CONDITIONAL ACCESS VIDEO SIGNAL DISTRIBUTION

摘要

A video signal distribution system contains a video stream source (10) that produces a data stream with an encrypted video signal, control word information for decrypting the video signal and fee information indicative of fees for viewing respective parts of the video signal. A plurality of video reproduction apparatuses (12) are coupled to a medium (14) to receive the data stream. Each of the video reproduction apparatuses (12) comprises a control word derivation unit (125) for supplying control words derived from the control word information to a video signal decryption device (121). A credit management unit with a credit memory (128) is provided, which enables or disables supply the control words, when the credit memory (128) indicates the availability of more than a threshold amount of credit, and reduces the amount of credit in the credit memory (128) according to the fee information for the part of the video signal for the decoding of which the control words are supplied.