Information about Blu Ray

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:	1x@36 Mbit/s & 2x@72 Mbit/s
Developed by:	Blu-ray Disc Association
Usage:	Data storage, High-definition video and PlayStation 3 Games

Optical disc authoring
Optical disc Optical disc image Recorder hardware Authoring software Recording technologies Recording modes Packet writing
Optical media types
Laserdisc Compact disc/CD-ROM: CD-R, CD-RW MiniDisc DVD: DVD-R, DVD-D, DVD-R DL, DVD+R,  DVD+R DL, DVD-RW, DVD+RW,  DVD-RW DL, DVD+RW DL, DVD-RAM Blu-ray Disc: BD-R, BD-RE HD DVD: HD DVD-R: HD DVD-RAM UDO UMD Holographic data storage 3D optical data storage History of optical storage media
Standards
Rainbow Books File systems ISO 9660 Joliet Rock Ridge Amiga Rock Ridge extensions El Torito Apple ISO9660 Extensions Universal Disk Format Mount Rainier

A Blu-ray Disc (also called BD) is a high-density optical disc format for the storage of digital information, including high-definition video.

Overview

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 single layer Blu-ray Disc can store 25 gigabytes (GB), over five times the size of a single layer DVD at 4.7 GB. A dual layer Blu-ray Disc can store 50 GB, almost 6 times the size of a dual layer DVD at 8.5 GB.

Blu-ray was developed by the Blu-ray Disc Association, a group of leading consumer electronics companies. The standard is covered by several patents belonging to different companies. As of March 2007, a joint licensing agreement for all the relevant patents has not yet been finalized.^[7]

As of 2 October 2007, 336^[8] titles have been released on Blu-ray Disc in the United States (32 of these titles have since been discontinued). Since January 2007, new releases on dual layer disc have represented about half of all new releases approximately 75 titles and 2.5 million discs.^[9]. As of 9 October 2007, 179 titles have been released in Japan, with 55 titles planned for release.^[10]

The Blu-ray standard is currently in a format war with its rival HD DVD, to determine which (if either) of the two formats will become the leading carrier for high-definition content to consumers.

History

In the mid 1990s, commercial HDTV sets were finally starting to enter a larger market. However, there was no good, cheap way to record or play back HD content. There was no cheap storage medium that could store that amount of data.^[11] 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.^[12]

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).^[13] The core technologies of the formats are essentially similar.

The first DVR Blue prototypes were unveiled at the CEATEC exhibition in October 2000 ^[14]. 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,^[15] and the Blu-ray Disc Association was founded by the nine initial members.

The first consumer devices were in stores on April 10 the next year. It was the Sony BDZ-S77 a BD-RE recorder that was only made available in Japan. The recommended price was US$3800.^[16] However, there was no standard for pre-recorded video (BD-ROM); no movies were released for that player. That standard was still years away, since a new and secure DRM system was needed before Hollywood studios would accept it. Nobody wanted to repeat the failure of the Content Scramble System for DVDs.

The DVD Forum (which was chaired by Toshiba) was deeply split over whether to go with the more expensive blue lasers 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.^[17][18] 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.^[19] In August, Toshiba and NEC announced their competing standard Advanced Optical Disc.^[20] It was finally adopted by the DVD forum and renamed to HD DVD the next year,^[21] after being voted down twice. Three new members had to be invited and the voting rules changed before the vote finally passed.^[22][23]

In the mean time, Sony spun off Professional Disc for DATA from the Blu-ray project. It was essentially Blu-ray with higher-quality media and components. The devices were too expensive for the consumer mass market. Instead, it was aimed at the professional data storage space market as a replacement for their line of 5.25" MO drives. It was announced in October 2003, with the first devices shipping in December of the same year.^[24][25]

The costs of a format war are large, both for consumers and for the industry. In an attempt to avoid that, Sony and Toshiba started to negotiate a compromise in early 2005. One of the issues was that the Blu-ray camp wanted to use a Java-based platform for interactivity (BD-J), while the DVD Forum was promoting Microsoft's MSTV (which became HDi).^[26] An agreement seemed close, but negotiations proceeded slowly.^[27]

