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VANDALISM
{{for|the binocular vision condition|Dissociated Vertical Deviation}}
{{for|the successor of DVD|Blu-ray Disc}}
{{Infobox media
|name = DVD
|image = [[File:DVD logo.svg|200px]]<br />[[Image:DVD.png|250px|DVD-R read/write side]]
|created = 1996
|caption =
|type = [[Optical disc]]
|
|capacity = ~4.7 &nbsp;[[gigabyte|GB]] (single-sided, single-layer) <br />~ 8.5&nbsp;[[gigabyte|GB]] (single-sided, double-layer)<br />~9.4&nbsp;[[gigabyte|GB]] (double-sided, single-layer) (rare—double-sided, double-layer)
|read = 650 nm laser, 10.5&nbsp;[[Megabit per second|Mbit/s]] (1×)
|write = 10.5&nbsp;[[Megabit per second|Mbit/s]] (1×)
|standard = DVD Forum's DVD Books<ref name="dvd-book">DVD FLLC (2009-02) [http://www.dvdfllc.co.jp/format/f_bconst.html DVD Book Construction - list of all available DVD Books], Retrieved on 2009-07-24</ref><ref name="dvd-books">DVD FLLC [http://www.dvdfllc.co.jp/format/f_histry.html DVD Format Book - History of Supplements for DVD Books], Retrieved on 2009-07-24</ref><ref name="dvd-books-overview">MPEG.org, [http://www.mpeg.org/MPEG/DVD/General/Books.html DVD Books overview], Retrieved on 2009-07-24</ref> and DVD+RW Alliance specifications
|owner =
|use = Data storage, video, audio, [[Xbox]], [[PlayStation 2]], [[Wii]], [[Xbox 360]] games
}}

'''DVD''', also known as '''Digital Versatile Disc''' or '''Digital Video Disc''',
<!--
NOTE: Please do not edit this explanation. See the Etymology section of this article and for further details refer to the talk page and archives.
-->
is an [[optical disc]] [[data storage device|storage]] media format, and was invented in [[1995]]. Its main uses are [[video]] and [[data]] storage. DVDs are of the same dimensions as compact discs ([[CD]]s), but store more than six times as much data.

Variations of the term ''DVD'' often describe the way data is stored on the discs: DVD-ROM (read only memory) has data that can only be read and not written; [[DVD-R]] and [[DVD+R]] (recordable) can record data only once, and then function as a DVD-ROM; [[DVD-RW]] (re-writable), [[DVD+RW]], and [[DVD-RAM]] (random access memory) can all record and erase data multiple times. The wavelength used by standard DVD lasers is 650&nbsp;nm;<ref>{{cite web|url=http://articles.techrepublic.com.com/5100-6349-1047035.html|title=Build Your Skills: A comparison between DVD and CD-ROM}}</ref> thus, the light has a [[red]] color.

[[DVD-Video]] and [[DVD-Audio]] discs refer to properly formatted and structured video and audio content, respectively. Other types of DVDs, including those with video content, may be referred to as DVD Data discs.

==History==
In [[1993]], two high-definition optical storage formats were being developed. One was the MultiMedia [[Compact Disc]] (MMCD), backed by [[Philips]] and [[Sony]], and the other was the Super Density (SD) disc, supported by [[Toshiba]], [[Time Warner]], [[Matsushita Electric]], [[Hitachi, Ltd.|Hitachi]], [[Mitsubishi Electric]], [[Pioneer Corporation|Pioneer]], [[Thomson SA|Thomson]], and [[JVC]].
{{Optical disc authoring}}
Representatives of the SD camp approached [[International Business Machines|IBM]], asking for advice on the file system to use for their disc as well as looking for support for their format for storing computer data. A researcher from IBM's [[Almaden Research Center]] received that request and also learned of the MMCD development project. Wary of being caught in a repeat of the costly [[videotape format war]] between [[VHS]] and [[Betamax]] in the 1980s, he convened a group of computer industry experts, including representatives from [[Apple Inc.|Apple]], [[Microsoft]], [[Sun Microsystems|Sun]], [[Dell]], and many others. This group was referred to as the Technical Working Group, or TWG. The TWG voted to boycott both formats unless the two camps agreed on a single, converged standard.<ref name="ecommerceandvideodistributiondvd.blogspot.com">{{cite web |title=E-commerce and Video Distribution: DVD and Blu-ray |url=http://ecommerceandvideodistributiondvd.blogspot.com/}}</ref> [[Lou Gerstner]], president of IBM, was recruited to apply pressure on the executives of the warring factions. Eventually, the computer companies won the day, and a single format, now called DVD, was agreed upon. The TWG also collaborated with the [[Optical Storage Technology Association]] (OSTA) on the use of their implementation of the ISO-13346 file system (known as [[Universal Disc Format]] [UDF]) for use on the new DVDs.

