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 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, 22 instead of 17 Gbyte, but may initially be costlier to support.
Blu-ray gets its name from the shorter wavelength (405 nm) blue 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.
History and background
The Blu-ray format, originally called DVR, was developed by Sony and Philips engineers beginning in 1995. The format was envisioned as an optical replacement for the magnetic tape being used in DV camcorders at the time. Mass replication, therefore, played a minor role in Blu-ray's design considerations.
As it became increasingly clear that DV camcorders would rely on solid-state media for storage, Blu-ray's marketing strategy changed. The time between design and marketing was almost ten years. The main reason for the delay was the lack of interest among consumers, but the high cost of the blue laser (around US$1,000) also played a role. It was not until late 2002 that Japan's Nichia Corporation, which holds key patents on the laser's design, agreed to license its technology to Sony. [1] The first consumer Blu-ray drive, a tabletop model that records HD video signals, was introduced by Sony in 2003.
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 now available, to be followed by the BD-R (recordable) and BD-ROM formats in mid-2004, as part of version 2.0 of the Blu-ray specifications. BD-ROM pre-recorded media are to be available by late 2005.
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.
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.
Because Blu-ray was not originally designed for mass replication, BDs require special equipment for mastering and replication. The HD-DVD standard, on the other hand, was designed to replace DVD and can be mass replicated with few changes to existing DVD equipment.
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.
from
www.wikipedia.com
Wats a Blue ray DVD?
8)
Linear Mode
