DVD

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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.

DVD is an optical disc storage technology which can hold video, audio, and computer data.[1] It is like a CD but can hold much more digital information.[1] 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.[1] 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.[1]

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.[2] 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.[2]

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[3] laser while it spins inside the computer. The format was invented by Sony and Philips in 1995.[4]

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,[5] in Europe in 1998, and Australia in 1999. In May 1997 the two firms released many DVD technical specifications to all companies[5] 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.[6] 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.[7][8][9][10]

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).[11][12] Every subscriber must sign a non-disclosure agreement as certain information in the DVD Book is proprietary and confidential.[11]

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.[13] 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

Capacity and nomenclature[14]
SS = single-sided, DS = double-sided, SL = single-layer, DL = dual-layer
Designation Sides Layers
(total)
Diameter Capacity
(cm) (GB) (GiB)
DVD-1[15] SS SL 1 1 8 1.46 1.36
DVD-2 SS DL 1 2 8 2.66 2.47
DVD-3 DS SL 2 2 8 2.92 2.72
DVD-4 DS DL 2 4 8 5.32 4.95
DVD-5 SS SL 1 1 12 4.70 4.38
DVD-9 SS DL 1 2 12 8.54 7.95
DVD-10 DS SL 2 2 12 9.40 8.75
DVD-14[16] DS DL/SL 2 3 12 13.24 12.33
DVD-18 DS DL 2 4 12 17.08 15.90
Capacity and nomenclature of (re)writable disks
Designation Sides Layers
(total)
Diameter Capacity
(cm) (GB) (GiB)
DVD-R SS SL (1.0) 1 1 12 3.95 3.68
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 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 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 cm diameter and hybrid variants, acquired similar numeric names with even larger deviation.

The 12 cm type is a standard DVD, and the 8 cm variety is known as a MiniDVD. These are the same sizes as a standard CD and a mini-CD, respectively. The capacity by surface (MiB/cm2) varies from 6.92 MiB/cm2 in the DVD-1 to 18.0 MiB/cm2 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., 109, or 1,000,000,000 bytes). For distinction, gibibyte (with symbol GiB) is used (i.e., 230, or 1,073,741,824 bytes). Most computer operating systems display file sizes in gibibytes, mebibytes, and kibibytes, 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:

Capacity differences of writable DVD formats
Type Sectors Bytes MB MiB GB GiB
DVD−R SL 2,298,496 4,707,319,808 4,707.320 4,489.250 4.707 4.384
DVD+R SL 2,295,104 4,700,372,992 4,700.373 4,482.625 4.700 4.378
DVD−R DL 4,171,712 8,543,666,176 8,543.666 8,147.875 8.544 7.957
DVD+R DL 4,173,824 8,547,991,552 8,547.992 8,152.000 8.548 7.961

Technology

Picture of a DVD with a pink light to one side.
DVD-RW Drive operating with the protective cover removed.

DVD uses 650 nm wavelength laser diode light as opposed to 780 nm for CD. This permits a smaller pit to be etched on the media surface compared to CDs (0.74 µm for DVD versus 1.6 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 nm, and one dual-layer disk has a 50 GB storage capacity.

Writing speeds for DVD were 1×, that is, 1350 kB/s (1,318  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 KiB/s (153.6 kB/s), approximately 9 times slower.[15]

DVD drive speeds
Drive speed Data rate ~Write time (min)[17]
(Mbit/s) (MB/s) (MiB/s) SL DL
10.80 1.35 1.29 61 107
21.60 2.70 2.57 31 54
2.4× 25.92 3.24 3.09 25 45
2.6× 28.08 3.51 3.35 23 41
43.20 5.40 5.15 15 27
64.80 8.10 7.72 10 18
86.40 10.80 10.30 8 13
10× 108.00 13.50 12.87 6 11
12× 129.60 16.20 15.45 5 9
16× 172.80 21.60 20.60 4 7
18× 194.40 24.30 23.17 3 6
20× 216.00 27.00 25.75 3 5
22× 237.60 29.70 28.32 3 5
24× 259.20 32.40 30.90 3 4

DVD recordable and rewritable

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).[18]

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.[19] 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.[18] 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.[20] 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.[21] 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 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. Double dvds writers are faster and more convienent.

Commercial video DVDs are encrypted with the Contents Scrambling System or CSS. This has been broken. The CSS is a digital rights management or DRM scheme used on commercial DVDs which uses a 40-bit stream cipher algorithm which was initially introduced around 1996. It was reverse engineered in 1999. One source suggests the 1996 encoding scheme was susceptible to a brute force attack because export regulations of the United States discouraged cryptosystems which had more than 40 keys. Since then, new codes have been used to encrypt DVDs such as the Cryptomeria cipher.

