3471-ddc.ib.rev2.doc
page 3 of 20
17/10/2007
General description
The DDC-34XX series forms a family of data transcoders for converting between the commonly used MPEG2
Transport Stream formats by the broadcast industry for video distribution.
The series is a development of the previous 3200 series modules incorporating changes for EMC compliance and
simplification of product coding to cover the various fixed G.703 data rates.
MPEG2 propounded a method of data encoding without defining the physical transport layer. This was left to the
manufacturers to decide, with the result that a number of proprietary systems emerged with incompatible electrical
characteristics. Whilst some of these have quickly disappeared, there remain reasons for using particular systems for
some purposes.
Commonly used formats include:
SPI (Synchronous Parallel Interface MPEG2)
Unframed G.703 at 2, 8, 34 & 45 Mb/s
ASI-C (Asynchronous Serial Interface 270 Mb/s Coaxial cable)
ASI-O (Asynchronous Serial Interface 270 Mb/s Fibre optic cable)
In an effort to standardise, the DVB has recommended the use of the ASI format where possible.
However, it is often convenient to use Telecom data networks for transport. These generally use G.703 formats at
particular fixed rates.
Test instrument manufacturers, on the other hand, often prefer the use of SPI format, due to its lower processing
speed requirements.
The ASI-O interface is of limited usefulness, due to the specification of multimode fibre with only a short haul
capability. Optical transport of ASI can be better achieved by the use of IRT’s DVT/DVR-3210 single mode
SDI/ASI fibre optic link, which has a capability of transporting ASI signals more than 50 Km.
IRT’s 34XX series of adapters provide a modular approach to connecting between the different transport types.
The 34XX series find particular application in CATV Headends where equipment from different manufacturers uses
different formats. They may also be used for monitoring connections to test equipment.
In addition, the DDC-3471 provides facilities for changing certain coding features of the MPEG transport stream to
ensure compatibility between signals.
Note: The DDC-3471 allows Reed Solomon correction and the insertion or removal of interleaving and MPEG2
transport stream spectrum shaping randomisation. This makes it an ideal adjunct to test equipment or for matching
signal from various sources using different encoding options.
Product
Data rates
Input
DDC-3460
/34
G.703-E3
ASI
/45
G.703-DS-3
ASI
DDC-3471
2 to 60 Mb/s
SPI
SPI
ASI
DDC-3480
/34
ASI
G.703-E3
/45
ASI
G.703-DS-3
DDC-3330
1.5 to 50 Mb/s ASI
SPI
DDC-3340
1.5 to 50 Mb/s SPI
ASI
MFC-3465
/34
G.703-E3
ASI
/45
G.703-DS-3
ASI
MFC-3485
/34
ASI 1.5 to 30 Mb/s
SPI
G.703-E3
/45
ASI 1.5 to 39 Mb/s
SPI
G.703-DS-3
Outputs
Product Selection Chart
IRT
Communications
www.irtcommunications.com