Difference between revisions of "DVD"

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'''DVD''', also known as '''Digital Video Disc''' or '''Digital Versatile Disc''',<!--
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A [[DVD]] or '''Digital Video Disc''' is a circular shaped plastic disc used for playing video, and storing data. Data is read by reflecting a concentrated [[laser]] beam at a thin metallic layer within the disc. Fine holes or pits in the layer are picked up by the laser mechanism, and converted into data or video.
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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.
 
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--> is an optical disc storage media format, and was invented and developed by Philips, Sony, Toshiba, and Time Warner in 1995. Its main uses are video and data storage. DVDs are of the same dimensions as compact discs (CDs), but are capable of storing almost seven times as much data.
 
  
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Variations of the term ''DVD'' often indicate 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.
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A DVD uses the same concepts as a [[CD-ROM]], but with higher speeds, and larger data storage, without increasing the physical disc size.
  
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[[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.
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A standard sized writable DVD stores approximately 4,700MB (4.7GB) of uncompressed data.
  
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== History ==
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[[category:Technology]]
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In 1993, two optical disc storage formats were being developed. One was the MultiMedia [[Compact Disc]] (MMCD) also called CDi, 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]].
 
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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 seeking support for their format for storing computer data. [[Alan E. Bell]], a researcher from IBM's [[Almaden Research Center]] received that request and also learned of the [[Sony#Products, technologies and proprietary formats|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.
 
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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.
 
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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.
 
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EFMPlus was chosen because of its great resilience to 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.
 
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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 Europe in October 1998, and in Australia in February 1999.
 
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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>
 
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== Specifications ==
 
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DVD specifications created and updated by the [[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">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>
 
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Some specifications for mechanical, physical and optical characteristics of DVD optical discs can be downloaded as ''freely available standards'' from the [[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> Also, the [[DVD+RW Alliance]] publishes 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>
 
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Some of DVD specifications (e.g. for DVD-Video) are not publicly available and can be obtained only from the DVD Format/Logo Licensing Corporation for a fee of US $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" />
 
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== Etymology ==
 
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The official DVD specification documents have never defined the [[Acronym and initialism|initialism]] DVD.{{Citation needed|date=April 2010}} 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.
 
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'''''DVD''''' was originally used as an initialism for the unofficial term
 
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'''''digital videodisk'''''.<!--
 
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NOTE: Please do not edit this spelling unless you have an authoritative source that predates than the one cited.
 
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--><ref>{{cite news
 
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|title=A Battle for Influence Over Insatiable Disks
 
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|publisher=''[[The New York Times]]''
 
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|date=1996-01-11
 
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|url=http://query.nytimes.com/gst/fullpage.html?res=990CEEDA143CF932A25752C0A963958260
 
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|accessdate=2007-04-09
 
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| first=John
 
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| last=Markoff}}</ref>
 
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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
 
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|title=DVD FAQ
 
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|publisher=DVD Demystified
 
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|date=2006-09-12
 
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|url=http://www.dvddemystified.com/dvdfaq.html#1.1
 
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|accessdate=}}</ref>
 
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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
 
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|title=DVD Primer
 
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|publisher=DVD Forum
 
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|date=2004-11-14
 
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|url=http://www.dvdforum.org/faq-dvdprimer.htm#1
 
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|accessdate=2008-01-23}}
 
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</ref>
 
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== Identification (MID) ==
 
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The DVD is made of a spiral groove read or written starting at the center. The form of the groove encodes unalterable identification data known as [[Media Identification Code]] (MID). The MID contains data such as the manufacturer and model, byte capacity, allowed data rates (also known as speed), etc.
 
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== Design ==
 
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=== As a movie delivery medium ===
 
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DVD was adopted by movie and home entertainment distributors to replace the ubiquitous VHS tape as the primary means of distributing films to consumers in the home entertainment marketplace. DVD was chosen for its superior ability to reproduce moving pictures and sound, for its superior durability, and for its interactivity. Interactivity had proven to be a feature which consumers, especially collectors, favored when the movie studios had released their films on laser disk. When the price point for a laser disk at approximately $100 per disk moved to $20 per disk at retail, this luxury feature became available for mass consumption. Simultaneously the movie studios decided to change their home entertainment release model from a rental model to a for purchase model. This allowed all fans to become collectors and pushed the movie DVD into a demand position that essentially made it the most successful consumer product of all time.
 
