SIST EN 62298-2:2006

Teleweb application -- Part 2: Delivery methods

This part of IEC 62298 specifies the transmission layer of TeleWeb. TeleWeb services can be broadcast in a number of different ways, for example, VBI, DVB, DAB, etc., and to a variety of decoder types, for example, TVs, portable decoders, PCs, etc. This standard specifies the transmission layer for VBI and DVB broadcasts.

TeleWeb-Anwendung -- Teil 2: Übertragungsverfahren

Application Teleweb -- Partie 2: Méthodes de distribution

specifies the transmission layer of TeleWeb for VBI and DVB broadcasts

Televizijski splet (teleweb) – 2. del: Dobavne metode (IEC 62298-2:2005)

General Information

• Status: Published
• Publication Date: 31-Dec-2005
• ICS: 33.170 - Television and radio broadcasting
• ICS: 35.240.95 - Internet applications
• Technical Committee: AVM - Audio, video and multimedia systems and equipment
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jan-2006
• Due Date: 01-Jan-2006
• Completion Date: 01-Jan-2006
• Ref Project: EN 62298-2:2005 - Teleweb application - Part 2: Delivery methods

Standards Content (Sample)

SLOVENSKI SIST EN 62298-2:2006

STANDARD
januar 2006
Televizijski splet (teleweb) – 2. del: Dobavne metode (IEC 62298-2:2005)
(istoveten EN 62298-2:2005)
Teleweb application – Part 2: Delivery methods (IEC 62298-2:2005)
ICS 33.170; 35.240.99 Referenčna številka
SIST EN 62298-2:2006(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

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EUROPEAN STANDARD EN 62298-2
NORME EUROPÉENNE
EUROPÄISCHE NORM June 2005

ICS 33.170; 35.240.99


English version


Teleweb application
Part 2: Delivery methods
(IEC 62298-2:2005)


Application Teleweb TeleWeb-Anwendung
Partie 2: Méthodes de distribution Teil 2: Übertragungsverfahren
(CEI 62298-2:2005) (IEC 62298-2:2005)






This European Standard was approved by CENELEC on 2005-06-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 62298-2:2005 E

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EN 62298-2:2005 - 2 -
Foreword
The text of document 100/923/FDIS, future edition 1 of IEC 62298-2, prepared by IEC TC 100, Audio,
video and multimedia systems and equipment, was submitted to the IEC-CENELEC parallel vote and
was approved by CENELEC as EN 62298-2 on 2005-06-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-03-01
-– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-06-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 62298-2:2005 was approved by CENELEC as a European
Standard without any modification.
__________

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- 3 - EN 62298-2:2005
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
1) 2)
IEC 62298-1 - Teleweb application EN 62298-1 2005
Part 1: General description

1) 2)
IEC 62298-3 - Part 3: Superteletext profile EN 62298-3 2005

3)
IEC 62298-4 - Part 4: Hyperteletext profile - -

1)
ISO/IEC 13818-1 - Information technology - Generic coding - -
of moving pictures and associated audio
information
Part 1: Systems

1)
ISO/IEC 13818-6 - Part 6: Extensions for DSM-CC - -

1)
ISO 639-2 - Codes for the representation of names of - -
languages
Part 2: Alpha-3 code

1)
ISO/IEC 8859-1 - Information technology - 8-bit single-byte - -
coded graphic character sets
Part 1: Latin alphabet No.1

1)
ETSI TR 101 154 - Digital Video Broadcasting (DVB); - -
Implementation guidelines for the use of
MPEG-2 Systems, Video and Audio in
satellite, cable and terrestrial
broadcasting applications

1)
ETSI TR 101 202 - Digital Video Broadcasting (DVB); - -
Implementation guidelines for Data
Broadcasting

1)
ETSI EN 300 421 - Digital Video Broadcasting (DVB); - -
Framing structure, channel coding and
modulation for 11/12 GHz satellite
services


1)
Undated reference.
2)
Valid edition at date of issue.
3)
To be published.

