Transport_Error (2Nd Priority) - Tektronix MTD200 User Manual

Transport_error (2nd priority)

MTD200 MPEG Test Decoder User Manual
The second byte of every packet header in the transport stream contains the
transport_error_indicator, which is a flag that serves to indicate bit errors in the
following packet. This flag is generated and inserted by the Viterbi or Reed-Sol-
omon decoder at the receiver end if the decoder is no longer capable of correct-
ing all bit and byte errors in the transport stream.
Because it is not possible in case of a set transport_error_indicator to predict
which bit or byte contains an error, this packet must not be evaluated by an
MPEG-2 decoder. For this reason, the MPEG test decoder only indicates the
Transport_Error, which means that the packet is not checked for further transport
stream errors.
In the DVB Measurement Guidelines (ETR 290) the preconditions for a
Transport_Error message are set as follows:
Transport ERROR is signaled if
a transport_error_indicator bit is set in the packet header
An error of this type (cumulative message) is indicated by the LED labeled
TRANS lighting (line of LEDs at the front panel). As additional information, the
PID of the packet containing the error can be obtained from the monitoring
report.
NOTE. The PID information contained in the monitoring report may be wrong if
a transport error is indicated and if the bit error concerns the PID information
of the packet header.
Measurement Functions
2–11