Questions Frequently Asked of EtherGuide Systems

Who sends a Program Association Table ?

This question has recently been asked in more than one Internet search that landed on this web site. Strictly speaking, persons or entities that emit an MPEG-2-, ATSC-, DVB- or ARIB-compliant transport stream must emit a Program Association Table (usually abbreviated as PAT). You can get hyperlinked details on the structure of a PAT here. At a minimum, the PAT provides the transport_stream_identifier (also known as the tsid) and an entry for each of the program services (also known as virtual channels) in the transport stream.

However, we think the question should actually be: what device or devices creates and sends out a Program Association Table?

The answer is, either an encoder or a broadcast metadata generator, such as EtherGuide Prophecy. If your situation is such that, once the number of program services (or virtual channels) in the transport stream, once established, will never change, and the locations (packet_ids) of the program services will never change, then relying on an encoder to send out the PAT is probably okay. However, if you anticipate adding or subtracting the number of virtual channels while keeping everything else running, or you plan to remap virtual channels or dynamically change which packet id or Program Map Table (PMT) applies to a particular virtual channel, then you are most likely to need a broadcast metadata generator to create and transmit the Program Association Table.

As a practical matter, an ATSC digital broadcast station that provides dynamic PSIP with different parental ratings (via the content_advisory_descriptor) or changes captioning or AC-3 audio settings on a television program-by-television program basis MUST transmit dynamic Program Map Tables, and this is something easily accomodated by EtherGuide Prophecy. EtherGuide Prophecy and EtherGuide Emissary can transmit MPEG-2 Program Specific Information (PAT + PMTs) when set to do so (in addition to PSIP), but cannot be configured to split responsibilties between and encder and the broadcast metadata generator.

What is PMCP and why should I be interested in it?

PMCP is a standard, published by the Advanced Television Systems Committee, for a data-exchange format and associated procedures for data elements that are used to create broadcast metadata that is transmitted by ATSC-compliant digital broadcast stations.

PMCP stands for Programming Metadata Communications Protocol and is formally an "XML Schema" because the data format is written in and all PMCP exhanges are expressed as eXtensible Markup Language (XML).

PMCP provides for exchanging data using file transfer protocol (ftp) and via UDP/IP and TCP/IP "sockets" transfers. Virtually all the information needed to create Program and System Information Protocol (PSIP) metadata and metadata used in creating MPEG-2 Program Specific Information (PSI) and Conditional Access tables (CATs.)

PMCP is platform-independent, as a wide variety of computer and non-computer platforms can create and process XML messages without favoring one platform over another.  As PMCP is supported by a wide variety of vendors of PSIP generators, and makers of traffic, automation and program management systems, using PMCP means that a broadcast station or group operator is not bound to a particular vendor's proprietary interface or interfaces, making system upgrades and rearrangments easier and cheaper to implement.

PMCP also lowers the cost for custom extensions to a station's metadata exchanges, through the use of built-in private PMCP data elements. StorerTV, for example, exchanges data used in their program- and asset-management systems using PMCP.  TitanTV's MediaStar program listing system directly supports PMCP, and interoperates well with EtherGuide Systems PSIP generators.
 
PMCP is comlementary to, and coordinated with, the BXF protocol (SMPTE-2021) that is emerging to make exchanges of traffic and program data between traffic, automation, program management and asset management systems.  Indeed, if a BXF-compliant system doesn't understand PMCP, the vendor has made a conscious decision to ignore PMCP.

How dynamic are EtherGuide Systems PSIP generators?

As dynamic as you can manually (through the EtherGuide Prophecy or EtherGuide Emissary user interface), or via the TitanTv.com Master Control Utility, or under PMCP control of your traffic, master control or automation system want the generator to be.  However, you cannot make changes in PSIP or PSI table more often than once in any period of 20 seconds.  If you require frame-accurate changes, we should talk..

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