Program-specific information (PSI) is metadata about a program (channel) and part of an MPEG transport stream.
The PSI data as defined by ISO/IEC 13818-1 (MPEG-2 Part 1: Systems) includes four tables: The MPEG-2 specification does not specify the format of the CAT and NIT.
The PSI data will never be scrambled so that the decoder at the receiving end can easily identify the properties of the stream.
At the decoder side the PSI section filter listens to the incoming TS packets.
This table is used for conditional access management of the cypher keys used for decryption of restricted streams.
This table contains privately defined descriptors of the system used and the associated EMM PID.
This optional table may group transport stream identifiers into a network, providing access parameters and other details.
The European Broadcasting Union DVB specification ETSI EN 300 468 (DVB-SI)[4] does.
The purpose of mentioning but not defining this table in H.222 is that it has reserved program number 0 (zero) in the PAT.
The Table ID extension is used to identify the local network together with a directory listing of transport streams.