DVB-CI
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Digital Video Broadcasting – Common Interface (or DVB-CI), is a normative for DTV Receiver in order to enable the addition of a conditional access module, CAM, in a Receiver DVB-CI « standard » to adapt it to different kinds of cryptography. Indeed, one of DVB's main strengths is the option of implementing the required conditional access capability on the common interface.
This allows broadcasters to use modules containing solutions from different suppliers in the same broadcast system, thus increasing their choice and anti-piracy options.
Technical
A DVB receiver may have one or two slots implementing the common interface. They use the PCMCIA connector and are conform to the Common Scrambling Algorithm (CSA), the normative which specify that such a receiver must be able to accept DES (Data Encryption Standard) keys in some miliseconds intervals and to use them to decode private channels according to one algorithm.
Those algorithms are providers issues. Each one uses his own algorithms and there are no normative for that.
The receiver can send the full MPEG-2 transport data stream as it comes out of the demodulator and error correction units through the card plugged into the Common Interface, before it will be processed by the MPEG demultiplexer in the DTV Receiver. If several CI cards are present, the MPEG transport data stream will be passed sequentially through all these cards.
An embedded CAM may not physically exist as it may be in CPU software. In such as case only the ISO card reader normally in the CAM is fitted and not the PCMCIA type CI slots.
Even if the Common Interface has been created to resolve cryptography issues, it can have other functions using other types of modules such as Web Browser, iDTV (Interactive Television)...
In Europe, DVB-CI is obligatory in all iDTV terminals.
Standard
The normative DVB-CI has been defined in 1997 by the CENELEC, European Committee for Electrotechnical Standardization EN 50221.
According to the Common Interface scheme:
- host : A device where module(s) can be connected, for example : an IRD (Integrated receiver/decoder), a VCR, a PC ...
- module : A small device, not working by itself, designed to run specialised tasks in association with a host, for example : a conditional access sub system, an electronic program guide application module, or to provide resources required by an application but not provided directly by the host
The specification only defines two aspects, two logical interfaces to be included on the same physical interface,. The first interface is the MPEG-2 Transport Stream.The link and physical layers are defined in this specification and the higher layers are defined in the MPEG-2 specifications. The second interface, the command interface, carries commands between the host (receiver) and the module.
The specification does not define the operation or functionality of a conditional access system application on the module. The applications which may be performed by a module communicating across the interface are not limited to conditional access or to those described in this specification. More than one module may be supported concurrently.
See also
References
- DVB-CI normative.
- ETSI TS 101 699 - DVB Extensions to the Common Interface Specification
- R206-001:1998 - Guidelines for Implementation and Use of the Common Interface for DVB Decoder Applications
- Gerard O'Driscoll, The essential Guide to Digital Set-Boxes and Interactive TV, reprinted April 2000
- Jerry whitaker, Television Receivers, 2001