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EN 62298-2:2005 - 4 -
Publication Year Title EN/HD Year
1)
ETSI EN 300 429 - Digital Video Broadcasting (DVB); - -
Framing structure, channel coding and
modulation for cable systems

1)
ETSI EN 300 706 - Enhanced teletext specification - -

1)
ETSI EN 300 708 - Data transmission within Teletext - -

1)
ETSI EN 300 744 - Digital Video Broadcasting (DVB) - - -
Framing structure, channel coding and
modulation for digital terrestrial television
(DVB-T)

1)
ETSI EN 301 192 - Digital Video Broadcasting (DVB) - - -
DVB specification for data broadcasting,
V1.2.1

1)
ETSI EN 300 472 - Digital Video Broadcasting (DVB) - - -
Specification for conveying ITU-R system
B teletext in DVB bitstreams

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INTERNATIONAL IEC


STANDARD 62298-2





First edition
2005-05


TeleWeb application –
Part 2:
Delivery methods

 IEC 2005  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale W
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

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– 2 – 62298-2  IEC:2005(E)
CONTENTS
FOREWORD.3
INTRODUCTION.5

1 Scope.6
2 Normative references .6
3 Terms, definitions and abbreviations .7
3.1 Terms and definitions .7
3.2 Abbreviations .8
4 Delivery profiles .8
4.1 TeleWeb delivered via Teletext packets in VBI lines .8
4.2 TeleWeb delivered via PES packets in an MPEG-2 TS .9
4.3 TeleWeb delivered via DSM-CC sections in an MPEG-2 TS .10
4.4 TeleWeb delivered via other methods.10
5 Transport layer protocols.10
5.1 DSM-CC data carousel.10
5.2 Interaction channel.25
6 TeleWeb DSM-CC transmission via Teletext.29
6.1 Transmission of data carousels .29
6.2 Transmission protocol .29
6.3 Teletext packet format.30
7 Signalling TeleWeb in DVB.31
7.1 Signalling in the program map table (PMT).31
7.2 Signalling in the service description table (SDT).33
7.3 Service detection time .35
7.4 Multiple TeleWeb services.35
8 Transport in DVB.35
8.1 Transport in PES packets.35
8.2 Transport in DSM-CC sections .35

Annex A (informative)  CCITT CRC-16.36

Bibliography.37

Figure 1 – Delivery method for TeleWeb using Teletext packets in VBI lines.9
Figure 2 – Delivery method for TeleWeb using PES packets in an MPEG-2 TS .9
Figure 3 – Delivery method for TeleWeb using DSM-CC sections in an MPEG-2 TS .10
Figure 4 – Structure of one-layer and two-layer data carousels.11
Figure 5 – Format of transactionId field.13
Figure 6 – Format of the profile_flags byte.24
Figure 7 – Message transmission sequence.29

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62298-2  IEC:2005(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

TELEWEB APPLICATION –

Part 2: Delivery methods


FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62298-2 has been prepared by IEC technical committee 100:
Audio, video and multimedia systems and equipment.
This standard cancels and replaces IEC/PAS 62298 published in 2002.
This first edition constitutes a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
100/923/FDIS 100/961/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

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– 4 – 62298-2  IEC:2005(E)
IEC 62298 consists of the following parts, under the general title TeleWeb application:
Part 1: General description
Part 2: Delivery methods
Part 3: Superteletext profile
Part 4: Hyperteletext profile

The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under http://webstore.iec.ch in the
data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.

A bilingual version of this publication may be issued at a later date.

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62298-2  IEC:2005(E) – 5 –
INTRODUCTION
The aim of TeleWeb is to deliver World Wide Web-style content to the living-room TV to give
the viewer an enhanced television experience. A TeleWeb service broadcasts data files
containing text and high-definition graphics to suitable decoders. The data transmitted can be
closely linked to events within the accompanying TV programmes or can be more general in
nature to emulate a traditional, but higher definition, superteletext service. Different profiles
are defined.
It is intended that TV-based decoders be implemented in a cost-effective manner without
recourse to the technology normally associated with personal computers. In part, this is
achieved by limiting the number of different types of multimedia data that can be used within a
service. By careful design of the user interface, decoder manufacturers will be able to offer
easy-to-use equipment for accessing TeleWeb services without requiring the consumer to be
computer-literate. In addition, they will be able to customize their products to differentiate
them from those of their competitors.
This standard focuses on the transmission layer.

