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Blu-ray Disc (also known as Blu-ray or BD) is an optical disc storage medium. Its main uses are high-definition video and data storage. The disc has the same physical dimensions as standard DVDs and CDs.
The name Blu-ray Disc is derived from the blue laser (violet-colored) used to read and write to this type of disc. Because of the wavelength (405 nanometres), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red (650 nm) laser.
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Encyclopedia
Blu-ray Disc (also known as Blu-ray or BD) is an optical disc storage medium. Its main uses are high-definition video and data storage. The disc has the same physical dimensions as standard DVDs and CDs.
The name Blu-ray Disc is derived from the blue laser (violet-colored) used to read and write to this type of disc. Because of the wavelength (405 nanometres), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red (650 nm) laser. A two-layer Blu-ray Disc can store 50 gigabytes, almost six times the capacity of a two-layer DVD, or ten and a half times that of a single-layer DVD.
During the format war over high-definition optical discs, Blu-ray Disc competed with the HD DVD format. On February 19, 2008, Toshiba—the main company supporting HD DVD—announced that it would no longer develop, manufacture, or market HD DVD players and recorders, leading almost all other HD DVD companies to follow suit, effectively ending the format war.
Blu-ray Disc was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. As of December 21, 2008, more than 890 Blu-ray disc titles are available in Australia, more than 720 Blu-ray Disc titles are available in Japan, more than 1,140 Blu-ray Disc titles are available in the United Kingdom, and more than 1,220 Blu-ray Disc titles are available in the United States.
History
Commercial HDTV sets began to appear in the consumer market around 1998, but there was no commonly-accepted, inexpensive way to record or play HD content. In fact, there was no medium with the storage required to accommodate HD codecs, except JVC's Digital VHS and Sony's HDCAM. Nevertheless, it was well known that using lasers with shorter wavelengths would enable 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. Dr. Dave Irvine-Halliday was given the proceeds from the patent lawsuit to continue his ongoing work for the Light Up the World Foundation.
Origins
Philips 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 Disc (more specifically, BD-RE). The core technologies of the formats are essentially similar.
The first DVR Blue prototypes were unveiled at the CEATEC exhibition in October 2000. Because the Blu-ray Disc standard places the data recording layer close to the surface of the disc, early discs were susceptible to contamination and scratches and had to be enclosed in plastic cartridges for protection. 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 first consumer devices were in stores on April 10, 2003. This device was the Sony BDZ-S77; a BD-RE recorder that was made available only in Japan. The recommended price was US$3800; however, there was no standard for pre-recorded video and no movies were released for this player. The Blu-ray Disc standard was still years away as a newer, more secure DRM system was needed before Hollywood studios would accept it, not wanting to repeat the failure of the Content Scramble System used on DVDs.
Blu-ray Disc format finalized
The Blu-ray Disc physical specifications were finished in 2004. In January 2005, TDK announced that they had developed a hard coating polymer for Blu-ray Discs. The cartridges, no longer necessary, were scrapped.
The BD-ROM specifications were finalized in early 2006. AACS LA, a consortium founded in 2004, had been developing the DRM platform that could be used to securely distribute movies to consumers. However, the final AACS standard was delayed, and then delayed again when an important member of the Blu-ray Disc group voiced concerns. At the request of the initial hardware manufacturers, including Toshiba, Pioneer and Samsung, an interim standard was published which did not include some features, like managed copy.
Launch and sales developments
The first BD-ROM players were shipped in the middle of June 2006, though HD DVD players beat them in the race to the market by a few months.
The first Blu-ray Disc titles were released on June 20, 2006. The earliest releases used MPEG-2 video compression, the same method used on DVDs.
The first releases using the newer VC-1 and AVC codecs were introduced in September 2006. The first movies using dual layer discs (50 GB) were introduced in October 2006. The first audio-only release was made in March 2008.
The first mass-market Blu-ray Disc rewritable drive for the PC was the BWU-100A, released by Sony on July 18, 2006. It recorded both single and dual layer BD-R as well as BD-RE discs and had a suggested retail price of US $699.
