IRT DDC-3480 User manual

3480-ddc.ib.rev8.doc page 1 of 20 17/10/2007
IRT Eurocard
Type DDC-3480
MPEG Transport Stream Adapter
Designed and manufactured in Australia
IRT can be found on the Internet at:
http://www.irtelectronics.com
I R T Electronics Pty Ltd A.B.N. 35 000 832 575
26 Hotham Parade, ARTARMON N.S.W. 2064 AUSTRALIA
National: Phone: [phone] Fax: [phone]
International: [phone] [phone]
Email: [e-mail]
Web: www.irtelectronics.com
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 2 of 20 17/10/2007
IRT Eurocard
Type DDC-3480
MPEG Transport Stream Adapter
Instruction Book
Table of Contents
Section Page
General description 3
Block diagram 4
Technical specifications 5
Technical description 6
Internal adjustments 7
Configuration 7
Links & options 7
Installation 8
Operational safety 8
Pre-installation 8
Installation in frame or chassis: 8
Connections: 9
Front & rear panel connector diagrams 9
Operation 10
Basic operation 10
Front indicators 10
Maintenance & storage 11
Warranty & service 11
Equipment return 11
Characteristics of signal types 12
Coding characteristics 12
G.703 12
Synchronous Parallel Interface 12
Asynchronous Serial Interface 13
MPEG-2 transport layer coding 14
Electrical characteristics 16
G.703 16
SPI 17
ASI 17
References 18
Glossary of terms 19
Drawing index 20
This instruction book applies to units later than S/N 9900000.
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.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-3470 provides facilities for changing certain coding features of the MPEG transport stream to
ensure compatibility between signals.
Note: The DDC-3470 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-3470 /34 SPI SPI ASI
/45 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

3480-ddc.ib.rev8.doc page 4 of 20 17/10/2007
Applications:
• Block length indication and error detection.
• Interface to test equipment.
• Interfacing to Telecoms switched data network.
• Interfacing various MPEG2 TS formats.
• Interleaving or de-interleaving. *
• Reed Solomon insertion & correction. *
• Spectrum dispersion correction. *
• Signal monitoring for remote alarm indications.
*DDC-3470 only.
Block diagram
DDC-3480
8B
Alarms & Indications
188 BYTE BLOCK
204 BYTE BLOCK
SYNC ERROR
INPUT LOSS
10B
NRZ
G.703
ASI
(270 Mb/s) coax
Input Output
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 5 of 20 17/10/2007
DDC-3480 Technical Specifications
(Preliminary)
Input:
Type 1 x ASI, BNC connector.
75Ω, 800 mVp-p,
Data rate 1.5 to 3 Mb/s (DDC-3480/2)
Data rate 6 to 12 Mb/s (DDC-3480/8)
Data rate 22 to 48 Mb/s (DDC-3480/34 & DDC-3480/45)
Output:
Type 1 x Reclocked unframed G.703 2 Mb/s (DDC-3480/2)
8 Mb/s (DDC-3480/8)
34 Mb/s (DDC-3480/34)
45 Mb/s (DDC-3480/45)
Data rate out = data rate of ASI input.
BNC standard connector - 1.6/5.6 optional.
Alarm:
General alarm Sync error / input loss/ power loss.
1 set N/O or 1 set N/C contacts, set by on board link.
2 pin 0.1" IDC male connector.
Power Requirements 28 Vac CT (14-0-14) or ±16 Vdc.
Power consumption <5 VA.
Other:
Temperature range 0 - 50° C ambient
Mechanical Mounts in IRT FRU-1030 1 RU 19" rack chassis with input, output and power
connections on the rear panel.
Finish: Front panel Grey enamel, silk-screened black lettering & red IRT logo.
Rear assembly Detachable silk-screened PCB with direct mount connectors to Eurocard and
external signals.
Dimensions 6 HP x 3 U x 220 mm IRT Eurocard.
Supplied accessories Rear connector assembly including matching connector for alarm output.
Due to our policy of continuing development, these specifications are subject to change without notice.
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 6 of 20 17/10/2007
Technical description
The DDC-3480 converts ASI to unframed G703. This module does not perform any processing (e.g. RS coding,
interleaving scrambling etc) but rather serialises the SPI input detects MPEG TS sync. This module is a complement
of the DDC-3460.