Philips and Sony decided it was in their best interest to avoid another format war over their MultiMedia Compact Disc, and agreed to unify with companies backing the Super Density Disc to release a single format with technologies from both. The specification was mostly similar to Toshiba and Matsushita's Super Density Disc, except for the dual-layer option (MMCD was single-sided and optionally dual-layer, whereas SD was single-layer but optionally double-sided) and [[Eight-to-Fourteen Modulation|EFMPlus]] modulation. EFMPlus was chosen due to its great resilience against disc damage, such as scratches and fingerprints. EFMPlus, created by [[Kees A. Schouhamer Immink|Kees Immink]] (who also designed [[Eight-to-Fourteen Modulation|EFM]]), is 6% less efficient than the modulation technique originally used by Toshiba, which resulted in a capacity of 4.7&nbsp;GB, as opposed to the original 5&nbsp;GB. The result was the DVD specification, finalized for the DVD movie player and DVD-ROM computer applications in December 1995. The DVD Video format was first introduced by Toshiba in Japan in November 1996, in the United States in March 1997 (test marketed),<ref name="uni_PR">{{cite news |title=For the DVD, Disney Magic May Be the Key |author=Johnson, Lawrence B. |work=[[The New York Times]] |date=September 7, 1997 |url=http://query.nytimes.com/gst/fullpage.html?res=9407EEDC1730F934A3575AC0A961958260 |accessdate=2009-05-25 }}</ref> in Western Europe in May 1998, in Eastern Europe in October that same year, and in Australia in February 1999. In May 1997, the [[DVD Consortium]] was replaced by the [[DVD Forum]], which is open to all other companies.<ref name="uni_PR">{{cite press release |title=DVD Format Unification |publisher=Toshiba |date=December 8, 1995 |url=http://www.toshiba.co.jp/about/press/1995_12/pr0802.htm |accessdate=2007-07-12 }}</ref> DVD specifications created and updated by DVD Forum are published as so-called ''DVD Books'' (e.g. DVD-ROM Book, DVD-Audio Book, DVD-Video Book, DVD-R Book, DVD-RW Book, DVD-RAM Book, DVD-AR Book, [[DVD-VR]] Book, etc).<ref name="dvd-book" /><ref name="dvd-books" /><ref name="dvd-books-overview" /> Some specifications for mechanical, physical and optical characteristics of DVD optical discs can be downloaded as ''freely available standards'' from [[ISO]] website.<ref name="iso-free">ISO [http://standards.iso.org/ittf/PubliclyAvailableStandards/index.html ISO Freely Available Standards], Retrieved on 2009-07-24</ref> There is also [[DVD+RW Alliance]], which publish competing DVD specifications such as DVD+R, DVD+R DL, DVD+RW or [[DVD+RW DL]]. These DVD formats are also ISO standards.<ref>ISO [http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=52065 ISO/IEC 17344:2009, Data interchange on 120 mm and 80 mm optical disc using +R format -- Capacity: 4,7 Gbytes and 1,46 Gbytes per side (recording speed up to 16X)], Retrieved on 2009-07-26</ref><ref>ISO [http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=51140 ISO/IEC 25434:2008, Data interchange on 120 mm and 80 mm optical disc using +R DL format -- Capacity: 8,55 Gbytes and 2,66 Gbytes per side (recording speed up to 16X)], Retrieved on 2009-07-26</ref><ref>ISO [http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=52064 ISO/IEC 17341:2009, Data interchange on 120 mm and 80 mm optical disc using +RW format -- Capacity: 4,7 Gbytes and 1,46 Gbytes per side (recording speed up to 4X)], Retrieved on 2009-07-26</ref><ref>ISO [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=52066 ISO/IEC 26925:2009, Data interchange on 120 mm and 80 mm optical disc using +RW HS format -- Capacity: 4,7 Gbytes and 1,46 Gbytes per side (recording speed 8X)], Retrieved on 2009-07-26</ref> Some of DVD specifications (e.g. for DVD-Video) are not publicly available and can be obtained only from DVD Format/Logo Licensing Corporation for a fee of $ 5000.<ref name="dvdbook-subscribe">DVD FLLC (2009) [http://www.dvdfllc.co.jp/format/f_nosbsc.html DVD Format Book], Retrieved on 2009-08-14</ref><ref>DVD FLLC (2009) [http://www.dvdfllc.co.jp/license/l_howto.html How To Obtain DVD Format/Logo License (2005-2009)], Retrieved on 2009-08-14</ref> Every subscriber must sign a [[non-disclosure agreement]] as certain information in the DVD Book is proprietary and confidential.<ref name="dvdbook-subscribe" />

=== Etymology ===
The official DVD specification documents have never defined the [[Acronym and initialism|initialism]] DVD. Usage in the present day varies, with '''''Digital Versatile Disc''''',<ref>[http://www.dvdforum.org/faq-dvdprimer.htm#1 DVD Primer at DVDForum.org]</ref> '''''Digital Video Disc''''', and '''''DVD''''' being the most common.