Competition from HD DVD
The DVD Forum (which was chaired by Toshiba) was deeply split over whether to develop the more expensive blue laser technology or not. 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. In spite of this decision, however, 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 HD DVD the next year, after being voted down twice by DVD Forum members who were also Blu-ray Disc Association members, prompting the U.S. Department of Justice to make preliminary investigations into the situation.
HD DVD had a head start in the high definition video market as Blu-ray Disc sales were slow to gain market share. The first Blu-ray Disc player was perceived as expensive and buggy, and there were few titles available. This changed when PlayStation 3 launched, since every PS3 unit also functioned as a Blu-ray Disc player. At CES 2007 Warner proposed Total Hi Def which was a hybrid disc containing Blu-ray on one side and HD DVD on the other but it was never released. By January 2007, Blu-ray discs had outsold HD DVDs, and during the first three quarters of 2007, BD outsold HD DVDs by about two to one. In February 2008, Toshiba withdrew its support for the HD DVD format, leaving Blu-ray as the victor.
Some analysts believe that Sony's PlayStation 3 video game console played an important role in the format war, believing it acted as a catalyst for Blu-ray Disc, as the PlayStation 3 used a Blu-ray Disc drive as its primary information storage medium. They also credited Sony's more thorough and influential marketing campaign. More recently Twentieth Century Fox has cited Blu-ray Disc's adoption of the BD+ anti-copying system as the reason they supported Blu-ray Disc over HD DVD.
End of the format war & future prospects
On January 4, 2008, a day before CES 2008, Warner Bros., the only major studio still releasing movies in both HD DVD and Blu-ray Disc format, announced it would release only in Blu-ray Disc after May 2008. This effectively included other studios which came under the Warner umbrella, such as New Line Cinema and HBO, though in Europe HBO distribution partner the BBC announced it would, while keeping an eye on market forces, continue to release product on both formats. This led to a chain reaction in the industry, including major U.S. retailers such as Best Buy, Wal-Mart, and Circuit City, and Canadian chains such as Future Shop, dropping HD DVD in their stores. A former major European retailer, Woolworths, dropped HD DVD from its inventory. Netflix and Blockbuster – major DVD rental companies – said they would no longer carry HD DVDs. Following these new developments, on February 19, 2008, Toshiba announced it would end production of HD DVD devices, allowing Blu-ray Disc to become the industry standard for high-density optical disks. Universal Studios, the sole major movie studio to back HD DVD since inception, shortly after Toshiba's announcement, said "while Universal values the close partnership we have shared with Toshiba, it is time to turn our focus to releasing new and catalog titles on Blu-ray Disc." Paramount Studios, which started releasing movies only in HD DVD format during late 2007, also said it would start releasing in Blu-ray Disc. Both studios announced initial Blu-ray lineups in May 2008. With this, all major Hollywood studios now support Blu-ray.
According to Adams Media Research, high-definition software sales were slower in the first two years than DVD software sales. 16.3 million DVD software units were sold in the first two years (1997-1998) compared to 8.3 million high-definition software units (2006-2007). One reason given for this difference was the smaller marketplace (26.5 million HDTVs in 2007 compared to 100 million SDTVs in 1998). Former HD DVD supporter Microsoft has stated that they are not planning to make a Blu-ray Disc drive for the Xbox 360.
Blu-ray Disc began making serious strides as soon as the format war ended. Nielsen VideoScan sales numbers showed that with some titles, such as 20th Century Fox's Hitman, up to 14% of total disc sales were from Blu-ray, although the average for the first half of the year was around 5%. Shortly after the format war ended, a study by The NPD Group found that awareness of Blu-ray Disc had reached 60% of U.S. households. In December 2008 The Dark Knight Blu-ray Disc sold 600,000 copies on the first day of its launch in the United States, Canada, and United Kingdom. A week after launch the The Dark Knight Blu-ray Disc had sold over 1.7 million copies worldwide making it the first Blu-ray Disc title to sell over a million copies in the first week of release.
