Measurement Functions
MTD200 MPEG Test Decoder User Manual
2–9
Continuity_count_error (1st priority)
Each packet of the transport stream is preceded by a header consisting of four
bytes. The fourth byte of the header contains the count of a four-bit continuity
counter. The count must be increased by one for every packet of the transport
stream that has the same PID. The count may consist of values ranging from 0 to
15; beyond 15, it will start from 0 again (modulo-16 counter). The continuity
counter serves to recognize packets of a TV or audio program that are either
missing or repeated more than once.
The MPEG-2 standard also tolerates counter discontinuity, provided this is
indicated by a discontinuity indicator in the optional adaptation field (AF) of the
same packet. This method is primarily used for the suppression of error messages
when changing programs preceded by remultiplexing of the transport stream.
In the case of null packets (packets that do not contain any useful data but have a
PID of 0x1FFF), continuity is not checked, since the value of the continuity
counter in zero packets is not defined in the MPEG-2 standard.
In the DVB Measurement Guidelines (ETR 290), the preconditions for a
Continuity_Count_Error message are set as follows (abbreviated designations in
parentheses are the text displayed in the monitoring report):
Continuity Count ERROR is signaled if
the same packet has been transmitted more than twice without discontinuity indicator
or
(MORE THAN TWICE)
a packet is missing, (new count = old count + 2 without discontinuity indicator
or
(LOST PACKET))
there is a wrong sequence of packets (discontinuity without discontinuity indicator, without
any of the above conditions present (PACKET ORDER))
An error of this type (cumulative fault) is indicated by the LED labeled CONT
lighting (line of LEDs at front panel). More detailed information on the type of
Continuity_Count Errors as listed in the above table can be obtained from the
monitoring report.
Summary of Contents for MTD200
Page 1: ...User Manual MTD200 MPEG Test Decoder 070 9951 00...
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Page 29: ...Introduction to Digital TV Transmission Technique 1 14 MTD200 MPEG Test Decoder User Manual...
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Page 167: ...Remote Control 5 70 MTD200 MPEG Test Decoder User Manual...
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Page 174: ...Maintenance and Checking 6 6 MTD200 MPEG Test Decoder User Manual...
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Page 204: ...Glossary Glossary 10 MTD200 MPEG Test Decoder User Manual...
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Page 209: ...Index Index 4 MTD200 MPEG Test Decoder User Manual...
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