|Type:||High-density optical disc|
|Encoding:||VC-1, H.264, and MPEG-2|
|Capacity:||15 GB (single layer)|
30 GB (dual layer)
|Read:||1× @ 36 Mbit/s & 2× @ 72 Mbit/s|
|Use:||Data storage, including high-definition video|
HD DVD (short for High-Definition/Density DVD) is a discontinued high-density optical disc format for storing data and high-definition video. HD DVD was supported principally by Toshiba, and was envisaged to be the successor to the standard DVD format. However, in February 2008, Toshiba abandoned the format, announcing it would no longer develop or manufacture HD DVD players or drives.
Since all variants except the 3× DVD employed a blue laser with a shorter wavelength, HD DVD can store about 3¼ times as much data per layer as its predecessor (maximum capacity: 15 GB per layer instead of 4.7 GB per layer).
Much like the VHS vs. Betamax format war during the late 1970s and early 1980s, HD DVD was competing with rival format Blu-ray Disc. In 2008, major content manufacturers and key retailers began withdrawing their support for the format. Toshiba's withdrawal from the format ended the high definition optical disc format war, effectively making rival Blu-ray Disc the dominant format for high definition video discs. The HD DVD Promotion Group was dissolved on March 28, 2008.
In the mid 1990s, commercial HDTV sets started to enter a larger market. However, there was no cheap way to record or play back HD content. There was no cheap storage medium that could store that amount of data, except JVC's Digital VHS and Sony's HDCAM. However, it was well known that using lasers with shorter wavelengths would yield optical storage with higher density. When Shuji Nakamura invented practical blue laser diodes, it was a sensation, although a lengthy patent lawsuit delayed commercial introduction.
Sony started two projects applying the new diodes: UDO (Ultra Density Optical) and DVR Blue (together with Pioneer), a format of rewritable discs which would eventually become Blu-ray (more specifically, BD-RE). The two formats share several technologies (such as the AV codecs and the laser diode). In February 2002, the project was officially announced as Blu-ray, and the Blu-ray Disc Association was founded by the nine initial members.
The DVD Forum (which was chaired by Toshiba) was deeply split over whether to go with the more expensive blue lasers or not. Although today's Blu-ray Discs appear virtually identical to a standard DVD, when the Blu-ray Discs were initially developed they required a protective caddy to avoid mis-handling by the consumer. (Early CD-Rs also featured a protective caddy for the same purpose.) The Blu-ray prototype's caddy was both expensive and physically different from DVD, posing several problems. In March 2002, the forum voted to approve a proposal endorsed by Warner Bros. and other motion picture studios that involved compressing HD content onto dual-layer DVD-9 discs.  However, in spite of this decision, the DVD Forum's Steering Committee announced in April that it was pursuing its own blue-laser high-definition solution. In August, Toshiba and NEC announced their competing standard Advanced Optical Disc. It was finally adopted by the DVD forum and renamed to HD DVD the next year, after being voted down twice by some of the Blu-ray group members, and the U.S. Department of Justice making preliminary investigations into the situation.  The voting rules on abstentions not being counted was changed before HD DVD format was approved. 
The HD DVD Promotion Group was a group of manufacturers and media studios formed to exchange thoughts and ideas to help promote the format worldwide. Its members comprised Toshiba Corporation as the Chair Company and Secretary, Memory-Tech Corporation and NEC Corporation as Vice-Chair companies, and Sanyo Electric as Auditors; there were 61 general members and 72 associate members in total. The HD DVD promotion group was officially dissolved on March 28, 2008, following Toshiba's announcement on February 19, 2008 that it would no longer develop or manufacture HD DVD players and drives.
See main article: High definition optical disc format war. In an attempt to avoid a costly format war, the Blu-ray Disc Association and DVD Forum attempted to negotiate a compromise in early 2005. One of the issues was that Blu-ray companies wanted to use a Java-based platform for interactivity (BD-J based on Sun Microsystem's Java TV standards), while HD DVD companies wanted to use Microsoft's "iHD" (which became HDi). Another issue was the physical formats of the discs themselves. The negotiations proceeded slowly and ultimately stalled.
On August 22, 2005, the Blu-ray Disc Association and DVD Forum announced that the negotiations to unify their standards had failed. Rumors surfaced that talks had stalled; publicly, the same reasons of physical format incompatibility were cited.  In the end of September, Microsoft and Intel jointly announced their support for HD DVD.
