table_id_extension [MPEG-2 Semantics]
The table_id_extension is present as the fourth and fifth byte in every MPEG-2 private table section that uses the "long" format.
Various table implementations use the table_id_extension for different purposes.
Program Association tables (PATs) transmit the transport stream identifier of the transport stream using the table_id_extension. With Program Map Table (PMT) sections, the table_id_extension identifies the program_number of the program service being defined in the PMT section.
ATSC Master Guide tables set the table_id_extension to all zeros, while the Terrestrial and Cable Virtual Channel tables like the PAT, identify the transport_stream_identifier via the table_id_extension. Satellite Virtual Channel tables split the table_id_extension into two values, the SVCT_subtype and SVCT_id. Rating Region tables set the first 8 bits of the table_id_extension to all 1's, and use the second 8 bits to signify the region being defined in the RRT.
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