1154 Chapter 30
encryption scheme is used such that each player has a
unique set of decryption keys. Content providers can
revoke the decryption keys in individual players. If a
given key is compromised, that key can be revoked in
future content, rendering it useless for decrypting future
content. In addition, BD+ is a virtual machine resident
in authorized players. It allows inclusion of executable
security programs on BD. For example, programs can
verify that AACS keys have not been altered, that hard-
ware has not been tampered with, and can fix insecure
systems. The BD-ROM Mark is cryptographic data that
is physically stored in a manner that is different from
other BD data; disc copies that do not contain the mark
are not playable.
BDs can contain geographic region coding; content
coded in a certain region will only play on that region’s
players. Region coding is optional; discs coded without
a region code are playable in any player. There are three
worldwide regions. Region A: North America, Central
America, South America, Japan, Taiwan, North Korea,
South Korea, Hong Kong, Southeast Asia; Region B:
Europe, Greenland, French territories, Middle East,
Africa, Australia, New Zealand. Region C: India,
Bangladesh, Nepal, Mainland China, Pakistan, Russia,
Central, South Asia. BDs use the Java software platform
(a version called BD-J) for interactive content on discs.
BD-J is a part of the Globally Executable MHP (GEM)
standard; GEM is a version of the Multimedia Home
Platform (DVB-MHP) standard.
A number of experimental BD architectures have
been developed. They include a four-layer disc holding
100 GB, a six-layer disc holding 200 GB, and a
ten-layer disc holding 250 GB. Alternative formats have
been developed. The BD9 (Mini Blu-ray) format uses a
red laser DVD to hold BD data. The disc is rotated at 3×
speed to provide a minimum bit rate of 30.24 Mbps.
Playing times are thus shorter than a conventional BD
disc. The AVCREC format also uses red-laser DVD
discs to hold BD content; H.264/MPEG-4 AVC
compression is used. An experimental three-layer
hybrid disc can hold both DVD-Video and BD data.
Recordable (BD-R) and rewritable (BD-RE) Blu-ray
disc formats are available, using phase-change tech-
nology. Dual-layer recordable discs are contemplated.
Disc formats such as Blu-ray will further extend the
opportunities of optical disc storage for professional and
consumer applications.References
- K. C. Pohlmann, The CD Handbook, Second Edition, Madison, WI: A-R Editions Inc., 1992.
- K. C. Pohlmann, Principles of Digital Audio, Fifth Edition, New York, NY: McGraw-Hill, 2005.
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