Digital versatile disk: Difference between revisions

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imported>Thomas Wright Sulcer
(updated with new information courtesy User:Daniel Mietchen; changing article title to DVD not "Digital versatile disk" as per discussion in talk pages)
imported>Thomas Wright Sulcer
(Changing this page to the redirect page, so users go to DVD)
 
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#REDIRECT [[DVD]]
[[Image:DVD in hand.jpg|thumb|right|alt=Picture of a DVD held in an adult-sized hand with a keyboard in the background.|A DVD can fit in the palm of a person's hand.]]
{{TOC|right}}
'''DVD''' is an optical disc storage technology which can hold video, audio, and computer data.<ref name=twsMAR02k12>{{cite news
|title=  What is DVD?
|quote= It's an optical disc storage technology for video, audio, and computer data. DVD is essentially a bigger, faster CD that can hold high-quality digital video, better-than-CD audio, pictures, and any other sort of digital information. DVD encompasses home entertainment, computers, and business information with a single digital format. It replaced laserdisc, videotape, many video game cartridge formats, and many CD-ROM applications. DVD has widespread support from all major electronics companies, all major computer hardware companies, and all major movie and music studios. With this unprecedented support, DVD became the most successful consumer electronics product of all time in less than three years of its introduction. In 2007, ten years after launch, there were over one billion DVD playback devices worldwide, counting DVD players, DVD PCs, and DVD game consoles.
|publisher= DVD Forum: Usenet groups
|date= 2010-03-02
|url= http://www.dvddemystified.com/dvdfaq.html#1.1
|accessdate= 2010-03-02
}}</ref> It is like a ''CD'' but can hold much more digital information.<ref name=twsMAR02k12/> The technology replaced laserdisc, videotape, video game cartridges, and CD-ROM applications and enjoys wide support among major electronics firms and computer makers as well as movie and music studios.<ref name=twsMAR02k12/> It was launched in 1997; by 2007, according to one estimate, there were over a billion DVD playback devices including DVD players, personal computers, and game consoles.<ref name=twsMAR02k12/>
 
Officially the letters ''DVD'' signify nothing, although there have been many proposals about what the letters were intended to mean; one popular version is ''Digital video disc'' and another is ''Digital versatile disc''.<ref name=twsMAR02k>{{cite news
|title=  What do the letters DVD stand for?
|quote= All of the following have been proposed as the words behind the letters DVD. * Delayed, very delayed (referring to the many late releases of DVD formats) * Diversified, very diversified (referring to the proliferation of recordable formats and other spinoffs) ...  * Digital video disc (the original meaning proposed by some of DVD's creators) * Digital versatile disc (a meaning later proposed by some of DVD's creators)  * Nothing ... And the official answer is... "nothing."
|publisher= DVD Forum: Usenet groups
|date= 2010-03-02
|url= http://www.dvddemystified.com/dvdfaq.html#1.1
|accessdate= 2010-03-02
}}</ref> An international forum in 1999 decreed that "DVD, as an international standard, is simply three letters" although there were reports that [[Toshiba]] continues to support the "digital video disc" acronym.<ref name=twsMAR02k/>
 
The physical disks are round, shiny, silver colored, and easily scratched, and are inserted into a computer player with a spinning motor which has an optical disk reader which reads information stored on the disk with a red-colored<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> [[laser]] while it spins inside the computer. The format was invented by [[Sony]] and [[Philips]] in 1995.<ref name=twsMAR03g>{{cite news
|author= JIM MCMANUS
|title= Sorting Out the Proposals for Improving Digital Sound
|quote= In 1995 the DVD Consortium, consisting of 10 companies representing all aspects of the recording and electronics industries, gathered with the intent of ironing out these issues. The result has been not one but two proposals for a new standard. Sony and Philips Electronics decided to work jointly on its proposal for DVD-audio, known as the Super Audio Compact Disk, and the remaining members of the development team (referred to as Work Group 4) focused on another proposal, DVD-Audio.
|publisher= The New York Times
|date=  May 7, 1998
|url= http://www.nytimes.com/1998/05/07/technology/sorting-out-the-proposals-for-improving-digital-sound.html?pagewanted=1
|accessdate= 2010-03-03
}}</ref>
 
There are different formats:
* DVD-ROM (ROM = "read only memory") has data that can only be read.
* DVD-R and DVD+R (R = "recordable") can be recorded only once.
* DVD-RW or DVD+RW (RW = "re-writable") or DVD-RAM (RAM = ""random access memory") can be rewritten again and again.
* DVD-video is formatted for video content.
* DVD-audio is formatted for audio content.
* Data DVDs are used to store data.
* A new format emerging is [[Blu-ray]] which promises to store more data and offer crisper pictures.
 
