Introduction
Blu-ray Disc (BD) is a next-generation optical disc format meant for storage of high-definition video and high-density data. The Blu-ray standard was jointly developed by a group of consumer electronics and PC companies called the Blu-ray Disc Association (BDA). 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 produce.
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.
Blu-ray unveiled their plans for a Spring 2006 launch at the Consumer Electronics Show (CES) in January 2006. It will be released on May 23rd, 2006.
Variations and sizes
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.
Also, in addition to 12 cm discs, an 8 cm variation for use with camcorders is planned that will have a capacity of 15 GB.
Technology - Laser and Optics
Blu-ray systems use 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.
Technology - 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 inconvenience, 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 of caddies.
The solution to this problem arrived in January 2004 with the introduction of a clear polymer coating 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 current CDs and DVDs. Presumably HD DVDs are similarly frail, as they are manufactured by the same process as the older optical media. Bare BDs with the coating are reportedly able to withstand attack by a screwdriver. TDK have used the same coating on their current range of "Scratchproof" DVD media.
Technology - Codecs
The codecs used to encode video and audio largely determine the amount of space needed to store the content on the disc. Some or all of the initial movies released in blu-ray format will use MPEG-2.
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 Blu-ray'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 top boxes capable of decoding them are rolled out.
Technology - 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 Globally Executable MHP (GEM) standard. GEM is the world-wide version of the Multimedia Home Platform standard.
Technology - Compatability
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
Technology - Digital Rights Management
Blu-ray has an experimental security feature titled BD+ that allows for dynamically changing encryption schemes. Should the encryption be compromised, 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. It also uses the Mandatory Managed Copy system allowing users to securely rip a file into a secure format, a feature originally requested by HP. 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 reproduced 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.
In addition, Blu-ray players are only allowed to output the full resolution video signal through encrypted interfaces. This means that early HDTVs sold without an HDCP-enabled interface (excluding HDMI or HDCP-enabled DVI) will not be able to display high definition video from a Blu-ray disc. Analog output must be resampled to 960x540 for the same reason.
Applications - Standalone Recorders and Games Consoles
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.
Sony has announced that the PlayStation 3 will be shipped with a Blu-Ray drive, but possibly just a read-only one. Sony's machine will also support BD-ROM pre-recorded media, which are expected to be available in early 2006.
Microsoft, who did not include Blu-Ray technology in its Xbox 360 console, had previously stated that it is possible that they could add a Blu-Ray drive to the unit. However, further comments from Microsoft state that they have no plans to do so, and were merely just trying to illustrate the flexibility of the Xbox 360. In February 2006 (3 months after the console's release), Microsoft announced the development of an external HD-DVD drive for use with the Xbox 360, opposing Sony's new Blu-Ray format though they have since said that if Blu-Ray wins the format war Microsoft may then release a Blu-Ray drive add-on.
PC Data Storage
Blu-ray drives currently in production can transfer approximately 36 Mbit/s (54 Mbit/s for BD-ROM), but 2x speed prototypes with a 108 Mbit/s transfer rate are in development. Rates of 8x or more are planned for the future.
North American Pioneer BDR-101AHewlett Packard has announced plans to sell Blu-ray-equipped desktop PCs and laptops. In December 2005, HP announced that they would also be supporting the rival HD DVD technology. Philips was scheduled to debut a Blu-ray computer drive in the second half of 2005, but it was also delayed. On March 10, 2005 Apple Computer joined the Blu-ray Disc Association.
In July 2005, information was leaked about an upcoming Pioneer Blu-ray drive; the OEM BDR 101-A. On December 27, 2005, Pioneer formally announced the drive with an expected release at the end of January 2006. The drive will write at 2x on BD-R and BD-RE, 8x on DVD+R and DVD-R, and 4x on DVD-RW and DVD+RW. The drive will not support reading CD or reading/writing CD-R or CD-RW media.
Optical heads allowing the reading of CD/DVD/Blu-ray discs have already been developed and are expected to be included after first release of DVD/Blu-ray only drives.
The Panasonic Blu-ray SW-5582 is the first drive to support all 3 formats.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Blu-ray" |
