Program Specific Information

Program Specific Information

Program Specific Information (PSI) is metadata, part of MPEG transport stream.

The PSI data contains four tables: PAT (Program Association Table), CAT (Conditional Access Table), PMT (Program Map Table) and NIT (Network Information Table). This last table is normally not used with MPEG-2 PSI.

PSI is carried in the form of a table structure. The table structure can span multiple transport stream packets. Adaptation field also occurs in TS packets carrying PSI data. The PSI data will never be scrambled so that the decoder at the receiving end can easily identify the properties of the stream.

The PSI data contains five tables: * PAT (Program Association Table) * CAT (Conditional Access Table) * PMT (Program Map Table) * NIT (Network Information Table) * TDT (Time and Date Table)

Some tables are associated with predefined PID as explained in the respective sections.And each table has predefined structure.

PAT (Program Association Table)

The PAT is assigned PID 0x0000 and table id of 0x00. The transport stream contains at least one or more TS packets with PID 0x0000. Some of these consecutive packets form the PAT.At the decoder side the PSI [ section filter] listens to the incoming TS packets. After the filter identifies the PAT table they assemble the packet and decode it.A PAT has information about all the programs contained in the TS. The PAT contains information showing the association of Program Map Table PID and Program Number.

CAT (Conditional Access Table)

This table is used for conditional access to the streams. This table provides association with EMM stream. When the TS is scrambled then this section contains the EMM PID. This EMM pid is encrypted using the smart card number.

PMT (Program Map Table)

This table contains PID numbers of elementary streams associated with the program. In addition it also contains the encrypted messages ECM. The table has information about the type of elementary stream.

NIT (Network Information Table)

This table provides information about the multiplexes and transport streams on a given network.

Information about the current network uses table_id of 0x40, that about other networks uses table_id of 0x41.

It is segmented into network information sections and is carried on PID 0x0010. [ref EN300468]

Also this table contains the private stream information too. For example, TeleText, Subtitle and MHEG

TDT (Time and Date Table)

Provides UTC (Universal Time) coded as MJD (Modified Julian Date). The PID value is 0x0014.

For TDT - Table ID is 0x70For TOT - Table ID is 0x73


External links

* [ DVB system information chart]
* [ mpeg-2 DVB]

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