'''''DVD''''' was originally used as an initialism for the unofficial term
'''''digital videodisk'''''.<!--
NOTE: Please do not edit this spelling unless you have an authoritative source that predates than the one cited.
--><ref>{{cite web
|title=A Battle for Influence Over Insatiable Disks
|publisher=''[[The New York Times]]''
|date=1995-01-11
|url=http://query.nytimes.com/gst/fullpage.html?res=990CEEDA143CF932A25752C0A963958260
|accessdate=2007-04-09}}</ref>

It was reported in 1995, at the time of the specification finalization, that the letters officially stood for '''''Digital Versatile Disc''''' (due to nonvideo applications).<ref>{{cite web
|title=DVD designers go with AC-3 Final specs for 'digital versatile disc'...
|date=1995-12-11
|url=http://login.vnuemedia.com/h/login/login_subscribe.jsp?id=EhTA1werc%2F8oJkXd3AvIhVqJMQ%2BEsnoUjFFnmSZpudrVtJLf7Nv3guKhcy0wXloTw1ec8wBZwjOB%0A62XN0BJm24K0G1zDvlaa2k6JKCFzE7ePjrRq%2BP7fzOttoVmmk0ji0Ak9XMyUDOLcVVHvY1YAAu7R%0A9%2FWEig9DTbEWMSZ81VibQ8Yr05&nbsp;cHz6%2BtV7gQyZ7v2cr1AiqljrxXu9IdD%2FTDqGSb8vhhZNMn6q9G%0Aegam8cJXu9IdD%2FTDqOmFpnXV7XcQIVOkoLrk6Bs%3D
|accessdate=2007-04-16}}</ref>

However, the text of the press release announcing the specification finalization only refers to the technology as "DVD", making no mention of what (if anything) the letters stood for.<ref name="uni_PR" />


A newsgroup [[FAQ]] written by Jim Taylor (a prominent figure in the industry) claims that four years later, in 1999, the DVD Forum stated that the format name was simply the three letters "DVD" and did not stand for anything.<ref>{{cite web
|title=DVD FAQ
|publisher=DVD Demystified
|date=2006-09-12
|url=http://www.dvddemystified.com/dvdfaq.html#1.1
|accessdate=}}</ref>

The [[DVD Forum]] website has a section called "DVD Primer" in which the answer to the question, "What does DVD mean?" reads, "The keyword is 'versatile.' Digital Versatile Discs provide superb video, audio and data storage and access—all on one disc."<ref>{{cite web
|title=DVD Primer
|publisher=DVD Forum
|date=2004-11-14
|url=http://www.dvdforum.org/faq-dvdprimer.htm#1
|accessdate=2008-01-23}}
</ref>

