Digital Signal Processing Reference
In-Depth Information
11 Measurements on the MPEG2 Transport
Stream
With the introduction of digital television, neither the hopes of the users
nor the fears of the test equipment makers were confirmed: there is still a
large need for test instruments for digital television, but of a different type.
Where it was mainly video analyzers for evaluating the test lines of an ana-
log baseband signal in analog television, it is mainly MPEG-2 test decod-
ers which are being used in digital TV. Throughout the world, taking
measurements directly at the transport stream has become the most impor-
tant digital TV test technology with regard to turnover and demand. Thus,
e.g., every MPEG-2 transport stream to be broadcast is analyzed and moni-
tored by means of a MPEG-2 test decoder at almost every transmitter site
of DVB-T networks in some countries.
The input interface of an MPEG-2 test decoder is either a parallel 25-pin
MPEG-2 interface or a serial TS-ASI BNC connector, or both at the same
time.
The MPEG-2 analyzer consists of the essential circuit blocks of
MPEG-2 decoder, MPEG-2 analyzer - usually a signal processor - and a
control computer which acquires all the results, displays them on the dis-
play and performs and manages all operating and control operations. A test
decoder is capable of decoding all the video and audio signals contained in
the transport stream and of performing numerous analyses and measure-
ments on the data structure. The MPEG-2 transport stream analysis is a
special type of logic analysis.
The Measurement Group in the DVB Project has defined numerous
measurements on the MPEG-2 transport stream within its Measurement
Guidelines ETR 290. These measurements will be described in more detail
in the following chapters. According to ETR 290, the errors to be detected
by means of these measurements were graded into three levels of priority:
Priority 1, 2, 3.
MPEG-2 transport stream errors:
•
Priority 1 - no decodability
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