ATSC Program and System Information Protocol (PSIP)
The ATSC Program and System Information Protocol (PSIP) is specified in standards document A/65, and provides extension to MPEG 2 for the identification of streams associated with a program and time of day information. It provides sufficient data for a program guide function, and is structured such that a broadcaster may provide data independently for his own service (in which case the receiver can assemble a guide form several sources), or in cooperation with other broadcasters.
A/65 Annex D supplies an informative overview of PSIP.
PSIP consists of a hierarchical set of tables.
The tables are divided into groups, base tables and tables defined in the Master Guide Table (whichis one of the base tables).
The base tables (Sytem Time Table, STT; Rating Region table, RRT; Master Guide Table, MGT; and Virtual Channel Table, VCT) are all labeled with the base packet ID (base PID), 0x1FFB.
Tables of the second type are the Event Information Tables (EIT) and the Extended Text Tables (ETT). The EIT and ETT PIDs are defined in the MGT.
A brief description of the tables follows.
The System Time Table (STT) fits in one MPEG packet, and provides time-of-day information.
The Rating Region Tble (RRT) is designed to transmit program rating information for any country that may adopt the standard.
The Master Guide Table (MGT) provides information on all the other PSIP tables, including table sizes, version numbers of updatable tables, and PIDs for non-base tables.
The Virtual Channel Table (VCT) provides information on all the channels that are or will be on line, including such items as channel name, navigation identifier, stream components and types.
There is an Event Information Table (EIT) for each event or TV program associated with each of the virtual channels. EAch EIT covers a period of three hours. The total number of EITs available is 128. EIT-0 covers the current programs, EIT-1 covers the next three hours, and so on. The transport stream must contain a minimum of the EIT-0 through EIT-3 (12 hours coverage). EIT start times are constrained to integer multiples of 3:00 in UTC time, i.e. 00:00 (midnight), 3:00 (3 am), etc.
There can be several Extended Text Tables (ETT) each associated with an EIT or the VCT. The EITs and the VCT may each have only one ETT.
To review: the minimum tables required for PSIP are the VCT, MGT, RRT, STT, and first four EITs. All other tables are optional.
The reader is referred to the complete ATSC Standard for PSIP, Document A/65.
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