== DVD capacity ==
{| class="wikitable"
|+ Capacity and nomenclature<ref>{{cite web|url=http://www.mpeg.org/MPEG/DVD/Book_A/Specs.html |title=DVD Book A: Physical parameters |publisher=Mpeg.org |date= |accessdate=2009-08-22}}</ref><ref>[http://www.cinram.com/dvd/tech/dvdindetail.pdf Cinram: DVD in Detail]{{dead link|date=August 2009}}</ref><br /><small>SS = single-sided, DS = double-sided, SL = single-layer, DL = dual-layer</small>
!colspan="2" rowspan="2"| Designation
!rowspan="2"| Sides !!rowspan="2"| Layers<br />(total) !! Diameter !!colspan="2"| Capacity <!-- raw or user data? exact number of sectors would be nice -->
|-
! (cm) !! ([[Gigabyte|GB]]) !!align=right| ([[Gibibyte|GiB]])
|-
| DVD-1<ref name="DVD Demystified">{{cite web|author=Jim Taylor |url=http://www.dvddemystified.com/dvdfaq.html |title=DVD Demystifed FAQ |publisher=Dvddemystified.com |date= |accessdate=2009-08-22}}</ref> ||title="single-sided, single-layer"| SS SL
| style="text-align:right;" | 1 || style="text-align:right;" | 1 || style="text-align:right;" | 8 || style="text-align:right;" | 1.46 || style="text-align:right;" | 1.36
|-
| DVD-2 ||title="single-sided, double-layer or double-sided, single layer"| SS DL
| style="text-align:right;" | 1 || style="text-align:right;" | 2 || style="text-align:right;" | 8 || style="text-align:right;" | 2.66 || style="text-align:right;" | 2.47
|-
| DVD-3 ||title="double-sided, single-layer"| DS SL
| style="text-align:right;" | 2 || style="text-align:right;" | 2 || style="text-align:right;" | 8 || style="text-align:right;" | 2.92 || style="text-align:right;" | 2.72
<!--|-
| DVD-4? ||title="double-sided, double- and single-layer"| DS DL/SL
| align="right" | 2 || align="right" | 3 || align="right" | 8 || align="right" | 4.12 || align="right" | 3.84--><!-- calculated, doubtful such discs ever existed -->
|-
| DVD-4<!--6?--> ||title="double-sided, double-layer"| DS DL
| style="text-align:right;" | 2 || style="text-align:right;" | 4 || style="text-align:right;" | 8 || style="text-align:right;" | 5.32 || style="text-align:right;" | 4.95
|-
| DVD-5 ||title="single-sided, single-layer"| SS SL
| style="text-align:right;" | 1 || style="text-align:right;" | 1 || style="text-align:right;" | 12 || style="text-align:right;" | 4.70 || style="text-align:right;" | 4.38
|-
| DVD-9 ||title="single-sided, double-layer"| SS DL
| style="text-align:right;" | 1 || style="text-align:right;" | 2 || style="text-align:right;" | 12 || style="text-align:right;" | 8.54 || style="text-align:right;" | 7.95
|-
| DVD-10 ||title="double-sided, single-layer"| DS SL
| style="text-align:right;" | 2 || style="text-align:right;" | 2 || style="text-align:right;" | 12 || style="text-align:right;" | 9.40 || style="text-align:right;" | 8.75
|-
| DVD-14<ref>{{cite web|title=DVD-14|publisher=AfterDawn Ltd.|url=http://www.afterdawn.com/glossary/terms/dvd-14.cfm|accessdate=2007-02-06}}<!--there should be a better source--></ref> ||title="double-sided, double- and single-layer"| DS DL/SL
| style="text-align:right;" | 2 || style="text-align:right;" | 3 || style="text-align:right;" | 12 || style="text-align:right;" | 13.24 || style="text-align:right;" | 12.33 <!--calculated from data above-->
|-
| DVD-18 ||title="double-sided, double-layer"| DS DL
| style="text-align:right;" | 2 || style="text-align:right;" | 4 || style="text-align:right;" | 12 || style="text-align:right;" | 17.08|| style="text-align:right;" | 15.90
|}<!-- CD/DVD hybrid discs not included-->
{| class="wikitable" style="float:right;"
|+ Capacity and nomenclature of (re)writable discs
!colspan="2" rowspan="2"| Designation
!rowspan="2"| Sides !!rowspan="2"| Layers<br />(total) !! Diameter !!colspan="2"| Capacity <!-- raw or user data? exact number of sectors would be nice -->
|-
! (cm) !! ([[Gigabyte|GB]]) !!align=right| ([[Gibibyte|GiB]])
|-
|DVD-R || SS SL (1.0) || 1 || 1 || 12 || 3.95 || 3.68
<!--|-
|DVD±R[W] || SS SL || 1 || 1 || 12 || 4.70 || 4.37-->
|-
|DVD-R || SS SL (2.0) || 1 || 1 || 12 || 4.70 || 4.37
|-
|DVD-RW || SS SL || 1 || 1 || 12 || 4.70 || 4.37
|-
|DVD+R || SS SL || 1 || 1 || 12 || 4.70 || 4.37
|-
|DVD+RW || SS SL || 1 || 1 || 12 || 4.70 || 4.37
<!--|-
|DVD±R[W] || DS SL || 2 || 2 || 12 || 9.40 || 8.75-->
|-
|DVD-R || DS SL || 2 || 2 || 12 || 9.40 || 8.75
|-
|DVD-RW || DS SL || 2 || 2 || 12 || 9.40 || 8.75
|-
|DVD+R || DS SL || 2 || 2 || 12 || 9.40 || 8.75
|-
|DVD+RW || DS SL || 2 || 2 || 12 || 9.40 || 8.75
|-
|DVD-RAM || SS SL || 1 || 1 || 8 || 1.46 || 1.36*
|-
|DVD-RAM || DS SL || 2 || 2 || 8 || 2.65 || 2.47*
|-
|DVD-RAM || SS SL (1.0) || 1 || 1 || 12 || 2.58 || 2.40
|-
|DVD-RAM || SS SL (2.0) || 1 || 1 || 12 || 4.70 || 4.37
|-
|DVD-RAM || DS SL (1.0) || 2 || 2 || 12 || 5.16 || 4.80
|-
|DVD-RAM || DS SL (2.0) || 2 || 2 || 12 || 9.40 || 8.75*
|}

The basic types of DVD (12&nbsp;cm diameter, single-sided or homogenous double-sided) are referred to by a rough approximation of their capacity in gigabytes. In draft versions of the specification, DVD-5 indeed held five gigabytes, but some parameters were changed later on as explained above, so the capacity decreased. Other [[DVD formats|formats]], those with 8&nbsp;cm diameter and hybrid variants, acquired similar numeric names with even larger deviation.

The 12&nbsp;cm type is a standard DVD, and the 8&nbsp;cm variety is known as a [[MiniDVD]]. These are the same sizes as a standard CD and a [[mini CD|mini-CD]], respectively. The capacity by surface (MiB/cm<sup>2</sup>) varies from 6.92 MiB/cm<sup>2</sup> in the DVD-1 to 18.0 MiB/cm<sup>2</sup> in the DVD-18.

As with hard disk drives, in the DVD realm, [[gigabyte]] and the symbol GB are usually used in the [[SI]] sense (i.e., 10<sup>9</sup>, or 1,000,000,000 bytes). For distinction, [[gibibyte]] (with symbol GiB) is used (i.e., 2<sup>30</sup>, or 1,073,741,824 bytes). Most computer operating systems display file sizes in gibibytes, [[mebibyte]]s, and [[kibibyte]]s, labeled as gigabyte, megabyte, and kilobyte, respectively.