The module does not change the data rate and so for a valid G.703 fixed data rate the ASI input data rate must be at
the correct G.703 rate to obtain a valid G.703 output.
ASI Input
The ASI cable input is via a 75 Ohm BNC connector. ASI operates at 270 Mbit/s and uses 8B/10B coding with
K28.5 stuffing bytes. The DDC-3480 removes the K28.5 stuffing bytes to return a signal at the encoding data rate.
As all stuffing bytes are removed it is apparent that the encoded data rate must exactly match the designated G.703
data rate for a valid G.703 signal to be presented at the output.
G.703 Output
The G.703 output is the processed TS format. The G.703 output is disabled during loss of ASI input.
Input Loss Alarms
The Input Loss Alarm will be asserted in the absence of a valid ASI input.
Input TS Sync Error
After 2 consecutive TS syncs are missed a TS Sync Error is deemed to have occurred. The Sync error is reset only
after 5 consecutive TS syncs have been detected. The SYNC Error LED lights when a Sync error has been detected
and remains lit for approximately 300 ms after the Sync error has been reset.
188 TS Sync length indicator
If the number of bytes between TS syncs is 188 then the 188 LED lights.
204 TS Sync length indicator
If the number of bytes between TS syncs is 204 then the 204 LED lights.
Alarm relay
Alarm outputs are available on the rear assembly using the J 3 connector. N/O & N/C outputs can be selected using
LK 6. The relay is triggered upon loss of input or sync error. The N/O contact is preferred as it switches upon loss
of power or removal of the DDC-3480 from its rear assembly.
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 7 of 20 17/10/2007
Internal adjustments
The following adjustable resistors are factory set. They should not be adjusted by the user. The following
information is included for general information purposes only. Any adjustment of these controls without factory test
facilities is likely to render inoperable the corresponding section of the module.
RV 2 G.703 clock phase adjust.
RV 3 G.703 clock recovery bias.
Configuration
Links & options:
Warning:
Some of the following links are for factory use only during set-up and should not be changed.
Links may be changed without disconnecting power. However, when any link is changed, normal decoding of the
MPEG TS will be disturbed. The time taken before normal decoding resumes is dependent on the decoder in use
and may be up to five seconds.
Note: The DDC-3480 is available for different G.703 rates. The changes necessary to convert from one rate to
another involve changing firmware, crystals and other components in addition to setting links detailed below. After
making these changes, the whole module must be tested for accuracy of the G.703 output. The scope of these
changes is such that they cannot be accomplished outside the factory.
Indiscriminate changing of the following links may make the whole module inoperable.
LK 1: OUT Reserved factory setup
LK 2: OUT Reserved factory setup
LK 3: OUT Reserved factory setup
LK 4: OUT Reserved factory setup
LK 5: OUT DS3 shaped output for <225 feet DDC-3480/45
IN DS3 unshaped output for >225 feet DDC-3480/45
LK 6: J 2 Alarm relay output
LK 7: OUT B3ZS G.703 coding for DDC-3480/45
IN HDB3 G.703 coding for DDC-3480/34
LK 8: OUT Reserved future use
LK 9: OUT Reserved factory setup
J 7: This is not a series of links!
These pins are reserved for factory testing of the microprocessor whilst in circuit.
Linking these pins may result in permanent damage to the module.
1 2
LK 6
NO NC
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 8 of 20 17/10/2007
Installation
Operational Safety:
WARNING
Operation of electronic equipment involves the use of voltages and currents that
may be dangerous to human life. Note that under certain conditions dangerous
potentials may exist in some circuits when power controls are in the OFF position.
Maintenance personnel should observe all safety regulations.
Do not make any adjustments inside equipment with power ON unless proper
precautions are observed. All internal adjustments should only be made by suitably
qualified personnel. All operational adjustments are available externally without the
need for removing covers or use of extender cards.
Pre-Installation:
Handling:
This equipment may contain or be connected to static sensitive devices and proper static free handling precautions
should be observed.
Where individual circuit cards are stored, they should be placed in antistatic bags and proper antistatic procedures
should be followed when inserting or removing cards from these bags.
