§ Although the PSI/SI information is well adapted to the representation of service information parameters, it is not flexible enough to accurately represent the complex set of services and programs that a commercial system would make available to its subscribers.
§ Service discovery in DVB-T networks is based purely on the PSI/SI information carried in the transport stream.
§ DVB-H networks also rely on the PSI/SI information with IP specific extensions, but in addition, the Electronic Service Guide (ESG) is introduced for service and content discovery.
§ It can know where to find the ESG data in the stream thanks to the PSI/SI tables.
§ Service discovery signaling within DVB-H is considered to consist of two parts: transmission parameter signaling (TPS) and Program-Specific Information/ Service Information (PSI/SI).
§ In DVB-H protocol stack (in L1/L2), TPS is carried as part of the physical layer (L1) and the PSI/SI is carried within the data link layer (L2).
§ ETSI EN 300 468 defines the format of the service information (SI) in DVB systems, including DVB-H.
§ The Program Specific Information (PSI) and Service Information (SI) are carried in tables within the transport stream to map the programs and services, which it contains.
§ PSI/SI signaling consists of tables that are carried over transport streams (TSs) of the IPDC over the DVB-H network.
§ The PSI/SI signaling needed for the service discovery in IPDC over DVB-H consists of the following tables: Network Information Table (NIT), Program Association Table (PAT), Program Map Table (PMT), IP/MAC Notification Table (INT), and Time and Date Table (TDT).
§ Each table, excluding PAT and TDT, carries a number of different descriptors that contain most of the actual information that is carried within the tables.
The PSI data is structured as four types of table.
1.1) Program Association Table (PAT):
1.2) Program Map Table (PMT):
1.3) Conditional Access Table (CAT):
1.4) Network Information Table (NIT):
§ The PAT contains information about every DVB service in the transport stream and associates them to the corresponding PMTs.
§ The PMT provides the mapping of a specific program with its elements (video, audio, subtitles).
§ The INT is used to announce the addresses of the IP streams and map them with the services. In the DVB-H network data are delivered as IP streams.
§ The NIT announces available transport streams with their IDs and linkage descriptors to other tables.
§ Available channels and services are found by using the Program Map Table (PMT) and the Program Association Table (PAT), where the services are mapped.
§ Note: In the traditional DVB-T network services are mapped by using PATs and PMTs.
§ Note: Each table, in turn, excluding PAT and TDT, carries a number of different descriptors that contain most of the actual information that is carried within the tables.
2). The tables defined by DVB are called the service information (SI) tables.
2.1) Service Description Table (SDT):
§ the SDT contains data describing the services in the system e.g. names of services, the service provider, etc.
2.2) Event Information Table (EIT):
§ the EIT contains data concerning events or programmes such as event name, start time, duration, etc.;
§ the use of different descriptors allows the transmission of different kinds of event information e.g. for different service types.
2.3) Time and Date Table (TDT):
§ the TDT gives information relating to the present time and date. This information is given in a separate table due to the frequent updating of this information.
2.4) Bouquet Association Table (BAT):
§ the BAT provides information regarding bouquets. As well as giving the name of the bouquet, it provides a list of services for each bouquet.
2.5) Running Status Table (RST):
§ the RST gives the status of an event (running/not running). The RST updates this information and allows timely automatic switching to events.
2.6) Time Offset Table (TOT):
§ the TOT gives information relating to the present time and date and local time offset. This information is given in a separate table due to the frequent updating of the time information.
2.7) Stuffing Table (ST):
§ the ST is used to invalidate existing sections, for example at delivery system boundaries.
2.8) Discontinuity Information Table (DIT)
§ the DIT is used only in
2.9) Selection Information Table (SIT):
§ the SIT is used only in
3). The tables defined in MPEG-2 and DVB standards:
3.1). PSI organized in the form of tables:
(1) Program Association Table (PAT):
(2) Program Map Table (PMT):
(3) Conditional Access Table (CAT):
(4) Network Information Table (NIT):
(5) Service Description Table (SDT):
(6) Event Information Table (EIT):
(7) Time and Date Table (TDT):
(8) Bouquet Association Table (BAT):
(9) Running Status Table (RST):
(10) Time Offset Table (TOT):
(11) Stuffing Table (ST)
Storage Media Interoperability table
(12) Discontinuity Information Table (DIT)
(13) Selection Information Table (SIT)
PID Value for SI Table: (N/A)
4). Service Discovery in ESG with PSI/SI
§ Once the terminal has connected to a valid DVB-H transport stream carrying IPDC services on a particular IP Platform, it receives from the PSI/SI tables the location (PID) where the well-known IP address for the ESG bootstrap information of that IP Platform is located (see TR 102 469).
§ From the ESG bootstrap information, the terminal can figure out how many ESGs are available on that IP Platform, what is the relevant ESG to consume and the required information to configure the selected ESG session.
§ Once the terminal located the IP stream of the selected ESG, it can initialize the file delivery session on the terminal and the ESG processing. Then the terminal can start to receive the ESG information.
§ Service Information (SI) in Service Discovery provides supplementary information about services, both audio programme and data.
§ Note that for starting on the selected ESG, the terminal needs to know the location of the related IP stream, through the PSI/SI tables.
5.1). Program-Specific Information (PSI)
§ DVB-H and DVB-T use the program-specific information (PSI) defined in the MPEG standard.
5.2). Service Information (SI):
§ The service information features of DVB-H are also similar to those of DVB-T, in the sense that they both follow the global DVB standard in this matter.
§ The lowest-level parameters of a program are transmitted using DVB-H signaling, which is basically identical to DVB-T signaling with a limited number of extensions.
§ In addition to video and audio data, an MPEG-2 transport stream also needs to carry so-called service information.
§ This information is meant to help receivers navigate around the services offered by a DVB system as well as to learn about network and signal parameters required for the technical servicing.