PSI is called Program Specific Information. PSI contains the data that enable the STB to demultiplex the services. These services are carried out in one or more streams all of these streams are having the PIDs. The services are scrambled but the PSI tables are not scrambled because it would be difficult for STB to demultiplex.
In a transport stream the PSI table is carried out in a private data structure. These private data structure is set of tables. It would be difficult to insert these tables directly in a transport stream while these tables are segmented into sections and inserted in a transport stream. In which some PIDs are predetermined while some PIDs are select-able for operator.
Thus PSI is metadata of a channel which is inserted in to the Transport Stream and also as mentioned before that PSI is set of tables these are as follows,
PAT – Program Association Table
PMT – Program Mapping Table
CAT – Conditional Access Table
TSDT – Transport Stream Description Table
PAT is called Program Association Table. PAT is the correspondence between the Program number of a service with the PID of that transport stream. This program number is numeric. PAT table contains one or more than one sections.
PAT is inserted into transport stream as the PID 0x0000. m=MPEG2 transport stream for audio and video coding it is recommended that all the sections of the PAT PID should be send in every 100ms.
This is called the Program Mapping Table. PMT is the mapping with program elements and program number. PMT contains all the definition of the transport stream.
PMT PID shows that PCR PID and Component PID. PMT PID also shows the component types
Component Descriptor (language descriptor) and CA Descriptor.
It is called the Conditional Access Table. CAT describes the conditional access system and their EMM (Entitled Management Message). PID Value for CAT is 0x0001.
TSDT is called the Transport Stream Description Table. TSDT provide the description of the transport stream like type of receiver.
PSI tables provides the information about the services in it while SI tables provides some additional information of the service which is carried by different type of multiplexer and other service network. Thus SI is the additional information.
This is called the Network Information Table. NIT contains the information about the DVB network. There are two kind of NIT.
We can transmit the NIT for other network also . The difference between these network can be identified by table_id value. NIT contains the linkage descriptor. NIT PID value is 0x0010.
It is called the Bouquet Association Table. A bouquet is called the group of transport streams. BAT PID value is 0x0011. In bouquet the services can be blocked by CA System.
it is called the Service Description Table the PID value for it is 0x0011. SDT describe the service names and also the status of the service while its running or not. These service types are the NVOD, TV , interactive and Radio.
EIT is called the Event Information Table. The PID value for EIT is 0x0012. It sends the information of the program in the current transport stream.
TDT is called the Time Date Table. TDT updates the time and date of STB. It is generated by the MUX or iStreamer. PID value for TDT is 0x0014.
TOT is called the Time Offset Table. TOT is used for the support of local time offset.PID value for TOT is 0x0014.
This was all about the PSI SI Tables.