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DVD-R

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Optical discs
General
Optical media types
Standards
See also

DVD-R is a digital optical disc storage format. A DVD-R is a DVD that can be written once and read arbitrarily many times.

A DVD-R typically has a storage capacity of 4.7 GB. Pioneer has also developed an 8.5 GB dual layer version, DVD-R DL, which appeared on the market in 2005.

DVD-R(W) is one of three competing industry standard DVD recordable formats; the others are DVD+R(W) and DVD-RAM. A DVD-R can be written only once, in contrast with a rewritable DVD formats such as DVD-RW or DVD+RW which can be rewritten multiple (1000+) times.

History

The DVD-R format was developed by Pioneer in 1997.[1] It is supported by most normal DVD players and is approved by the DVD Forum.

Technical specifications

The larger storage capacity of a DVD-R compared to a CD-R is achieved through smaller pit size and smaller track pitch of the groove spiral which guides the laser beam. Consequently, more pits can be written on the same physical sized disc. In order to write smaller pits onto the recording dye layer, a red laser beam with a wavelength of 640 nm (for general use recordable DVD, versus a wavelength of 780 nm for CD-R) is used in conjunction with a higher numerical aperture lens. Because of this shorter wavelength, DVD-R and DVD+R use different dyes from CD-R to properly absorb this wavelength.

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 data containing layer 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 used for motor control, etc.

In 2011, JVC announced an archival DVD recording media 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.[2]

Competing formats

A single DVD-R disc
File:Appledvdr.jpg
A DVD-R jewel case
A spindle with 50 Verbatim DVD-R discs

A 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 (and sometimes in other sizes), it is useful in applications that require 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 writing 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 discs with fewer PI/PO errors.[3]

This new format, among other things, resulted in DVD-R being unofficially referred to, in error, as DVD "minus" R. However, 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.

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 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.[4] 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.[5]

Recordable DVD capacity comparison

For comparison, the table below shows storage capacities of the four most common DVD recordable media, excluding DVD-RAM. SL stands for standard single-layer discs, while DL denotes the double-layer variants. See articles on the formats in question for information on compatibility issues.

DVD capacity
Diameter Disk Type Data sectors
(2,048 B each) 		Capacity
cm Bytes MB GB
12 DVD-R, DVD-RW (SS-SL) 2,298,496 4,707,319,808 4489.250 4.7
DVD+R, DVD+RW (SS-SL) 2,295,104 4,700,372,992 4482.625 4.7
DVD-R DL (SS) 4,171,712 8,543,666,176 8147.875 8.5
DVD+R DL (SS) 4,173,824 8,547,991,552 8152.000 8.5
DVD-R DS, DVD-RW DS (SL) 4,596,992 9,414,639,616 8978.500 9.4
DVD+R DS, DVD+RW DS (SL) 4,590,208 9,400,745,984 8965.250 9.4
DVD-R DS (DL) 8,343,424 17,087,332,352 16,295.750 17.0
DVD+R DS (DL) 8,347,648 17,095,983,104 16,304.000 17.0
  • SL / DL – Single/Dual layer
  • SS / DS – Single/Double sided

Speed

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.

The write time may vary (± 30 s) between writer and media used. For high speed, the write strategy changes from constant linear velocity (CLV) to constant angular velocity (CAV), or zoned constant linear velocity (ZCLV). The table below largely assumes CAV.

Drive speed Data rate (MB/s) Data rate (Mbit/s) Write time for single-layer DVD-R
1× 1.32 10.56 1 hour
2× 2.64 21.12 30 minutes (CLV)
4× 5.28 42.24 15 minutes (CLV)
8× 10.56 84.48 8 minutes (ZCLV)
16× 21.12 168.96 5 min 45 sec (CAV)
18× 23.76 190.08 5 min 30 sec (CAV)
20× 26.40 211.20 5 minutes (CAV)
22× 29.04 232.32 4 min 30 sec (CAV)
24×[6] 31.68 253.44 ~4 minutes (CAV)

See also

References

  1. ^ "History". EU: Pioneer. Retrieved 2008-12-02.
  2. ^ JVC introduces archival grade DVD-R media, Broadcast engineering, November 23, 2011 {{citation}}: External link in |publisher= (help).
  3. ^ "How To Choose CD/DVD Archival Media", Ad Terras Per Aspera (World Wide Web log), Oct 30, 2006.
  4. ^ DMR-EX769 (user manual), Panasonic, Machine will not record 16:9 format video to DVD+R(W).
  5. ^ "What is DVD?". Video help. Retrieved 2008-07-23.
  6. ^ "Sony's 'miracle' DVD writer hits 24x write speed". TG daily. Retrieved 2009-02-26.

Bibliography

  • Bennett, Hugh (July 1998), "In DVD's Own Image: DVD-R Technology and Promise", EMedia Professional, pp. 30+.
  • ——— (Apr 2004), Understanding Recordable & Rewritable DVD, Cupertino: Optical Storage Technology Association.
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