[[Image:Dvdpencilrsizecomparison.png|thumb|Size comparison: a 12&nbsp;cm [[DVD+RW]] and a 19&nbsp;cm [[pencil]].]]
Each DVD sector contains 2,418 bytes of data, 2,048 bytes of which are user data. There is a small difference in storage space between ''+'' and ''-'' (hyphen) formats:

{| class="wikitable"
|+ Capacity differences of writable DVD formats<!--DVD-5 and DVD-9 should be listed for comparison-->
! Type || Sectors || Bytes || MB || MiB ||GB || GiB
|- style="text-align:right;"|
| DVD−R SL || 2,298,496 || 4,707,319,808 || 4,707.320 || 4,489.250 || 4.707 || 4.384
|- style="text-align:right;"|
| DVD+R SL || 2,295,104 || 4,700,372,992 || 4,700.373 || 4,482.625 || 4.700 || 4.378
|- style="text-align:right;"|
| DVD−R DL || 4,171,712 || 8,543,666,176 || 8,543.666 || 8,147.875 || 8.544 || 7.957
|- style="text-align:right;"|
| DVD+R DL || 4,173,824 || 8,547,991,552 || 8,547.992 || 8,152.000 || 8.548 || 7.961
|}

=== Technology ===
[[Image:Dismdvd.jpg|220px|thumb|right|Internal mechanism of a DVD-ROM Drive.]]

[[Image:Dvd-burning-cutaway3.JPG|220px|thumb|right|DVD-RW Drive operating with the protective cover removed.]]

DVD uses 650&nbsp;nm wavelength [[laser diode]] light as opposed to 780&nbsp;nm for CD. This permits a smaller pit to be etched on the media surface compared to CDs (0.74&nbsp;µm for DVD versus 1.6&nbsp;µm for [[CD]]), allowing for a DVD's increased storage capacity.

In comparison, [[Blu-ray]], the successor to the DVD format, uses a wavelength of 405&nbsp;nm, and one dual-layer disc has a 50&nbsp;GB storage capacity.

Writing speeds for DVD were 1×, that is, 1350&nbsp;[[kilobyte|kB]]/s (1,318&nbsp;[[Binary prefix|KiB]]/s), in the first drives and media models. More recent models, at 18× or 20×, have 18 or 20 times that speed. Note that for CD drives, 1× means 150&nbsp;[[Kibibyte|KiB]]/s (153.6&nbsp;kB/s), approximately 9 times slower.<ref name="DVD Demystified" />

{| class="wikitable"
|+ DVD drive speeds
!rowspan="2"| Drive speed
!colspan="3"| Data rate
!colspan="2"| ~Write time (min)<ref>The write time is wildly optimistic for higher (>4x) write speeds, due to being calculated from the maximum drive write speed instead of the average drive write speed.{{cite}}</ref>
|-
! (Mbit/s) !! (MB/s) !! (MiB/s)
! SL !! DL
|- style="text-align:right"
! 1×
| 10.80 || 1.35 || 1.29 || 61 || 107
|- style="text-align:right"
! 2×
| 21.60 || 2.70 || 2.57 || 31 || 54
|- style="text-align:right"
! 2.4×
| 25.92 || 3.24 || 3.09 || 25 || 45
|- style="text-align:right"
! 2.6×
| 28.08 || 3.51 || 3.35 || 23 || 41<!--exact? 3.50?-->
|- style="text-align:right"
! 4×
| 43.20 || 5.40 || 5.15 || 15 || 27
|- style="text-align:right"
! 6×
| 64.80 || 8.10 || 7.72 || 10 || 18
|- style="text-align:right"
! 8×
| 86.40 || 10.80 || 10.30 || 8 || 13
|- style="text-align:right"
! 10×
| 108.00 || 13.50 || 12.87 || 6 || 11
|- style="text-align:right"
! 12×
| 129.60 || 16.20 || 15.45 || 5 || 9
|- style="text-align:right"
! 16×
| 172.80 || 21.60 || 20.60 || 4 || 7
|- style="text-align:right"
! 18×
| 194.40 || 24.30 || 23.17 || 3 || 6
|- style="text-align:right"
! 20×
| 216.00 || 27.00 || 25.75 || 3 || 5
|- style="text-align:right"
! 22×
| 237.60 || 29.70 || 28.32 || 3 || 5
|- style="text-align:right"
! 24×
| 259.20 || 32.40 || 30.90 || 3 || 4
|}

== DVD recordable and rewritable ==
{{main|DVD recordable}}
[[Hewlett-Packard|HP]] initially developed recordable DVD media from the need to store data for backup and transport.

DVD recordables are now also used for consumer audio and video recording. Three formats were developed: DVD-[[DVD-R|R]]/[[DVD-RW|RW]] (hyphen), DVD+[[DVD+R|R]]/[[DVD+RW|RW]] (plus), and [[DVD-RAM]].

