| 主权项 |
1. A head-end system for preparing digital content for transmission to a plurality of receivers, the digital content comprising a sequence of content portions, the system comprising:
a pre-processor arranged to generate at least first and second copies of each content portion; a content protection and content packaging system arranged to output each of the at least first and second copies of each content portion into a separate group of transport stream packets, each of the at least first and second copies of each content portion distributed into transport stream packets being differently encrypted to the other or others of the copies of that content portion, and to merge all of the said transport stream packets for each content portion into an original transport stream in which at least some of the transport stream packets deriving from the same content portion but differently encrypted are interleaved; and a post-processor arranged to reorder the original transport stream to form a re-multiplexed transport stream in which transport stream packets containing parts of the same content portion but being differently encrypted are not interleaved. |
