Digital Signal Processing Reference
In-Depth Information
27.2 Object Carousels
DSM-CC sections have already been discussed in detail in the DVB-H sec-
tion. DSM-CC sections are table-like structures and are considered to be
private sections according to MPEG-2 Systems. The basic structure of a
DSM-CC (Fig. 27.2.) section corresponds to the structure of a so-called
long section with a checksum at the end. A DSM-CC section has a length
of up to 4 kbytes and begins with a table_ID in the range of 0x3A ... 0x3E.
This is followed by the section header with version administration, already
discussed in detail in other chapters. Data services such as object carousels
or general datagrams or IP packets as in DVB-H (MPE, multiprotocol en-
capsulation) are then transmitted in the actual trunk of the section. The ta-
ble_ID shows the type of data services involved.
Table_ID's:
•
0x3A and 0x3C provide for the broadcasting of object/data carou-
sels
•
0x3D provides for the signalling of stream events
•
0x3E provides for the transmission of datagrams or IP packets
DDB
DII
DDB
DDB
DDB
DDB
DDB
Logical
entry
point
DII
DSI
DDB
DDB
Transmission
sequency
DSI = Download Server Initializing
DII = Download Info Identification
DDB = Data Download Block
Fig. 27.3.
Principle of an object carousel
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