+R(W) and DVD-RAM.
DVD-R discs are composed of two 0.6 mm polycarbonate 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 data containing layer from scratches by a thick "dummy" disk, 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 of polycarbonate, 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 used for motor control etc.
A previous DVD recordable format called DVD-RAM (DVD random access memory) predates DVD-R. Developed in 1996, DVD-RAM is a rewritable optical disc usually encased in a cartridge. Currently available in standard 4.7 GB (4.377 GiB), it is ideal for use that requires quick revisions and rewriting. In 2002 a new format was developed called DVD+R (or "plus" R). Created by a coalition called the DVD+RW Alliance, this format uses a number of improved technologies that, while generally unnoticeable to the end user, make a more reliable technology. One example is the ADIP (ADdress In Pregroove) system of tracking and speed control used by DVD+R being less susceptible to interference and error than the LPP (Land Pre Pit) system used by DVD-R, which makes the ADIP system more accurate at higher speeds. 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. 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 disks with fewer PI/PO errors.
This new format, among other things, resulted in DVD-R being unofficially referred to as DVD "minus" R (though in countries where British English is dominant, the term "minus R" was already common; not just in contrast to "plus 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.
As of 2006, the market for recordable DVD technology shows 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; it has become very difficult to find new devices that can only record to one of the formats. 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, and when creating DVDs for distribution (where the playing unit is unknown or older) the DVD-R format would normally be preferable.
|Drive speed||Data rate||Write time for Single Layer DVD-R|
|1X||1.32 MB/s||60 minutes|
|2X||2.64 MB/s||30 minutes|
|4X||5.28 MB/s||15 minutes|
|8X||10.56 MB/s||8 minutes|
|16X||21.12 MB/s||5 minutes|
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