| 摘要 |
Encrypted data is sent from a decoder 120 to a conditional access module CAM 130 over a common interface CI 160, 170 for decryption. The decoder includes a data packet generator configured to form packets including a header and a payload for storing the encrypted data, and a transport stream TS interface module configured to send the data packets to the CAM over a TS interface of the CI. The decoder is able to convert encrypted data from a first file format, being a format other than MPEG-2 TS, to a second file format to be transmitted to the CAM. The packet generator may form an encapsulated IP packet with the TS interface module sending the packets using multiprotocol encapsulation. An initialisation message including information about a selected format may be sent to the CAM over a control interface of the CI, and the CAM may send data request messages over the control interface to request specific data.
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