According to Singulus Technologies AG, Blu-ray is being adopted faster than the DVD format was at the same period of its development. This conclusion was based on the fact that Singulus Technologies has received orders for 21 Blu-ray dual-layer machines during the first quarter of 2008, while 17 DVD machines of this type were made in the same period in 1997. According to GfK Retail and Technology in the first week of November 2008 sales of Blu-ray recorders surpassed DVD recorders in Japan. According to the Digital Entertainment Group the total number of Blu-ray Disc playback devices (both set-top box and game console) had reached 9.6 million by the end of 2008. According to Swicker & Associates Blu-ray Disc software sales in the United States and Canada were 1.2 million in 2006, 19.2 million in 2007, and 82.4 million in 2008.
Technical specifications
| Type | Physical size | Single layer capacity | Dual layer capacity |
|---|
| Standard disc size | 12 cm, single sided | 25 GB (23.28 GiB) | 50 GB (46.57 GiB) | | Mini disc size | 8 cm, single sided | 7.8 GB (7.26 GiB) | 15.6 GB (14.53 GiB) |
High-definition video may be stored on Blu-ray ROM discs with up to 1920x1080 pixel resolution at up to 60 frames per second interlaced or 24 frames per second progressive:
| Resolution | Frame rate | Aspect ratio | Codec |
|---|
| 1920x1080 | 59.94-i, 50-i | 16:9 | | | 1920x1080 | 24-p, 23.976-p | 16:9 | | | 1440x1080 | 59.94-i, 50-i | 16:9 | MPEG-4 AVC / SMPTE VC-1 only | | 1440x1080 | 24-p, 23.976-p | 16:9 | MPEG-4 AVC / SMPTE VC-1 only | | 1280x720 | 59.94-p, 50-p | 16:9 | | | 1280x720 | 24-p, 23.976-p | 16:9 | | | 720x480 | 59.94-i | 4:3/16:9 | | | 720x576 | 50-i | 4:3/16:9 | |
Laser and optics
Blu-ray Disc uses a "blue" (technically violet) laser operating at a wavelength of 405 nm to read and write data. Conventional DVDs and CDs use red and near infrared lasers at 650 nm and 780 nm respectively.
The blue-violet laser's shorter wavelength makes it possible to store more information on a 12 cm CD/DVD sized disc. The minimum "spot size" on which a laser can be focused is limited by diffraction, and depends on the wavelength of the light and the numerical aperture of the lens used to focus it. By decreasing the wavelength, increasing the numerical aperture from 0.60 to 0.85 and making the cover layer thinner to avoid unwanted optical effects, the laser beam can be focused to a smaller spot. This allows more information to be stored in the same area. For Blu-ray Disc, the spot size is 580 nm. In addition to the optical improvements, Blu-ray Discs feature improvements in data encoding that further increase the capacity. (See Compact Disc for information on optical discs' physical structure.)
Hard-coating technology
Because the Blu-ray Disc data layer is closer to the surface of the disc, compared to the DVD standard, it was at first more vulnerable to scratches. The first discs were housed in cartridges for protection.
TDK was the first company to develop a working scratch protection coating for Blu-ray Discs. It was named Durabis. In addition, both Sony and Panasonic's replication methods include proprietary hard-coat technologies. Sony's rewritable media are spin-coated with a scratch-resistant and antistatic coating. Verbatim's recordable and rewritable Blu-ray Disc discs use their own proprietary hard-coat technology called ScratchGuard.
Recording speed
| Drive speed | Data rate | Write time for Blu-ray Disc (minutes) |
|---|
Mbit/s | MB/s | Single Layer | Dual Layer | 1× | 36 | 4.5 | 90 | 180 | 2× | 72 | 9 | 45 | 90 | 4× | 144 | 18 | 23 | 45 | 6× | 216 | 27 | 15 | 30 | 8×* | 288 | 36 | 12 | 23 | 12×** | 432 | 54 | 8 | 15 |
* On August 8, 2008, Japanese electronics company Buffalo announced that it will ship the first 8x Blu-ray burners in Japan starting from September 2008. On September 22, 2008, Buffalo announced one internal and one external 8x Blu-ray burners for the United States, to be released the same month. The following day Sony announced the BWU-300S, an internal 8x Blu-ray burner for the United States.
