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Blu-ray Disc (BD) is a next-generation optical disc format meant for storage of high-definition video and data. The Blu-ray standard was jointly developed by a group of leading consumer electronics and PC companies called the Blu-ray Disc Association (BDA), led by Sony and Philips. As compared to the HD DVD format, its main competitor, Blu-ray has more information capacity per layer, 25 instead of 15 gigabytes, but may initially be more expensive to support.

Blu-ray gets its name from the shorter wavelength (405 nm) of a "blue" (technically blue-violet) laser that allows it to store substantially more data than a DVD, which has the same physical dimensions but uses a longer wavelength (650 nm) red laser.

Variations and sizes

File:Bluraydiscs.jpg
Blu-ray discs with and without cartridge

A single-layer Blu-ray disc (BD) can fit 23.3, 25, or 27 GB; this is enough for approximately four hours of high-definition video with audio. A dual-layer BD can fit 46.6, 50, or 54 GB, enough for approximately eight hours of HD video. Capacities of 100 GB and 200 GB, using four and eight layers respectively, are currently being researched; TDK has already announced a prototype four-layer 100 GB disc .

The BD-RE (rewritable) standard is available, along with the BD-R (recordable) and BD-ROM formats, which became available in mid-2004, as part of version 2.0 of the Blu-ray specifications. BD-ROM pre-recorded media are to be available by early 2006.

To ensure that the Blu-ray Disc format is easily extendable (future-proof) it also includes support for multi-layer discs, which should allow the storage capacity to be increased to 100GB-200GB (25GB per layer) in the future simply by adding more layers to the discs.

Technology

Laser and optics

Blu-ray systems 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

Because the Blu-ray standard places data so close to the surface of the disc, early discs were susceptible to dust and scratches and had to be enclosed in plastic caddies for protection. Such an aggravation, the consortium worried, would hobble Blu-ray's adoption in the face of the rival HD DVD standard; HD DVDs can be handled bare (caddyless) like CDs and DVDs, making them familiar to consumers as well as attractive to manufacturers and distributors who might be deterred by additional costs.

The solution to this problem arrived in January 2004 with the introduction of a clear polymer that gives Blu-ray discs unprecedented scratch resistance. The coating, developed by TDK Corporation under the name "Durabis," allows BDs to be cleaned safely with only a tissue--a procedure that can damage CDs, DVDs, and (presumably) HD DVDs, which are manufactured by the same process as these older optical media. Bare BDs with the coating are reportedly able to withstand attack by a screwdriver.

Codecs

The BD-ROM format specifies at least three video codecs: MPEG-2, the standard used for DVDs; MPEG-4's H.264/AVC codec; and VC-1, a codec based on Microsoft's Windows Media 9. The first of these only allows for about two hours of high-definition content on a single-layer BD-ROM, but the addition of the two more advanced codecs allows up to four hours per layer.

For audio, BD-ROM supports linear (uncompressed) PCM, Dolby Digital, Dolby Digital Plus, DTS, DTS-HD, and Dolby Lossless (a lossless compression format also known as MLP).

In order to remain backwards compatible, BD-RE (and by extension BD-R) will by and large support the MPEG2 codec. For users recording digital television broadcasts, the BluRay's baseline datarate of 36Mbit will be more than adequate to record high definition broadcasts. Support for new codecs will evolve as new codecs are encapsulated by broadcasters into their MPEG2 transport streams and consumer set tops are rolled out which can support the decode of all the supported formats.

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 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 and is considerably more primitive. 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 GEM (Globally Executable MHP) standard. GEM is the world-wide version of the Multimedia Home Platform standard.

Compatibility

While it is not compulsory for manufacturers, the Blu-ray Disc Association recommends that Blu-ray drives should be capable of reading DVDs, ensuring backward compatibility.

JVC has developed a three layer technology that allows putting both standard definition DVD data and HD data on a BD/DVD combo disc. 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.