The DVD video format was first introduced by Toshiba in [[Japan]] in November 1996 and in the [[United States]] in March 1997,<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 1998, and [[Australia]] in 1999. In May 1997 the two firms released many DVD technical specifications to all 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> and published them as ''DVD Books'', such as the DVD-ROM Book, DVD-Audio Book, DVD-Video Book, DVD-R Book, DVD-RW Book, DVD-RAM Book, DVD-AR Book, DVD-VR Book, and so forth. Many specifications for mechanical, physical and optical characteristics are 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. 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 disk 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 disk 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 disk 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 disk using +RW HS format -- Capacity: 4,7 Gbytes and 1,46 Gbytes per side (recording speed 8X)], Retrieved on 2009-07-26</ref>
 
Some DVD specifications are not publicly available and can be obtained only from the DVD Format/Logo Licensing Corporation for a fee of $5000 (USD).<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" />
 
When playing a DVD, if the picture skips or there are video problems, it's possible that some dirt or grime got on the surface of the DVD; it's possible to gently clean a DVD by soaking a washcloth with alcohol -- even mouthwash will work -- and wiping it gently to dissolve fingerprints.<ref name=twsMAR02i>{{cite news
|title= Low-Tech Fixes for High-Tech Problems: Dirty Discs
|quote= You need to clean a skipping DVD or CD, but as a bachelor you don’t have any sissy cleaning fluids? Soak a washcloth with vodka or mouthwash. Alcohol is a powerful solvent, perfectly capable of dissolving fingerprints and grime on the surface of a disc. A $5 bottle of Listerine in your medicine cabinet may do the job as effectively as a $75 bottle of DVD cleaning fluid. Also, swabbing your copy of “Lost Weekend” with Stoli instead of fussing with a Discwasher kit is a lot more manly.
|publisher= The New York Times
|date= February 18, 2009
|url= http://www.nytimes.com/2009/02/19/technology/personaltech/19basics.html?pagewanted=2
|accessdate= 2010-03-02
}}</ref> Be careful not to scratch the disk's surface; a deep cut or tear will probably render the DVD unusable, but there are reports that minor scratches can be fixed with a repair kit.
 
== Technical issues==
=== 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><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 disks 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
|}
 
{| class="wikitable"
|+ Capacity and nomenclature of (re)writable disks
!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 DL || 2 || 2 || 12 || 9.40 || 8.75-->
|-
|DVD-R  || DS DL || 2 || 2 || 12 || 9.40 || 8.75
|-
|DVD-RW  || DS DL || 2 || 2 || 12 || 9.40 || 8.75
|-
|DVD+R  || DS DL || 2 || 2 || 12 || 9.40 || 8.75
|-
|DVD+RW  || DS DL || 2 || 2 || 12 || 9.40 || 8.75
|-
|DVD-RAM || SS SL || 1 || 1 ||  8 || 1.46 || 1.36*
|-
|DVD-RAM || DS DL || 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 DL (1.0) || 2 || 2 || 12 || 5.16 || 4.80
|-
|DVD-RAM || DS DL (2.0) || 2 || 2 || 12 || 9.40 || 8.75*
|}
 
=== Basic types===
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, 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.
 
===Sector analysis===
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:Dvd-burning-cutaway3.JPG|thumb|right|alt=Picture of a DVD with a pink light to one side.|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 disk has a 50&nbsp;GB storage capacity.
 
Writing speeds for DVD were 1×, that is, 1350&nbsp;[[kilobyte|kB]]/s (1,318&nbsp; 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.</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
|- 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 ==
[[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/DVD+RW] (plus), and DVD-RAM.
 
== Dual-layer recording ==
Dual-layer recording (sometimes also known as '''double-layer recording''') allows DVD-R and DVD+R disks to store significantly more data—up to 8.54 gigabytes per disk, 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 disk differs from its usual DVD counterpart by employing a second physical layer within the disk 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 disks 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 disk packaging.
 
DVD recordable disks 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'', used on many DVD Video disks, 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 and one lead-out. However, some DVD Video disks also use a parallel track, such as those authored episodically, as in a disk 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.
 
== DVD Video ==
'''DVD Video''' is a standard for content on DVD media. The format went on sale in Japan in November 1996, in the United States in March 1997, in Europe in October 1998 and in Australia in February 1999.<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>{{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 disks use either 4:3 or 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 23.976 framerate. Audio is commonly stored using the Dolby Digital AC-3 or Digital Theater System 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 support all possible formats. DVD Video also supports features such as menus, selectable subtitles, multiple camera angles, and multiple audio tracks. Double dvds writers are faster and more convienent
 
== 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&nbsp;kHz versus Compact disk Digital Audio'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 additional channels for [[spatial sound]] reproduction.
 
