Talk:DVD

History[edit]

Development and launch[edit]

There were several formats developed for recording video on optical discs before the DVD. Optical recording technology was invented by David Paul Gregg and James Russell in 1963 and first patented in 1968. A consumer optical disc data format known as the LaserDisc was developed in the United States, and first came to market in Atlanta, Georgia in December 1978. It used much larger discs than the later formats. Due to the high cost of players and discs, consumer adoption of the LaserDisc was very low in both North America and Europe, and was not widely used anywhere outside Japan and the more affluent areas of Southeast Asia, such as Hong Kong, Singapore, Malaysia and Taiwan.^{[citation needed]}

The Super Density logo would later be reused in Secure Digital.^{[citation needed]}

Representatives from the SD camp asked IBM for advice on the file system to use for their disc, and sought support for their format for storing computer data. Alan E. Bell, a researcher from IBM's Almaden Research Center, got 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 Microsystems, Dell, and many others. This group was referred to as the Technical Working Group, or TWG.^{[citation needed]}

...and EFMPlus modulation designed by Kees Schouhamer Immink.^{[citation needed]}

Shortly after the format's finalization, talks began in mid-December 1995 on how to distribute the format at retail.^{[citation needed]}

Adoption[edit]

They embraced DVD as it produced higher quality video and sound, provided superior data lifespan, and could be interactive.^{[citation needed]} Interactivity on LaserDiscs had proven desirable to consumers, especially collectors. When LaserDisc prices dropped from approximately $100 per disc 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,^{[citation needed]} and large numbers of DVDs were sold.^{[citation needed]}

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.^{[citation needed]}

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 to re-invent the home entertainment distribution model. It also gave companies an inexpensive way to provide business and product information on full motion video through direct mail.^{[citation needed]}

Specifications[edit]

Additionally the DVD6C patent pool holds patents used by DVD drives and discs.^{[citation needed]}

The capacity of DVDs is conventionally stated in gigabytes (GB), with the decimal definition of this term such that 1 GB = 10⁹ bytes.^{[citation needed]}

Discs with multiple layers[edit]

Like other optical disc formats before it, a basic DVD disc—known as DVD-5 in the DVD Books, while called Type A in the ISO standard—contains a single data layer readable from only one side. However, the DVD format also includes specifications for three types of discs with additional recorded layers, expanding disc data capacity beyond the 4.7 GB of DVD-5 while maintaining the same physical disc size.^{[citation needed]}

Double-sided discs[edit]

Double-sided discs identify the sides as A and B. The disc structure lacks the dummy layer where identifying labels are printed on single-sided discs, so information such as title and side are printed on one or both sides of the non-data clamping zone at the center of the disc.^{[citation needed]}

DVD-10 discs fell out of favor because, unlike dual-layer discs, they require users to manually flip them to access the complete content (a relatively egregious scenario for DVD movies) while offering only a negligible benefit in capacity. Additionally, without a non-data side, they proved harder to handle and store.^{[citation needed]}

Dual-layer discs[edit]

Dual-layer discs also employ a second recorded layer, however both are readable from the same side (and unreadable from the other). These DVD-9 discs (Type C in ISO) nearly double the capacity of DVD-5 discs to a nominal 8.5 GB, but fall below the overall capacity of DVD-10 discs due to differences in the physical data structure of the additional recorded layer. However, the advantage of not needing to flip the disc to access the complete recorded data – permitting a nearly contiguous experience for A/V content whose size exceeds the capacity of a single layer – proved a more favorable option for mass-produced DVD movies.^{[citation needed]}

Most dual-layer discs are mastered with layer 0 starting at the inside diameter and proceeding outward—as is the case for most optical media, regardless of layer count—while Layer 1 starts at the absolute outside diameter and proceeds inward. Additionally, data tracks are spiraled such that the disc rotates the same direction to read both layers. DVD video DL discs can be mastered slightly differently: a single media stream can be divided between the layers such that layer 1 starts at the same diameter that layer 0 finishes. This modification reduces the visible layer transition pause because after refocusing, the laser remains in place rather than losing additional time traversing the remaining disc diameter.^{[citation needed]}

DVD-9 was the first commercially successful implementation of such technology.^{[when?][citation needed][citation needed]}

Combinations of the above[edit]

DVD-18 discs (Type D in ISO) effectively combines the DVD-9 and DVD-10 disc types by containing four recorded data layers (allocated as two sets of layers 0 and 1) such that only one layer set is accessible from either side of the disc. These discs provide a total nominal capacity of 17.0 GB, with 8.5 GB per side. This format was initially used for television series released on DVD (like the first releases of Miami Vice and Quantum Leap), but was eventually abandoned in favor of single sided discs for reissues.^{[citation needed]}

DVD recordable and rewritable[edit]

Although most current DVD writers can write in both the DVD+R/RW and DVD-R/RW formats (usually denoted by "DVD±RW" 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 hardware plays both kinds of discs, though older models can have trouble with the "plus" variants.^{[citation needed]}

