| 摘要 |
A method of partially scrambling a data stream ( 6 ) including transport stream packets ( 7 ), each transport stream packet ( 7 ) having a header ( 8 ) and a payload ( 9 ), wherein a sequence of transport stream packets ( 7 ) has payloads carrying encoded data elements, arranged in units ( 15 ), includes: selecting transport stream packets ( 7 ) forming a subsequence of the sequence, and scrambling at least part of the payloads ( 9 ) of each transport stream packet ( 7 ) in the subsequence. The method further includes monitoring the payloads ( 9 ) of at least some of the transport stream packets ( 7 ) in the sequence for the presence of data ( 22 ) indicating a boundary between two subsequent units ( 15 ), and, for selected units ( 15 ), including at least one of the transport stream packets ( 7 ) carrying data forming part of the selected unit ( 15 ) in the sub-sequence.
|