** Theoretical
Software standards
Codecs
The BD-ROM specification mandates certain codec compatibilities for both hardware decoders (players) and the movie-software (content). For video, all players are required to support MPEG-2, H.264/MPEG-4 AVC, and SMPTE VC-1. MPEG-2 is the codec used on regular DVDs, which allows backwards compatibility. MPEG-4 AVC was developed by MPEG and VCEG. VC-1 is a codec that was mainly developed by Microsoft. BD-ROM titles with video must store video using one of the three mandatory codecs. Multiple codecs on a single title are allowed.
The choice of codecs affects the producer's licensing/royalty costs, as well as the title's maximum runtime, due to differences in compression efficiency. Discs encoded in MPEG-2 video typically limit content producers to around two hours of high-definition content on a single-layer (25 GB) BD-ROM. The more advanced video codecs (VC-1 and MPEG-4 AVC) typically achieve a video runtime twice that of MPEG-2, with comparable quality.
MPEG-2 was used by many studios, including Paramount Pictures (which initially used the VC-1 codec for HD DVD releases) for the first series of Blu-ray discs that were launched throughout 2006. Modern releases are now often encoded in either MPEG-4 AVC or VC-1, allowing film studios to place all content on one disc, reducing costs and improving ease of use. Using these codecs will also free many GBs of space for storage of bonus content in HD (1080i/p) as opposed to the SD (480i/p) typically used for most titles. Some studios (such as Warner Bros.) have released bonus content on discs encoded in a different codec than the main feature title; for example the Blu-ray release of Superman Returns uses VC-1 for the feature film and MPEG-2 for bonus content (presumably because it is simply ported from the DVD release).
For audio, BD-ROM players are required to support Dolby Digital, DTS, and linear PCM. Players may optionally support Dolby Digital Plus and DTS-HD High Resolution Audio, as well as lossless formats Dolby TrueHD and DTS-HD Master Audio. BD-ROM titles must use one of the mandatory schemes for the primary soundtrack. A secondary audiotrack, if present, may use any of the mandatory or optional codecs.
For users recording digital television programming, the recordable Blu-ray Disc standard's initial data rate of 36 Mbit/s is more than adequate to record high-definition broadcasts from any source (IPTV, cable/satellite, or terrestrial). BD-Video movies have a maximum data transfer rate of 54 Mbit/s, a maximum AV bitrate of 48 Mbit/s (for both audio and video data), and a maximum video bitrate of 40 Mbit/s. This compares to HD DVD movies which have a maximum data transfer rate of 36 Mbit/s, a maximum AV bitrate of 30.24 Mbit/s, and a maximum video bitrate of 29.4 Mbit/s.
Java software support
At the 2005 JavaOne trade show, it was announced that Sun Microsystems' Java cross-platform software environment would be included in all Blu-ray Disc players as a mandatory part of the standard. Java is used to implement interactive menus on Blu-ray Discs, as opposed to the method used on DVD video discs, which uses pre-rendered MPEG segments and selectable subtitle pictures, which is considerably more primitive and rarely seamless. Java creator James Gosling, at the conference, suggested that the inclusion of a Java Virtual Machine as well as network connectivity in some BD devices will allow updates to Blu-ray Discs via the Internet, adding content such as additional subtitle languages and promotional features that are not included on the disc at pressing time. This Java Version is called BD-J and is a subset of the Globally Executable MHP (GEM) standard. GEM is the worldwide version of the Multimedia Home Platform standard.
