Patent ID: 7978852

Claim:
A method comprising: partially scrambling a data stream including transport stream packets, each transport stream packet having a header and a payload, wherein the payload comprises at least a part of a program elementary stream, wherein a sequence of transport stream packets has payloads carrying one or more packet elementary streams comprising a PES packet payload, wherein the PES packet payload carries encoded data elements, arranged in units, the method including: receiving the data stream at a port; selecting transport stream packets forming a sub-sequence of the sequence, and scrambling the payloads of each transport stream packet in the sub-sequence, the method further including: monitoring the payloads of the transport stream packets in the sequence for the presence of data indicating a boundary between two subsequent units; determining a type of one of the two subsequent units following the data indicating the boundary; and if the type corresponds to a predefined type, including at least one of the transport stream packets carrying data forming part of the one of the two subsequent units in the sub-sequence.