Hewlett Packard (HP) attempted to broker a compromise between the Blu-ray Disc Association and Microsoft by demanding that Blu-ray use Microsoft's HDi instead of BD-J and threatening to support HD DVD instead. However, the Blu-ray Disc Association did not agree to HP's demands.
On March 31, 2006 Toshiba released their first consumer-based HD DVD player in Japan at ¥110,000 (US$934), beating Blu-ray to the market by about three months. HD DVD was released in United States on April 18, 2006, with players priced at $499 and $799.
The first HD DVD titles were released on April 18, 2006. They were The Last Samurai, Million Dollar Baby, and The Phantom of the Opera by Warner Home Video and Serenity by Universal Studios. The first independent HD film released on HD DVD was One Six Right. 
In the middle of 2007, the first HD DVD Recorders were released in Japan.
In November 2007, the Toshiba HD-A2 was the first high definition player to be sold at a sale price of less than US$100; this was done through several major retailers to make room for the new HD-A3 models. These closeout sales lasted less than a day each due to both limited quantities and high demand at that price point. In the same month, the HD DVD promotion group announced that 750,000 HD DVD players had been sold, which included stand-alone players and the Xbox 360 add-on.
In January 2008 Toshiba announced that close to one million dedicated HD DVD players had been sold.
On January 4, 2008 citing consumer confusion and indifference as a reason for lackluster high-definition software sales, Warner Bros. announced it would stop supporting HD DVD by June 2008, and the company would release HD titles only on Blu-ray Disc. This was followed by news of Netflix phasing out support for the format, and Best Buy's decision to recommend Blu-ray Disc over HD DVD in its retail locations and to remove HD DVD players as part of its ongoing "HDTV advantage" promotion. Finally, retailer Wal-Mart announced that it would be supporting only Blu-ray by June 2008. On February 19, 2008, Toshiba announced plans to discontinue development, marketing and manufacturing of HD DVD players while still providing product support and after-sale service to consumers of the format (including Firmware updates). The company cited "recent major changes in the market". Shipments of HD DVD machines to retailers were reduced and eventually stopped by the end of March 2008.
The final HD DVD releases in the United States from a major studio were Warner's P.S. I Love You and Twister, on May 27, 2008. In June, the final HD DVD to be released was Freedom: 6 from Bandai Visual. Disco Pigs was, however, postponed, with no new date announced for release. Bandai Visual acknowledges the demise of HD DVD, but says that it wants to complete the release of the seven-part Freedom Project of which six parts have already been released . The sixth part was released in August 2008.
The final HD DVD release worldwide was Death Proof, released by Senator Films in Germany on December 15, 2008. HD DVD pre-orders for Shallow Grave and Trainspotting have been announced for March 30, 2009. 
The current specification books for HD DVD are listed at the DVD FLLC website.
HD DVD-ROM, HD DVD-R and HD DVD-RW have a single-layer capacity of 15 GB, and a dual-layer capacity of 30 GB. HD DVD-RAM has a single-layer capacity of 20 GB. Like the original DVD format, the data layer of an HD DVD is 0.6 mm below the surface to physically protect the data layer from damage. The numerical aperture of the optical pick-up head is 0.65, compared with 0.6 for DVD. All HD DVD players are backward compatible with DVD and CD.
|Physical size||Single layer capacity||Dual layer capacity|
|12 cm, single sided||15 GB||30 GB|
|12 cm, double sided||30 GB||60 GB|
|8 cm, single sided||4.7 GB||9.4 GB|
|8 cm, double sided||9.4 GB||18.8 GB|
|Drive speed||Data rate||Write time for HD DVD Disc (minutes)|
|Mbit/s||MB/s||Single Layer||Dual Layer|
The HD DVD format supports encoding in up to 24-bit/192 kHz for two channels, or up to eight channels of up to 24-bit/96 kHz encoding.
All HD DVD players are required to decode linear (uncompressed) PCM, Dolby Digital AC-3, Dolby Digital EX, DTS, Dolby Digital Plus and Dolby TrueHD. A secondary soundtrack, if present, can be stored in any of the aforementioned formats, or in one of the HD DVD optional codecs: DTS-HD High Resolution Audio and DTS-HD Master Audio. For the highest-fidelity audio experience, HD DVD offers content-producers the choice of LPCM, Dolby TrueHD and DTS-HD Master Audio.