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At the same time, a demand for interactive design talent and services was created. Movies in the past had uniquely designed title sequences. Suddenly every movie being released required information architecture and interactive design components that matched the film's tone and were at the quality level that Hollywood demanded for its product. Whole mini-studios to perform this type of work, such as 1K Studios and Canned Interactive, either formed or created service departments to fulfill this need in Hollywood.
 
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New DVD releases are released weekly by all major studios. DVDs are typically released on Tuesdays of every week. Sites such as [[FilmCrave]] display new DVD releases as they are released <ref>[http://www.filmcrave.com/dvd_new.php - displays New DVD releases as they are released each week].</ref>. Information includes plots, actors, directors, release date and movie title. With the advent of Blu-ray releases, studios now rely on both Blu-ray and DVDs to supplement their revenue for a particular movie.
 
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=== As an interactive medium ===
 
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DVD as a format had two qualities at the time that were not available in any other interactive medium: 1. Enough capacity and speed to provide high quality, full motion video and sound, and 2. low cost delivery mechanism provided by consumer products retailers who quickly moved to sell their players for under $200 and eventually for under $50 at retail. In addition, the medium itself was small enough and light enough to mail using general first class postage. Almost over night, this created a new business opportunity and model for business innovators like Netflix to re-invent the home entertainment distribution model. It also opened up the opportunity for business and product information to be inexpensively provided on full motion video through direct mail.
 
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Again, a demand for unique interactive design talent and services was created. Companies as large as Nike and Mattel went in search of new start-ups such as 1K Studios and Canned Interactive to fulfill their information architecture and design needs.
 
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== Capacity ==
 
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{| class="wikitable"
 
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|+ 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>
 
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!colspan="2" rowspan="2"| Designation
 
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!rowspan="2"| Sides !!rowspan="2"| Layers<br />(total) !! Diameter !!colspan="2"| Capacity <!-- raw or user data? exact number of sectors would be nice -->
 
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|-
 
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! (cm) !! ([[Gigabyte|GB]]) !!align=right| ([[Gibibyte|GiB]])
 
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|-
 
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| 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
 
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| 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
 
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|-
 
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| DVD-2 ||title="single-sided, double-layer or double-sided, single layer"| SS DL
 
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| 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
 
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|-
 
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| DVD-3 ||title="double-sided, single-layer"| DS SL
 
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| 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
 
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|-
 
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| DVD-4 ||title="double-sided, double-layer"| DS DL
 
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| 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
 
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|-
 
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| DVD-5 ||title="single-sided, single-layer"| SS SL
 
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| 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;" | 4.37
 
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|-
 
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| DVD-9 ||title="single-sided, double-layer"| SS DL
 
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| 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
 
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|-
 
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| DVD-10 ||title="double-sided, single-layer"| DS SL
 
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| 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
 
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|-
 
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| 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 SL+DL
 
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| 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-->
 
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|-
 
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| DVD-18 ||title="double-sided, double-layer"| DS DL
 
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| 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
 
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|}<!-- CD/DVD hybrid discs not included-->
 
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{{-}}
 
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{| class="wikitable" style="float:right;"
 
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|+ Capacity and nomenclature of (re)writable discs
 
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!colspan="2" rowspan="2"| Designation
 
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!rowspan="2"| Sides !!rowspan="2"| Layers<br />(total) !! Diameter !!colspan="2"| Capacity <!-- raw or user data? exact number of sectors would be nice -->
 
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|-
 
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! (cm) !! ([[Gigabyte|GB]]) !!align=right| ([[Gibibyte|GiB]])
 
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|-
 
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|DVD-R  || SS SL (1.0) || 1 || 1 || 12 || 3.95 || 3.68
 
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|-
 
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|DVD-R  || SS SL (2.0) || 1 || 1 || 12 || 4.70 || 4.37
 
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|-
 
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|DVD-RW || SS SL || 1 || 1 || 12 || 4.70 || 4.37
 
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|-
 
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|DVD+R  || SS SL || 1 || 1 || 12 || 4.70 || 4.37
 
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|-
 
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|DVD+RW || SS SL || 1 || 1 || 12 || 4.70 || 4.37
 
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|-
 
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|DVD-R  || DS SL || 2 || 2 || 12 || 9.40 || 8.75
 
