US Patent 7895616 Reconstitution of program streams split across multiple packet identifiers

A method and apparatus for reconstituting packetized data streams representing a television program when the program uses multiple packet identifiers (PID) as in selective encryption schemes. Transmission of multiple sets of system information (SI) is avoided by incorporating a lookup table within a private data packet. A dual buffer arrangement in the set-top box provides ease of reconstitution of a data stream by generation of an interrupt upon receipt of a packet with a shadow PID. The buffers are toggled as a result of the interrupt and a corresponding packet can be found either at the beginning of the newly active buffer or the end of the inactive buffer. The stream of packets representing a program can then be reconstituted by creation of a new packet having the primary PID and shadow packet's payload.