Power:
AC mains supply: Ensure that operating voltage of unit and local supply voltage match and that correct
rating fuse is installed for local supply.
Earthing:
Particular care should be taken to ensure that the frame is connected to earth for safety reasons.
Signal earth: For safety reasons a connection is made between signal earth and chassis earth. No attempt should be
made to break this connection.
Installation in frame or chassis:
The 3400 series of modules may only be mounted in IRT’s FRU-1030 type 1 RU chassis/PSU. This chassis may
house either one or two of the cards in the series.
The rear assembly should be attached first. Power for the module is connected via a short flying lead that connects
to the inside of the rear assembly on a three pin IDC connector. This should be connected first.
The rear assembly should then be aligned with the mounting holes on the rear of the chassis taking care to ensure
that the power connection lies as flat as possible against the bottom of the chassis. The rear assembly is then fixed to
the chassis using the two M2.5 screws provided.
Before inserting the main module check that the power lead is lying flat against the chassis floor. Failure to do this
may result in the module connector being fouled by this lead. If the lead is not flat, it may be coaxed into position
by a ruler inserted through the front module opening.
The module is then inserted in the frame by gently aligning the edges of the printed circuit board into the slots in the
guide rails and pushing it home.
Final tightening of the two front securing screws ensures good mating of the module with the rear assembly. If the
module does not appear to seat properly, do not force it. Withdraw the module, check the position of the power lead
and try again.
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 9 of 20 17/10/2007
Connections:
Signal connections:
ASI input:
This BNC input is terminated in 75 Ohms. Input cable compensation is automatic for up to 300 metres of high
quality 75 Ohm coaxial cable (Belden 8281 or 1694A equivalent). No adjustments are required.
G.703 output:
This BNC output has a 75 Ohms characteristic output impedance. Only high quality 75 Ohm coaxial cable (Belden
8281 or 1694A equivalent) should be used. Cable must be terminated in 75 Ohms at the connected load.
For the DDC-3480/34 no other adjustments are required.
For the DDC-3480/45 a choice of shaped or unshaped output is available. This is set by link LK 5 and should be set
to correspond to the length of cable connected to the output. This is necessary only if a shaped characteristic is
required for short cable lengths. Where the connected equipment has automatic equalisation (such as IRT DA’s and
converters) this is not required.
LK 5: OUT DS3 shaped output for <225 feet DDC-3480/45
IN DS3 unshaped output for >225 feet DDC-3480/45
Alarm connections:
J 3 Alarm relay output
Front & rear panel connector diagrams
The following front panel and rear assembly drawings are not to scale and are intended to show relative positions of
connectors, indicators and controls only.
3480
ALARM
G703 OUT
A
SI IN
1 2 1 2
LK 6
NO NC
INPUT
SYNC 204
188
DC
DDC-3480
N140
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 10 of 20 17/10/2007
Operation
Basic Operation:
Apart from the DDC-3470 (see below), there are no operational controls for these modules. Setting up consists only
of connecting the input and selected output. Once this is done the front panel indicators should react and the output
should present the correct format signal.
Any change in signal will be indicated by the front panel LED’s and or alarm output as outlined below.
Front indicators:
Input loss alarm:
This LED lights when no data transmission is detected at the input for a given time. MPEG-2
TS always contain a sync byte every 204 or 188 bytes irrespective of data content. Therefore,
if 2040 or more, consecutive 1’s or 0’s are been detected; then the input is deemed lost.
Sync loss alarm:
This LED lights for at least 300 ms when two or more MPEG-2 TS sync bytes are absent. The LED extinguishes
when five or more correct SYNC bytes are detected.
188 byte indicator:
This LED lights when a valid MPEG-2 TS stream containing 188 bytes between sync bytes is detected.
204 byte indicator:
This LED lights when a valid MPEG-2 TS stream containing 204 bytes between sync bytes is detected.
INPUT
SYNC
188
204
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 11 of 20 17/10/2007
Maintenance & storage
Maintenance:
No regular maintenance is required.
Care however should be taken to ensure that all connectors are kept clean and free from contamination of any kind.
This is especially important in fibre optic equipment where cleanliness of optical connections is critical to
performance.
