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The Program and System Information Protocol (PSIP) is the MPEG (a video and audio industry group) and privately defined program-specific information originally defined by General Instrument for the DigiCipher 2 system and later extended for the ATSC digital television system for carrying metadata about each channel in the broadcast MPEG transport stream of a television station and for publishing information about television programs so that viewers can select what to watch by title and description.
PSIP can also send:
PSIP also supersedes the A/55 and A/56 protocol methods of delivering program guide information (which the ATSC has deleted). TV Guide On Screen is a different, proprietary system provided by datacasting on a single station, while PSIP is required, at least in the United States, to be sent by every digital television station.
PSIP information may be passed through the airchain using proprietary protocols or through use of the Programming Metadata Communication Protocol metadata scheme.
PMCP, defined in the Advanced Television Systems Committee's A/76B, provides ATSC broadcasters with a standardized means to exchange system information (SI) among systems that create and manage these data elements. These systems can be outside Program listing services, program management systems, traffic (commercial and program scheduling) and broadcast automation systems, which all contribute a portion of the PSIP data to a PSIP Generator.
At the heart of PMCP is an XML Schema (actually a collection of XML Schema Definition files), which provide a standardized structure into which PSI and PSIP-related data may be exchanged. PMCP does not dictate systems' internal database structures; it is simply a platform-independent protocol for the exchange of data.
PMCP was first published as A/76 in November 2004, and enjoys adoption from a variety of broadcast equipment and system vendors. Two revisions (largely backwards-compatible) with the standard have been made. ATSC A/76a extended PMCP to include metadata necessary for proper signaling of ACAP data broadcast elements, and A/76B, was released in 2007, fixed some errors and made the schema usable with the related SMPTE S2021 (BXF) schema.