| 摘要 |
The invention provides a headend system, a receiver, a smartcard and a conditional access system enabling distribution of multiple variants of a part of a digital signal, such as multiple variants of an audio part or a video part of a data stream, without requiring receivers to be updated. The digital signal generated by the headend system enables a receiver to receive and process the digital signal without requiring identification of the copies in the second digital signal. Error handling capabilities of the receiver ensure that only one copy is used in the output of the receiver. The error handling capabilities are triggered by having the receiver use one decryption key for descrambling all copies, resulting in one copy being descrambled correctly and the other copies being descrambled incorrectly. |