Storage:
If the equipment is not to be used for an extended period, it is recommended the whole unit be placed in a sealed
plastic bag to prevent dust contamination. In areas of high humidity a suitably sized bag of silica gel should be
included to deter corrosion.
Where individual circuit cards are stored, they should be placed in antistatic bags. Proper antistatic procedures
should be followed when inserting or removing cards from these bags.
Warranty & Service
Equipment is covered by a limited warranty period of three years from date of first delivery unless contrary
conditions apply under a particular contract of supply. For situations when “No Fault Found” for repairs, a
minimum charge of 1 hour’s labour, at IRT’s current labour charge rate, will apply, whether the equipment is within
the warranty period or not.
Equipment warranty is limited to faults attributable to defects in original design or manufacture. Warranty on
components shall be extended by IRT only to the extent obtainable from the component supplier.
Equipment return:
Before arranging service, ensure that the fault is in the unit to be serviced and not in associated equipment. If
possible, confirm this by substitution.
Before returning equipment contact should be made with IRT or your local agent to determine whether the
equipment can be serviced in the field or should be returned for repair.
The equipment should be properly packed for return observing antistatic procedures.
The following information should accompany the unit to be returned:
1. A fault report should be included indicating the nature of the fault
2. The operating conditions under which the fault initially occurred.
3. Any additional information, which may be of assistance in fault location and remedy.
4. A contact name and telephone and fax numbers.
5. Details of payment method for items not covered by warranty.
6. Full return address.
7. For situations when “No Fault Found” for repairs, a minimum charge of 1 hour’s labour will apply,
whether the equipment is within the warranty period or not. Contact IRT for current hourly rate.
Please note that all freight charges are the responsibility of the customer.
The equipment should be returned to the agent who originally supplied the equipment or, where this is not
possible, to IRT direct as follows.
Equipment Service
IRT Electronics Pty Ltd
26 Hotham Parade
ARTARMON
N.S.W. 2064
AUSTRALIA
Phone: [phone] Fax: [phone]
Email: [email protected]
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 12 of 20 17/10/2007
Characteristics of signal types
Coding characteristics
G.703:
The HDB3 (High Density Bi-polar of order 3) code as defined in G.703 for 34,368 Kbits/s is as follows:
Binary 1 bits are represented by alternate positive and negative pulses and binary 0 bits by spaces.
Exceptions are made when strings of successive 0 bits occur in the binary signal.
Each block of 4 successive zeros is replaced by 000V or B00V where B is an inserted pulse of the correct
polarity and V is an inserted pulse violating the polarity rule. The choice of 000V or B00V is made so that
the number of B pulses between consecutive V pulses is odd so that successive V pulses are of alternate
polarity and so no DC component is introduced.
The B3ZS (Bipolar with Three Zero Substitution) (Also designated HDB2 - High Density Bi-polar of order 2) code
as defined in G.703 for 44,736 Kbits/s is as follows:
Binary 1 bits are represented by alternate positive and negative pulses and binary 0 bits by spaces.
Exceptions are made when strings of successive 0 bits occur in the binary signal.
Each block of 3 successive zeros is replaced by 00V or B0V. The choice of 00V or B0V is made so that the
number of B pulses between consecutive V pulses is odd, so that successive V pulses are of alternate polarity
and so no DC component is introduced.
Synchronous Parallel Interface (SPI)
SPI is a system for parallel transmission of variable data rates. The data transfer is synchronised to the Byte clock of
the MPEG transport stream.
The data to be transmitted are MPEG-2 transport packets. The data signals are synchronised to the clock depending
on the transmission rate.
The parallel interface has three allowable transmission formats:
188 byte packets
204 Byte packets (188 data Bytes + 16 dummy Bytes)
204 byte packets (188 data Bytes + 16 additional valid Bytes)
The clock, data and synchronisation signals are transmitted in parallel. They comprise 8 data bits together with one
(MPEG-2) PSYNC signal and a DVALID signal.
The DVALID signal indicates in the 204 Byte mode that the additional space is filled with dummy Bytes.
All signals are synchronous to the clock signal. The signals are coded in NRZ form.
The clock is a square wave signal where the 0-1 transition represents the data transfer time. The clock frequency
depends on the transmission rate. The frequency corresponds to the useful bitrate of the MPEG2 transport layer and
shall not exceed 13.5 MHz.