== Dual-layer recording ==<!-- This section is linked from [[DVD-DL]] -->
Dual-layer recording (sometimes also known as '''double-layer recording''') allows [[DVD-R]] and [[DVD+R]] discs to store significantly more data—up to 8.54 [[gigabyte]]s per disc, compared with 4.7 gigabytes for single-layer discs. Along with this, DVD-DL's have slower write speeds as compared to ordinary DVD's and when played on a DVD player, a slight transition can be seen between the layers. [[DVD-R DL]] was developed for the DVD Forum by [[Pioneer Corporation]]; [[DVD+R DL]] was developed for the DVD+RW Alliance by [[Philips]] and Mitsubishi Kagaku Media (MKM).<ref name="Dual-layer-BurnWorld">{{cite web|url=http://www.burnworld.com/howto/articles/intro-to-dual-layer.htm|title=Understanding Dual Layer DVD Recording |publisher=BurnWorld.com |author=Robert DeMoulin |accessdate=2007-07-06}}</ref>

A dual-layer disc differs from its usual DVD counterpart by employing a second physical layer within the disc itself. The drive with dual-layer capability accesses the second layer by shining the laser through the first semitransparent layer. In some DVD players, the layer change can exhibit a noticeable pause, up to several seconds.<ref>{{cite web|url=http://www.hometheaterhifi.com/cgi-bin/shootout.cgi?function=search&articles=all&type=&manufacturer=0&maxprice=0&deInt=0&mpeg=0#SamsungBD-P1000%20Blu-ray/DVD%20Player%20(HDMI)|title=DVD players benchmark|publisher=hometheaterhifi.com |accessdate=2008-04-01}}</ref> This caused some viewers to worry that their dual-layer discs were damaged or defective, with the end result that studios began listing a standard message explaining the dual-layer pausing effect on all dual-layer disc packaging.

DVD recordable discs supporting this technology are backward-compatible with some existing DVD players and DVD-ROM drives.<ref name="Dual-layer-BurnWorld" /> Many current DVD recorders support dual-layer technology, and the price is now comparable to that of single-layer drives, although the blank media remain more expensive. The recording speeds reached by dual-layer media are still well below those of single-layer media.

There are two modes for dual-layer orientation. With ''Parallel Track Path'' (PTP), used on DVD-ROM, both layers start at the inside diameter (ID) and end at the outside diameter (OD) with the lead-out. With ''[[Opposite Track Path]]'' (OTP), used on many DVD Video discs, the lower layer starts at the ID and the upper layer starts at the OD, where the other layer ends; they share one [[Lead-in (CD)#Lead-In|lead-in]] and one lead-out. However, some DVD Video discs also use a parallel track, such as those authored episodically, as in a disc with several separate episodes of a TV series—where more often than not, the layer change is in-between titles and therefore would not need to be authored in the opposite track path fashion. {{citation needed|date=August 2008}} <!-- Original cite removed as it links to irrelevant material --> <!-- It must be garbage as it would require the DVD-ROM to reverse direction - something it doesn't do. -->

== DVD Video ==
{{main|DVD Video}}

'''DVD Video''' is a standard for content on DVD media. In the U.S., mass retailer sales of DVD Video titles and players began in August 1997.<ref>{{cite web
|title=Discount stores are a video lover's channel of choice
|publisher=''[[Discount Store News]]'' (via findarticles.com)
|date=1998-08-10 |url=http://findarticles.com/p/articles/mi_m3092/is_15_37/ai_50241583
|accessdate=2008-03-06}}</ref> By June 2003, weekly DVD Video rentals began outnumbering weekly VHS cassette rentals, reflecting the rapid adoption rate of the technology in the U.S. marketplace.<ref name="ecommerceandvideodistributiondvd.blogspot.com" /><ref>{{cite web
|first=Anna |last=Bakalis
|title=It's unreel: DVD rentals overtake videocassettes
|publisher=''[[Washington Times]]''
|date=2003-06-20 |url=http://washingtontimes.com/business/20030620-113258-1104r.htm
|accessdate=}}</ref>
Currently, DVD Video is the dominant form of home video distribution worldwide.

Although many resolutions and formats are supported, most consumer DVD Video discs use either 4:3 or [[Anamorphic widescreen|anamorphic]] 16:9 [[aspect ratio]] [[MPEG-2]] video, stored at a resolution of 720/704×480 ([[NTSC]]) or 720/704×576 ([[PAL]]) at 29.97, 25, or [[24p#24p on DVD|23.976]] [[framerate|FPS]]. Audio is commonly stored using the [[Dolby Digital]] (AC-3) or [[Digital Theater System]] (DTS) formats, ranging from 16-bits/48 kHz to 24-bits/96 kHz format with [[monaural]] to 6.1-channel "[[Surround Sound]]" presentation, and/or [[MPEG-1]] Layer 2 and/or LPCM Stereophonic. Although the specifications for video and audio requirements vary by global region and television system, many DVD players support all possible formats. DVD Video also supports features such as menus, selectable subtitles, multiple camera angles, and multiple audio tracks.

== DVD Audio ==
{{main|DVD Audio}}

'''DVD Audio''' is a format for delivering high fidelity audio content on a DVD. It offers many channel configuration options (from [[monaural|mono]] to 5.1 [[surround sound]]) at various sampling frequencies (up to 24-bits/192 kHz versus [[Compact Disc Digital Audio|CDDA]]'s 16-bits/44.1 kHz). Compared with the CD format, the much higher-capacity DVD format enables the inclusion of considerably more music (with respect to total running time and quantity of songs) and/or far higher audio quality (reflected by higher [[sampling rate]]s and greater sample resolution, and/or additional channels for [[spatial sound]] reproduction).

