AP401FULL-HD_rev.09_UK
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8.
MPEG4/MPEG2 DECODER
8.1.
Introduction
The MPEG card allows for unencrypted digital transmissions to be viewed. This however is
not the most useful function that it performs within the instrument in which it is installed, as
the quality of a digital signal cannot be judged by the video image, but only by means of
specific measurements like the BER or the C/N ratio (albeit much less reliable and accurate).
The importance of the module becomes truly significant in the identification of the channels’
contents. Digital channels appear as bands of noise of variable width: just a few MHz for
SCPC transmissions, around 7 MHz for cable or terrestrial and approximately 18 to 30 MHz
for MCPC transmissions. Specialized magazines provide all the data regarding satellite
transmissions, but in the case of systems with frequency conversion, channel exchange is
always possible. The same problems may be caused by transmodulation from QPSK to
QAM
1F
2
.
The MPEG card receives the TS (Transport Stream) from the QPSK, QAM or OFDM decoder
and provides the name of the transponder, the Network, the television or audio programs
available separately and the list of the audio channels associated with each video program;
that is, if the program is not encrypted and the decryption allows for it to be viewed.
8.2.
Use of the Card
The MPEG signal to be decoded and viewed must be furnished by the QPSK/8PSK, QAM or
OFDM modules. For correct use, please refer to the relative chapters.
The card can be enabled by pressing the
TV
button from the digital measurement screen.
8.2.1.
Description of the Network information table
If present in the TS, the name of the network will appear on one line at the top of the
screen. In the case of satellite signals, the second line will contain data regarding the
satellite and the transponder.
1.
The orbital position in degrees followed by E or W, for East or West respectively
2.
Polarization with indications of HL (horizontal line), VL (vertical line), RC (right circular)
LC (left circular).
Please note that the data may sometimes not be accurate due to transmodulation,
transponder relays from the satellite, or other issues.
Below is a list of the radio or video programs available, taken from NIT
3
, and the HELP
indications for the operations that can be carried out. Each line is made up of:
3.
A sequential number.
4.
The channel name.
5.
The Video PID.
6.
The number of the available audio channels.
The lines for programs declared to be unencrypted by the Broadcaster are green, while
those declared to be encrypted are red.
2
Transmodulation demodulates and decodes the digital channels of a satellite
transponder, which normally occupies 30 MHz and generates a digital carrier in terrestrial
band, containing all of the same channels in 7 MHz of bandwidth.
3
Network Information Table.