At the end of June 2005, Sun announced that the Blue-ray Association had chosen a Java-based interactivity platform developed by HP, instead of Microsoft's HDi. At the same time, Microsoft and Toshiba jointly announced that they would cooperate in developing high-definition DVD players.^[28] In a top-level meeting in July, Microsoft's Bill Gates argued that the Blu-ray standard had to change to "work more smoothly with personal computers". Sony's representatives defended the technology.^[29]

On August 22, 2005, Sony and Toshiba announced that the negotiations to unify their standards had failed.^[30] An unnamed partner had pressured Toshiba to stick with HD DVD,^[31] in spite of Blu-ray's strong support among Hollywood studios and some analysts saying that HD DVD's days were numbered.^[29] In the end of September, Microsoft and Intel jointly announced their support for HD DVD.^[32]

HP made a last attempt to broker a peace between Sony and Microsoft. The company demanded that the Blu-ray association adopted Microsoft's HDi instead of its own Java solution, and that Blu-ray would adopt a mandatory managed copy feature. If the demands weren't met, HP threatened to support HD DVD instead.^[33] In a research report, Gartner analysts Van Baker, Laura Behrens and Mike McGuire wrote that if HP's proposal was accepted, Blu-ray would become the winner of the format war.^[34] However, the Blu-ray disc group did not accept HP's offer.^[35]

The Blu-ray physical specifications were finished in 2004.^[36] In January 2005, TDK announced that they had developed a hard coating polymer for Blu-ray discs.^[37] The cartridges, no longer necessary, were scrapped. The BD-ROM specifications were finalized in early 2006.^[38] AACS LA, a consortium founded in 2004,^[39] had been developing the necessary DRM platform that could securely distribute movies to consumers. However, the final AACS standard was delayed,^[40] and then delayed again when an important member of the Blu-ray group voiced concerns.^[41] At the request of Toshiba, an interim standard was published which did not include some features, like managed copy.^[42]

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.^[43][44]

The first Blu-ray Disc titles were released on June 20 2006. The earliest releases used MPEG-2 video compression. This is the compression method used on DVDs. The first releases using the newer VC-1 and AVC codecs were introduced in September 2006.^[45] The first movies using dual layer discs (50 GB) were introduced in November 2006.

The first mass-market Blu-ray 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.

HD DVD had a head start, and the Blu-ray market was slow at first. The first Blu-ray player was perceived as expensive and buggy, and there were few titles available.^[46] That changed when PlayStation 3 launched, since every PS3 unit also functioned as a Blu-ray player. In February, 2007, Blu-ray discs had outsold HD DVDs.^[47]. During the first three quarters of 2007, BD discs outsold HD DVDs by about two to one.^[48]

Disc structure

Laser and optics

Like its rival format HD DVD, Blu-ray use a "blue" (technically blue-violet) laser operating at a wavelength of 405 nm to read and write data. Conventional DVDs and CDs use red and 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, using a higher numerical aperture (0.85, compared with 0.6 for DVD), higher quality, dual-lens system, and making the cover layer thinner to avoid unwanted optical effects, the laser beam can be focused much more tightly at the disk surface. This produces a smaller spot on the disc and allows more information to be physically contained in the same area. In addition to the optical improvements, Blu-ray Discs feature improvements in data encoding, allowing for even more data to be packed in. (See Compact disc for information on optical discs' physical structure.)

Hard-coating technology

Since the Blu-ray data layer is closer to the surface of the disk, 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 caddies unnecessary.

TDK was the first company to develop a working scratch protection coating for Blu-ray discs. It was named Durabis. Both Sony and Panasonic replication methods include proprietary hard-coat technologies. Sony's rewritable media are sprayed with a scratch-resistant and antistatic coating. Verbatim recordable and rewritable Blu-ray Disc discs use their own proprietary hard-coat technology called ScratchGuard.

Software standards

Codecs

Codecs are compression schemes that reduce data storage requirements; both lossy and lossless compression techniques have been developed and are being used. Depending on the application, either can be used to greatly increase the amount of audio or video storable on fixed bit-capacity media.

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 ISO MPEG-2, H.264/AVC, and SMPTE VC-1. MPEG-2 video allows decoder backward compatibility for DVDs. H.264, sometimes called MPEG-4 part 10, is a more recent video codec. VC-1 is a competing MPEG-4 derivative codec proposed by Microsoft (based on Microsoft's previous work in Windows Media 9). BD-ROM titles with video must store video using one of the three mandatory codecs (multiple codecs on a single title are allowed).