Despite DVD Audio's superior technical specifications, there is debate as to whether the resulting audio enhancements are distinguishable in typical listening environments. DVD Audio currently forms a niche market, probably due to the very sort of format war with rival standard [[Super Audio CD|SACD]] that DVD Video avoided.

=== Security ===
{{main|Content Protection for Recordable Media}}

DVD Audio discs employ a [[Digital rights management|DRM]] mechanism, called [[Content Protection for Prerecorded Media]] (CPPM), developed by the 4C group (IBM, Intel, Matsushita, and Toshiba).

Although CPPM was supposed to be much harder to crack than DVD Video's [[Content Scramble System|CSS]], it was too eventually cracked in 2007 with the release of the ''dvdcpxm'' tool. The subsequent release of the libdvdcpxm library (which is based on dvdcpxm) allowed for the development of open source DVD-Audio players and ripping software, such as [[DVD-Audio Explorer]]<ref>{{cite web |url= http://forum.doom9.org/showthread.php?p=1099342#post1099342|title= DVD-Audio ripper|accessdate=2008-04-09}}</ref>. As a result, making 1:1 copies of DVD-Audio discs is now possible with relative ease, much like DVD-Video discs.

== Improvements and succession ==
In 2006, a new format called [[Blu-ray Disc]] (BD), designed by [[Sony]], [[Philips]], and [[Panasonic]], was released as the successor to DVD. Another format, [[HD DVD]], competed unsuccessfully with this format in the [[format war]] [[High definition optical disc format war|of 2006–08]]. A dual layer Blu-ray Disc can store 50 GB.<ref>{{cite web |title=What is Blu-ray Disc? |publisher=Sony |url=http://www.sonystyle.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10551&storeId=10151&langId=-1&identifier=S_BrandShowcase_Blu-ray|accessdate=2008-11-25}}</ref><ref>{{cite web |title=DVD FAQ: 3.13 - What about the new HD formats? |url=http://www.dvddemystified.com/dvdfaq.html#3.13 |accessdate=2008-11-25 |date=2008-09-21}}</ref>

However, unlike previous format changes (e.g., audio tape to compact disc, VHS videotape to DVD), there is no immediate indication that production of the standard DVD will gradually wind down, as they still dominate, with around 87% of video sales and approximately one billion DVD player sales worldwide. In fact experts claim that the DVD will remain the dominant medium for at least another five years as Blu-Ray technology is still in its introductory phase, write and read speeds being poor as well as the fact of necessary hardware being expensive and not readily available.<ref name="ecommerceandvideodistributiondvd.blogspot.com" /><ref>{{cite web|url=http://www.movieweb.com/dvd/news/20/26720.php |title=High-Definition Sales Far Behind Standard DVD's First Two Years |publisher=Movieweb.com |date=2008-02-20 |accessdate=2009-08-22}}</ref> Blu-ray players have struggled partly because the MPEG I-frames stored on DVD discs were based on [[JPEG]], which carries [[JPEG#Discrete cosine transform|DCT]] information that can be exploited to improve interpolation for higher resolutions.

Consumers initially were also slow to adopt Blu-ray due to the cost{{cn|date=October 2009}}. By 2009, 85% of stores were selling [[Blu-ray Disc]]s. A high-definition TV and appropriate connection cables are also required to take advantage of Blu-ray disc. Some analysts suggest that the biggest obstacle to replacing DVD is due to its installed base; a large majority of consumers are satisfied with DVDs.<ref>{{cite magazine|url=http://www.businessweek.com/magazine/content/04_16/b3879008_mz001.htm |title=Gates And Ballmer On "Making The Transition" |publisher=BusinessWeek |date=2004-04-19 |accessdate=2009-08-22}}</ref> The DVD succeeded because it offered a compelling alternative to VHS. In addition, Blu-ray players are designed to be [[backward-compatible]], allowing older DVDs to be played since the media are physically identical; this differed from the change from vinyl to CD and from tape to DVD, which involved a complete change in physical medium.

This situation can be best compared to the changeover from [[78 rpm]] shellac recordings to 45 rpm and 33⅓ rpm vinyl recordings; because the medium used for the earlier format was virtually the same as the latter version (a disc on a turntable, played using a needle), [[phonographs]] continued to be built to play obsolete 78s for decades after the format was discontinued. Manufacturers have announced standard DVD releases well into 2009, and the format remains the preferred one for the release of older television programs and films, with some programs such as ''[[Star Trek: The Original Series]]'' requiring remastering and replacement of certain elements such as special effects in order to be better received in high-definition viewing.<ref>{{cite web|url=http://www.aintitcool.com/display.cgi?id=24344 |title=Kirk/Spock STAR TREK To Get All-New HD Spaceships |publisher=Aintitcool.com |date= |accessdate=2009-08-22}}{{Unreliable source?|date=August 2009}}</ref>

The [[Holographic Versatile Disc]] (HVD) is an optical disc technology that may one day hold up to 3.9 terabytes (TB) of information, albeit the current maximum is 500GB. It employs a technique known as collinear holography.