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|-
 
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|DVD-RW || DS SL || 2 || 2 || 12 || 9.40 || 8.75
 
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|-
 
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|DVD+R  || DS SL || 2 || 2 || 12 || 9.40 || 8.75
 
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|-
 
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|DVD+RW || DS SL || 2 || 2 || 12 || 9.40 || 8.75
 
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|-
 
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|DVD-RAM || SS SL || 1 || 1 || 8 || 1.46 || 1.36*
 
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|-
 
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|DVD-RAM || DS SL || 2 || 2 || 8 || 2.65 || 2.47*
 
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|-
 
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|DVD-RAM || SS SL (1.0) || 1 || 1 || 12 || 2.58 || 2.40
 
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|-
 
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|DVD-RAM || SS SL (2.0) || 1 || 1 || 12 || 4.70 || 4.37
 
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|-
 
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|DVD-RAM || DS SL (1.0) || 2 || 2 || 12 || 5.16 || 4.80
 
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|-
 
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|DVD-RAM || DS SL (2.0) || 2 || 2 || 12 || 9.40 || 8.75*
 
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|}
 
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The basic types of DVD (12&nbsp;cm diameter, single-sided or homogeneous 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.
 
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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.
 
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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., 1024<sup>3</sup> (2<sup>30</sup>), or 1,073,741,824 bytes).
 
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[[Image:Dvdpencilrsizecomparison.png|thumb|Size comparison: a 12&nbsp;cm [[DVD+RW]] and a 19&nbsp;cm [[pencil]].]]
 
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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:
 
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{| class="wikitable"
 
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|+ Capacity differences of writable DVD formats<!--DVD-5 and DVD-9 should be listed for comparison-->
 
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! Type || Sectors || Bytes || KB || MB || GB || KiB || MiB || GiB
 
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|- style="text-align:right;"|
 
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| DVD-R SL || 2,298,496 || 4,707,319,808 || 4,707,319.808 || 4,707.320 || 4.707 || 4,596,992 || 4,489.250 || 4.384
 
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|- style="text-align:right;"|
 
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| DVD+R SL || 2,295,104 || 4,700,372,992 || 4,700,372.992 || 4,700.373 || 4.700 || 4,590,208 || 4,482.625 || 4.378
 
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|- style="text-align:right;"|
 
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| DVD-R DL || 4,171,712 || 8,543,666,176 || 8,543,666.176 || 8,543.666 || 8.544 || 8,343,424 || 8,147.875 || 7.957
 
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|- style="text-align:right;"|
 
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| DVD+R DL || 4,173,824 || 8,547,991,552 || 8,547,991.552 || 8,547.992 || 8.548 || 8,347,648 || 8,152.000 || 7.961
 
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|}
 
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=== Technology ===
 
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[[Image:Dvd-burning-cutaway3.JPG|220px|thumb|right|DVD-RW Drive operating with the protective cover removed.]]
 
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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.
 
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In comparison, [[Blu-ray Disc]], 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.
 
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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 153.6&nbsp;kB/s (150&nbsp;[[Kibibyte|KiB]]/s), about one-ninth as swift.<ref name="DVD Demystified" />
 
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{| class="wikitable"
 
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|+ DVD drive speeds
 
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!rowspan="2"| Drive speed
 
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!colspan="3"| Data rate
 
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!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.{{Citation needed|date=April 2010}}</ref>
 
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|-
 
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! (Mbit/s) !! (MB/s) !! (MiB/s)
 
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! SL !! DL
 
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|- style="text-align:right"
 
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! 1×
 
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| 10.80 || 1.35 || 1.29 || 61 || 107
 
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|- style="text-align:right"
 
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! 2×
 
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| 21.60 || 2.70 || 2.57 || 31 || 54
 
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|- style="text-align:right"
 
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! 2.4×
 
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| 25.92 || 3.24 || 3.09 || 25 || 45
 
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|- style="text-align:right"
 
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! 2.6×
 
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| 28.08 || 3.51 || 3.35 || 23 || 41<!--exact? 3.50?-->
 
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|- style="text-align:right"
 
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! 4×
 
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| 43.20 || 5.40 || 5.15 || 15 || 27
 
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|- style="text-align:right"
 
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! 6×
 
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| 64.80 || 8.10 || 7.72 || 10 || 18
 
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|- style="text-align:right"
 
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! 8×
 
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| 86.40 || 10.80 || 10.30 || 8 || 13
 
