In a major step toward automated generation of PSIP data, the ATSC published its newest standard A/76, "Programming and Metadata Communication Protocol." This standard makes it possible to integrate the various information sources needed to compile the key PSIP tables. PMCP is designed to permit broadcasters, professional equipment manufacturers and program service providers to interconnect and transfer data among systems that eventually must be communicated to the PSIP generator. These systems include traffic, program management, listing services, automation and MPEG encoders.
PSIP--Program and System Information Protocol, specified in ATSC document A/65B--is a critical element of digital television that provides the methodology for transporting DTV system information and electronic program guide data. Because PSIP, along with other DTV metadata, is typically developed and/or processed by several separate systems, communicating the appropriate metadata to the PSIP generator can be problematic.
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PMCP is intended to solve this problem by defining a method for communicating metadata that the PSIP generator requires. The overall goal is to ensure proper PSIP implementation while requiring minimum manual intervention by the broadcaster. Equipment manufacturers, system designers and broadcasters can use the tools provided in PMCP to help achieve that goal. Although targeted primarily at PSIP, the schema is extensible for other types of metadata and can be used to carry private information within the current structure.
(click thumbnail)PMCP is based on a protocol using extensible markup language (XML) message documents. The heart of the standard is an XML schema that defines the message structure, the elements allowed and their relationships and attributes. XML is widely recognized as flexible and usable for various system architectures. Equally important, it is capable of deployment without extensive development costs to equipment vendors and/or service providers. XML is a W3C standard that allows structuring of information in a text document that is both human- and machine-readable.
Because PSIP and other DTV metadata originate or are processed by several separate systems and equipment, there have been difficulties in communicating the metadata to the PSIP generator. Implementing PMCP will help ensure that transmitted PSIP information is complete and correct, with minimum manual intervention.
PMCP references and is complementary to other existing ATSC standards. It also supports the ISO V-ISAN standard for identification of program content and carries all the information needed in one message structure for virtual channels, PSIP events, programs, system time tables, regional ratings tables and private information.
PMCP received final approval by ATSC Nov. 10 and was published shortly thereafter. A companion "Guide to the Use of the PMCP Standard" is also planned, along with future extensions to support metadata communications for datacasting, ACAP, directed channel change and E-VSB. This work will be undertaken by ATSC specialist group T3/S1, which developed A/76, and led by Graham Jones of NAB.
Approval of the PMCP standard could not have come at a better time. The FCC incorporated the entire PSIP standard (A/65B) into its DTV rules, and all stations are required to implement the standard by Feb. 1.
For the viewer, PSIP permits suitably equipped receivers to build an on-screen DTV program guide. For broadcasters, PSIP maintains local brand identification through the "major channel number." In addition, PSIP tells the receiver whether multiple program channels are being broadcast and, if so, how to find them. It also identifies whether the programs are closed-captioned and conveys available content advisory information, among other things.
To provide full functionality, the PSIP generator must populate the appropriate PSIP tables (See Table 1).
More information on ATSC Standard A/76, "Programming Metadata Communication Protocol," and Standard A/65B, "Program and System Information Protocol for Terrestrial Broadcast and Cable," can be found at http://www.atsc. org/standards.html. More information on FCC regulations and guidelines are available at http://www.fcc.gov