The [[5D DVD]], being developed at the [[Swinburne University of Technology]] in [[Melbourne]], [[Australia]], uses a multilaser system to encode and read data on multiple layers. Disc capacities are estimated at up to 10 terabytes, and the technology could be commercially ready within ten years. <ref>{{cite news | title='5D' storage could hold 2,000 times more than 1 DVD | url=http://www.cbc.ca/technology/story/2009/05/22/tech-5d-storage-dvd-polarization-colours-3d-swinburne-chon-nature.html | publisher=Canadian Broadcasting Corporation |agency=CBC News | date=2009-05-22 | accessdate=2009-05-29}}</ref>

== DVD as an archival medium ==
There are two considerations for an archival medium: [[obsolescence]] and durability. If there is no device that can read the medium, it is obsolete and the data is unavailable and thus lost.

Durability of DVDs is measured by how long the data may be read from the disc, assuming compatible devices exist that can read it: that is, how long the disc can be stored until data is lost. Five factors affect durability: sealing method, reflective layer, organic dye makeup, where it was manufactured, and storage practices.<ref name="adterrasperaspera.com">{{cite web|title=How To Choose CD/DVD Archival Media|date=2006-10-30|url=http://adterrasperaspera.com/blog/2006/10/30/how-to-choose-cddvd-archival-media|accessdate=2009-03-14}}</ref>

According to the [[Optical Storage Technology Association]] (OSTA), "manufacturers claim life spans ranging from 30 to 100 years for DVD, DVD-R and DVD+R discs and up to 30 years for DVD-RW, DVD+RW and DVD-RAM",<ref>{{cite web|title=How long will data recorded on writable DVD discs remain readable?|url=http://www.osta.org/technology/dvdqa/dvdqa11.htm|accessdate=2009-03-14}}</ref> although a manufacturer of 24-karat gold-based DVDs claims lifespans of up to 300 years.<ref>{{cite web|title=New Gold KODAK CD and DVD Promise a 80 to 300 Years of Lifetime|date=2006-04-18|url=http://www.cdrinfo.com/Sections/News/Details.aspx?NewsId=16833|accessdate=2009-03-14}}</ref> Of more conventional manufacturing processes, [[Taiyo Yuden]] is frequently recommended for longer durability.<ref name="adterrasperaspera.com" />

== DVD consumer rights ==
DVDs that have commercial movies and television content recorded on them are subject to [[copyright]]. The rise of [[filesharing]] and "piracy" has prompted many copyright owners to display notices on DVD packaging or displayed on screen when the content is played that warn consumers of the illegality of certain uses of the DVD.

Such notices do not always offer a reliable summary of DVD owners' rights.{{citation needed|date=October 2009}}

Generally, retail buyers of commercial prerecorded DVDs are free to sell or exchange their property.{{citation needed|date=October 2009}} Arrangements for renting and lending differ more by geography. In the U.S., the right to rent or lend out bought DVDs is protected by the [[first-sale doctrine]] under the [[Copyright Act of 1976]]. In Europe, rental and lending rights are more limited, under a 1992 European Directive that gives copyright holders broader powers to restrict the commercial renting and public lending of DVD copies of their work.

== See also ==
* [[Book type]]
* [[Content Scramble System]]
* [[DVD authoring]]
* [[DVD region code]]
* [[DVD TV game]]
* [[IFO]], [[BUP]] and [[VOB]]

== References ==
{{reflist|2}}
DVD Manufacturing

== Further reading ==
* {{cite web |first=Hugh |last=Bennett |title=Understanding Recordable & Rewritable DVD |publisher=Optical Storage Technology Association |date=April 2004 |url=http://www.osta.org/technology/dvdqa/ |accessdate=2006-12-17 }}
* Labarge, Ralph. ''DVD Authoring and Production''. Gilroy, Calif.: CMP Books, 2001. ISBN 1-57820-082-2.
* Taylor, Jim. ''DVD Demystified, 2nd edition''. New York: McGraw-Hill Professional, 2000. ISBN 0-07-135026-8.

== External links ==
{{wikibooks|All About Converting From Several Video Formats To DVD}}
* [http://search.dmoz.org/cgi-bin/search?search=dvd DVD] at the [[dmoz|Open Directory Project]]
* [http://www.burnworld.com/howto/articles/intro-to-dual-layer.htm Dual Layer Explained] – Informational Guide to the Dual Layer Recording Process
* [http://www.dvddemystified.com/dvdfaq.html DVD Frequently Asked Questions (and Answers)]

{{Video storage formats}}

{{DEFAULTSORT:Dvd}}
[[Category:Computer storage media]]
[[Category:Audio storage]]
[[Category:Video storage]]
[[Category:DVD]]
[[Category:120 mm discs]]
[[Category:Consumer electronics]]
[[Category:1995 introductions]]
[[Category:Joint ventures]]

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Revision as of 04:21, 9 December 2009

VANDALISM

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