A high-capacity optical disc for high-definition (HD) movies. Developed primarily by Sony, Blu-ray and DVD discs have the same diameter and look similar, but Blu-ray's blue-violet laser reads pits a third the size of a DVD on tracks packed much tighter together. Blu-ray players support DVDs and CDs, plus resolutions up to 1080p and advanced video (see H.264 and VC-1). In addition, they support high-definition audio, including Dolby Digital Plus, TrueHD and DTS-HD (see Dolby Digital and DTS).

Blu-ray was designed for interactive content via the Java programming language, and every Blu-ray player executes Java programs for menus and user interaction (see Java Virtual Machine).

BonusView and BD Live (Blu-ray 1.1 and 2.0)
Features are defined in "profiles," and all players support Profile 1.0. However, older players may not support the extras in newer profile discs.

Profile 1.1 (BonusView) uses a second audio and video codec to enable picture-in-picture. Players have 256MB of non-volatile memory.

Profile 2.0 (BD Live) accesses the Internet for additional content. Players have 1GB of non-volatile memory.

ROM, R and RE Formats
A Blu-ray disc (BD) comes in ROM (read-only memory), R (recordable) and RE (rewritable) formats. Used for commercial movies, BD-ROMs are pressed and cannot be changed. BD-Rs can be recorded only once by the user, and BD-RE discs can be rewritten over and over.

Blu-ray History
Blu-ray was announced in 2002 by Sony, Hitachi, Philips and other vendors, and the first recorders were sold in Japan a year later. In 2006, Sony's PlayStation 3 game console included a Blu-ray drive as one of its primary features.

From approximately 2005 up to 2008, Blu-ray competed with HD DVD, another high-def video format. However, having two similar technologies slowed adoption, and attempts to solve the problem by including both formats on a hybrid disc from Warner Home Video in 2006 or by creating the dual-format Super Blu player from LG in 2007 offered little help. In early 2008, HD DVD was discontinued, and Blu-ray became "the" HD format. See high-def DVD formats, DVD and DTV.

   FULL-SIZE BLU-RAY DISK (120 mm) CAPACITIES

            SINGLE SIDED       DOUBLE SIDED

                     HD                 HD
   Layers   Storage  Hours     Storage  Hours

   Single   25GB     4.5         50GB   9

   Dual     50GB     9