Some early DVD players would cause damage to DVD±R/RW/DL when attempting to read them.^{[citation needed]}

The form of the spiral groove that makes up the structure of a recordable DVD 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..^{[citation needed]}

Dual-layer recording[edit]

Many current DVD recorders support dual-layer technology, and while the costs became comparable to single-layer burners over time, blank dual-layer media has remained more expensive than single-layer media.^{[citation needed]}

Capacity[edit]

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.^{[citation needed]}

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 area (MiB/cm²) varies from 6.92 MiB/cm² in the DVD-1 to 18.0 MB/cm² in the DVD-18.^{[clarification needed]}

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:^{[citation needed]}

Laser and optics[edit]

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All three common optical disc media (Compact disc, DVD, and Blu-ray) use light from laser diodes, for its spectral purity and ability to be focused precisely. DVD uses light of 650 nm wavelength (red), as opposed to 780 nm (far-red, commonly called infrared) for CD. This shorter wavelength allows a smaller pit on the media surface compared to CDs (0.74 µm for DVD versus 1.6 µm for CD), accounting in part for DVD's increased storage capacity.^{[citation needed]}

In comparison, Blu-ray Disc, the successor to the DVD format, uses a wavelength of 405 nm (violet), and one dual-layer disc has a 50 GB storage capacity.^{[citation needed]}

Transfer rates[edit]

However, in practice, discs should never be spun at their highest possible speed, to allow for a safety margin and for slight differences between discs, and to prevent material fatigue from the physical stress.^{[citation needed]}

Errors on DVDs are measured as:

• PIE — Parity Inner Error
• PIF — Parity Inner Failure
• POE — Parity Outer Error
• POF — Parity Outer Failure

A higher rate of errors may indicate a lower media quality, deteriorating media, scratches and dirt on the surface, and/or a malfunctioning DVD writer.

PI errors, PI failures and PO errors are correctable, while a PO failure indicates a CRC error, one 2048 byte block (or sector) of data loss, a result of too many consecutive smaller errors.

Additional parameters that can be measured are laser beam focus errors, tracking errors, jitter and beta errors (inconsistencies in lengths of lands and pits).^{[citation needed]}

Security[edit]

The Content Scramble System (CSS) is a digital rights management (DRM) and encryption system employed on almost all commercially produced DVD-video discs. CSS utilizes a proprietary 40-bit stream cipher algorithm. The system was introduced around 1996 and was first compromised in 1999.^{[citation needed]}

While most CSS-decrypting software is used to play DVD videos, other pieces of software (such as DVD Decrypter, AnyDVD, DVD43, Smartripper, and DVD Shrink) can copy a DVD to a hard drive and remove Macrovision, CSS encryption, region codes and user operation prohibition.^{[citation needed]}

Consumer restrictions[edit]

The rise of filesharing 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 advertisement warning that most forms of copying the contents are illegal. Many DVDs prevent skipping past or fast-forwarding through this warning.^{[citation needed]}

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.^{[citation needed]}

DVD-Audio[edit]

Main article: 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 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) or far higher audio quality (reflected by higher sampling rates, greater sample resolution and additional channels for spatial sound reproduction).^{[citation needed]}

DVD-Audio briefly formed a niche market, probably due to the very sort of format war with rival standard SACD that DVD-Video avoided.^{[citation needed]}

Security[edit]

Main article: Content Protection for Recordable Media

DVD-Audio discs employ a DRM mechanism, called Content Protection for Prerecorded Media (CPPM), developed by the 4C group (IBM, Intel, Matsushita, and Toshiba).^{[citation needed]}

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 (based on dvdcpxm) allowed for the development of open source DVD-Audio players and ripping software. As a result, making 1:1 copies of DVD-Audio discs is now possible with relative ease, much like DVD-Video discs.^{[citation needed]}

Successors and decline[edit]

The DVD succeeded because it offered a compelling alternative to VHS. In addition, the uniform media size lets manufacturers make Blu-ray players (and HD DVD players) backward-compatible, so they can play older DVDs. This stands in contrast to the change from vinyl to CD, and from tape to DVD, which involved a complete change in physical medium. As of 2019^[update] it is still commonplace for studios to issue major releases in "combo pack" format, including both a DVD and a Blu-ray disc (as well as a digital copy). Also, some multi-disc sets use Blu-ray for the main feature, but DVDs 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). 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.^{[citation needed]}

This situation is similar to the changeover from 78 rpm shellac recordings to 45 rpm and 33⅓ rpm vinyl recordings. Because the new and old media were virtually the same (a disc on a turntable, played by a needle), phonograph player manufacturers continued to include the ability to play 78s for decades after the format was discontinued.^{[citation needed]}

However, What We Left Behind included small amounts of remastered Deep Space Nine footage.^{[citation needed]}