Tektronix MTD200, User Manual

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Measurement Functions
MTD200 MPEG Test Decoder User Manual
2–7
PAT_error (1st priority)
The Program Association Table (PAT) contains a list of all programs and PIDs
contained in the transport stream and of associated PMTs (Program Map Tables),
which contain detailed program descriptions. The PAT is of key importance for
decoding TV and audio programs. If the PAT is not available or contains an
error, the MPEG-2 decoder will not be able to select and decode a program from
the transport stream multiplex.
The syntactic structure of a PAT is comprehensively defined in MPEG-2 systems
(ISO/IEC 13818–1). The PAT is exclusively transmitted in packets with 0x0000
as PID. The table may be divided into a maximum of 256 sections with the table
index (table_id) of each section being 0x00.
In the DVB Measurement Guidelines (ETR290), the preconditions for a
PAT_Error message are set as follows (abbreviated designations in parentheses
are the text displayed in the monitoring report):
PAT ERROR is signaled if
PAT table index does not equal 0x00 (TABLE ID) or
PAT is transmitted in encrypted form (SCRAMBLED) or
PAT is not transmitted at least every 0.5 second (UPPER DISTANCE)
An error of this type (cumulative message) is indicated by the LED labeled PAT
lighting (line of LEDs at front panel). Detailed information on the type of PAT
error as defined in the above table can be obtained from the monitoring report.