Emitters and receivers use the signal information to share information about the network, frequencies of the multiplex, services, channels guide… Each digital television broadcast standard uses a different signaling tables and descriptors to provide information to the receiver though all the signaling data is based on the MPEG-2 standard.
The Program Specific Information (PSI) contains metadata about the programs (channels) and it is part of MPEG-2 TS. The PSI data contains the following tables:
- PAT (Program Associated Table, PID=0x00): location of all the programs contained in the TS. It shows the association of PMT PID and Program Number.
- PMT (Program Mat Table, tableId=0x02): PID numbers of ES associated with the program and information about the type of ES (audio, video or data).
- CAT (Condition Access Table, PID=0x01, tableId=0x01): It is used for the conditional access and provides association with EMM stream.
- NIT (Network Information Table): information about the multiplexes and transport streams on a given network.
- TSDT (Transport Stream Descriptor Table): information about services and associated MPEG-2 descriptors in the TS. Descriptors are used for additional information.
The Service Information (SI) are additional tables used in the DVB standard to identify the services and the associated events contained in the TS. Most relevant signaling tables are:
- NIT (Network Information Table): Information about the physical network such as network provider name, transmission parameters…
- BAT (Boutquet Association Table): describes the program structure of several phyisical channels.
- SDT (Service Description Table): describes the program structure or one physical channel.
- EIT (Event Information Table): contains the program guide (EPG). There are 4 EITs to cover a period of 12h.
- TDT (Time and Date Table) and TOT (Time Oset Table): Information about time and date.
- RST (Running Statuts Table): allows rapid updating of the timing status of one or more events
- ST (Stung Table): features of the packetization.
- Other tables:
- DIT (Discontinuity Information Table) and SIT (Selection Information Table) are used in storage environments.
- AIT (Application Information Table) is used in interactive applications.
- INT (IP/MAC Notication Table) is used in transmission.
- UNT (Update Notification Table) is used for System Software Updates.
PSIP is the protocol used in the ATSC television standard in United States, Canada and Mexico. It is based on MPEG-2 to encode the content but defines new signaling tables:
- STT (System Time Table): current time.
- MGT (Master Guide Table): data pointers to other PSIP tables.
- VCT (Virtual Channel Table): denes each virtual channels and enables EITs to be associated with the channel.
- RRT (Rating Region Table): content ratings for each country or region.
- EIT (Event Information Table): titles and program guide data
- ETT (Extended Text Table): detailed descriptions of channels and aired events.
- DCCT (Directed Channel Change Table): allows automatic changes to the channel width in response to noise conditions.
- DCCSCT (Directed Channel Change Selection Code Table): update states, counties and program genres used in DCCT tables.
ISDB is the Japanesse boradcast digital TV standard. It is based on MPEG-2 and it uses some PSI tables but also defines new ones:
- PSI: PMT, CAT and PAT with specic descriptors.
- Equivalents to SI (DVB) with specifc descriptors]: NIT, SDT, BAT, EIT, TDT, RST, TOT and ST.
- PCAT (Broadcaster Information Table): conveys partial content announcement for data broadcasting.
- BIT (Boutquet Association Table): it is used to submit broadcaster information on network.
- NBIT (Network Board Information Table): board information on the network such as a guide.
- LDT (Linked Description Table): it is used to link various descriptions from other tables.
The ISDB Japanese standard also use extended SI Information to describe local events and their information. It uses the LIT (Local Information Table), ERT (Event Relation Table) and ITT (Program Index Transmission Information Table). It also defines new descriptors to add new functionalities.
Signal tables in the DTMB standard
DTMB is the standard used in China, Hong Kong and Middle East countries. It is similar to DVB in terms of service information but there are some differences in the transmission parameters as you can see in the previous post.