ADInstruments S7200 Operation Manual page 200

AD INSTRUMENTS S7200 TV Signal Analyzer Operation Manual
as do packets with a PID=200. It is the purpose of this counter to enable one to
recognize missing or repeated transport stream packets of the same PID in order
to draw attention to any multiplexer problems.
Such problems can also arise as a result of errors in remultiplexing or due to
random bit errors in the transmission link. Although MPEG-2 allows
discontinuities in the transport stream, they must be indicated in the adaptation
field, e.g. after a switch-over (discontinuity indicator=1). In the case of zero
packets (PID=0x1FF), discontinuities are allowed and are not verified.
A continuity_error occurs when
• The same TS packet is transmitted twice without a discontinuity being indicated,
or
• If a packet is missing (count incremented by 2) without a discontinuity being
indicated, or
• The sequence of packets is wrong.
(5) PMT_error
For each program, a Program Map Table (PMT) is transmitted at maximum
intervals of 500 ms. The PIDs of the MAPs are listed in the PAT. The PMT contains
the respective PIDs of all elementary streams belonging to this program. If a PMT
referred to in the PAT is missing, the set top box or decoder will be unable to
demultiplex or decode them. If a PMT is listed in the PAT but is either missing,
errored or scrambled, will lead to the error message "PMT_error".
A "PMT error" occurs when
• A PMT listed in the PAT is missing,
• A section of the PMT is not repeated after 500 ms or less,
• A PMT is scrambled,
• The table ID is not 2.
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