The initial version of Sony's Blu-ray Disc-authoring software shipped with support for only 1 video-codec: MPEG-2. Consequently, all launch titles were encoded in MPEG-2 video. A subsequent update allowed the content producers to author titles in any of the 3 supported codecs: MPEG-2, VC-1, or H.264. 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.

For audio, BD-ROM players are required to support Dolby Digital AC-3, DTS, and Linear PCM (up to 7.1 channels). Dolby Digital Plus, and lossless formats Dolby TrueHD and DTS HD are player optional. BD-ROM titles must use one of mandatory schemes for the primary soundtrack (linear PCM, Dolby Digital, or DTS). A secondary audiotrack, if present, may use any of the mandatory or optional codecs ^[49]. If Dolby Digital Plus is used, it must be accompanied by an AC-3 soundtrack (which provides the "core" bitstream). For uncompressed PCM and lossless audio in Dolby TrueHD or DTS-HD Master Audio formats, Blu-ray Discs support encoding in up to 24-bit/192 kHz for a maximum of six channels, or up to eight channels with at most 24-bit/96 kHz sampling.^[50]

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 36.55 Mbit/s in HD DVD movies for audio and video data.^[51]

Java software support

Main article: BD-J

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 will be 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 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 will be called BD-J and will be a subset of the Globally Executable MHP (GEM) standard. GEM is the world-wide version of the Multimedia Home Platform standard.

Region codes

Blu-ray discs may be encoded with a region code indended to restrict the area of the world in which they can be played, similar to the DVD region codes. Blu-ray players sold in a certain region should only be able to 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 can also be produced without region coding, so they can be played on all devices.

Region code	Area[53]
A	North America, Central America, South America, Japan, Taiwan, North Korea, South Korea, Hong Kong and Southeast Asia.
B	Europe, Greenland, French territories, Middle East, Africa, Australia and New Zealand.
C	India, Bangladesh, Nepal, Mainland China, Pakistan, Russia, Central and South Asia.

This arrangement puts the countries of the major Blu-ray manufacturers (Japan, Korea, Malaysia) in the same region as the U.S., thus ensuring early releases of U.S. content to those markets, whereas they weren't before. Reportedly early BD releases (including Casino Royale) are "ALL" region and therefore compatible in various BD players around the globe.

Digital rights management (DRM)

The Blu-ray Disc format employs several layers of Digital rights management.^[54][55]

Advanced Access Content System 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 Brothers, 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).

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:^[54]

• 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 only available to licensed device manufacturers. A list of licensed adopters is available from the BD+ website[1].

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.

Mandatory Managed Copy allows users to copy content a limited number of times, but requiring registration with the content provider to acquire the keys needed; this feature was originally requested by HP.^[56]

When the first AACS keys were leaked, some Blu-ray titles became available on file-sharing networks. There was also a commercial PC software player (AnyDVD HD) that allowed users to watch Blu-ray Disc movies on non-HDCP compliant PC hardware or copy them. However, early titles did not use BD+, while most new Blu-ray titles do. As of October 2007, BD+ had not been circumvented.^[57]

Player profiles

The BD-ROM specification defines four profiles of Blu-ray Disc players. All video-based profiles are required to have a full implementation of BD-J.

Feature[58]	BD-Video (Grace Period Profile - Profile 1.0)	BD-Video (Final Standard Profile - Profile 1.1)	BD-Live (Profile 2)
Minimum built-in persistent memory	64 KB	64 KB	64 KB
Minimum local storage capability [1]	-	256 MB	1 GB
Secondary video decoder (PiP)	Optional	Mandatory	Mandatory
Secondary audio decoder [2]	Optional	Mandatory	Mandatory
Virtual file system	Optional	Mandatory	Mandatory
Internet connection capability	No	No	Mandatory

^ a A secondary audio decoder is typically used for interactive audio and commentary

^ b 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 a USB flash memory.

After October 31 2007, the Grace Period Profile will be superseded by Final Standard Profile as the minimum profile for new players.^[59] Some profile 1.0 players may be upgradeable via firmware update to profile 1.1 if they have the appropriate hardware. Notably, Sony has said that Playstation 3 will receive such an update.^[60] When software authored with interactive features dependent on Profile 1.1 hardware capabilities are played on profile 1.0 players some features may not be available or may offer limited capability. Profile 1.0 players will still be able to play the main feature of the disc, however.