Region codes
Blu-ray Discs may be encoded with a region code, intended to restrict the area of the world in which they can be played, similar in principle to the DVD region codes, although the used geographical regions differ. Blu-ray Disc players sold in a certain region may only play discs encoded for that region. This is primarily used for market segmentation, or price discrimination, but it also allows motion picture studios to control the various aspects of a release (including content and release date) according to the region. Discs may also be produced without region coding, so they can be played on all devices. The countries of the major Blu-ray manufacturers (Japan, Malaysia, South Korea, etc.) are in the same region as the Americas. As of late 2008, almost 70% of all released discs were region-free.
Major studios have different region coding policies. Paramount Pictures and Universal Studios have released all of their titles region free. Sony Pictures and Warner Bros. have released most of their titles region free, but titles released by Warner's New Line division were, initially, region-coded but subsequently have been released without being locked. Titles released by other labels on behalf of New Line are still subject to some region locking. Lionsgate and Walt Disney Pictures have released a mix of titles that were region free and region coded. 20th Century Fox has released all but three of their titles region coded.
In the Blu-ray region coding system, the United States is placed in region A while regions B and C are used for countries which can experience localization delays before U.S. titles are officially released. The opposite, though, is sometimes true and a few new titles such as Harry Potter and the Goblet of Fire and Running Scared were released in certain European countries before the U.S. release. In response to the DVD region system, multi-region and region-free DVD players became dominant in certain markets; certain Blu-ray player models have been modified to allow for playback of Blu-ray and DVD discs with any region code.
Digital rights management
The Blu-ray Disc format employs several layers of digital rights management.
AACS
Advanced Access Content System (AACS) is a standard for content distribution and digital rights management. It is developed by AS Licensing Administrator, LLC (AACS LA), a consortium that includes Disney, Intel, Microsoft, Matsushita (Panasonic), Warner Bros., IBM, Toshiba and Sony.
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). Since keys can be revoked in newer releases, this is only a temporary attack and new keys must continually be discovered in order to decrypt the latest discs. This cat-and-mouse game has gone through several cycles and as of August 2008 all current AACS decryption keys are available on the Internet.
BD+
BD+ was developed by Cryptography Research Inc. and is based on their concept of Self-Protecting Digital Content. BD+ is effectively a small virtual machine embedded in authorized players. It allows content providers to include executable programs on Blu-ray Discs. Such programs can:
- examine the host environment, to see if the player has been tampered with. Every licensed playback device manufacturer must provide the BD+ licensing authority with memory footprints that identify their devices.
- verify that the player's keys have not been changed.
- execute native code, possibly to patch an otherwise insecure system.
- transform the audio and video output. Parts of the content will not be viewable without letting the BD+-program unscramble it.
If a playback device manufacturer finds that its devices have been hacked, it can potentially release BD+-code that detects and circumvents the vulnerability. These programs can then be included in all new content releases.
The specifications of the BD+ virtual machine are available only to licensed device manufacturers. A list of licensed commercial adopters is available from the .
The first titles using BD+ were released in October 2007. Versions of the BD+ protection have been circumvented by various versions of the AnyDVD HD program, including a new version of BD+ released in November 2008, and later cracked by AnyDVD on December 29, 2008.
BD-ROM Mark
BD-ROM Mark is a small amount of cryptographic data that is stored separately from normal Blu-ray Disc data. Bit-by-bit copies that do not replicate the BD-ROM Mark are impossible to decode. A specially licensed piece of hardware is required to insert the ROM-mark into the media during replication. Through licensing of the special hardware element, the BDA believes that it can eliminate the possibility of mass producing BD-ROMs without authorization.
