Program and System Information Protocol
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The Program and System Information Protocol (PSIP) is the protocol used in the ATSC digital television standard for carrying metadata about each channel in the broadcast transport stream of a TV station.
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[edit] What PSIP does
PSIP defines virtual channels and content ratings, as well as program guides with titles and descriptions to be decoded and displayed by the ATSC tuner.
Other PSIP services
- PSIP sends the exact time referenced to UTC
- station ID, as well as network IDs; typically KQED-DT for example
- And can possibly send conditional access information
PSIP was defined in ATSC standard A/65, the most recent revision of which is A/65C, published in 2006. For Taiwan, A/68 is the extension of the A/65 standard which relates mainly to the transmission of the Chinese language using Unicode 3.0. A/69 is a recommended practice for implementing PSIP in a TV station.
PSIP also supersedes A/55, now a deprecated (though not yet officially deleted) method of delivering the program guide. TV Guide On Screen is a different system provided by datacasting on a single station, while PSIP is sent by every station to some extent.
PSIP information is passed through the airchain by the XML-based Programming Metadata Communication Protocol (PMCP).
[edit] Included tables
- STT (system time table)¹ - current time, once per second, within ±4
- MGT (master guide table)¹ - data pointers to other PSIP tables
- VCT (virtual channel table)¹ - assigns numbers to each channel
- RRT (rating region table) - content ratings for each country
- EIT (event information table)¹ - titles and program guide data
- ETT (extended text table) - detailed descriptions of channels and programs
- DCCT (directed channel change table) -
- DCCST (directed channel change selection code table) -
¹ indicates a US FCC requirement
[edit] Directed channel change
The DCC function lets broadcasters tell a DTV receiver where to change, based upon the viewer's settings. This is most likely to be a ZIP or other postcode, which can select demographically-based programming to show, such as television commercials or weather bulletins, possibly taken from an accompanying datacasting channel.
Implementation of the DCC feature is entirely optional, and depends on development of receiver and decoder technology. For example, a digital video recorder could record commercials broadcast at other times for later replay, so that many more different commercials could be shown in different parts of a large metro area than can actually be transmitted at once.