In the Blu-ray specifications, there's also a third profile, which is meant for an audio-only player and does not require video decoding or BD-J.

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. For instance, Samsung's first Blu-ray Disc drive can read CDs, regular DVDs, and Blu-ray Discs. All other Blu-ray Disc players released support DVD playback as well, however not all support CD playback. This includes Sony, Panasonic, Philips, LG, Pioneer and PC-based players from Alienware, Sony, and Dell.

List of Blu-ray devices

Device name	Manufacturer	Type of device	Release date	Approximate price
PlayStation 3	Sony	Video game console	November 11, 2006	US$399-599
DMP-BD10	Panasonic	Stand-alone player	2006
BDP-S1	Sony	Stand-alone player	December 4, 2006	US$1000
BD-P1200	Samsung	Stand-alone player	January 8, 2007	US$799
BDP-S300	Sony	Stand-alone player		US$499
BD-P1400	Samsung	Stand-alone player		US$499
DMR-E700BD	Panasonic	Recordable stand-alone player		US$2,780[61]
DMR-BW200	Panasonic	Recordable stand-alone player
DMR-BR100[62]	Panasonic	Recordable stand-alone player
VidaBox MAX and VidaBox LUX	VidaBox	media center PC (supports both Blu-ray and HD DVD)
BH-100[63]	LG Electronics	Stand-alone player (supports both Blu-ray and HD DVD)	January 7, 2007
BD-UP5000[64]	Samsung	Stand-alone player (supports both Blu-ray and HD DVD)
VAIO AR Series	Sony	Laptop computer	2006
VAIO FZ Series	Sony	Laptop computer	2007
XPS M1710	Dell	Laptop computer	December 2006	US$3,599
XPS M1730	Dell	Laptop computer
XPS M2010	Dell	Laptop computer
Pavilion Desktop	Hewlett-Packard	Desktop computer (can be customized to include a Blu-ray drive)	9 May 2007
TravelMate 8215WLMi[65]	Acer	Laptop computer	2006
ASUS Lamborghini VX2[66]	ASUSTek	Laptop computer
ASUS Lamborghini W2W[67]	ASUSTek	Laptop computer
BDC-2202	Pioneer	PC drive	May 2, 2007	US$299[68]
BC-1205PT[69]	ASUS	PC drive	9 September 2007
BWU-100A	ASUS	Recordable PC drive	July 18 2006	US$699 [70]

Sony has said that it will release the first portable BD player in 2008. Hitachi is developing Blu-ray camcorders, to be released in Japan during fall 2007 ^[71]

Corporate support

Main article: List of corporations supporting Blu-ray

Blu-ray Disc has gained a large amount of support in the corporate world,^[72] with companies such as Apple Inc., Dell, and Panasonic backing it. Blu-ray Disc was started by Hitachi, LG, Panasonic, Pioneer, Philips, Samsung, Sharp, Sony, and Thomson in February 19, 2002, with Sony as the back-bone of the foundation.^[73] Blu-ray Disc Founders was established in May, 2002. This became the Blu-ray Disc Association on May 18, 2004.

It had been reported by various sources (PC World, Ars Technica, CNN, et al) that pornography had been disallowed on Blu-ray Disc, which may have had an effect on the success of the format.^[74] However, this is inaccurate, as both formats have said they fully support all material, including porn, and have no control over what companies release with their license.^[75]

Currently, Blu-ray Disc is exclusively supported in the United States by Sony Pictures Entertainment and MGM (20% of MGM's stake is owned by Sony) as well as Disney, 20th Century Fox, and Lionsgate. Outside of the United States, movies from these studios are often distributed by different companies, such as StudioCanal in Europe. Thus many of these Blu-ray exclusive titles are available outside the U.S. on HD DVD.^[76] Likewise, movies that are exclusive to HD DVD in the United States have Blu-ray releases in other regions. An example of this is the Universal Studios film Bruce Almighty, which has been released exclusively on HD DVD in the U.S., but has been released as a Blu-ray exclusive in Europe due to the distribution rights held by Buena Vista. Many Blu-ray discs are multi-region, making import of these titles easier.^[77]

It is non-exclusively supported by Warner Bros., and New Line Cinema. Warner Bros. has several HD DVD exclusive titles at the moment that are scheduled for release on Blu-ray in the near future. It should be noted that some of New Line Cinema's titles, the first being Hairspray, were originally announced as limited time Blu-ray exclusives due to lack of region coding with HD DVD.^[78][79] All future catalog titles will be released simultaneously in both formats.