Clock 1 pair
Data (0-7) 8 pair
TX DVALID 1 pair RX
PSYNC 1 pair
= 11 pair in total.
Electrical characteristics of the interface
Each of the eleven line drivers (source) has a balanced output and each line receiver (destination) a balanced input
employing LVDS drivers / receivers. All digital signal time intervals are measured between the half-amplitude
points.
Logic convention
A binary 1 is represented by the non-inverted output being positive with respect to the inverted output.
A binary 0 is represented by the non-inverted output being negative with respect to the inverted output.
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 13 of 20 17/10/2007
Asynchronous Serial Interface (ASI)
The Asynchronous Serial Interface (ASI) provides a system for serial encoded transmission of different data rates
with a constant transmission rate of 270 Mbit/s.
The ASI standard supports coaxial cable and multi-mode fibre-optic cable (using LED emitters).
ASI Protocol Architecture Description
The ASI protocol is divided into three architectural layers: Layer-0, Layer-1 and Layer-2.
MPEG Transport Packets form the top layer (Layer 2), and the bottom layers are based upon the Fibre Channel
Standard (Layers 1 and 0). Layer 2 is defined using the MPEG-2 Standard ISO/IEC 13818-1 (Systems). Layers 1
and 0 are based upon a subset of ANSI Standard X3T11/ Levels FC-1 and FC-0.
Layer-O: Physical Requirements
The physical Layer defines the transmission media, the drivers and receivers, and the transmission speeds. The
physical interface provides for both LED-driven multimode fibre and copper coaxial cable.
Line Rates and Bit Timing
The encoded line rate with the 8B/10B block code is 270 Mbit/s which results in a media transmission rate of
270 MBaud. At the transmitter, the serialisation is done using a fixed oscillator to establish this 270 MBaud rate
from which a phase-locked Byte clock is derived and used to shift in parallel Bytes.
Receivers recover the serial transmission clock. A phase-locked Byte clock is derived from this recovered serial bit
clock and is used to shift parallel Bytes out to Layer- 1 processing elements. It is required that the encoded line rate
shall be 270 MBaud ±100 ppm.
Layer-1 Data Encoding
The ASI Transmission Layer 1 deals with encoding/decoding aspects, which are independent of the transmission
medium characteristics. The encoding method utilised is specified in the fibre channel document X3T11
At Layer-1, Bytes are 8B/10B coded, which produces one 10-bit word for each 8-bit Byte presented.
The 8B/10B transmission coding provides for both a self checking capability and Byte synchronisation of the link.
The 10B transmission code is defined in terms of "disparity": the difference in the number of "1" bits and "0" bits in
the transmitted serial data stream. The disparity characteristics of the code maintain DC balance.
Special characters are defined as extra code points beyond the need to encode a Byte of data. One in particular is
used to establish Byte synchronisation in the ASI transmission link.
The 10-bit words are then passed through a parallel-to-serial converter, which operates at a fixed output bit-rate of
270 Mbit/s.. If the converter requests a new input word and the data source does not have one ready, a
synchronisation word is inserted. These sync words are ignored by receive equipment.
The resulting serial bit stream is passed to the output driver circuit for coaxial or fibre-optic cable.
Receive data arriving on a coaxial cable or fibre is first coupled to a circuit, which recovers clock and data.
Recovered serial data bits are passed to a 10B/8B decoder that converts the 10-bit transmission words back into the
8-bit Bytes originally transmitted. In order to recover Byte alignment, the 10B/8B decoder initially searches for
synchronisation words. Once found, the start of the synchronisation word marks the boundary of subsequent
received data words and establishes proper Byte-alignment of decoder output Bytes.
NOTE - The ASI coding is sensitive to logical inversion of the transmitted bits. Therefore, to ensure correct
operation, care must be taken that equipment interface circuitry of the non-inverting type is used.
The Bit-Error-Rate (BER) Performance shall be less than one part in 1013.
Layer-2 Transport Protocol
The ASI Transmission Layer-2 standard uses the MPEG-2 Transport Stream Packet as defined in ISO/IEC 13818-1
(Systems) as its basic message unit. Optionally the RS coded Byte structure as specified in ETS 300 429 is also
supported.