HD DVD video can be encoded using VC-1, AVC, or MPEG-2. A wide variety of resolutions are supported, from low-resolution CIF, all SDTV resolutions supported by DVD-Video, and of course the HDTV formats: 720p, 1080i, and 1080p. All studio-released movie titles have featured video in a 1080-line format, with companion supplements in 480i or 480p. The vast majority of releases were encoded with VC-1, and most of the remaining titles encoded with AVC.
See main article: Advanced Access Content System. If a publisher wishes to restrict use of their HD DVD content, they may use the Advanced Access Content System (AACS) although this is not required for normal disc playback. AACS is a standard for content distribution and digital rights management. It is developed by AACS Licensing Administrator, LLC (AACS LA), a consortium that includes Disney, Intel, Microsoft, Matsushita (Panasonic), Warner Bros., IBM, Toshiba and Sony. One of the advantages over CSS, the content restriction system for DVDs, is that AACS allows content providers to revoke an individual player device if its cryptographic keys have been compromised (meaning that it will not be able to decrypt subsequently released content). There is no Region Coding in the existing HD DVD specification, which means that titles from any country can be played in players in any other country.
Since appearing in devices in 2006, several successful attacks have been made on the format. The first known attack relied on the trusted client problem. In addition, decryption keys have been extracted from a weakly protected player (WinDVD). Notably, a Processing Key was found that could be used to decrypt all HD content that had been released at the time. The processing key was widely published on the Internet after it was found and the AACS LA sent multiple DMCA takedown notices in the aim of censoring it. This caused trouble on some sites that rely on user-submitted content, like Digg and Wikipedia, when administrators tried to remove any mentions of the key. 
AACS has also been circumvented by SlySoft with their program AnyDVD HD, which allows users to watch HD DVD movies on non-HDCP-compliant PC hardware. Slysoft has stated that AnyDVD HD uses several different mechanisms to disable the encryption, and is not dependent on the use of a single compromised encryption key. Other AACS circumvention programs have become available, like DVDFab HD Decrypter.
Backward compatibility is available with all HD DVD players, allowing users to have a single player to play all types of HD DVD, DVD and CD. There is also a hybrid HD DVD format which contains both DVD and HD DVD versions of the same movie on a single disc, providing a smooth transition for the studios in terms of publishing movies, and allowing consumers with only DVD players to still use the discs. DVD replication companies can continue using their current production equipment with only minor alterations when changing over to the format of HD DVD replication. Due to the structure of the single-lens optical head, both red and blue laser diodes can be used in smaller, more compact HD DVD players.
HD DVD drives can also be used with a desktop/laptop personal computer (PC) running Windows XP, Windows Vista, Mac OS X v10.5 "Leopard", and many varieties of Linux. Third-party player software for Windows and Linux have successfully played HD DVD titles using the add-on drive. First-party (Apple, Inc.) player software is included with Leopard, making it the first operating system (OS) to ship with native HD DVD playing software, albeit limited to HD DVDs authored by DVD Studio Pro.
For more details on this topic, see Xbox 360 HD DVD Player
Released at the end of November 2006, the Microsoft HD DVD drive for the Xbox 360 game-console gives the Xbox 360 the ability to play HD DVD movies. The drive was announced with an MSRP of US$199 and includes a USB 2.0 cable for connection to the console. The first drives also included Peter Jackson's King Kong on HD DVD. The final "regular" for the drive was US$129.99 as of February 25, 2008. On February 23, 2008 Microsoft discontinued the Xbox 360 HD DVD player. On February 26, 2008, Microsoft "officially" announced that the Xbox 360 HD DVD add on drive would reflect a heavily discounted price down to $49.99.
In 2007, LG and Samsung released standalone consumer players that could read both HD DVD and Blu-ray discs. The machines were sold at premium prices, but failed to sell in large quantities. In May 2008, both companies announced they would stop manufacturing dual-compatibility drives.
See main article: Comparison of high definition optical disc formats. HD DVD competed primarily with Blu-ray Disc. Both formats were designed as successors to DVD, capable of higher quality video and audio playback, and of greater capacity when used to store video, audio, and computer data. Blu-ray and HD DVD share most of the same methods of encoding media onto disks with each other, resulting in equivalent levels of audio and visual quality, but differ in other aspects such as interactive capabilities, internet integration, usage control and enforcement, and in which features were mandatory for players. The storage size also varies: A dual-layer HD DVD holds a maximum of 30 GB of data, while a dual-layer Blu-ray carries 50 GB.
