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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.
Representatives of the SD camp approached 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 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, Microsoft, Sun, Dell, and many others. This group was referred to as the Technical Working Group, or TWG.
The TWG voted to boycott both formats unless the two camps agreed on a single, converged standard. Lou Gerstner, president of IBM, was recruited to apply pressure on the executives of the warring factions. Eventually, the computer companies won the day, and a single format, now called DVD, was agreed upon. The TWG also collaborated with the Optical Storage Technology Association (OSTA) on the use of their implementation of the ISO-13346 file system (known as Universal Disc Format [UDF]) for use on the new DVDs.
Philips and Sony decided it was in their best interest to avoid another format war over their MultiMedia Compact Disc, and agreed to unify with companies backing the Super Density Disc to release a single format with technologies from both. The specification was mostly similar to Toshiba and Matsushita's Super Density Disc, except for the dual-layer option (MMCD was single-sided and optionally dual-layer, whereas SD was single-layer but optionally double-sided) and EFMPlus modulation.
EFMPlus was chosen because of its great resilience to disc damage, such as scratches and fingerprints. EFMPlus, created by Kees Immink (who also designed EFM), is 6% less efficient than the modulation technique originally used by Toshiba, which resulted in a capacity of 4.7 GB, as opposed to the original 5 GB. The result was the DVD specification, finalized for the DVD movie player and DVD-ROM computer applications in December 1995.
The DVD Video format was first introduced by Toshiba in Japan in November 1996, in the United States in March 1997 (test marketed), in Europe in October 1998, and in Australia in February 1999.
In May 1997, the DVD Consortium was replaced by the DVD Forum, which is open to all other companies.
Some specifications for mechanical, physical and optical characteristics of DVD optical discs can be downloaded as freely available standards from the ISO website. 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.
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. Every subscriber must sign a non-disclosure agreement as certain information in the DVD Book is proprietary and confidential. Digital Video Disc, and DVD being the most common.
DVD was originally used as an initialism for the unofficial term digital videodisk.
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.
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."
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.
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 . 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.
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.
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 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., 10243 (230), or 1,073,741,824 bytes).
and a 19 cm pencil.]] Each DVD sector contains 2,418 bytes of data, 2,048 bytes of which are user data. There is a small difference in storage space between + and - (hyphen) formats:
{| class="wikitable" |+ Capacity differences of writable DVD formats ! Type || Sectors || Bytes || KB || MB || GB || KiB || MiB || GiB |- style="text-align:right;"| | 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 |- style="text-align:right;"| | 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 |- style="text-align:right;"| | 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 |- style="text-align:right;"| | 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 |}
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 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, 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 153.6 kB/s (150 KiB/s), about one-ninth as swift. |- ! (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 |}
This mechanism is shown right side up; the disc is above it. The laser and optical system "looks at" 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. 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.
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.
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. It's likely that this disc rotates half a turn to position a different set of optics (the other "hole") for CDs vs. DVDs.
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.
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".
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).
DVD recordables are now also used for consumer audio and video recording. Three formats were developed: DVD-R/RW, DVD+R/RW (plus), and DVD-RAM. DVD-R is available in two formats, General (650 nm) and Authoring (635 nm), where Authoring discs may be recorded with encrypted content but General discs may not.
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.
== 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 8.54 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 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).
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. 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. 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. 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.
Although many resolutions and formats are supported, most consumer DVDs 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 FPS. Audio is commonly stored using the Dolby Digital (AC-3) or Digital Theater System (DTS) formats, ranging from 16-bits/48 kHz to 24-bits/96 kHz format with monaural to 6.1-channel "Surround Sound" presentation, and/or MPEG-1 Layer 2 and/or LPCM Stereophonic. Although the specifications for video and audio requirements vary by global region and television system, many DVD players support all possible formats. DVD Video also supports features such as menus, selectable subtitles, multiple camera angles, and multiple audio tracks.
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.
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 CDDA's 16-bits/44.1 kHz). Compared with the CD format, the much higher-capacity DVD format enables the inclusion of considerably more music (with respect to total running time and quantity of songs) and/or far higher audio quality (reflected by higher sampling rates and greater sample resolution, and/or additional channels for spatial sound reproduction).
Despite DVD-Audio's superior technical specifications, there is debate as to whether the resulting audio enhancements are distinguishable in typical listening environments. DVD-Audio currently forms a niche market, probably due to the very sort of format war with rival standard SACD that DVD-Video avoided.
DVD-Audio discs employ a 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 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. As a result, making 1:1 copies of DVD-Audio discs is now possible with relative ease, much like DVD-Video discs.
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.
Consumers initially were also slow to adopt Blu-ray due to the cost. By 2009, 85% of stores were selling Blu-ray Discs. 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. 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).
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 2010, and the format remains the preferred one for the release of older television programs and films, with some programs such as 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). 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).
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.
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, 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".
Category:Computer storage media Category:Audio storage Category:Video storage Category:DVD Category:120 mm discs Category:Consumer electronics Category:1995 introductions Category:Joint ventures
This text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
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