Introduction to digital TV broadcasting technology
General
Objective With the help of data reduction by means of minimizing redundant moving picture in-
formation as well as flexible organisation of the signal quality, transmission capacity
shall be increased.
Realization First data with regard to picture and sound are reduced. Out of the condensed data
streams a multiplex data stream is composed together with additional information (e.g.
teletext).
The necessary methods for that are defined in the MPEG-2 standard. For the additio-
nal information only the syntactic frame is defined here. Which kind of data and in
which form data are to be integrated into the multiplex data stream is layed down by
the European DVP-project.
For decoding a high transmission quality and an approximative zero bit error rate must
be guaranteed. For digital modulation methods QPSK and QAM channel coding is
used. By that a certain amount of bit errors can be corrected on the receiver side.
The corresponding procedures for coding and transmission are defined by the Europe-
an DVP-project.
MPEG-2 The MPEG-2 standard (ISO/IEC 13818) set up by the MPEG standardization commit-
tee regulates the coding of moving pictures and the accompanying sound.
DVB In addition to the transmission procedures defined by the MPEG-2, the European
DVB-project (Digital Video Broadcasting) has layed down a number of definitions
which were forwarded to the organisations ETSI / CENELEC for standardization.
MPEG-decoding For decoding the MPEG data stream several steps are necessary.
For that different elements out of the data stream are used.
Transport stream
synchronization
The transport stream packet consists of the different substream data packets. The
data packets are transmitted with a length of 188 bytes. At the beginning of each pa-
cket is the sync-byte (0x47). Because this value is not only reserved for the sync-byte,
the repetitive occurrence of the sync-byte every 188 bytes has to be checked too to
ensure stable synchronization.
Packet identifying To identify the individual packets there is a Packet Identity (PID) contained at the be-
ginning of each packet (after the sync-byte). Each substream (e.g. video, audio) gets
its own PID. Some PIDs are assigned automatically and cannot be changed (e.g.:
PAT, CAT , .. siehe table 1)
Introduction
QPE 8600
1 - 4 QPSK-receiver