Several members of the Blu-ray organization's Board of Directors who had originally pledged to support Blu-ray Disc, such as Hewlett-Packard, Samsung, and LG, later also supported HD DVD.

Blu-ray is currently exclusively backed by several adult-movie studios/publishers,^[80] including Taisei Co. Ltd. and Total Media Agency Inc. Contrary to many internet blogs, it has been reported by ABC News that the porn industry will not be a factor in the current format war.^[81] The main reason is that many pornographic websites have movie downloads as an option, thus making the disc format less important.

Beginning July 2007, Blockbuster Video, one of the largest chain of DVD and video game rental stores in the world, will be carrying only Blu-ray Discs in 1,450 more stores,^[82] in addition to the original 250 that carried both HD DVD and Blu-ray Disc. Online they will still be offering both formats.^[83] Blockbuster will continue to offer both formats at its initial 250 stores that currently carry both high-definition formats.^[84]

On July 25 2007, Target Corporation announced they will carry Sony Blu-ray Disc stand alone players in their stores and promote them with end cap displays including exclusive Blu-ray Disc movies from Sony and Walt Disney. While Target will not carry HD DVD stand alone players on its shelves, the chain will continue to sell both Blu-ray Disc and HD DVD movies in all stores and HD DVD players online.^[85]

In a past interview with GameSpot, when quizzed on the new LG HD DVD/Blu-ray Disc combo players, Sir Howard Stringer, CEO of Sony, had this to say:

However, on August 20 2007, Paramount Pictures, DreamWorks Pictures and DreamWorks Animation, announced they would no longer be supporting the Blu-ray Disc format. Citing HD DVD's lower consumer equipment and disc replication costs (due to its simarlarities to the standard DVD format), all future Paramount/Dreamworks titles will be released exclusively on HD DVD. Together, Paramount and DreamWorks are currently the 2007 box office leaders and their first two HD DVD exclusive titles Shrek 3 and Transformers are both poised to be top sellers during the 2007 holiday season.^[86][87] Movies directed by Steven Spielberg are not included in this announcement as Spielberg controls his films.^[88] In an interview with PC World Alan Bell the Executive Vice President and Chief Technology Officer for Paramount Pictures stated the support for HD DVD exclusively is currently indefinite.^[89] However, two Viacom executives who spoke to the New York Times disclosed that the terms of the agreement were for $150 million in incentives in exchange for the exclusivity lasting at least 18 months, or through the next two holiday seasons.^[90]

Blu-ray Disc / HD DVD comparison

Main article: Comparison of high definition optical disc formats

The primary rival to Blu-ray Disc is HD DVD. At the moment, Blu-ray Disc has the advantage in maximum disc capacity with 50 GB over HD DVD's 30 GB. However, in September 2007 the DVD Forum approved the triple-layer, single-sided 51 GB HD DVD-ROM. It is unknown at this time whether the final specification will be compatible with current players ^[91]

The first 50 GB dual-layer Blu-ray Disc release was for Click, on October 10 2006, several months after the Blu-ray Disc format was released.^[92] As of September 2007 40% of Blu-ray titles use the 50 GB disc and 60% use the 25 GB disc^[93] while almost all HD DVD movies are in the 30 GB dual layer format.^[94]

In terms of audio/video compression, Blu-ray Disc and HD DVD are similar on the surface: both support MPEG-2, VC-1, and H.264 for video compression, and Dolby Digital, PCM, and DTS for audio compression. The first generation of Blu-ray Disc movies released used MPEG-2 (the standard currently used in DVDs, although encoded at a much higher video resolution and a much higher bit rate than those used on conventional DVDs), while initial HD DVDs releases used the VC-1 codec. Due to greater total disc capacity, the Blu-ray Disc producers may choose in the future to utilize a higher maximum video bit rate, as well as potentially higher average bit rates. As of September 2007, 50% of Blu-ray Discs are encoded in MPEG-2 while AVC is used on 27.48% discs and VC-1 at 22.52%.^[93]

