One of the characteristics that distinguishes a fully standards-compliant transport stream from a fully standards-compliant program stream is the presence of MPEG-2 program specific information (PSI) in the former. The highest level in the PSI hierarchy is the Program Association Table or PAT, which simply provides the transport_stream_id of the transport stream and describes where to find the Program Map Table (PMT) sections in the transport stream. Optionally, the packet id (or pid) where the Network Information Table (NIT) can be found can be published in the PAT. Like all the PSI sections listed below, PATs must be provided with instances that are currently effective, and may include "next" editions to inform receivers of changes before they become effective. There must be one Program Map Table (PMT) section for each program included in the transport stream. Each PMT section furnishes the program_number for each program service and gives the pid and stream_type for each program element that comprises the program service. PMT sections also include variable-length fields called descriptors that can include optional data describing the entire program or individual streams within the program service.. Program Association Table (PAT) Program Map Table (PMT) Conditional Access Table (CAT) Transport Stream Description Table (TSDT) Each of the MPEG-2 users, such as ARIB, ATSC, DVB and SCTE may impose additional constraints on PAT and PMT sections. Program Association Table (PAT) [MPEG Syntax]A Program Association table (PAT) has two simple function: it lists the program_number and packet id (location) of Program Map Table sections in a transport stream and secondly and optionally, the packet id where the Network Information Table (NIT) can be found. However, NITs are not used in the ATSC world.
One PAT is required to be present in every MPEG-2 transport stream that contains one or more program services. The PAT must be transmitted on packet id 0, and no other use can be made of this pid. MPEG-2 does not specify how frequently a PAT must be transmitted, but ATSC A/53 requires a PAT to be transmitted at least once every 100 milliseconds. However, if the PAT is comprised of so many large sections that pid 0 might exceed the maximum of 80,000 bits per second permited for pids carrying MPEG-2 PSI sections, the repetition rate can be extended to no more than 140 milliseconds. If a new PAT is to be more than one table section, it may be useful to send a "next" table so that when the "next" table becomes the current table, the change can be effected immediately.
Program map table (PMT) [MPEG Syntax]The Program Map table (PMT) is comprised of sections for each program_number represented in a transport stream, each section of which contains the packet id and characteristics of each elementary stream in the program service.
The Program Map table is comprised of one of more sections, each pertaining to a single program service.
Conditional Access tables (CAT) are designed to deny general users access to premium or otherwise restricted content, and to establish protocols and systems to grant authorized users access. As a practical matter, MPEG only establishes the data structure for CAT and leave the details up to MPEG users like ATSC, ARIB, DVB and SCTE. Building upon the MPEG work, ATSC has established further protocols for terrestrial conditional access in ATSC A/70, but has largely left the implementation details up to the end-user.
Transport Stream Description Tables(SDT) [MPEG Syntax]A transport stream description table is a purely optional MPEG-2 Program Specific Information (PSI) table section that permits the carriage of one or more descriptors whose scope includes the entire transport stream. When used, transport stream descriptor tables shall be carried in packets with the packet id = 2 / 0x0002.
The Transport Stream Description table is comprised of one of more sections, each pertaining to a single program service.
EtherGuide Prophecy can manage the generation of transport stream description tables, and EtherGuide Emissary injects transport stream description tables, other MPEG-2 PSI table sections, and ATSC PSIP table sections. From: http://www.etherguidesystems.com/Help/SDOs/MPEG/Syntax/TableSections/Default.aspx | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||