Blu-Ray
The name Blu-ray Disc is derived from the blue-violet laser used to read and write this type of disc. Because of this shorter wavelength (405 nm), substantially more data can be stored on a Blu-ray Disc than on the common DVD format, which uses a red, 650 nm laser. Blu-ray Disc can store 25 GB on each layer, as opposed to a DVD's 4.7 GB. Several manufacturers have released single layer and dual layer (50 GB) recordable BDs and rewritable discs. All supporting studios have either already released or have announced release of movies on 50GB discs.
Blu-ray Disc is similar to PDD, another optical disc format developed by Sony but offering higher data transfer speeds. PDD was not intended for home video use and was aimed at business data archiving and backup. Blu-ray Disc is currently in a format war with rival format HD DVD.
Specs
About 9 hours of high-definition (HD) video can be stored on a 50 GB disc.
About 23 hours of standard-definition (SD) video can be stored on a 50 GB disc.
On average, a single-layer disc can hold a High Definition feature of 135 minutes using MPEG-2, with additional room for 2 hours of bonus material in standard definition quality. A dual layer disc will extend this number up to 3 hours in HD quality and 9 hours of SD bonus material.
HD-DVD
The HD DVD disc is designed to be the successor to the standard DVD format. It can store about three times as much data as its predecessor. The HD DVD standard was jointly developed by a group of consumer electronics and PC companies, spearheaded by Toshiba. On November 19, 2003, the DVD Forum voted to support HD DVD as the HDTV successor of the standard DVD. At this meeting, they also renamed it HD DVD. The format had previously been called the "Advanced Optical Disc".
At CES 2006, Microsoft announced that there would be an external add-on HD DVD drive for the Xbox 360 game console; this was released in November 2006. Also at CES 2006, companies backing HD DVD said that nearly 200 titles would be available for the format by the end of the year.
On March 31, 2006, Toshiba released their first HD DVD player in Japan at ¥110,000 ($934). HD DVD was released in U.S on April 18, 2006, with players priced at $499 and $799.
The current specification version for HD DVD-ROM and HD DVD-Rewritable is version 1.0. The specification for HD DVD-R is currently at 0.9. The first HD DVD-ROM drives were expected to be unveiled by Q4 2006, with mass production to start in Q1 2007. The actual product launch of both CE and PC units occurred in late 2006. As of December 2006, more than 120,000 HD DVD's had been sold in the United States.
As of February 2007, HD DVD is in a format war with Blu-ray Disc.