Scrambling and descrambling method for the transport of MPEG2 audio video data streams

摘要

A scrambling and descrambling method that includes reading of original PID and TSC bits in the PID and TSC fields of a packet header of an MPEG2 stream which is at least partially scrambled. A temporary PID may be written in a PID field in place of the original PID, and may be a function of the original PID value and TSC bits according to a correspondence table of an original PID and TSC bits with the temporary PIDs. The value zero may be written in the TSC field in place of the original value, and scrambling of the stream with modified fields may occur. Applications include the satellite transmission of partially scrambled MPEG2 digital signals.

主权项

1. Scrambling method for an over-scrambling of a MPEG2 stream at least partially scrambled, the stream being structured in packets, a packet header comprising a packet identifier (PID) field defining the service to which the packet is affected, a transport scrambling control (TSC) field, the TSC field having bits being relative to the scrambling of the packet, a continuity counter field, comprising the following steps:
reading of an original PID and TSC bits in the PID and TSC fields of a packet header of said stream, writing of a temporary PID in a PID field in place of the original PID, as a function of the original PID value and TSC bits according to a correspondence table of an original PID and TSC bits with the temporary PIDs, and overscrambling of the stream with modified fields.