In terms of audio, there are some differences. To ensure backwards compatibility with older receivers with Dolby Digital decoders, Blu-ray Disc allows conventional Dolby Digital audiotracks at 640 kbit/s and this is the primary audio track for 33% of Blu-ray titles, while it has gone unused for HD DVD titles. The newer Dolby Digital Plus is mandatory for HD DVD players at 3 Mbit/s (which is used for 90% of HD DVD titles), while optional for BD players with support at a bitrate of 1.736 Mbit/s for mixes that require more than 5.1 channels (has only been used on two titles).^[95] Both formats optionally support DTS-HD High Resolution Audio, a lossy compression scheme that extends the core DTS audio for better fidelity but yet is still not lossless.

As for lossless audio, 41.23% Blu-ray Discs have 5.1 LPCM uncompressed audio,^[93] which is is the only lossless format that is mandatory for Blu-ray players. Blu-ray Disc also has optional support for Dolby TrueHD lossless encoding of up to 8 channels of audio, and DTS-HD Master Audio, a lossless encoding of up to 8 channels of audio.^[96] As of September 2007, 4.62% of Blu-ray Discs are encoded in Dolby TrueHD while DTS-HD Master Audio is used on 10.77% on discs.^[93] In total, 55.38% of Blu-ray Discs have either uncompressed or lossless audio. HD DVD also supports LPCM, but unlike Blu-ray, it has mandatory support for Dolby TrueHD, although only 17.43% of HD DVD movies have lossless audio.

Both HD DVD and Blu-ray Disc support the 24p (traditional movie) frame rate, but technical implementations of this mode are different between the formats. Blu-ray Disc supports 24p with its native timing, while HD DVD uses 60i timing for 24p (encoded progressively, replacing missing fields with "repeat field flags"). Decoders can ignore the “flags” to output 24p.^[97] There is no impact on picture resolution and minimal impact on storage space as a result of this, as the HD DVD format often uses the same encoded video—it simply adds notational overhead.

A Table Comparing the High-definition Optical Media Formats
DVD included for comparison

Mandatory codecs must be supported by the player. Each disc must use one or more of the mandatory codecs.

•  • [ e]			Blu-ray Disc	HD DVD	DVD
Laser wavelength			405 nm (blue-violet laser)		650 nm (red laser)
Numerical aperture			0.85	0.65	0.6
Storage capacity	single layer		25 GB	15 GB	4.7 GB
	dual layer		50 GB	30 GB	8.5 GB
Playback time in (video only)[3]	SD with MPEG-2 at 5 Mbit/s		22.2 hours	13.3 hours	3.8 hours
	HD with	AVC or VC-1 at 13 Mbit/s	8.5 hours	5.1 hours	N/A
		MPEG-2 at 20 Mbit/s	5.6 hours	3.3 hours	N/A
Mandatory Video codecs			MPEG-4 AVC (H.264) / VC-1 / MPEG-2		MPEG-1 / MPEG-2
Audio codecs	lossy	Dolby Digital	Mandatory @ 640 Kbit/s	Mandatory @ 504 Kbit/s	Mandatory @ 448 Kbit/s
		DTS	Mandatory @ 1.5 Mbit/s	Mandatory @ 1.5 Mbit/s	Optional @ 1.5 Mbit/s
		Dolby Digital Plus[4]	Optional @ 1.7 Mbit/s	Mandatory @ 3.0 Mbit/s	N/A
		DTS-HD High Resolution	Optional @ 6.0 Mbit/s	Optional @ 3.0 Mbit/s	N/A
	lossless	Linear PCM	Mandatory	Mandatory	Mandatory
		Dolby TrueHD	Optional	Mandatory[5]	N/A
		DTS-HD Master Audio	Optional @ 24.0 Mbit/s	Optional @ 18.0 Mbit/s	N/A
Maximum bitrate	Raw data transfer		53.95 Mbit/s	36.55 Mbit/s	11.08 Mbit/s
	Audio+Video		48.0 Mbit/s	30.24 Mbit/s	10.08 Mbit/s
	Video		40.0 Mbit/s	29.4 Mbit/s	9.8 Mbit/s
Secondary video decoder (PiP)			Optional (Profile 1.1)[6]	Mandatory	N/A
Secondary audio decoder			Optional (Profile 1.1)	Mandatory	N/A
Interactivity			Blu-ray Disc Java	HDi Interactive Format	N/A
Internet support			Optional (Profile 2.0)	Mandatory	N/A
Video resolution (maximum)			19201080 24p or 50/60i HDTV	19201080 24/25/30p or 50/60i HDTV	720480 60i and 720576 50i SDTV
Content protection system			AACS-128bit / BD+	AACS-128bit	CSS 40-bit
Region code			3 Regions	Region free	6 Regions
Hardcoating of disc			Mandatory	Optional	Optional

