Patent ID: 7620180

Claim:
A method of pre-processing content in a video on demand (VOD) system, wherein the content is identified by a first set of packet identifiers (PIDs), the method comprising: carrying out the following process at a VOD service provider site: receiving content, the content having marked packets designating packets that are to be encrypted by a first encryption system, the packets that are to be encrypted being marked by a set encryption flag for all packets designated to be encrypted; selecting packets in the content according to a selective encryption selection criterion to produce selected packets; at a packet duplicator, duplicating the selected packets to produce duplicate copies of the original packets; identifying the duplicate copies using a second set of PIDs; inserting the duplicate copies of the original packets identified by the second set of PIDs into the content; clearing all encryption flags in the content except for the selected packets having the first set of PIDs, thereby producing content having identifiable duplicate selected packets suitable for selective encryption; encrypting the content having the identifiable duplicate selected packets using the first encryption system; storing the encrypted content having the identifiable duplicate selected packets and the duplicate copies at a VOD server for a period of time during which the VOD server awaits receipt of a request for the content from a subscriber device; and receiving the request for the stored content from a subscriber device that uses a second encryption system, and in response to the request at the VOD server: retrieving the content from storage; stripping out the encrypted content having the identifiable duplicate selected packets; and encrypting the duplicate copies using the second encryption system.