DVD

DVD


DVD-R read/write side
Media type Optical disc
Capacity 4.7 GB (single-sided, single-layer – common)
8.5–8.7 GB (single-sided, double-layer)
9.4 GB (double-sided, single-layer)
17.08 GB (double-sided, double-layer – rare)
Read mechanism 650 nm laser, 10.5 Mbit/s (1×)
Write mechanism 10.5 Mbit/s (1×)
Standard DVD Forum’s DVD Books[3] and DVD+RW Alliance specifications

DVD is an Compact Discs while having the same dimensions.

Pre-recorded DVDs are mass-produced using DVD-RAM) can be recorded and erased multiple times.

DVDs are used in DVD-Video consumer digital video format and in DVD-Audio consumer digital audio format, as well as for authoring AVCHD discs. DVDs containing other types of information may be referred to as DVD data discs.

Contents

[edit] History

Before the advent of DVD in 1995, JVC.

Representatives of the SD camp approached Dell, and many others. This group was referred to as the Technical Working Group, or TWG.

The TWG voted to boycott both formats unless the two camps agreed on a single, converged standard.Universal Disk Format) for use on the new DVDs.

Philips and Sony decided that it was in their best interests 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 EFMPlus modulation.

[edit] Specifications

DVD specifications created and updated by the [3]

Some specifications for mechanical, physical and optical characteristics of DVD optical discs can be downloaded as freely available standards from the [11]

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.[12]

[edit] Etymology

The official DVD charter documents specify that the basis of the DVD name stems from the term digital versatile disc.[15] Digital Video Disc, and DVD being the most common.

DVD was originally used as an initialism for the unofficial term digital videodisc.[16]

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.[17]

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.”[18]

[edit] Identification (MID)

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.

[edit] Design

Comparison of several forms of disk storage showing tracks (not-to-scale); green denotes start and red denotes end.
* Some CD-R(W) and DVD-R(W)/DVD+R(W) recorders operate in Constant linear velocity (CLV) mode.

[edit] As a movie delivery medium

DVD was adopted by LaserDisc. When the price point for a LaserDisc at approximately $100 per disc moved to $20 per disc 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, and large numbers of DVDs were sold.

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.

[edit] As an interactive medium

DVD as a format had two qualities at the time that were not available in any other interactive medium: enough capacity and speed to provide high quality, full motion video and sound, and low cost delivery mechanism provided by consumer products retailers. Retailers would quickly move 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 overnight, this created a new business opportunity and model for business innovators, such as 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.

[edit] Capacity

Capacity and nomenclature[20]
SS = single-sided, DS = double-sided, SL = single-layer, DL = dual-layer
Designation Sides Layers
(total)
Diameter
(cm)
Capacity
(GB) (GiB)
DVD-1[21] 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 4.37
DVD-9 SS DL 1 2 12 8.54 7.95
DVD-10 DS SL 2 2 12 9.40 8.75
DVD-14[22] DS SL+DL 2 3 12 13.24 12.33
DVD-18 DS DL 2 4 12 17.08 15.90


Size comparison: a 12 cm DVD+RW and a 19 cm pencil.

Capacity and nomenclature of (re)writable discs
Designation Sides Layers
(total)
Diameter
(cm)
Capacity
(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 SL 2 2 12 9.40 8.75
DVD-RW DS SL 2 2 12 9.40 8.75
DVD+R DS SL 2 2 12 9.40 8.75
DVD+RW DS SL 2 2 12 9.40 8.75
DVD-RAM SS SL 1 1 8 1.46 1.36*
DVD-RAM DS SL 2 2 8 2.65 2.47*
DVD-RAM SS SL (1.0) 1 1 12 2.58 2.40
DVD-RAM SS SL (2.0) 1 1 12 4.70 4.37
DVD-RAM DS SL (1.0) 2 2 12 5.16 4.80
DVD-RAM DS SL (2.0) 2 2 12 9.40 8.75*

Scan of a DVD 4.5 capacity disc

The basic types of DVD (12 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 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 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, gibibyte (with symbol GiB) is used (i.e., 10243 (230), or 1,073,741,824 bytes).

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 kB MB GB KiB MiB GiB
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
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
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
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

[edit] Technology

DVD-RW Drive operating with the protective cover removed.

Comparison of various optical storage media

DVD uses 650 nm wavelength CD), allowing in part for DVD’s increased storage capacity.

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

Writing speeds for DVD were 1×, that is, 1,385 kB/s (1,353 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 kB/s (150 KiB/s), about one-ninth as swift.[21][23]

DVD drive speeds
Drive speed Data rate ~Write time (minutes)[24]
Mbit/s MB/s Single-Layer Dual-Layer
11.08 1.39 57 103
22.16 2.77 28 51
2.4× 26.59 3.32 24 43
2.6× 28.81 3.60 22 40
44.32 5.54 14 26
66.48 8.31 9 17
88.64 11.08 7 13
10× 110.80 13.85 6 10
12× 132.96 16.62 5 9
16× 177.28 22.16 4 6
18× 199.44 24.93 3 6
20× 221.60 27.70 3 5
22× 243.76 30.47 3 5
24× 265.92 33.24 2 4

[edit] Internal mechanism of a drive

Internal mechanism of a DVD-ROM Drive. See text for details.