^ a Playback times are quoted for dual layer discs, for single layer discs divide by two. The numbers represent video only and the choice of audio codec and extra content also affects playback time.
^ b All HD DVD players are required to be able to decode Dolby TrueHD to two channels, however all current players support 5.1 channel decoding.^{[98] [99]}
^ c Secondary video decoder will become mandatory for new Blu-ray Disc players with Profile 1.1 on October 31 2007.
^ d On Blu-ray, Dolby Digital Plus (DD+) must be accompanied by a primary Dolby Digital (DD) 5.1 audiotrack. 640 Kbit/s is allocated to the primary DD 5.1 audiotrack (which is independently playable on players that do not support DD+), and 1 Mbit/s is allocated for the 'extension' DD+ bitstream. Furthermore, the DD+ audiotrack itself may only carry additional channel-information, and hence, Blu-ray DD+ may only be used for 6.1/7.1 audiotracks. On HD DVD, Dolby Digital Plus may be used in any legal channel configuration (up to 7.1), at any supported bitrate up to the maximum of 3 Mbit/s

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."). ^[100][101] Hitachi stated that such a disc could be used to store 7 hours of 32 Megabit/s video (HDTV) or 3.5 hours of 64 Megabit/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.^[102]

Also behind closed doors at CES 2007, Ritek has revealed that they had successfully developed a High Definition optical disc process that extends the disc capacity of both competing formats to 10 layers. That increases the capacity of the discs to 250 GB for Blu-ray compared to 150 GB for HD DVD using the same process. However, they noted that the major obstacle is that current reader and writer technology does not support the additional layers.^[103]

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.^[104] This hybrid disc does not appear to be ready for production and no titles have been announced that would utilize this disc structure.

Hitachi has recently showcased 100GB Blu-ray Disc, which consists of four layers containing 25GB each. Unlike TDK and Panasonic's 100GB disc, this disc is readable on standard Blu-ray 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.^[105] TDK has also produced a 200GB six-layer prototype. ^[106]

Variants

BD9 / Mini-Blu-ray Disc

BD9 is a red laser DVD with BD contents on it. This disc should be rotated at 3x speed or more to satisfy the minimum transfer rate of 30.24 Mbit/s. These disks can be used for private storing and can be authored even without implementing AACS.^[107] BD9 was originally proposed by Warner Home Video, as a cost-effective alternative to regular Blu-ray discs.^[108] It is similar to HD DVD's 3x DVD

AVCREC

AVCREC is a standard for storing BD content on red laser DVDs using H.264/MPEG-4 AVC compression.^[109] It is similar to HD REC for HD DVD.

Blu-ray Disc recordable

Main article: 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 March 2007, BD-R/RE drives up to 4x retail are sold for about $600 and 2x single-layer BD-R discs, with a capacity of 25 GB, can be found for around $12. The theoretical maximum 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.

See also

• HD DVD
• List of Blu-ray Movies
• Blu-ray Disc Association
• Format war
• Professional Disc for DATA (PDD or ProDATA)
• Comparison of high definition optical disc formats
• MUSE LD – an earlier optical disc which contained analog HDTV signals
• D-VHS - a tape-based format that allows recording of 720 or 1080 high-def DTV, while remaining compatible with older VHS libraries
• Blu-ray Disc recordable

Alternative disc technologies

• HD DVD
• AVCHD
• Digital Multilayer Disk – the successor technology to Fluorescent Multilayer Disc
• Enhanced Versatile Disc (EVD)
• Forward Versatile Disc (FVD) – Taiwanese backed red laser format
• Fluorescent Multilayer Disc
• Holographic Versatile Disc – standards with 200 and 300 GB storage are under development and prototypes expected in 2008
• 3D optical data storage - a next-generation technology expected to provide TB-capacity discs
• PH-DVD
• Protein-coated disc
• Tapestry Media
• Ultra Density Optical
• Versatile Multilayer Disc
• LS-R - a "layer selection" technology allowing the stacking of very large numbers of DVD-like data layers in a single disc.