Data to be transmitted are presented in Byte-synchronised form as MPEG-2 Transport packets. Transport Packets
may be presented to Layer-2 either as a burst of contiguous Bytes, or as individual Bytes spread out in time.
The ASI Interface Layer-2 definition employs the MPEG-2 Transport Stream packet syntax with the additional
requirement that every Transport Packet shall be preceded with at least two synchronisation characters. This allows
re-sync within one transport packet in the event that a line disturbance causes loss of sync.
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 14 of 20 17/10/2007
MPEG-2 transport layer coding
The MPEG-2 Transport Layer is defined in ISO/IEC DIS 13818-1 [1]. The Transport Layer for MPEG-2 data is
comprised of packets having 188 Bytes, with one Byte for synchronisation purposes, three Bytes of header
containing service identification, scrambling and control information, followed by 184 Bytes of MPEG-2 or
auxiliary data.
The framing organisation is based on the MPEG-2 transport packet structure.
Channel coding
To achieve the appropriate level of error protection required for cable transmission of digital data, a FEC based on
Reed-Solomon encoding is used. In contrast to the Baseline System for satellite described in ETS 300 421, no
convolutional coding is applied to cable transmission. Protection against burst errors is achieved by the use of Byte
interleaving.
Randomisation for spectrum shaping (Scrambling)
The System input stream is organised in fixed length packets (see figure 2), following the MPEG-2 transport
multiplexer. The total packet length of the MPEG-2 transport MUX packet is 188 Bytes. This includes 1 sync-word
Byte (i.e. 47HEX). The processing order at the transmitting side shall always start from the MSB (i.e. 0) of the sync
word-Byte (i.e. 01000111).
In order to comply with the System for satellite, (see ETS 300 421) and to ensure adequate binary transitions for
clock recovery, the data at the output of the MPEG-2 transport multiplex is randomised.
The polynomial for the Pseudo Random Binary Sequence (PRBS) generator is:
1 + X14 + X15
Loading of the sequence 100101010000000" into the PRBS registers, is initiated at the start of every eight transport
packets. To provide an initialisation signal for the de-scrambler, the MPEG-2 sync Byte of the first transport packet
in a group of eight packets is bitwise inverted from 47HEX to B8HEX.
The first bit at the output of the PRBS generator is applied to the first bit of the first Byte following the inverted
MPEG-2 sync Byte (i.e.B8HEX). To aid other synchronisation functions, during the MPEG-2 sync Bytes of the
subsequent 7 transport packets, the PRBS generation continues, but its output is disabled, leaving these Bytes
unrandomised. The period of the PRBS sequence shall therefore be 1,503 Bytes.
The randomisation process is active also when the modulator input bit-stream is non-existent, or when it is non-
compliant with the MPEG-2 transport stream format (i.e. 1 sync Byte + 187 packet Bytes). This is to avoid the
emission of an unmodulated carrier from the modulator.
Reed-Solomon coding
Following the energy dispersal randomisation process, systematic shortened Reed-Solomon encoding is performed
on each randomised MPEG-2 transport packet, with T = 8. This means that 8 erroneous Bytes per transport packet
can be corrected. This process adds 16 parity Bytes to the MPEG-2 transport packet to give a codeword (204, 188).
NOTE: RS coding is applied also to the packet sync Byte, either non-inverted (i.e. 47HEX)or inverted (i.e. B8HEX).
Code Generator Polynomial: g(x) = (x+λ0)(x+λ1)(x+λ2) ... (x+λ15), where λ= 02HEX
Field Generator Polynomial: p(x) = x8 + x4 + x3 + x2 + 1
The shortened Reed-Solomon code is implemented by appending 51 Bytes, all set to zero, before the information
Bytes at the input of a (255, 239) encoder; after the coding procedure these Bytes are discarded.
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 15 of 20 17/10/2007
Convolutional interleaving
Convolutional interleaving with depth I = 12 is applied to the error protected packets (see figure 2c). This results in
an interleaved frame.
The convolutional interleaving process is based on the Forney approach which is compatible with the Ramsey type
III approach, with I = 12. The Interleaved Frame is composed of overlapping error-protected packets and is
delimited by MPEG-2 sync Bytes (preserving the periodicity of 204 Bytes).
