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The Blu-ray disc (official abbreviation BD) is positioned as the big competitor to HD DVD as the successor to DVD.
Its technology is based on a blue laser beam) whereas CDs use a technology based on a red beam and DVD an orange beam), hence the name ‘blue ray’, contracted to ‘Blu-ray’ and registered as a brand name. Compared to red or orange laser, it allows more information to be stored in the same area thanks to a finer beam using narrower recording grooves, closer together, and shorter PITs.
A single-layer Blu-ray disk contains approximately 25 GB (23.3 GB) or two hours of HDTV audio and video coded in MPEG2 format and a double-layer disk can contain approximately 50 GB (46.6 GB). The transfer rate is 36 Mbits per second (or 4.5 MB per second), but prototype players with a transfer rate of 72 Mbits per second (or 9 MB) are under development.
Plans for discs with a capacity of 100 to 200 GB are currently in development, using four and eight layers respectively. TDK has developed a six-layer prototype with 200 GB (33 GB per layer).
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