This mechanism is shown right side up; the disc would sit on top of it. The laser and optical system scans the underside of the disc.

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. There is a disc-shaped round clamp, loosely held inside the cover and free to rotate; it’s not in the photo. After the disc tray stops moving inward, as the motor and its attached parts rise, a magnet near the top of the rotating assembly contacts and strongly attracts the clamp to hold and center the disc. This motor has an external rotor – every visible part of it spins.

The gray metal chassis is shock-mounted at its four corners to reduce sensitivity to external shocks, and to reduce drive noise from residual imbalance 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.

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.

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. 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. These servos are comparatively wideband.

To select tracks (or files) as well as advancing the “sled” during continuous read or write operations, a motor (it could be a stepping motor; one would hear it if it were) 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 is the rod with evenly-spaced darker details; these are the helical groove that engages a pin on the “sled”.

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).

[edit] DVD recordable and rewritable

Sony DVD Read & 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-[25]

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.

Some first generation DVD players would cause damage to DVD±R/RW/DL when attempting to read them.

[edit] Dual-layer recording

Dual-layer recording (sometimes also known as double-layer recording) allows DVD-R and DVD+R discs to store significantly more data—up to 8.5 gigabytes 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. When played, a slight transition can sometimes be seen in the playback when the player changes 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).[26]

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.[27] This caused some viewers to worry that their dual-layer discs were damaged or defective, with the end result that studios began listing a standard message explaining the dual-layer pausing effect on all dual-layer disc packaging.

DVD recordable discs supporting this technology are backward-compatible with some existing DVD players and DVD-ROM drives.[26] 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. A potential reason is how Dual Layer discs are not as well matured compared to the Single Layer discs, as well as consumers, on a whole, have no desire for increased burning speeds.

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 and one lead-out.

[edit] DVD-Video

DVD-Video is a standard for storing and distributing video/audio content on DVD media. The format went on sale in Japan in 1996, in the United States in 1997, in Europe in 1998 and in Australia in 1999.[28] DVD-Video 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.[5][29] 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.

[edit] Security

The Content Scramble System (CSS) is a stream cipher algorithm. The system was introduced around 1996 and was first compromised in 1999.

The purpose of CSS is twofold:

  1. CSS prevents byte-for-byte copies of an MPEG (digital video) stream from being playable since such copies do not include the keys that are hidden on the lead-in area of the restricted DVD.
  2. CSS provides a reason for manufacturers to make their devices compliant with an industry-controlled standard, since CSS scrambled discs cannot in principle be played on noncompliant devices; anyone wishing to build compliant devices must obtain a license, which contains the requirement that the rest of the DRM system (region codes, Macrovision, and user operation prohibition) be implemented.[30]

While most CSS-decrypting software is used to play DVD videos, other pieces of software (such as user operation prohibition.

[edit] Consumer restrictions

The rise of 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.

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 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.

[edit] DVD-Audio

DVD-Audio is a format for delivering high fidelity audio content on a DVD. It offers many channel configuration options (from citation needed]

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 SACD that DVD-Video avoided.

[edit] Security

DVD-Audio discs employ a 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 a DVD-Video 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.[31] As a result, making 1:1 copies of DVD-Audio discs is now possible with relative ease, much like DVD-Video discs.

[edit] Blu-ray Disc/HD DVD

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 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.[32][33]

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 75% of video sales and approximately one billion DVD player sales worldwide as of 3 April 2011. 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.[35]

Consumers initially were also slow to adopt Blu-ray due to the cost.Blade Runner). Another reason cited (July 2011) for the slower transition to Blu-ray from DVD is the necessity of and confusion over “firmware updates” and needing an internet connection to perform updates.

This situation can be best compared to the changeover from 78 rpm shellac recordings to 45 rpm and 33⅓ rpm vinyl recordings; because the medium used for the earlier format was virtually the same as the latter version (a disc on a turntable, played using a needle), phonographs continued to be built to play obsolete 78s for decades after the format was discontinued. Manufacturers continue to release standard DVD titles as of 2012, 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).[38] 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.