Player profiles
The BD-ROM specification defines four Blu-ray Disc player profiles which includes an audio only player profile (BD-Audio) that does not require video decoding or BD-J. All three of the video based player profiles (BD-Video) are required to have a full implementation of BD-J, but with varying levels of hardware support.
| Feature | BD-Audio | BD-Video |
|---|
Grace Period | Bonus View | BD-Live | Profile 3.0 | Profile 1.0 | Profile 1.1 | Profile 2.0 | Built-in persistent memory | No | 64 KB | 64 KB | 64 KB | | No | Optional | 256 MB | 1 GB | Secondary video decoder (PiP) | No | Optional | Mandatory | Mandatory | | No | Optional | Mandatory | Mandatory | Virtual file system | No | Optional | Mandatory | Mandatory | Internet connection capability | No | No | No | Mandatory |
a This is used for storing audio/video and title updates. It can either be built in memory or removable media, such as a memory card or USB flash memory.
b A secondary audio decoder is typically used for interactive audio and commentary.
c Profile 3.0 is a separate audio only player profile. The first Blu-ray album to be released was Divertimenti by record label Linberg Lyd and it has been confirmed to work on the PS3.
d Is also known as Initial Standard profile.
e Is also known as Final Standard profile.
On November 1, 2007, the Grace Period Profile was superseded by Bonus View as the minimum profile for new BD-Video players released to the market. When Blu-ray software authored with interactive features dependent on Bonus View or BD-Live hardware capabilities are played on Profile 1.0 players they will be able to play the main feature of the disc but some extra features may not be available or may offer limited capability.
The biggest difference between Bonus View and BD-Live is that BD-Live requires the Blu-ray Disc player to have a internet connection (usually via a standard Ethernet RJ-45 network port) to access internet based content. BD-Live features have included internet chats, scheduled chats with the director, internet games, downloadable featurettes, downloadable quizzes, and downloadable movie trailers. Note that while some Bonus View players may have an Ethernet port, these are used for firmware updates and are not used for internet based content. In addition, to handle this content, Profile 2.0 also requires more local storage.
With the exception of the LG-BH100, the LG-BH200, the PlayStation 3, and the Samsung BD-UP5000, Profile 1.0 players can not be upgraded to be Bonus View or BD-Live compliant.
Backward compatibility
Though not compulsory, the Blu-ray Disc Association recommends that Blu-ray Disc drives should be capable of reading standard DVDs and CDs for backward compatibility. A few early Blu-ray Disc players released in 2006 could play DVDs but not CDs (the LG BH100, Pioneer BDP-HD1, and Sony BDP-S1)
Ongoing development
Although the Blu-ray Disc specification has been finalized, engineers continue working to advance the technology. Quad-layer (100 GB) discs have been demonstrated on a drive with modified optics (TDK version) and standard unaltered optics ("Hitachi used a standard drive.").
Hitachi stated that such a disc could be used to store 7 hours of 32 Mbit/s video (HDTV) or 3.5 hours of 64 Mbit/s video (Cinema 4K). In August 2006, TDK announced that they have created a working experimental Blu-ray Disc capable of holding 200 GB of data on a single side, using six 33 GB data layers.
Also behind closed doors at CES 2007, Ritek revealed that they had successfully developed a High Definition optical disc process that extends the disc capacity to 10 layers. That increases the capacity of the discs to 250 GB. However, they noted that the major obstacle is that current reader and writer technology does not support the additional layers.
JVC has developed a three-layer technology that allows putting both standard-definition DVD data and HD data on a BD/DVD combo. If successfully commercialized, this would enable the consumer to purchase a disc which could be played on current DVD players, and reveal its HD version when played on a new BD player. The first 'hybrid' Blu-Ray/DVD combo is announced to be released February 18. The Japanese optical disc manufacturer Infinity has announced this. 'Code Blue' will feature four hybrid discs, which feature a single Blu-ray layer (25GB) and two DVD layers (9 GB) on the same side of the disc.
In January 2007, Hitachi showcased a 100 GB Blu-ray Disc, which consists of four layers containing 25 GB each. Unlike TDK and Panasonic's 100 GB discs, they claim this disc is readable on standard Blu-ray Disc drives that are currently in circulation, and it is believed that a firmware update is the only requirement to make it readable to current players and drives.
