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Fundamentals and Evolution of MPEG-2 Systems: Paving the MPEG Road by Jan Van der Meer

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10Conditional Access and Scrambling

Why conditional access is important for many MPEG-2 system applications. Scrambling in transport streams and the use of conditional access sections and descriptors. The role of simulcast in transport stream applications. Scrambling in program streams.

10.1 Support of Conditional Access Systems

For many MPEG-2 system applications, unauthorized access to the content carried in an MPEG-2 system stream is to be prevented. For example, content in a Pay TV service should only be available to subscribers to such a service, while an optical disc may contain free content, as well as content that may be accessed only if an additional payment is made. For this purpose, Conditional Access (CA) systems are used. A conditional access system specifies how to encrypt the content at the encoder side prior to its distribution, so as to make the content unreadable by anyone, unless access to the content is granted explicitly by means of providing the information needed to decrypt the content back into the original format. While the specification of CA systems is beyond the scope of MPEG, it should be possible to apply practical CA systems in MPEG-2 system based applications. Therefore the use of CA systems in a MPEG-2 system stream was an important design consideration.

As an example for the use of a CA system in an MPEG-2 system environment, Figure 10.1 depicts a typical conditional access system for an MPEG-2 transport stream, as often applied by Pay TV ...

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