About: PSI/PSIP Statistics

The PSI/PSIP statistics contain information about the Program Specific Information (PSI) and ATSC Program and System Information Protocol (PSIP) data contained within the MPTS.

An example of the report is:

TVCT Sat Apr 21 2018 20:21:02.993
    Event: refresh
    Last Observed: Thu Apr 26 2018 18:01:01.993
    Periodicity: 0.000999s - 0.89396s
    Version: 8
    Transport Stream ID: 381
    Programs: 3
        7-1: KGO-HD (program 3)
        7-2: LIVWELL (program 4)
        7-3: LAFFTV (program 5)

PAT Sat Apr 21 2018 20:21:02.993
    Event: refresh
    Last Observed: Thu Apr 26 2018 18:01:01.993
    Periodicity: 0.000999s - 0.792964s
    Version: 0
    Programs: 3
        Program PID: 0x30 (program 3)
        Program PID: 0x40 (program 4)
        Program PID: 0x50 (program 5)

PMT Wed Apr 25 2018 18:00:00.799
    Event: refresh
    Last Observed: Wed Apr 25 2018 18:51:00.799
    Periodicity: 0.296986s - 0.699968s
    Program Number: 3
    Version: 5
    PMT PID: 0x30
    Streams: 3
        0x31 - MPEG-2 Video (0x2)
        0x34 - AC-3 Audio (0x81)
        0x34 - AC-3 Audio (0x81)

PSI and PSIP are delivered via tables within the MPTS. The report indicates changes to the tables.  The following tables are processed:

  • Terrestrial Virtual Channel Table (TVCT)
  • Program Association Table (PAT)
  • Program Map Table (PMT), for those programs listed in the PAT. The PMT for programs not listed in the PAT are not processed.

Changes may occur because:

  • The table version has changed. This is a common occurrence and may not represent any actual change to the table’s contents.
  • A related table has changed. This is particular true of the Program Map Table (PMT). If the Program Association Table (PAT) changes, then all PMT tables are re-acquired.
  • The payload of a table (or table section) changed. This shouldn’t occur, however if a payload change is detected by the monitoring system then the table is logged.

Timestamps for a table represent the time when the first packet used to assemble the table was observed. Transport packets are timestamped as they are received by the monitoring system software.

  • Assembly of a section starts when a transport packet with the Payload Start Unit Indicator bit is observed.
  • Assembly of a table occurs when any section of the table is observed. Assembly of a table is completed when all sections of the table have been acquired. It is not required that sections appear in any particular order, and sections comprising a table may repeat at different frequencies.

For each table, the following information is logged:

  • The type of table (TVCT, PAT, PMT)
  • The time when the table as first observed.
  • The time when the table was last observed.
  • The periodicity of the table. Transport packets are timestamped as they are received by the monitoring system software. The timestamp for a table is considered to be the time when the first packet used to assemble the table is received. Once a full table is assembled, the PSI/PSIP processor begins to assemble a new table. The table period is the time between the first packet of one table arriving and the first packet of the next. Note that the periodicity may increase due to packet loss, as a full table cannot be assembled until the lost packet occurs again in the transport stream.
  • For the TVCT:
    • The Transport Stream ID of the MPTS.
    • For each virtual channel, the channel’s major and minor number, the name, and the program number.
  • For the PAT:
    • For each program, the PMT PID and the program number.
  • For each program’s PMT:
    • For each stream within the program, the stream’s PID and stream type.

The TVCT and PAT are constantly monitored by independent PSI/PSIP processors. Due to the potentially very large number of programs contained within an MPTS, however, a single PSI processor is used to acquire the PMTs. The PMT PSI processor is rotated among the programs advertised in the PAT – two PMTs for the target program are acquired to establish periodicity, then the processor is then targeted to the next program. Consequently an irregularity in the periodicity for a particular program’s PMT may be missed if the PMT PSI processor is, at the time of the irregularity, processing another program.