References

External links

• Blu-ray Disc Association
• Blu-ray Disc License Web Site
• AACS LA
• Panasonic Blu-ray Portal Site
• PlayStation.com: Blu-ray Disc Technology
• Dolby Laboratories
• DTS
• HDMI Licensing
• The Authoritative Blu-ray Disc FAQ by Hugh Bennett
• The High Definition DVD FAQ – FAQ for Blu-ray, HD DVD, EVD, FVD...
• Studios Currently Supporting Blu-ray

News

• Home Media Magazine.com
• Video Business Online
• High-Def Digest
• AllthingsHiDef News
• Hollywood In Hi-Def
• DVDTOWN.com
• Ultimate AV
• Blu-ray.com
• EMediaLive
• CD Freaks.com
• The Digital Bits
• JVC Develops World's First Blu-ray/DVD Combo ROM Disc Technology – JVC Press Releases 2004-12-24.
• Next-generation DVD battle begins – BBC News Online 2006-04-19.
• TDK Prototypes 200 GB Recordable Blu-ray Disc with Six Layers – Nikkei Business Publications 2006-04-27.
• Hitachi Demonstrates 4 Layer BD Playback Using 'Standard Drive' – Nikkei Business Publications 2007-01-11.
• Establishment of Industry-leading Monthly Capacity of 1.7 million Blue-violet Diodes(lower costs) – SONY Press Releases 2007-04-07.
• Mixed Messages From HD DVD Camp – Ultimate AV News Desk 2007-06-14.
• Starz to go Blu – Home Media Magazine Top Story 2007-06-19.
• Volume Unique Keys for released Blu-ray titles

•  • [ e] Industrial & home video media
Magnetic tape	Analog VERA (1952) • 2 inch Quadruplex videotape (1956) • 1 inch type A videotape (1965) • 1/4 inch Akai (1967) • U-matic (1969) • Cartrivision (1972) • Video Cassette Recording (aka VCR) (1972) • V-Cord (1974) • VX (aka "The Great Time Machine") (1974) • Betamax (1975) • IVC 2 inch Helical scan (1975) - 1 inch type B videotape (1976) • 1 inch type C videotape (1976) • VHS (1976) • VK (1977) • SVR (1979) • Video 2000 (1980) • CVC (1980) • VHS-C (1982) • M (1982) • Betacam (1982) • Video8 (1985) • MII (1986) • S-VHS (1987) • Hi8 (1989) • S-VHS-C (1987) • W-VHS (1994) Digital D1 (1986) • D2 (1988) • D3 (1991) • D5 (1994) • Digital-S (D9) (199?) • Digital Betacam (1993) • DV (1995) • DVCPRO (1995) • DVCAM (1996) • HDCAM (1997) • DVCPRO50 (1998) • D-VHS (1998) • Digital8 (1999) • DVCPRO HD (2000) • D6 HDTV VTR (2000) • MicroMV (2001) • HDV (2003)• HDCAM SR (2003)
Optical disc	Analog Laserdisc (1978) • Laserfilm (1984) Digital CD Video • VCD (1993) • MovieCD (1995?) • DVD-Video (1995) • MiniDVD • CVD (1998) • SVCD (1998) • FMD (2000) • EVD (2003) • FVD (2005) • UMD (2005) • VMD (2006) • HD DVD (2006) • Blu-ray Disc (BD) (2006) • DMD (2006?) • AVCHD (2006) • Tapestry Media (2007) • Total Hi Def (2008) • HVD (TBA) • PH-DVD (TBA) • SVOD (TBA) • Protein-coated disc (TBA)
Grooved Videodiscs	Analog Baird Television Record aka Phonovision (1927) • TeD (1974) • Capacitance Electronic Disc aka CED (1981) • VHD (1983)