In December 2008, Pioneer Corporation unveiled a 400 GB Blu-ray disc, which contains 16 data layers, 25 GB each, and will be compatible with current players after a firmware update. A planned launch is in the 2009-2010 time frame for ROM and 2010-2013 for rewritable discs. Ongoing development is under way to create a 1 TB Blu-ray disc as soon as 2013..
At CES 2009 Panasonic unveiled the DMP-B15, the first portable Blu-ray Disc player and Sharp showed off the LC-BD60U and LC-BD80U series, the first LCD HDTVs with integrated Blu-ray players.
, a joint licensing agreement for Blu-ray Disc has not yet been finalized. A joint licensing agreement would make it easier for companies to get a license for Blu-ray Disc without having to go to each individual company that owns a Blu-ray Disc patent. For this reason a joint licensing agreement was eventually made for DVD by the DVD6C Licensing Agency..
Variants
Mini Blu-ray Disc
The Mini Blu-ray Disc (also, Mini-BD and Mini Blu-ray) is a compact 8 cm (~3in) diameter variant of the Blu-ray Disc that can store approximately 7.5 GB of data. It is similar in concept to the MiniDVD. Recordable (BD-R) and rewritable (BD-RE) versions of Mini Blu-ray Disc have been developed specifically for compact camcorders and other compact recording devices.
BD9/BD5 Blu-ray Disc
BD9 and BD5 are lower capacity variants of the Blu-ray Disc that contain Blu-ray compatible video and audio streams contained on a conventional DVD (650 nm wavelength / red laser) optical disc. Such discs offer the use of the same advanced compression technologies available to Blu-ray discs (including H.264/MPEG-4 AVC, VC-1 and MPEG-2) while using lower cost legacy media. BD9 uses a standard 8152MB DVD9 dual-layer disc while BD5 uses a standard 4482MB DVD5 single-layer disc.
BD9/BD5 discs can be authored using home computers for private showing using standard DVD±R recorders. AACS digital rights management is optional. The BD9/BD5 format was originally proposed by Warner Home Video, as a cost-effective alternative to regular Blu-ray Discs. It was adopted as part of the BD-ROM basic format, file system, and AV specifications. BD9/BD5 is similar to 3× DVD for HD DVD.
AVCREC
AVCREC is an official lower capacity variant of the Blu-ray Disc used for storing Blu-ray Disc compatible content on conventional DVD discs. It is being promoted for use in camcorders, distribution of short HD broadcast content and other cost-sensitive distribution needs. It is similar to HD REC for HD DVD.
Note that AVCREC is not the same as AVCHD content stored on DVD. The latter is a media independent format and is used presently in tapeless camcorders that record onto DVD and Blu-ray Discs, as well as onto SecureDigital and MemoryStick memory cards. Playing back AVCHD content on a Blu-ray player may require modification of AVCHD directory structure, but does not require re-encoding of video files themselves.
Blu-ray Disc recordable
Blu-ray Disc recordable refers to two optical disc formats that can be recorded with an optical disc recorder. BD-R discs can be written to once, whereas BD-RE can be erased and re-recorded multiple times. The theoretical maximum speed for Blu-ray Discs is about 12×. Higher speeds of rotation (10,000+ rpm) cause too much wobble for the discs to be read properly, as with the 20× and 52× respective maximum speeds of DVDs and CDs.
Since September 2007, BD-RE was also available in the smaller 8 cm Mini Blu-ray Disc diameter size.
On September 18, 2007, Pioneer and Mitsubishi co-developed BD-R LTH ("Low to High" in groove recording), which features an organic dye recording layer that can be manufactured by modifying existing CD-R and DVD-R production equipment, significantly reducing manufacturing costs.
In February 2008, Taiyo Yuden, Mitsubishi and Maxell released the first BD-R LTH Discs, and in March 2008, Sony's PlayStation 3 gained official support for BD-R LTH Discs with the 2.20 firmware update.
Unlike the previous releases of 120 mm optical discs (i.e. CDs and DVDs), Blu-ray recorders hit the market almost simultaneously with Blu-ray's debut (at least in Japan).
See also
External links
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