The interleaver may be composed of I = 12 branches, cyclically connected to the input Byte-stream by the input
switch. Each branch is a First In First Out (FIFO) shift register, with depth (Mj) cells (where M = 17 = N/I,
N = 204 = error protected frame length, I = 12 = interleaving depth, = branch index). The cells of the FIFO shall
contain 1 Byte, and the input and output switches is synchronised.
For synchronisation purposes, the sync Bytes and the inverted sync Bytes are always routed into the branch 0" of
the interleaver (corresponding to a null delay).
The de-interleaver is similar, in principle, to the interleaver, but the branch indexes are reversed (i.e. j = 0
corresponds to the largest delay). The de-interleaver synchronisation can be carried out by routing the first
recognised sync Byte into the "0" branch.
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 16 of 20 17/10/2007
Electrical characteristics:
Electrical characteristics CCITT G.703 2048 Kb/s:
Pair each direction One coaxial pair.
Test load impedance 75 Ωresistive.
Signal level 2.37 V.
Nominal pulse width 244 ns.
Code conversion HDB3.
Pulse shape Fig. 15/G.703.
Jitter at input port § 3 of recommendation G.823.
Jitter at output port § 2 of recommendation G.823.
Return loss at input ports:
51 KHz to 102 KHz 12 dB
102 KHz to 2048 KHz 18 dB
2048 KHz to 3072 KHz 14 dB
Electrical characteristics CCITT G.703 8448 Kb/s:
Pair each direction One coaxial pair
Test load impedance 75 Ωresistive
Signal level 2.37 V
Nominal pulse width 59 ns
Code conversion HDB3
Pulse shape Fig. 16/G.703
Jitter at input port § 3 of recommendation G.823
Jitter at output port § 2 of recommendation G.823
Return loss at input ports:
211 KHz to 422 KHz 12 dB
422 KHz to 8448 KHz 18 dB
8448 KHz to 12672 KHz 14 dB
Electrical characteristics CCITT G.703 34368 Kb/s:
Cable type Coaxial.
Impedance 75 Ω
Signal level 1.0 V
Nominal pulse width 14.55 ns
Code conversion HDB3
Pulse shape Fig. 17/G.703
Jitter at input port § 3 of recommendation G.823
Jitter at output port § 2 of recommendation G.823
Return loss at input ports:
860 KHz to 1720 KHz >12 dB
1720 KHz to 34368 KHz >18 dB
34368 KHz to 51550 KHz >14 dB
Electrical characteristics CCITT G.703 Shaped 44736 Kb/s:
Cable type Coaxial.
Impedance 75 Ω
Signal level
Power at 22368 KHz +1.8 dBm to +5.7 dBm.
Power at 44736 KHz >20 dBm below power at 22368 KHz.
Code conversion B3ZS
Pulse shape Fig. 14/G.703
Electrical characteristics CCITT G.703 Unshaped 44736 Kb/s:
Cable type Coaxial.
Impedance 75 Ω
Signal level 1.0 V
Nominal pulse width 14.55 ns
Code conversion B3ZS
Pulse shape Fig. 17/G.703
Jitter at input port § 3 of recommendation G.823
Jitter at output port § 2 of recommendation G.823
Return loss at input ports:
860 KHz to 1720 KHz >12 dB
1720 KHz to 34368 KHz >18 dB
34368 KHz to 51550 KHz >14 dB
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 17 of 20 17/10/2007
Electrical characteristics SPI:
Line Driver Characteristics (Source)
Output impedance 100 Ωmaximum
Common mode voltage 1.125 V to 1.375 V
Signal amplitude 247 mV to 454 mV
Rise and fall times < T/7, measured between the 20% and 80% amplitude points, with a 100 Ω
resistive load. The difference between rise and fall times shall not exceed T/20.
Line Receiver Characteristics (Destination)
Input impedance 90 Ω to 132 Ω
Maximum input signal 2.0 Vp-p
Minimum input signal 100 mVp-p
General Information on DVB-ASI
For transport, the 270 Mb/s stream may be fed through DA’s and switchers without regard for the underlying data
rate, thus simplifying system design.
