Introduction and Applications
ProTelevision Technologies
PT 5780 DVB-T Modulator
Instruction Manual
Revision 3.11
2-4
2.3
Transport Stream Inputs
The standard version of the PT 5780 DVB-T modulator is provided with two serial (ASI) inputs.
By non-hierarchical mode the active input is selected either via the front panel or the remote
control. By hierarchical mode one input is assigned to the high priority stream and the other
input is assigned to the low priority stream. The inputs accept an MPEG transport stream
according to the DVB recommendation. Both 188 and 204 byte transport packets are supported
(in the 204 byte mode the last 16 bytes are always overwritten by the Reed-Solomon
redundancy data generated by the modulator). The available data rate for transmission is stated
in the tables below in accordance with the selected constellation, code rate and guard interval.
Please notice that separate tables applies to 8MHz , 7MHz, and 6MHz bandwidth respectively.
By hierarchical mode 64 QAM constellation and 16QAM constellation can be selected. The
available data rate is divided between the
high priority
channel and the
low priority
channel. The
bit rate for the
high priority
channel is equal to the capacity stated in the QPSK section of the
applicable table irrespective of the constellation chosen. For the
low priority
channel the
capacity depends on the chosen constellation (64Qam or 16QAM). By 64QAM constellation the
capacity of the hierarchical
low priority
channel is equal to the capacity stated in the 16QAM
section of the applicable table. By 16QAM constellation the capacity of the hierarchical
low
priority
channel is equal to the capacity stated in the QPSK section of the applicable table.
In Table 2-1 the maximum useful bit rates are indicated for all valid transmission modes in an
8 MHz system.
Modulation
Code rate
Guard interval
1/4
1/8
1/16
1/32
½
4,98
5,53
5,85
6,03
2/3
6,64
7,37
7,81
8,04
QPSK
¾
7,46
8,29
8,78
9,05
5/6
8,29
9,22
9,76
10,05
7/8
8,71
9,68
10,25
10,56
½
9,95
11,06
11,71
12,06
2/3
13,27
14,75
15,61
16,09
16-QAM
¾
14,93
16,59
17,56
18,10
5/6
16,59
18,43
19,52
20,11
7/8
17,42
19,35
20,49
21,11
½
14,93
16,59
17,56
18,10
2/3
19,91
22,12
23,42
24,13
64-QAM
¾
22,39
24,88
26,35
27,14
5/6
24,88
27,65
29,27
30,16
7/8
26,13
29,03
30,74
31,67
Table 2-1 Available data rate for 8MHz DVB-T
Summary of Contents for PT 5780
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