Even after finalizing the HD DVD standard, engineers continued developing the technology. A 51 GB triple-layer spec was approved at the DVD Forums 40th Steering Committee Meeting (held on November 15, 2007). However, no movies had been scheduled for this disc type, and Toshiba had declined to say whether the 51 GB disc was compatible with existing drives and players. Specification 2.0 Part 1 (Physical Specification) for triple layer HD DVD had been approved in November 2007.
At the CES 2007, Ritek revealed their high definition optical disc process that extended both competing high definition formats to ten layers, increasing capacity to 150 GB for HD DVD and 250 GB for Blu-ray Disc. However, a major obstacle to implementing this technology in either format (150 GB HD DVD will not be developed due to HD DVD's discontinuation) is that reader-writer technology available may not be able to support the additional data layers.
NEC, Broadcom, Horizon Semiconductors, and STMicroelectronics have separately developed a single chip/laser that can read both the HD DVD and the Blu-ray disc standard. Broadcom and STMicroelectronics will be selling their dual-format single chip/laser solution to any OEM willing to develop a product based on the chip.
HD DVD-R is the writable disc variant of HD DVD, available with a single-layer capacity of 15 GB or a dual-layer capacity of 30 GB. Write speeds depend on drive speed, with a data rate of 36.55 Mbit/s (4.36 MB/s) and a recording time of 56 minutes for 1× media, and 73 Mbit/s (8.71 MB/s) and a recording time of 28 minutes for 2×.
The Toshiba SD-L902A for notebooks was one of the first available HD DVD writers, although it was not meant for retail.  Burning HD DVD (including Dual Layer) with a 1× write speed, it could also burn DVDs and CDs. In a test of the SD-L902A by C't computer magazine with Verbatim discs, the written HD DVD-Rs suffered from high noise levels; as a result, the written discs could not be recognized by the external HD DVD drive of the Xbox 360, though they could be read back by the SD-L902A.
HD DVD-RW is the rewritable disc variant of HD DVD with equal storage capacity to an HD DVD-R. The primary advantage of HD DVD-RW over HD DVD-R is the ability to erase and rewrite to an HD DVD-RW disc, up to about 1,000 times before needing replacement, making them comparable with the CD-RW and DVD-RW standards. This is also of benefit if there are writing errors when recording data, as the disc is not ruined and can still store data by erasing the faulty data.
HD DVD-RAM was the proposed successor to DVD-RAM for random access on optical media using phase-change principals. It would hold 20 gigabytes per layer instead of 15 gigabytes for HD DVD-R, due to differences in recording methods used, yielding a higher density disc.
There are two types of hybrid formats which contain standard DVD-Video format video for playback in regular DVD players, and HD DVD video for playback in high definition on HD DVD players. The Combo disc is a dual sided disc with one side DVD and the other HD DVD, each of which can have up to two layers. The Twin disc is a single sided disc that can have up to three layers, with up to two layers dedicated to either DVD or HD DVD. These hybrid discs make retail marketing and shelf space management easier. Another advantage is hardware cross-compatibility. The average consumer doesn't have to worry about whether or not they can play a hybrid DVD: any standard home DVD player can access the DVD-encoded content and any HD DVD player can access both the DVD- and HD DVD-encoded content.
Warner Bros. officially announced Total Hi Def (THD or Total HD) at CES 2007. THD hybrid discs were to support both HD DVD and Blu-ray, with HD DVD on one side (up to two layers) and Blu-ray on the other side (up to two layers). However, in November 2007 Warner Bros. cancelled THD development.
The HD DVD format also applies to current red laser DVDs; this type of disc is called "3× DVD", as it is capable of three times the bandwidth of regular DVD-Video.
3× DVDs are physically identical to normal DVDs. Although 3× DVDs provide the same high definition content, their playback time is less. For example, an 8.5 GB DVD can hold about 85 minutes of 1080p video encoded with VC-1 or AVC at an average bitrate of 13 Mbit/s, suitable for short subjects (training films, home movies, very short feature films), but unsuitable for most feature film-length content.
It is technically possible for consumers to create HD DVD compatible discs using low cost DVD-R or DVD+R media. At least one such guide exists. The 3× DVD is comparable to Blu-ray BD5 and BD9 formats.
HD Rec is an extension of the HD DVD format for recording HD content on regular red laser DVD-Rs/DVD-RWs using H.264/MPEG-4 AVC compression. It was approved by the DVD Forum on September 12, 2007 It is comparable to Blu-ray's AVCREC.