Importance

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Abstract

A decoder in a multiservice communication system receives a plurality of services as data streams, including video, audio, teletext, and utility data, multiplexed in sequence of frames. Each service defines a virtual channel. Virtual channel packets contained in the multiplex include information for locating the data streams that compose the virtual channels and information for decrypting the data streams. Each virtual channel packet is transmitted in the multiplex each session of frames. When a user selects more than one virtual channel at a given time, the decoder extracts a virtual channel packet for a first selected virtual channel in a first session. The decoder can then provide the decrypted data streams for the first selected virtual channel to peripheral equipment. The decoder stores the information for locating and decrypting such data streams. In each succeeding session, the decoder extracts another selected virtual channel packet and provides the decrypted data streams for that selected virtual channel and for all previously authorized selected virtual channels. When a virtual channel packet for each selected virtual channel has been processed, the decoder repeats the cycle thereby providing the data streams for each selected virtual channel.

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First Claim