Blue-Ray Disc

Blue-ray Disc

Blu-ray Disc
Reverse side of a Blu-ray Disc
Media type High-density optical disc
Encoding MPEG-2, MPEG-4 AVC (H.264), and VC-1
Capacity 25 GB (single layer)
50 GB (dual layer)
Read mechanism 405 nm laser, 1x@36 Mbit/s & 2x@72 Mbit/s & 4x@144 Mbit/s & 6x@216 Mbit/s[1] & 12x@432 Mbit/s
Developed by Blu-ray Disc Association
Usage Data storage,
High-definition video
and PlayStation 3 games

Blu-ray Disc (also known as Blu-ray or BD) is an optical disc storage media format. Its main uses are high-definition video and data storage. The disc has the same dimensions as a standard DVD or CD.

The name Blu-ray Disc is derived from the blue-violet laser used to read and write this type of disc. Because of its shorter wavelength (405 nm), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red (650 nm) laser. A dual layer Blu-ray Disc can store 50 GB, almost six times the capacity of a dual layer DVD.

Blu-ray Disc was developed by the Blu-ray Disc Association, a group of companies representing consumer electronics, computer hardware, and motion picture production. The standard is covered by several patents belonging to different companies. As of March 2007, a joint licensing agreement for all the relevant patents had not yet been finalized.[2]

As of April 5, 2008, more than 530[3] Blu-ray Disc titles have been released in the United States, and more than 250 in Japan.

During the high definition optical disc format war, Blu-ray Disc competed with the HD DVD format. On February 19, 2008, Toshiba — the main company supporting HD DVD — announced it would no longer develop, manufacture and market HD DVD players and recorders,[4] leading almost all other HD DVD supporters to follow suit, effectively naming Blu-ray the victor of the format war.


Optical disc authoring
Optical media types

Further reading
A blank rewritable Blu-ray Disc (BD-RE)
A blank rewritable Blu-ray Disc (BD-RE)

In 1998, commercial HDTV sets began to appear in the consumer market; however, 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.[5] 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.[6]


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 Disc (more specifically, BD-RE).[7] The core technologies of the formats are essentially similar.

The first DVR Blue prototypes were unveiled at the CEATEC exhibition in October 2000.[8] 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,[9] 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;[10] 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, since a new and secure DRM system was needed before Hollywood studios would accept it, not wanting to repeat the failure of the Content Scramble System for DVDs.

Blu-ray Disc format finalized

The Blu-ray Disc physical specifications were finished in 2004.[11] In January 2005, TDK announced that they had developed a hard coating polymer for Blu-ray Discs.[12] The cartridges, no longer necessary, were scrapped. The BD-ROM specifications were finalized in early 2006.[13] AACS LA, a consortium founded in 2004,[14] had been developing the DRM platform that could be used to securely distribute movies to consumers. However, the final AACS standard was delayed,[15] and then delayed again when an important member of the Blu-ray Disc group voiced concerns.[16] 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.[17]

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.[18][19]

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.[20] The first movies using dual layer discs (50 GB) were introduced in October 2006.[21]

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.[22][23] 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.[24] It was finally adopted by the DVD Forum and renamed HD DVD the next year,[25] after being voted down twice by Blu-ray Disc Association members, prompting the U.S. Department of Justice to make preliminary investigations into the situation.[26][27]

HD DVD had a head start in the high definition video market and Blu-ray Disc sales were slow at first. The first Blu-ray Disc player was perceived as expensive and buggy, and there were few titles available.[28] This changed when PlayStation 3 launched, since every PS3 unit also functioned as a Blu-ray Disc player. By January 2007, Blu-ray discs had outsold HD DVDs,[29] and during the first three quarters of 2007, BD outsold HD DVDs by about two to one.[30]

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.[31] They also credited Sony's more thorough and influential marketing campaign.[32] More recently several studios have cited Blu-ray Disc's adoption of the BD+ anti-copying system as the reason they supported Blu-ray Disc over HD DVD.[33]

End of the format war

In January 2008, a day before CES 2008, Warner Brothers, 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 US retailers such as Wal-Mart dropping HD DVD in their stores. A major European retailer, Woolworths, dropped HD DVD from its inventory. Netflix, the major online DVD rental site, said it would no longer stock new HD DVDs. Following these new developments, on 19 February 2008, Toshiba announced it would be ending production of HD DVD devices,[34] 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."[35] Paramount Studios, which started releasing movies only in HD DVD format during late 2007, also said it would start releasing in Blu-ray Disc. With this, all major Hollywood studios now support Blu-ray.[36]