[edit] Use as backup medium

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.[39]

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,[42] 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”.[43]

[edit] See also

[edit] References

  1. ^ DVD Book Construction – list of all available DVD Books, Retrieved on 2009-07-24
  2. ^ DVD Format Book – History of Supplements for DVD Books, Retrieved on 2009-07-24
  3. ^ DVD Books overview, Retrieved on 2009-07-24
  4. http://www.ip.philips.com/view_attachment/2450/sl00812.pdf. Retrieved 2008-02-13
  5. ^ http://ecommerceandvideodistributiondvd.blogspot.com/.
  6. ^ Computer Shopper 16 (3): 189. March 1, 1996.
  7. ^ ISO ISO Freely Available Standards, Retrieved on 2009-07-24
  8. ^ ISO 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
  9. ^ ISO 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
  10. ^ ISO 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
  11. ^ ISO 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
  12. ^ DVD Format Book, Retrieved on 2009-08-14
  13. ^ DVD FLLC (2009) How To Obtain DVD Format/Logo License (2005–2009), Retrieved on 2009-08-14
  14. ^ “DVD Forum Charter”. Dvdforum.org. http://www.dvdforum.org/about-charter.htm. Retrieved 2011-11-26.
  15. http://www.dvdforum.org/faq-dvdprimer.htm#1. Retrieved 2011-08-10.
  16. ^ Markoff, John (1996-01-11). “A Battle for Influence Over Insatiable Disks”. The New York Times. http://query.nytimes.com/gst/fullpage.html?res=990CEEDA143CF932A25752C0A963958260. Retrieved 2007-04-09.
  17. http://www.dvddemystified.com/dvdfaq.html#1.1.
  18. http://www.dvdforum.org/faq-dvdprimer.htm#1. Retrieved 2008-01-23.
  19. ^ “DVD Book A: Physical parameters”. Mpeg.org. http://www.mpeg.org/MPEG/DVD/Book_A/Specs.html. Retrieved 2009-08-22.
  20. dead link]
  21. ^ http://www.dvddemystified.com/dvdfaq.html. Retrieved 2009-08-22.
  22. ^ “DVD-14”. AfterDawn Ltd.. http://www.afterdawn.com/glossary/terms/dvd-14.cfm. Retrieved 2007-02-06.
  23. ^ “Understanding DVD -Recording Speed”. Osta.org. http://www.osta.org/technology/dvdqa/dvdqa4.htm. Retrieved 2011-08-09.
  24. ^ 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]
  25. http://www.taperesources.com/dvd_media.html#article2. Retrieved 2011-08-09.
  26. ^ http://www.burnworld.com/howto/articles/intro-to-dual-layer.htm. Retrieved 2007-07-06.
  27. dead link]
  28. ^ “Discount stores are a video lover’s channel of choice”. Discount Store News (via findarticles.com). 1998-08-10. http://findarticles.com/p/articles/mi_m3092/is_15_37/ai_50241583. Retrieved 2008-03-06.
  29. ^ Bakalis, Anna (2003-06-20). “It’s unreel: DVD rentals overtake videocassettes”. Washington Times. http://washingtontimes.com/business/20030620-113258-1104r.htm.
  30. dead link]
  31. http://forum.doom9.org/showthread.php?p=1099342#post1099342. Retrieved 2008-04-09.
  32. ^ “What is Blu-ray Disc?”. Sony. http://www.sonystyle.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10551&storeId=10151&langId=-1&identifier=S_BrandShowcase_Blu-ray. Retrieved 2008-11-25.
  33. http://www.dvddemystified.com/dvdfaq.html#3.13. Retrieved 2008-11-25.
  34. ^ “High-Definition Sales Far Behind Standard DVD’s First Two Years”. Movieweb.com. 2008-02-20. http://www.movieweb.com/dvd/news/20/26720.php. Retrieved 2009-08-22.
  35. ^ “Blu-ray takes 25% Market share:”. 2008-09-21. http://www.blu-raystats.com/MarketShare/index.php. Retrieved 2011-06-28.
  36. ^ Robert Martorana (2009-11-04). “Slow Blu-ray Adoption: A Threat to Hollywood’s Bottom Line?”. Seeking Alpha. http://seekingalpha.com/article/171207-slow-blu-ray-adoption-a-threat-to-hollywood-s-bottom-line. Retrieved 2011-08-09.
  37. ^ “Gates And Ballmer On “Making The Transition””. BusinessWeek. 2004-04-19. http://www.businessweek.com/magazine/content/04_16/b3879008_mz001.htm. Retrieved 2009-08-22.
  38. ^ “Kirk/Spock STAR TREK To Get All-New HD Spaceships”. Aintitcool.com. http://www.aintitcool.com/display.cgi?id=24344. Retrieved 2009-08-22.[unreliable source?]
  39. ^ “How To Choose CD/DVD Archival Media”. 2006-10-30. http://adterrasperaspera.com/blog/2006/10/30/how-to-choose-cddvd-archival-media. Retrieved 2009-03-14.
  40. ^ “Optical Media Longetivity”. http://www.thexlab.com/faqs/opticalmedialongevity.html. Retrieved 2010-02-26.
  41. ^ “DVD Durability”. http://www.backupcritic.com/backup-media/dvd/durability.html. Retrieved 2010-02-26.
  42. ^ “The Life-Span of DVDs”. January 2006. http://www.larryjordan.biz/articles/lj_dvd_life.html. Retrieved 2010-02-26.
  43. ^ “How long will data recorded on writable DVD discs remain readable?”. http://www.osta.org/technology/dvdqa/dvdqa11.htm. Retrieved 2009-03-14.

[edit] Further reading

[edit] External links



Source: Wikipedia