Program Specific Information

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Program Specific Information (PSI) is metadata about a program (channel) and part of a MPEG transport stream.

The PSI data contains five tables:

PAT (Program Association Table)

CAT (Conditional Access Table)

PMT (Program Map Table)

NIT (Network Information Table)

TDT (Time and Date Table)

PSI is carried in the form of a table structure. The table structure can span multiple transport stream packets. Adaptation field also occurs in TS packets carrying PSI data. The PSI data will never be scrambled so that the decoder at the receiving end can easily identify the properties of the stream.

The PAT, CAT and TDT tables are associated with predefined PID as explained in the respective sections. There may be multiple independent PMT tables in a stream; these are given user-defined PID numbers (as are PES packets). PMT table PIDs are defined in the PAT, and are the only PIDs defined there (PES PIDs are defined in the PMT). Each table has predefined structure.

Contents

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1 PAT (Program Association Table)

2 CAT (Conditional Access Table)

3 PMT (Program Map Table)

4 NIT (Network Information Table)

5 TDT (Time and Date Table) / TOT (Time Offset Table)

6 References

7 External links

[edit]PAT (Program Association Table)

Partial PAT Format[1]When existsNameNumber

of bitsDescription

If TS payloadunit startPointer field8Present if payload_unit_start_indicator bit is set in the TS header bytes. Gives the number of bytes from the end of this field to the start of payload data.

Table ID80x00

Section Syntax Indicator1Always 1 for PAT

01Always 0 for PAT

Reserved2Always set to binary '11'

Section length2+10Informs how many programs are listed below by specifying the number of bytes of this section, starting immediately following this field and including the CRC. First two bits must be zero.

transport stream ID16User defined data. Value not important to demuxers or players.

Reserved2Set to 0

Version Number5Table version number. Incremented by 1 when data in table changes. Wraps around from 31 to 0.

Current/next indicator1If 0, table data isn't applicable yet (becomes applicable when set to 1)

Section number8Index of this section in the sequence of all PAT table sections. First section is numbered 0

Last section number8Index of last section of PAT table

Repeated N

times depending on

section lengthProgram num16

Reserved3Always set to binary '111'

Program PID13packets with this PID are assumed to be PMT tables (see below)

CRC3232

The PAT is assigned PID 0x0000 and table id of 0x00. The transport stream contains at least one or more TS packets with PID 0x0000. Some of these consecutive packets form the PAT. At the decoder side the PSI section filter listens to the incoming TS packets. After the filter identifies the PAT table they assemble the packet and decode it. A PAT has information about all the programs contained in the TS. The PAT contains information showing the association of Program Map Table PID and Program Number. The PAT should end with a 32-bit CRC

[edit]CAT (Conditional Access Table)

This table is used for conditional access to the streams. This table provides association with EMM stream. When the TS is scrambled then this section contains the EMM PID. The PID value is 0x0001.

[edit]PMT (Program Map Table)

Partial PMT FormatWhen existsNameNumber

of bitsDescription

If TS payloadunit startPointer field8Offset of first byte of first field. Usually 0x00

Table ID8Always 0x02 for PMT

Section syntax indicator1

Always set to 01

Reserved2Always set to binary '11'

Section length2+10Number of programs listed below. First two bits always zero.

Program num16

Reserved2

Version number5Incremented by 1 mod 32 each time the table data changes

Current Next indicator1If 1, this table is currently valid. If 0, this table will become valid next.

Section number8Always 0x00

Last Section number8Always 0x00

Reserved3

PCR PID13PID of general timecode stream, or 0x1FFF

Reserved4

Program Info length2+10Sum size of following program descriptors. First two bits must be zero.

Program DescriptorN*8

Repeated N

times depending on

section lengthstream type8

Reserved3Always set to binary '111'

Elementary PID13

Reserved4

ES Info length2+10First two bits must be zero. Entire value may be zero

ES DescriptorN*8If ES Info length is zero, this is omitted.

CRC3232

This table contains PID numbers of elementary streams associated with the program and it has information about the type of these elementary streams (video, audio, etc). In addition it also contains the ECM PID number of the entitlement control message, which is associated with the program.

[edit]NIT (Network Information Table)

This table provides information about the multiplexes and transport streams on a given network.

Information about the current network uses table_id of 0x40, that about other networks uses table_id of 0x41.

It is segmented into network information sections and is carried on PID 0x0010. [ref EN300468]

Also this table contains the private stream information too. For example, TeleText, Subtitle and MHEG

[edit]TDT (Time and Date Table) / TOT (Time Offset Table)

The TDT provides the UTC (Universal Time) coded as MJD (Modified Julian Date). The TOT provides information regarding the local time offset from the UTC time. This is used to define the local time. The PID value for both tables is 0x0014.

For TDT - Table ID is 0x70. For TOT - Table ID is 0x73.