DVD

Development and launch

Released in 1987, CD Video used analog video encoding on optical discs matching the established standard 120 mm (4.7 in) size of audio CDs. Video CD (VCD) became one of the first formats for distributing digitally encoded films in this format, in 1993.^[14] In the same year, two new optical disc storage formats were being developed. One was the Multimedia Compact Disc (MMCD), backed by Philips and Sony (developers of the CD and CD-i), and the other was the Super Density (SD) disc, supported by Toshiba, Time Warner, Matsushita Electric, Hitachi, Mitsubishi Electric, Pioneer, Thomson, and JVC. By the time of the press launches for both formats in January 1995, the MMCD nomenclature had been dropped, and Philips and Sony were referring to their format as Digital Video Disc (DVD).^[15][16]

On May 3, 1995, an ad hoc industry technical group formed from five computer companies (IBM, Apple, Compaq, Hewlett-Packard, and Microsoft) issued a press release stating that they would only accept a single format.^[17][18] The group voted to boycott both formats unless the two camps agreed on a single, converged standard. They recruited Lou Gerstner, president of IBM, to pressure the executives of the warring factions. In one significant compromise, the MMCD and SD groups agreed to adopt proposal SD 9, which specified that both layers of the dual-layered disc be read from the same side—instead of proposal SD 10, which would have created a two-sided disc that users would have to turn over. Philips/Sony strongly insisted on the source code, EFMPlus, that Kees Schouhamer Immink had designed for the MMCD, because it makes it possible to apply the existing CD servo technology. Its drawback was a loss from 5 to 4.7 Gigabytes of capacity.^[19][20]

As a result, the DVD specification provided a storage capacity of 4.7 GB (4.38 GiB)^[a] for a single-layered, single-sided disc and 8.5 GB (7.92 GiB) for a dual-layered, single-sided disc.^[21] The DVD specification ended up 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 two half-thickness, single-layer discs which were pressed separately and then glued together to form a double-sided disc.^[16]

Philips and Sony decided that it was in their best interests to end the format war, and on September 15, 1995 agreed to unify with companies backing the Super Density Disc to release a single format, with technologies from both.^[22] After other compromises between MMCD and SD, the group of computer companies won the day, and a single format was agreed upon. The computer companies also collaborated with the Optical Storage Technology Association (OSTA) on the use of their implementation of the ISO-13346 file system (known as Universal Disk Format) for use on the new DVDs. The format's details were finalized on December 8, 1995.^[23]

In November 1995, Samsung announced it would start mass-producing DVDs by September 1996.^[24] The format launched on November 1, 1996, in Japan, mostly with music video releases. The first major releases from Warner Home Video arrived on December 20, 1996, with four titles being available.^[b][4] The format's release in the U.S. was delayed multiple times, from August 1996,^[25] to October 1996,^[26] November 1996,^[27] before finally settling on early 1997.^[28] Players began to be produced domestically that winter, with March 24, 1997, as the U.S. launch date of the format proper in seven test markets.^[c][5][29] Approximately 32 titles were available on launch day, mainly from the Warner Bros., MGM, and New Line libraries,^[30][d] with the notable inclusion of the 1996 film Twister.^[31] However, the launch was planned for the following day (March 25), leading to a distribution change with retailers and studios to prevent similar violations of breaking the street date.^[32] The nationwide rollout for the format happened on August 22, 1997.^{[33][better source needed]}

DTS announced in late 1997 that they would be coming onto the format. The sound system company revealed details in a November 1997 online interview, and clarified it would release discs in early 1998.^[34] However, this date would be pushed back several times before finally releasing their first titles at the 1999 Consumer Electronics Show.^[35]

In 2001, blank DVD recordable discs cost the equivalent of $27.34 US dollars in 2022.^[36][37]

Adoption

Movie and home entertainment distributors adopted the DVD format to replace the ubiquitous VHS tape as the primary consumer video distribution format.^[38]

Immediately following the formal adoption of a unified standard for DVD, two of the four leading video game console companies (Sega and The 3DO Company) said they already had plans to design a gaming console with DVDs as the source medium.^[39] Sony stated at the time that they had no plans to use DVD in their gaming systems, despite being one of the developers of the DVD format and eventually the first company to actually release a DVD-based console.^[39] Game consoles such as the PlayStation 2, Xbox, and Xbox 360 use DVDs as their source medium for games and other software. Contemporary games for Windows were also distributed on DVD. Early DVDs were mastered using DLT tape,^[40] but using DVD-R DL or +R DL eventually became common.^[41] TV DVD combos, combining a standard definition CRT TV or an HD flat panel TV with a DVD mechanism under the CRT or on the back of the flat panel, and VCR/DVD combos were also available for purchase.^[42]

For consumers, DVD soon overtook VHS as the favored choice for home movie releases. In 2001, DVD players outsold VCRs for the first time in the United States. At that time, one in four American households owned a DVD player.^[43] By 2007, about 80% of Americans owned a DVD player, a figure that had surpassed VCRs; it was also higher than personal computers or cable television.^[44]