Former HD DVD supporter Microsoft has stated that they are not currently pursuing a Blu-ray Disc drive for the Xbox 360, and will instead focus on their digital downloads from the Xbox Live Marketplace.[37]

Disc structure

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 0.58µm.[38] 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. Advances in polymer technology eventually made the cartridges unnecessary.[39]

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 sprayed 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
1X 36 4.5 90 180
2X 72 9 45 90
4X 144 18 23 45
6X 216 27 15 30
8X* 288 36 12 23
12X* 432 54 8 15


Software standards

Codecs (coding-decoding)

Codecs are compression schemes that store audio and video more efficiently, either giving longer play time or higher quality per megabyte. There are both lossy and lossless compression techniques.

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/AVC, and SMPTE VC-1. MPEG-2 is the codec used on regular DVDs, which allows backwards compatibility. H.264/AVC was developed by MPEG and VCEG as a modern successor of MPEG-4. VC-1 is another MPEG-4 derivative codec mostly 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 H.264) typically achieve a video runtime twice that of MPEG-2, with comparable quality.

MPEG-2 was used by many studios including Paramount Pictures (which surprisingly used the efficient 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 H.264/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 GB 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 AC-3, DTS, and linear PCM. Players may optionally support Dolby Digital Plus, and lossless formats Dolby TrueHD and DTS HD. 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.[40]

For users recording digital television programming, the recordable Blu-ray Disc standard's datarate of 54 Mbit/s is more than adequate to record high-definition broadcasts from any source (IPTV, cable/satellite, or terrestrial). For Blu-ray Disc movies the maximum transfer rate is 48 Mbit/s (1.5x) (both audio and video payloads together), of which a maximum of 40 Mbit/s can be dedicated to video data. This compares favorably to the maximum of 30.24 Mbit/s in HD DVD movies for audio and video data.[41]

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 less 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 world-wide version of the Multimedia Home Platform standard.

Region codes

Regions for Blu-ray standard      Region A      Region B      Region C

Regions for Blu-ray standard[42] Region A Region B Region C

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. The purpose of this system is to allow motion picture studios to control the various aspects of a release (including content, date, and, in particular, price) according to the region. Discs may also be produced without region coding, so they can be played on all devices.

Region code Area
A Americas; East and Southeast Asia.
B Africa, Europe, Oceania; Middle East; French territories; Greenland.
C Central and South Asia; Mongolia, Russia, and People's Republic of China.

This places the countries of the major Blu-ray manufacturers (Japan, Korea, Malaysia) in the same region as North America. As of early 2008, about two-thirds of all released discs were region-free.[43]

In the Blu-ray region coding system the US is placed in region A while regions B and C are used for countries which can experience localization delays before US titles are officially released. The opposite though is sometimes true and a few new titles such as the Harry Potter and the Goblet of Fire and Running Scared were released in certain European countries before the US release.[44] 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 discs from Regions A and B and DVD discs from Regions 1 and 2.[45]

Digital rights management (DRM)

The Blu-ray Disc format employs several layers of digital rights management.[46][47]

AACS decryption process

AACS decryption process

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). However, even though some AACS cryptographic keys have been compromised, new releases will use new, uncompromised keys.[48]

BD+ was developed by Cryptography Research Inc. and is based on their concept of Self-Protecting Digital Content.[49] 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:[46]

  • 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 adopters is available from the BD+ website.

BD+ was made available for content publishers in June 2007.[50] The first titles using BD+ were released in October the same year. Players from Samsung and LG had problems playing back those titles until the manufacturers updated their firmware, but this problem was later identified as being related to BD-Java use, not BD+.[51] BD+ protection was fully circumvented with the release of AnyDVD HD program.

BD-ROM Mark is a small amount of cryptographical data that is stored physically differently 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 profiles of Blu-ray Disc players; in addition to the three listed in the table below, there is a fourth audio-only profile that does not require video decoding or BD-J.[52] All the video-based profiles are required to have a full implementation of BD-J, but with varying levels of hardware support.

Feature BD-Video Bonus View BD-Live BD-Audio
Grace Period – Profile 1.0 Final Standard – Profile 1.1 Profile 2.0 Profile 3.0 [c]
Built-in persistent memory 64 KB 64 KB 64 KB -
Local storage capability[a] 256 MB 1 GB -
Secondary video decoder (PiP) Optional Mandatory Mandatory -
Secondary audio decoder[b] Optional Mandatory Mandatory -
Virtual file system Optional Mandatory Mandatory -
Internet connection capability 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.
^ Profile 3.0 is a separate profile for audio discs, similar to the difference between DVD-Video and DVD-Audio. No BD-Audio releases have so far been announced.

