Glossary
MTD200 MPEG Test Decoder User Manual
Glossary–3
Continuity Counter
A continuity counter for each elementary stream (ES) is provided as a
four–bit counter in the fourth and last byte of each TS header. It counts the
TS packets of a PES, determines the correct order and checks whether the
packets of a PES are complete. The counter (15 is followed by zero) is
incremented with each new packet of the PES. Under certain circumstances,
exceptions are permissible (see Access to a Program on page 1–7).
Cyclic Redundancy Check (CRC)
The CRC serves for verifying whether data transmission was error–free. To
this effect, a bit pattern is calculated in the transmitter based on the data to be
monitored. This bit pattern is added to the corresponding data in such a way
that an equivalent computation in the receiver yields a fixed bit pattern in
case of error–free transmission after processing the data. Every transport
stream contains a CRC for the PSI tables (PAT, PMT, CAT, NIT) as well as
for some SI tables (EIT, BAT, SDT, TOT).
Decoding Time Stamp (DTS)
The DTS is a 33–bit value in the PES header and represents the decoding
time of the corresponding PES packet. The value refers to the 33 most
significant bits of the associated program clock reference. A DTS is only
available if it differs from the presentation time stamp (PTS). For video
streams this is the case if differential pictures are transmitted and if the order
of decoding does not correspond to that of output.
Digital Video Broadcasting (DVB)
The European DVB project stipulates methods and regulations for the digital
transmission of TV signals. Abbreviations such as DVB–C (for transmission
via cable), DVB–S (for transmission via satellite) and DVB–T (for terrestrial
transmission) are used as well.
Elementary Stream (ES)
The elementary stream is a ‘continuous’ data stream for vision, sound or
user–specific data. The data originating from the digitization of vision and
sound are compressed by means of methods defined in MPEG2–Video and
MPEG2–Audio.
Entitlement Control Messages (ECM)
ECM contain information for the descrambler in the receiver of a CA system
providing further details about the descrambling method.
Entitlement Management Messages (EMM)
EMM comprise information for the descrambler in the receiver of a CA
system providing further details about the access rights of the customer to
specific scrambled programs or broadcasts.
Summary of Contents for MTD200
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