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|- style="text-align:right"
 
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! 10×
 
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| 108.00 || 13.50 || 12.87 || 6 || 11
 
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|- style="text-align:right"
 
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! 12×
 
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| 129.60 || 16.20 || 15.45 || 5 || 9
 
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|- style="text-align:right"
 
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! 16×
 
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| 172.80 || 21.60 || 20.60 || 4 || 7
 
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|- style="text-align:right"
 
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! 18×
 
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| 194.40 || 24.30 || 23.17 || 3 || 6
 
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|- style="text-align:right"
 
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! 20×
 
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| 216.00 || 27.00 || 25.75 || 3 || 5
 
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|- style="text-align:right"
 
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! 22×
 
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| 237.60 || 29.70 || 28.32 || 3 || 5
 
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|- style="text-align:right"
 
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! 24×
 
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| 259.20 || 32.40 || 30.90 || 3 || 4
 
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|}
 
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=== Internal mechanism of a drive ===
 
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{{See also|optical disc drive}}
 
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[[Image:Dismdvd.jpg|220px|thumb|right|Internal mechanism of a DVD-ROM Drive. See text for details.]]
 
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This mechanism is shown right side up; the disc is above it. The laser and optical system "looks at" the underside of the disc.
 
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With reference to the photo, just to the right of image center is the disc spin motor, a gray cylinder, with its gray centering hub and black resilient drive ring on top. A clamp (not in the photo, retained in the drive's cover), pulled down by a magnet, clamps the disc when this mechanism rises, after the disc tray stops moving inward. This motor has an external rotor – every part of it that you can see spins.
 
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The gray metal chassis is shock-mounted at its four corners to reduce sensitivity to external shocks, and to reduce drive noise when running fast. The soft shock mount grommets are just below the brass-colored washers at the four corners (the left one is obscured). Running through those grommets are screws to fasten them to the black plastic frame that's underneath.
 
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Two parallel precision guide rods that run between upper left and lower right in the photo carry the "[[sled]]", the moving optical read-write head. As shown, this "sled" is close to, or at the position where it reads or writes at the edge of the disc.
 
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A dark gray disc with two holes on opposite sides has a blue lens surrounded by silver-colored metal. This is the lens that's closest to the disc; it serves to both read and write by focusing the laser light to a very small spot. It's likely that this disc rotates half a turn to position a different set of optics (the other "hole") for CDs vs. DVDs.
 
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Under the disc is an ingenious actuator comprising permanent magnets and coils that move the lens up and down to maintain focus on the data layer. As well, the actuator moves the lens slightly toward and away from the spin-motor spindle to keep the spot on track. Both focus and tracking are relatively quite fast and very precise. The same actuator rotates the lens mount half.a turn as described.
 
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To select tracks (or files) as well as advancing the "sled" during continuous read or write operations, a stepping motor rotates a coarse-pitch leadscrew to move the "sled" throughout its total travel range. The motor, itself, is the gray cylinder just to the left of the most-distant shock mount; its shaft is parallel to the support rods. The leadscrew, itself, is the rod with evenly-spaced darker details; these are the helical groove that engages a pin on the "sled".
 
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The irregular orange material is flexible etched copper foil supported by thin sheet plastic; these are "flexible printed circuits" that connect everything to the electronics (which is not shown).
 
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−
== DVD recordable and rewritable ==
 
−
{{Main|DVD recordable}}
 
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[[Image:Faceplate showing both dvd logo.jpg|thumb|left|Faceplate of a DVD Drive supporting both DVD+ and DVD- formats.]][[Hewlett-Packard|HP]] initially developed recordable DVD media from the need to store data for backup and transport.
 
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DVD recordables are now also used for consumer audio and video recording. Three formats were developed: DVD-[[DVD-R|R]]/[[DVD-RW|RW]], DVD+[[DVD+R|R]]/[[DVD+RW|RW]] (plus), and [[DVD-RAM]]. DVD-R is available in two formats, General (650&nbsp;nm) and Authoring (635&nbsp;nm), where Authoring discs may be recorded with encrypted content but General discs may not.<ref>http://www.taperesources.com/dvd_media.html#article2</ref>
 
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−
Although most DVD writers can nowadays write the DVD+R/RW and DVD-R/RW formats (usually denoted by "DVD±RW" and/or the existence of both the DVD Forum logo and the DVD+RW Alliance logo), the "plus" and the "dash" formats use different writing specifications. Most DVD readers and players will play both kinds of discs, although older models can have trouble with the "plus" variants.
 