On November 1, 2007, the Grace Period Profile was superseded by Bonus View as the minimum profile for new players released to the market.[53] 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.[54]

With the exceptions of the LG-BH100, PlayStation 3, and Samsung BD-UP5000 Profile 1.0 players can not be upgraded to be Bonus View or BD-Live compliant.[55][56][57] On December 17, 2007, the PlayStation 3 became Bonus View 1.1 compliant through PlayStation 3 System Software version 2.10.[58] On March 24, 2008 Sony released the 2.20 firmware update for the PlayStation 3 which is compliant with Blu-ray Disc Profile 2.0, making it the first in the market to have it.[59] The first BD Live titles (War and Saw IV) were released by Lionsgate in January 2008 though no players at that time existed to play the web-enhanced content.[60]

Backward compatibility

While it is not compulsory for manufacturers, the Blu-ray Disc Association recommends that Blu-ray Disc drives should be capable of reading standard DVDs for backward compatibility[61], but not all players can play back audio CDs (for example, the Sony BDP-S1). All other Blu-ray Disc players that have been released so far are also capable of CD and DVD playback[citation needed].

Ongoing development

Front of an experimental Blu-ray Disc

Front of an experimental Blu-ray Disc

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.").[62][63] 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). Furthermore TDK announced in August 2006 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.[64]

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.[65]

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.[66] This hybrid disc does not appear to be ready for production and no titles have been announced that would utilize this disc structure.

In January 2007, Hitachi showcased a 100 GB Blu-ray Disc, which consists of four layers containing 25 GB each.[67] 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.[68]


Mini Blu-ray Disc

See also: MiniDVD

The Mini Blu-ray Disc (also, Mini-BD and Mini Blu-ray) is a compact 8cm (~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 rewriteable (BD-RE) versions of Mini Blu-ray Disc have been developed specifically for compact camcorders and other compact recording devices.[69]

BD9 / BD5 Blu-ray Disc

See also: 3x DVD

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 MPEG-4-AVC/H.264, SMPTE-421M/VC-1 and MPEG-2) while utilizing lower cost legacy media. BD9 utilizes a standard 8152MB DVD9 dual-layer disc while BD5 utilizes a standard 4489MB DVD5 single-layer disc.[70]

Given that Blu-ray Discs are assumed to have a minimum transfer rate of 30.24 Mbit/s, BD9/BD5 discs must be spun at high speed, equivalent to a 3× DVD drive speed or greater.

BD9 and BD5 discs can be authored using home computers for private showing using standard DVD±R recorders. AACS digital rights management is optional.

The BD9 format was originally proposed by Warner Home Video, as a cost-effective alternative to regular Blu-ray Discs.[71] It was adopted as part of the BD-ROM basic format, file system and AV specifications. BD5 and BD9 are similar to 3x DVD.


See also: HD REC

AVCREC is an official[72] 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 that originated prior to the release of Blu-ray Disc.

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. As of January 2008, BD-R/RE drives up to 6x speed are available from retailers for about US$450,[73] and 4x single-layer BD-R discs, with a capacity of 25 GB, can be found for around US$12. The theoretical maximum speed for Blu-ray Discs is about 12x as the speed of rotation (10,000 rpm) causes too much wobble for the discs to be read properly, similar to the 20x and 52x 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.[69][74]

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.[75]

In February 2008, Taiyo Yuden, Mitsubishi and Maxell released the first BD-R LTH Discs,[76] and in March 2008, Sony's PlayStation 3 gained official support for BD-R LTH Discs with the 2.20 firmware update.[77]

HD DVD/Blu-ray Disc hybrid discs

Warner Brothers officially announced Total Hi Def at CES 2007. Total Hi Def hybrid discs support both HD DVD and Blu-ray Disc, HD DVD on one side (up to two layers) and Blu-ray Disc on the other side (up to two layers). However, in November 2007, Warner Brothers put development of the Total HD discs on hold for an indefinite amount of time.[78] The project was finally canceled in January 2008 when Warner declared that they were dropping HD DVD in favor of publishing exclusively on Blu-ray Disc — thus eliminating the need for a hybrid disc. Warner also cited a lack of interest from fellow studios to publish on hybrid discs, as all but one studio, Paramount Pictures, were exclusive to either Blu-ray Disc or HD DVD and when Paramount became HD DVD exclusive in August 2007 they left Warner as the only major studio publishing on both discs. In February 2008, Toshiba abandoned the HD DVD format, ending any need for a hybrid disc.