Security

Blu-ray has an experimental security feature titled BD+ that allows for dynamically changing encryption schemes. Should the encryption be cracked, manufacturers can update the encryption scheme and put it on all new discs, preventing a single crack from opening up the entire specification for the duration of its lifetime. The lack of a dynamic encryption model is what made DeCSS so disastrous in the industry's eyes: once CSS was cracked, all DVDs from then on were crackable. See Advanced Access Content System (AACS).

The Blu-ray Disc Association also agreed to add digital watermarking technology to the discs. Under the name "ROM-Mark," this technology will be built into all ROM-producing devices, and prevent content from being counterfeited in the event that a watermark is detected. Through licensing, the BDA believes that it can eliminate the possibility of mass producing BD-ROMs without authorization.

Next to that, Blu-ray players are only allowed to output the original compressed video signal digitally (on its original resolution) when it is encrypted. This means that a HDMI interface can be used as it uses HDCP encryption.

Applications

Stand-alone recorders and games consoles

Pioneer BRD-101A
Pioneer BRD-101A

The first Blu-ray recorder was unveiled by Sony on March 3, 2003, and was introduced to the Japanese market in April that year. On September 1, 2003, JVC and Samsung Electronics announced Blu-ray based products at IFA in Berlin, Germany. Both indicated that their products would be on the market in 2005.

In March 2004, both Sony and Matsushita announced plans to ship 50 GB Blu-ray recorders the same year. The Matsushita product is to ship in July 2004 in the Japanese market under the Panasonic brand. Sony is to follow by the end of 2004 and has announced that the PlayStation 3 will be shipped with a Blu-ray drive, but possibly only a read-only one . Meanwhile, LG Electronics is expected to ship a recorder equipped with a 200GB hard disk into the U.S. market by Q3 2004. These products are to support single-sided, dual-layer rewriteable discs of 54GB capacity. Sony's machine will also support BD-ROM pre-recorded media, which are expected to be available in early 2006.

PC data storage

Blu-ray drives currently in production can transfer approximately 36 Mbit/s (54 Mbit/s for BD-ROM), but 2× speed prototypes with a 72 Mbit/s transfer rate are in development. Rates of 8x or more are planned for the future.

Hewlett Packard has announced plans to begin selling Blu-ray-equipped desktop PCs in late 2005, with laptops to follow in early 2006. Philips is scheduled to debut a Blu-ray computer drive in the second half of 2005. On 10 March, 2005 Apple Computer joined the Blu-ray Disc Association.

In July 2005, Pioneer introduces the OEM Blu-Drive BDR 101-A into japanese market.

PC information updates: Blu-ray.com forums "PC Data Storage"

Corporate support

HD-DVD initially received more support than Blu-ray from film studios and distributors. One commonly cited reason is that it is less expensive to convert a production line from DVDs to HD DVDs than to convert to Blu-ray. This early lead has vanished, however.

The BDA has over 140 members. Its Board of Directors consists of Apple Computer Corp.; Dell, Inc.; Hewlett Packard Company; Hitachi, Ltd.; LG Electronics Inc.; Mitsubishi Electric Corporation; Panasonic (Matsushita Electric); Pioneer Corporation; Royal Philips Electronics; Samsung Electronics Co., Ltd.; Sharp Corporation; Sony Corporation; TDK Corporation; Thomson; Twentieth Century Fox; and Walt Disney Pictures and Television.

Alternatives

The primary rival to Blu-ray is HD DVD, championed by Toshiba and NEC Corporation. It has a lower data density and thus more limited disc capacity, but could in principle benefit from lower manufacturing costs for both the drive units and the pre-recorded/recordable media.

On 29 November, 2004 four Hollywood studios (New Line Cinema, Paramount Pictures, Universal Studios and Warner Bros.) announced non-exclusive agreements to support HD DVD.

Blu-ray is a very similar format to PDD, another optical disc format developed by Sony (and has been available since 2004) but offering higher data transfer speeds. PDD is not intended for home video use and is aimed towards data archival and backup use in business. The UDO format is also aimed for similar purposes.

Other competitors:

Trivia

  • The letter "e" was intentionally left out of the name to allow trademarking, as the term "blue ray" is a commonly used phrase and can't be registered as a trademark.

See also

External links

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