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−
== 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-DLs have slower write speeds as compared to ordinary DVDs 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>
 
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−
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.
 
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−
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 recorder]]s 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.
 
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−
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 Digital 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 DVDs 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 -->
 
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−
== DVD-Video ==
 
−
{{Main|DVD-Video}}
 
−
 
 
−
'''DVD-Video''' is a standard for content on DVD media. The format went on sale in Japan on November 1, 1996, in the United States on March 1, 1997, in Europe on October 1, 1998 and in Australia on February 1, 1999.<ref>{{cite web
 
−
|title=Discount stores are a video lover's channel of choice
 
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|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> DVD became the dominant form of home video distribution in Japan when it first went on sale in 1996, but did not become the dominant form of home video distribution in the United States until June 15, 2003, when weekly DVD-Video in the United States 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
 
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|title=It's unreel: DVD rentals overtake videocassettes
 
−
|publisher=''[[Washington Times]]''
 
−
|date=2003-06-20 |url=http://washingtontimes.com/business/20030620-113258-1104r.htm
 
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|accessdate=}}</ref>
 
−
Currently, DVD-Video is the dominant form of home video distribution worldwide, although in [[Japan]] it was surpassed by [[Blu-ray Disc]] when Blu-ray first went on sale in Japan on March 31, 2006.
 
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Although many resolutions and formats are supported, most consumer DVDs 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&nbsp;kHz to 24-bits/96&nbsp;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 [[Multi-standard television|support all possible formats]]. DVD Video also supports features such as menus, selectable subtitles, multiple camera angles, and multiple audio tracks.
 
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=== Security ===
 
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{{Main|Content Scramble System}}
 
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<!--
 
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Please add some basic summary content to this sub-section.
 
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-->
 
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=== Consumer rights ===
 
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The rise of [[filesharing]] and "[[Copyright infringement|piracy]]" has prompted many copyright holders 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. It is commonplace to include a 90 second advert warning that most forms of copying the contents are illegal. Many DVDs prevent skipping past or fast-forwarding through this warning, forcing the consumer to watch.
 
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<!--
 
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Add text about...
 
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... the DMCA, CSS encryption, and how making backups of one's own purchased video DVDs is illegal because one would be required to violate the DMCA by cracking the CSS encryption on the DVD;
 
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... how this has impacted free DVD playback software on free computer OSes such as Linux (see article on DeCSS);
 
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... consumer protest of the above (by printing CSS cracking software code on t-shirts, for example)
 
−
-->
 
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Arrangements for renting and lending differ by geography. In the U.S., the right to re-sell, 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. <!-- Add note about the Librarian of Congress's three-year exemption proclamations, and how DVDs have been at the forefront of the public discussions every time. -->
 
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−
== DVD-Audio ==
 
−
{{Main|DVD-Audio}}
 
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'''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&nbsp;kHz versus [[Red Book (CD standard)|CDDA]]'s 16-bits/44.1&nbsp;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).
 
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−
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.
 
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−
=== 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 too was 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 ==
 
−
=== HD DVD and Blu-ray Disc ===
 
−
In 2006, two new formats called [[HD DVD]] and [[Blu-ray Disc]] were released as the successor to DVD. HD DVD competed unsuccessfully with Blu-ray Disc in the [[format war]] [[High definition optical disc format war|of 2006–2008]]. A dual layer HD DVD can store up to 30GB and a dual layer Blu-ray disc can hold up to 50GB.<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 or 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>
 
−
 
 
−
Consumers initially were also slow to adopt Blu-ray due to the cost.<ref>http://seekingalpha.com/article/171207-slow-blu-ray-adoption-a-threat-to-hollywood-s-bottom-line</ref> By 2009, 85% of stores were selling [[Blu-ray Disc]]s. A high-definition television 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 journal|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. As of 2010 it is still commonplace for major releases to be issued in "combo pack" format, including both a DVD and a Blu-ray disc (as well as, in many cases, a third disc with an authorized digital copy). Also, some multi-disc sets use Blu-ray for the main feature, but DVD discs for supplementary features (examples of this include the ''[[Harry Potter]]'' "Ultimate Edition" collections, the 2009 re-release of the 1967 ''[[The Prisoner]]'' TV series, and a 2007 collection related to ''[[Blade Runner]]'').
 