DVD Audio

DVD Audio is a format for delivering high fidelity audio content on a DVD. It offers many channel configuration options (from mono to 5.1 surround sound) at various sampling frequencies up to 24-bits/192 kHz versus Compact disk Digital Audio'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 rates and greater sample resolution, and additional channels for spatial sound reproduction.

Emerging formats

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.[22]

A dual layer Blu-ray disk can store 50 to 100 GB.[23][24][22] In March 2008, a new format was introducted called "HD VMD[25] 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.[26] There were some indications that sales of blu-ray players were increasing as prices were dropping.[26] Blu-ray disks played on a good high-definition television made "a real difference" and gave a crisp, clear picture.[26] Another option is that some films will be offered in three-dimensional blu-ray format, such as the film Avatar directed by James Cameron.[27] In the sluggish economy from 2008–2010, sales of DVDs, including rentals of DVDs, have been lackluster, leading to layoffs at firms such as Sony.[28]

References

  1. 1.0 1.1 1.2 1.3 What is DVD?, DVD Forum: Usenet groups, 2010-03-02. Retrieved on 2010-03-02. “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.”
  2. 2.0 2.1 What do the letters DVD stand for?, DVD Forum: Usenet groups, 2010-03-02. Retrieved on 2010-03-02. “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."”
  3. Build Your Skills: A comparison between DVD and CD-ROM.
  4. JIM MCMANUS. Sorting Out the Proposals for Improving Digital Sound, The New York Times, May 7, 1998. Retrieved on 2010-03-03. “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.”
  5. 5.0 5.1 Johnson, Lawrence B.. For the DVD, Disney Magic May Be the Key, The New York Times, September 7, 1997. Retrieved on 2009-05-25.
  6. ISO ISO Freely Available Standards, Retrieved on 2009-07-24
  7. ISO 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
  8. ISO 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
  9. ISO 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
  10. ISO 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
  11. 11.0 11.1 DVD FLLC (2009) DVD Format Book, Retrieved on 2009-08-14
  12. DVD FLLC (2009) How To Obtain DVD Format/Logo License (2005-2009), Retrieved on 2009-08-14
  13. Low-Tech Fixes for High-Tech Problems: Dirty Discs, The New York Times, February 18, 2009. Retrieved on 2010-03-02. “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.”
  14. DVD Book A: Physical parameters. Mpeg.org. Retrieved on 2009-08-22.
  15. 15.0 15.1 Jim Taylor. DVD Demystifed FAQ. Dvddemystified.com. Retrieved on 2009-08-22.
  16. DVD-14. AfterDawn Ltd.. Retrieved on 2007-02-06.
  17. 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.
  18. 18.0 18.1 Robert DeMoulin. Understanding Dual Layer DVD Recording. BurnWorld.com. Retrieved on 2007-07-06.
  19. DVD players benchmark. hometheaterhifi.com. Retrieved on 2008-04-01.
  20. Discount stores are a video lover's channel of choice. Discount Store News (via findarticles.com) (1998-08-10). Retrieved on 2008-03-06.
  21. Bakalis, Anna (2003-06-20). It's unreel: DVD rentals overtake videocassettes. Washington Times.
  22. 22.0 22.1 Darren Waters. No ceasefire in DVD format battle, BBC News, 9 January 2007. Retrieved on 2010-03-03. “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.”
  23. What is Blu-ray disk?. Sony. Retrieved on 2008-11-25.
  24. DVD FAQ: 3.13 - What about the new HD formats? (2008-09-21). Retrieved on 2008-11-25.
  25. Eric A. Taub. DVD format battle attracts a new rival: HD VMD, The New York Times, March 10, 2008. Retrieved on 2010-03-03. “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.”
  26. 26.0 26.1 26.2 MATT RICHTEL and BRAD STONE. Blu-ray’s Fuzzy Future, The New York Times: Technology, January 5, 2009. Retrieved on 2010-03-03. “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.”
  27. Christopher John Farley. James Cameron on the Coming DVD Release of ‘Avatar’ [UPDATED], The Wall Street Journal, February 17, 2010. Retrieved on 2010-03-03. “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.”
  28. Associated Press. Sony Layoffs Blamed on Falling DVD Sales, CBS News, Feb. 2, 2010. Retrieved on 2010-03-03. “Sony Pictures To Lay Off 450 People, Close 100 Open Positions As DVD Sales Fall”