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РусскийThe transport stream tables: Their meaning, their content and their purpose
The Transport Stream (TS) tables carry standarized data provided by the broadcaster including instructions for the receiver to properly decode the digital services. What data is transmitted and what is it used for?
Broadcasting signals contain much more information besides video and audio. Digital services included in a multiplex carry a set of metadata used by the receiver (this is, the TV or the set-top-box) to find the service and to self-configure itself to decode it. These metadata must be properly defined and organized in the Transport Stream tables.
What happens when the broadcaster misconfigures the Transport Stream tables?
Then, the receiver is dependant on the error tolerance of its internal software to decode the digital services. This is why some television brands or models cannot decode the services that are readily decoded by other receiver.Even when both are connected to the same outlet and receive an optimal RF signal!
ANALYZE THE TS TABLES USING PROMAX SIGNAL & SPECTRUM ANALYZERS
The transport stream tables: Their meaning, their content and their purpose
Set of mandatory Transport Stream tables
- PROGRAM ASSOCIATION TABLE (PAT)
This table indicates the location of each service PMT table and identifies each multiplex by its unique PID (Packet IDentifier). - PROGRAM MAP TABLE (PMT)
It identifies the elementary data streams carrying audiovisual content (video, audio, subtitles, interactive applications or other data) that conform each service or programme. Each data stream is identified by its PID. - TIME AND DATE TABLE (TDT)
It holds the current UTC (Coordinated Universal Time) date and time. The TOT table, if present, applies the appropriate correction depending on the country/region time zone. - NETWORK INFORMATION TABLE (NIT)
Information about the network and the organization of its Muxes or TS. By combining their fields, each TS is uniquely identified among all the broadcasts regulated under the ETSI (European Telecommunications Standards Institute). - SERVICE DESCRIPTION TABLE (SDT)
It contains a description of the services available in the Transport Stream. It specifies the title or name of the service, among other data.
Optional Transport Stream tables
- EVENT INFORMATION TABLE (EIT)
For each digital service, it provides a description of the current and future events (up to several days). This is the information the receiver uses to build the EPG (Electronic Program Guide). - CONDITIONAL ACCESS TABLE (CAT)
This table provides information on the conditional access systems used in the multiplex. This table must be present for the receiver to open the encrypted services, if any. - APPLICATION INFORMATION TABLE (AIT)
It provides the decoder with data to gain access to the broadcasting interactive applicationssuch as HbbTV (providing the URL hosting the content). - BOUQUET ASSOCIATION TABLE (BAT)
It contains information on the bouquets. A bouquet is a set of grouped services that may come from one or several networks. - TIME OFFSET TABLE (TOT)
Just like the TDT table it contains the current UTC date and time, but this table adds the offset information of the current country/region time zone and provides the date of the next DST clock shift. - RUNNING STATUS TABLE (RST)
A program can begin before or after the specified time defined in the EIT (Event Information Table) because of last-minute schedule changes. This table updates the event time information quickly and accurately. - STUFFING TABLE (ST)
Sometimes the broadcaster needs to override Transport Stream tables. This table contains references linking to those tables to be overridden.
Transport stream tables NOT used in broadcast
The following tables are inserted in those Transport Stream not meeting the standards because they have been partially archived in storage media.
- DISCONTINUITY INFORMATION TABLE (DIT)
It is inserted in transition points where the service information is discontinuous. - SELECTION INFORMATION TABLE (SIT)
It describes the services and events contained in a partially stored Transport Stream.
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