Note that the ASI signal is polarity sensitive. Although most 270 Mb/s SDI DA’s and switchers will pass ASI
signals, the line drivers used usually have both inverted and non-inverted outputs. For ASI, only those outputs that
are non-inverted may be used.
Electrical characteristics ASI:
Transmitter output characteristics:
Output voltage 800 mVp-p ±10%.
Deterministic jitter <10% p-p.
Random jitter <8% p-p.
Rise/fall time (20-80%) <1.2 ns.
Receiver input characteristics:
Minimum sensitivity (D21.5 idle pattern) 200 mV
Maximum input voltage 880 mVp-p
s11 (range: 0.1 to 1.0 x bit rate) -17 dB
Minimum discrete connector return loss 15 dB (5 MHz - 270 MHz)
Coaxial link:
Impedance 75 Ohm
Equipment connector BNC female
(Electrical measurements made with 75 Ohm resistive termination.)
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 18 of 20 17/10/2007
References
ANSI Standard X3T1 1/ Levels FC-1 and FC-0.
DVB-PI-232 TM1449 Interfaces for CATV/SMATV Headends & similar Professional Equipment.
ETS 300 421. Digital broadcasting systems for Television, sound and data services; framing structure, channel
coding for 11/12 GHz satellite services.
ETS 300 429. Digital broadcasting systems for Television, sound and data services; framing structure, channel
coding and modulation for cable systems.
ETS 300 473. Digital broadcasting systems for Television, sound and data services; Satellite Master Antenna
Television (SMATV) distribution systems.
ISO/IEC 13818-1 (Systems). MPEG-2 Standard.
ITU-T Rec. G.703.
TM 1664 Rev 2 - DVB Interfaces for PDH Networks.
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 19 of 20 17/10/2007
Glossary of terms
8B/10B Eight to Ten Bit Conversion.
ASI Asynchronous Serial Interface.
ASI-C ASI Coaxial cable.
ASI-O ASI Fibre optic cable.
B3ZS Bipolar with Three Zero Substitution.
BB Baseband.
BER Bit Error Rate.
CCIR Comite Consultatif International des Radiocommunications.
CCITT Comite Consultatif International Telephonique et Telegraphique.
CPLD Custom Programmable Logic Device.
DJ Deterministic Jitter.
DTVC Digital Television by Cable.
DVB Digital Video Broadcasting.
DVG Digital Video Generator.
EBU European Broadcasting Union.
EBU European Broadcasting Union.
ETS European Telecommunication Standard.
ETSI European Telecommunications Standards Institute.
FEC Forward Error Correction.
FIFO First In First Out.
FPGA Field Programmable Gate Array.
G.703 ITU CCITT recommendation G.703.
HDB3 High Density Bi-polar of order 3.
IF Intermediate Frequency.
IRD Integrated Receiver Decoder.
ITU International Telecommunications Union.
LSB Least Significant Bit.
LVDS Low Voltage Differential Signalling.
Mb/s Megabits per second.
MPEG Moving Pictures Experts Group.
MPEG Motion Picture Experts Group.
MSB Most Significant Bit.
MSB Most Significant Bit.
MUX Multiplex.
NO Normally open contact set.
NC Normally closed contact set.
NRZ Non Return to Zero.
PDH Plesiochronic Digital Hierarchy.
PRBS Pseudo Random Binary Sequence.
QAM Quadrature Amplitude Modulation.
QEF Quasi Error Free.
QPSK Quarternary Phase Shift Keying.
R & S Rohde & Schwarz.
RF Radio Frequency.
RJ Random Jitter.
RS Reed Solomon.
SDI Serial Digital Interface.
SMATV Satellite Master Antenna Television.
SPI Synchronous Parallel Interface MPEG2.
SSI Synchronous Serial Interface.
TDM Time Division Multiplex.
TS Transport Stream.
TV Television.
IRT Communications
www.irtcommunications.com

3480-ddc.ib.rev8.doc page 20 of 20 17/10/2007
Drawing index
Drawing # Sheet # Description
804154 1 DDC-3480/45 ASI to G.703 circuit schematic
804154 2 DDC-3480/8 ASI to G.703 circuit schematic
IRT Communications
www.irtcommunications.com