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−
This situation can be best compared to the changeover from [[Gramophone record#78 rpm disc developments|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 continue to release standard DVD titles as of 2010, 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]]'' needing to be re-scanned to produce a high definition version from the original film recordings (certain special effects were also updated 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}}{{Verify credibility|date=August 2009}}</ref> In the case of ''[[Doctor Who]]'', a series primarily produced on standard definition videotape between 1963 and 1989, [[BBC Video]] reportedly intends to continue issuing DVD-format releases of that series until at least November 2013 (since there would be very little increase in visual quality from upconverting the standard definition videotape masters to high definition).<ref>{{cite web|url=http://www.dwin.org/expressionengine/index.php/site/comments/the_mind_of_evil_in_colour_just_not_yet_and_more/ |title=The Mind of Evil in Color Just Not Yet and More |publisher=Doctor Who Information Network |date= 2009-10-23|accessdate=2010-04-25}}</ref>
 
−
 
 
−
=== Holographic Versatile Disc ===
 
−
The [[Holographic Versatile Disc]] (HVD) is an optical disc technology that may one day hold up to 4 terabytes (TB) of information, although the current maximum is 500GB. It employs a technique known as collinear holography.
 
−
 
 
−
=== 5D DVD ===
 
−
The [[5D DVD]], being developed in 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>
 
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−
== Use as backup medium ==
 
−
There are two considerations for a [[backup]] medium: [[obsolescence]] and durability. If the [[Specification (technical standard)|specifications]] of the DVD format are not preserved and there is no device that can read the medium, it might be hard to re-create devices that can read DVDs, making it very hard to retrieve the data. {{or|date=October 2010}}
 
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−
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>
 
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−
The longevity of the ability to read from a DVD+R or DVD-R, is largely dependent on manufacturing quality ranging from 2 to 15 years,<ref>{{cite web|title=Optical Media Longetivity|url=http://www.thexlab.com/faqs/opticalmedialongevity.html|accessdate=2010-02-26}}</ref><ref>{{cite web|title=DVD Durability|url=http://www.backupcritic.com/backup-media/dvd/durability.html|accessdate=2010-02-26}}</ref><ref>{{cite web|title=The Life-Span of DVDs|url=http://www.larryjordan.biz/articles/lj_dvd_life.html|accessdate=2010-02-26|date=january 2006}}</ref> and is believed to be an unreliable medium for backup unless great care is taken for storage conditions and handling.
 
−
 
 
−
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>
 
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−
== See also ==
 
−
* [[Book type]]
 
−
* [[Content Scramble System]]
 
−
* [[Digital video recorder]] (DVR)
 
−
* [[DVD authoring]]
 
−
* [[DVD region code]]
 
−
* [[DVD TV game]]
 
−
* [[Evita (film)|Evita]] (first film to be ever released on DVD)
 
−
* [[IFO]], [[BUP]] and [[VOB]]
 
−
 
 
−
== References ==
 
−
{{Reflist|2}}
 
−
 
 
−
== 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 ==
 
−
{{commons}}
 
−
{{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]&nbsp;– Informational Guide to the Dual Layer Recording Process
 
−
* [http://www.dvddemystified.com/dvdfaq.html DVD Frequently Asked Questions (and Answers)]
 
−
* [http://dvd-burning-software.toptenreviews.com/dvd-burning-and-ripping.html DVD Burning and Ripping: A Primer, A Glossary]
 
−
* [http://www.youtube.com/user/eyeh8cbs#p/u/14/NSY5rVzsTBc YouTube: Segment from 1997 Toshiba DVD demo disc]&nbsp;– Technical information about the then-new DVD format, from "DVD Gallery," an in-store demonstration disc from Toshiba.
 

Revision as of 03:12, January 16, 2011

A DVD or Digital Video Disc is a circular shaped plastic disc used for playing video, and storing data. Data is read by reflecting a concentrated laser beam at a thin metallic layer within the disc. Fine holes or pits in the layer are picked up by the laser mechanism, and converted into data or video.

A DVD uses the same concepts as a CD-ROM, but with higher speeds, and larger data storage, without increasing the physical disc size.

A standard sized writable DVD stores approximately 4,700MB (4.7GB) of uncompressed data.

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