Definitions
MPEG
M
oving
P
ictures
E
xperts
G
roup: A standardization committee, whose task is the enco-
ding of moving pictures and sound information. Developed the basic standards for data
reduction. ( MPEG-1... MPEG-4 )
DVB
D
igital
V
ideo
B
roadcast: For digital broadcasting of TV-signals additional standards for
transmitting of MPEG-signals were defined.
Symbol rate
Data rate of the applied digital signal on the input. For correct decoding the data rate
is to be set on the receiver.
Code rate
According to the selected transmission path encoding is applied to ensure correct
transmission of the data signal. The code rate corresponds to the ratio between useful
data and total amount of data. The more additional data is transmitted, the better the
original useful signal can be restored in case of a transmission failure.
BER
B
it
E
rror
R
ate: The BER is measured by means of the Viterbi decoder. The BER
shows the ratio between the correctly received bits and the incorrect bits. For correct
processing of moving pictures the BER should not exceed a value of 1x10
-5
.
Multiplex
Several
P
acketized
E
lementary
S
treams (PES) are multiplexed into a transportstream
(acc. to time-multiplex for MPEG2/Packetgeneration). A single PES contains the video,
audio and data information of a single programme.
The length of the transmitted packets are 188 or 204 bytes. In order to be able to
re-assign the individual packets on the receiver side, the packets are provided with a
programme identification.
C/N
C
arrier to
N
oise: Carrier to noise ratio of the input signal. For digital signals this value
includes the thermic noise and other distortions of the signal.
(e.g. intermodulation, phase-jitter, ...). It is very difficult to measure this value, it is cal-
culated back from the necessary correction expense.
In order to enable correct processing of moving pictures the C/N-ratio in connection
with the code rate of the input signal should achieve a BER smaller than 1x10
-5
TS identifier
T
ransport
S
tream identifikation: Each MPEG-transport stream has a unique descriptor.
This descriptor identifies a transport stream independently of transmission path and
frequency.
Demux state
Demultiplexer status. The demultiplexer must adapt its signal processing clock to the
clock rate of the input signal. The necessary information for this is derived from the
MPEG-input signal. After successful syncronization the message “sync ok” occurs.
Introduction
IRD 8500/..
Intergrated Receiver Decoder
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