Double-sided discs

Borrowing from the LaserDisc format, the DVD standard includes DVD-10 discs (Type B in ISO) with two recorded data layers such that only one layer is accessible from either side of the disc. This doubles the total nominal capacity of a DVD-10 disc to 9.4 GB (8.75 GiB), but each side is locked to 4.7 GB. Like DVD-5 discs, DVD-10 discs are defined as single-layer (SL) discs.^[47]

Dual-layer discs

DVD hardware accesses the additional layer (layer 1) by refocusing the laser through an otherwise normally-placed, semitransparent first layer (layer 0). This laser refocus—and the subsequent time needed to reacquire laser tracking—can cause a noticeable pause in A/V playback on earlier DVD players, the length of which varies between hardware.^[58] A printed message explaining that the layer-transition pause was not a malfunction became standard on DVD keep cases. During mastering, a studio could make the transition less obvious by timing it to occur just before a camera angle change or other abrupt shift, an early example being the DVD release of Toy Story.^[59] Later in the format's life, larger data buffers and faster optical pickups in DVD players made layer transitions effectively invisible regardless of mastering.^{[citation needed]}

Dual-layer DVDs are recorded using Opposite Track Path (OTP).^[60]

Combinations of the above

The DVD Book also permits an additional disc type called DVD-14: a hybrid double-sided disc with one dual-layer side, one single-layer side, and a total nominal capacity of 12.3 GB.^[61] DVD-14 has no counterpart in ISO.^[47]

Both of these additional disc types are extremely rare due to their complicated and expensive manufacturing.^[61] For this reason, some DVDs that were initially issued as double-sided discs were later pressed as two-disc sets.

Note: The above sections regarding disc types pertain to 12 cm discs. The same disc types exist for 8 cm discs: ISO standards still regard these discs as Types A–D, while the DVD Book assigns them distinct disc types. DVD-14 has no analogous 8 cm type. The comparative data for 8 cm discs is provided further down.

Dual-layer recording

Dual-layer recording (occasionally called double-layer recording) allows DVD-R and DVD+R discs to store nearly double the data of a single-layer disc—8.5 and 4.7 gigabyte capacities, respectively.^[64] The additional capacity comes at a cost: DVD±DLs have slower write speeds as compared to DVD±R.^[65] DVD-R DL was developed for the DVD Forum by Pioneer Corporation; DVD+R DL was developed for the DVD+RW Alliance by Mitsubishi Kagaku Media (MKM) and Philips.^[66]

Recordable DVD discs supporting dual-layer technology are backward-compatible with some hardware developed before the recordable medium.^[66]

Transfer rates

Read and write speeds for the first DVD drives and players were 1,385 kB/s (1,353 KiB/s); this speed is usually called "1×". More recent models, at 18× or 20×, have 18 or 20 times that speed. For CD drives, 1× means 153.6 kB/s (150 KiB/s), about one-ninth as swift.^[69][70]

DVDs can spin at much higher speeds than CDs – DVDs can spin at up to 32000 RPM vs 23000 for CDs.^[73] In practice, they are not spun by optical drives anywhere close to these speeds to provide a safety margin. DVD drives limit reading speed to 16× (constant angular velocity), which means 9280 rotations per minute. Early-generation drives released before the mid-2000s have lower limits.^[74][75][76]

DVD recordable and rewritable discs can be read and written using either constant angular velocity (CAV), constant linear velocity (CLV), Partial constant angular velocity (P-CAV) or Zoned Constant Linear Velocity (Z-CLV or ZCLV).^[77]

Due to the slightly lower data density of dual layer DVDs (4.25 GB instead of 4.7 GB per layer), the required rotation speed is around 10% faster for the same data rate, which means that the same angular speed rating equals a 10% higher physical angular rotation speed. For that reason, the increase of reading speeds of dual layer media has stagnated at 12× (constant angular velocity) for half-height optical drives released since around 2005,^[g] and slim type optical drives are only able to record dual layer media at 6× (constant angular velocity), while reading speeds of 8× are still supported by such.^[82][75][74]

Disc quality measurements

The quality and data integrity of optical media is measureable, which means that future data losses caused by deteriorating media can be predicted well in advance by measuring the rate of correctable data errors.^[83]

The types of errors that can occur on a DVD are a PIE (Parity Inner Error), 8PIE (Parity Inner Sum Eight Error), PIF (Parity Inner Failure), POE (Parity Outer Error), and POF (Parity Outer Failure), the last of which indicates data loss. Too many small errors within a small space create a POF condition. The difference between POE and POF is that a POE is generated on a first failed read attempt whereas a POF indicates an uncorrectable error after repeated attempts to read the data.^[84][85]

Support of measuring the disc quality varies among optical drive vendors and models.^[84][86] Unreadable data can be found using any drive using general-purpose tools like badblocks.

Security

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.^[88]