== Emerging formats==
[[Image:Photo-magasin-HDLAND.png|thumb|right|alt=Picture of a store in Paris which sells Blu-ray discs.|Blu-ray is a new format promising clearer pictures.]]
In 2006, a new format called [[Blu-ray]], designed by [[Sony]], [[Samsung]], and [[Panasonic]], was released as the successor to DVD. Another format, [[HD DVD]], competed unsuccessfully with this format in the format war of 2006–08. In the battle between blu-ray and HD DVD battled for supremacy, there were indications that the battling was counter-productive for the industry as a whole; one analyst commented:
{{quote|There is an awful lot of people in the US and Europe who have HD displays and no hi-def content. That's a wasted opportunity at this point. The industry is not exploiting that opportunity.<ref name=twsMAR03a>{{cite news
|author= Darren Waters 
|title= No ceasefire in DVD format battle
|quote= The high definition DVD format war will continue until a winner is declared, technology watchers have heard. Blu-ray and HD-DVD are battling to become the pre-eminent hi-def format to replace the slowing DVD market.
|publisher= BBC News
|date= 9 January 2007
|url= http://news.bbc.co.uk/2/hi/6243383.stm?lsm
|accessdate= 2010-03-03
}}</ref>
 
A dual layer Blu-ray disk can store 50 to 100 GB.<ref>{{cite web |title=What is Blu-ray disk? |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><ref name=twsMAR03a/> In March 2008, a new format was introducted called "HD VMD<ref name=twsMAR03c>{{cite news
|author= Eric A. Taub
|title= DVD format battle attracts a new rival: HD VMD
|quote= No sooner has the battle for the next-generation high-definition DVD format ended, with Blu-ray triumphing over HD DVD, than a new contender has emerged. A new system that is incompatible with Blu-ray, called HD VMD, for versatile multilayer disk, is trying to find a niche. New Medium Enterprises, the London company behind HD VMD, says its system's quality is equal to Blu-ray's, but it costs less.
|publisher= The New York Times
|date=  March 10, 2008
|url= http://www.nytimes.com/2008/03/10/technology/10iht-dvd.1.10872306.html
|accessdate= 2010-03-03
}}</ref> In March 2010, it appears that the blu-ray format "has the floor largely to itself as the heir apparent to the DVD", but that the format's prominence was in jeopardy because of the possibility of consumers downloading content directly from the web to their TVs.<ref name=twsMAR03d>{{cite news
|author= MATT RICHTEL and BRAD STONE
|title= Blu-ray’s Fuzzy Future
|quote= But many eyes will be on Blu-ray, which for the first time has the floor largely to itself as the heir apparent to the DVD. Over the last decade, DVD players and disks have generated tens of billions of dollars for Hollywood and the consumer electronics industry, so the pressure for a blockbuster sequel is high.
|publisher= The New York Times: Technology
|date= January 5, 2009
|url= http://www.nytimes.com/2009/01/05/technology/05bluray.html
|accessdate= 2010-03-03
}}</ref> There were some indications that sales of blu-ray players were increasing as prices were dropping.<ref name=twsMAR03d/>
Blu-ray disks played on a good high-definition television made "a real difference" and gave a crisp, clear picture.<ref name=twsMAR03d/> Another option is that some films will be offered in three-dimensional blu-ray format, such as the film ''Avatar'' directed by James Cameron.<ref name=twsMAR03e>{{cite news
|author= Christopher John Farley
|title= James Cameron on the Coming DVD Release of ‘Avatar’ [UPDATED]
|quote= In a wide-ranging interview today, director James Cameron said that his blockbuster movie “Avatar” will have a 3-D Blu-ray release later this year.
|publisher= The Wall Street Journal
|date= February 17, 2010
|url= http://blogs.wsj.com/speakeasy/2010/02/17/james-cameron-says-avatar-will-have-a-3-d-blu-ray-release-this-year/tab/article/
|accessdate= 2010-03-03
}}</ref> In the sluggish economy from 2008&ndash;2010, sales of DVDs, including rentals of DVDs, have been lackluster, leading to layoffs at firms such as [[Sony]].<ref name=twsMAR03f>{{cite news
|author= Associated Press
|title= Sony Layoffs Blamed on Falling DVD Sales
|quote= Sony Pictures To Lay Off 450 People, Close 100 Open Positions As DVD Sales Fall
|publisher= CBS News
|date= Feb. 2, 2010
|url= http://www.cbsnews.com/stories/2010/02/01/entertainment/main6163919.shtml
|accessdate= 2010-03-03
}}</ref>
 
== References ==
{{reflist}}

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