ETSI
ETSI EN 302 769 V1.1.1 (2010
5.1.1 Input Formats
The input signals in terms of either single or multiple streams (one connected to each Mode Adaptation Module)
(see figure 1) shall be supplied to the Mode Adaptation Module(s). In the case of a Transport Stream (TS), the packet
rate will be a constant value, although only a proportion of the packets may correspond to service data and the
remainder may be Null Packets.
Each input stream (PLP) of the C2 System shall be associated with a modulation and FEC protection mode which is
statically configurable.
Each input PLP may take one of the following formats:
• Transport Stream (TS).
• Generic Encapsulated Stream (GSE) [i.2].
• Generic Continuous Stream (GCS) (a variable length packet stream where the modulator is not aware of the
packet boundaries).
• Generic Fixed-length Packetized Stream (GFPS); this form is retained for compatibility with DVB-S2, but it is
expected that GSE would now be used instead.
A Transport Stream shall be characterized by User Packets (UP) of fixed length O-UPL = 188 × 8 bits (one MPEG TS
packet), the first byte being a SYNC byte (47
HEX
) and shall be signalled in the BBHeader TS/GS field, see clause 5.1.6.
A GSE stream shall be characterized by variable length packets or constant length packets, as signalled within GSE
packet headers, and shall be signalled in the BBHeader by TS/GS field, see clause 5.1.6.
A GCS shall be characterized by a continuous bit-stream and shall be signalled in the BBHeader by TS/GS field and
UPL = 0
D
, see clause 5.1.6. A variable length packet stream where the modulator is not aware of the packet boundaries,
or a constant length packet stream exceeding 64 kbit, shall be treated as a GCS, and shall be signalled in the BBHeader
by TS/GS field as a GCS and UPL = 0
D
, see clause 5.1.6.
A GFPS shall be a stream of constant-length User Packets (UP), with length O-UPL bits (maximum O-UPL value
64 K), and shall be signalled in the BBHeader TS/GS field, see clause 5.1.6. O-UPL is the Original User Packet Length.
UPL is the transmitted User Packet Length, as signalled in the BBHeader.
5.1.2 Input Interface
The input interface sub-system shall map the input into internal logical-bit format. The first received bit will be
indicated as the Most Significant Bit (MSB). Input interfacing is applied separately for each single Physical Layer Pipe
(PLP), see figure 2(a).
The Input Interface shall read a data field, composed of DFL bits (Data Field Length), where:
0 <
DFL < (K
bch
- 80)
where K
bch
is the number of bits protected by the BCH and LDPC codes (see clause 6.1).
The maximum value of DFL depends on the chosen LDPC code, carrying a protected payload of K
bch
bits. The 10-byte
(80 bits) BBHeader is appended to the front of the data field, and is also protected by the BCH and LDPC codes.
The input interface shall either allocate a number of input bits equally to the available data field capacity, thus breaking
UPs in subsequent data fields (this operation being called "fragmentation"), or shall allocate an integer number of UPs
within the data field (no fragmentation). The available data field capacity is equal to K
bch
- 80. When the value of
DFL < K
bch
- 80, a padding field shall be inserted by the stream adapter (see clause 5.2) to complete the LDPC/BCH
code block capacity.