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– 6 – 62298-2  IEC:2005(E)
TELEWEB APPLICATION –

Part 2: Delivery methods



1 Scope
This part of IEC 62298 specifies the transmission layer of TeleWeb.
TeleWeb services can be broadcast in a number of different ways, for example, VBI, DVB,
DAB, etc., and to a variety of decoder types, for example, TVs, portable decoders, PCs, etc.
This standard specifies the transmission layer for VBI and DVB broadcasts.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 62298-1: TeleWeb application – Part 1: General description
IEC 62298-3: TeleWeb application – Part 3: Superteletext profile
1
IEC 62298-4: TeleWeb application – Part 4: Hyperteletext profile
ISO/IEC 13818-1, Information technology − Generic coding of moving pictures and associated
audio information: Systems
ISO/IEC 13818-6, Information technology − Generic coding of moving pictures and associated
audio information − Part 6: Extension for DSM-CC
ISO 639-2, Codes for the representation of names of languages – Part 2: Alpha-3 code
ISO 8859-1, Information technology − 8-bit single-byte coded graphic character sets − Part 1:
Latin alphabet No. 1
ETSI TR 101 154: V1.4.1, Digital Video Broadcasting (DVB); Implementation guidelines for
the use of MPEG-2 Systems, Video and Audio in satellite, cable and terrestrial broadcasting
applications
ETSI TR 101 202, Implementation guidelines for data broadcasting, V1.1.1
ETSI EN 300 421, Digital Video Broadcasting (DVB); Framing structure, channel coding and
modulation for 11/12 GHz satellite services
ETSI EN 300 429, Digital Video Broadcasting (DVB); Framing structure, channel coding and
modulation for cable systems
———————
1
To be published.

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62298-2  IEC:2005(E) – 7 –
ETSI EN 300 706, Enhanced Teletext Specification
ETSI EN 300 708, Television Systems; Data Transmission within Teletext
ETSI EN 300 744, Digital Video Broadcasting (DVB); Framing structure, channel coding and
modulation for digital terrestrial television
ETSI EN 301 192, Digital Video Broadcasting (DVB); DVB specification for data broadcasting,
V1.2.1
ETSI ETS 300 472, Digital Video Broadcasting (DVB); Specification for conveying ITU-R
System B Teletext in DVB bit streams
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of the present document, the following terms and definitions apply.
3.1.1
bit ordering
in all schematics, numeric values ordered with the most significant bit at the left-hand side
and the least significant bit at the right-hand side
3.1.2
conditional access (CA)
mechanism by which user access to service components can be restricted
3.1.3
Independent Data Line (IDL)
stand-alone Teletext packet containing both control and application data. It does not form part
of a Teletext page. The packet address is either 30 or 31
3.1.4
module
when broadcast within a DSM-CC data carousel, the contents of a file and its attributes (for
example, file type, creation date, etc.) are transmitted separately. The file itself is carried by a
number of DDB messages and its attributes appear as descriptors within its module loop
within a DII control message
3.1.5
signed integer
positive or negative integer value, in decimal notation. The first digit is preceded by a
mandatory plus (+) or minus (–) symbol with no white space between the symbol and the first
digit
3.1.6
text string
sequence of displayable Latin-1 characters
3.1.7
unsigned integer
integer value, in decimal notation, not preceded by a plus (+) or minus (–) symbol

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– 8 – 62298-2  IEC:2005(E)
3.2 Abbreviations
BSLBF Bit String, Left Bit First
CA Conditional Access
CRC Cyclic Redundancy Check
DAB Digital Audio Broadcasting
DDB Download Data Block message
DII Download Info Indication message
DSI Download Server Initiate message
DSM-CC Digital Storage Media Command and Control
DVB Digital Video Broadcasting
ETS European Telecommunication Standard
HTML Hyper Text Mark-up Language
IDL Independent Data Line
IEC International Electrotechnical Commission
ISO International Organisation for Standardization
LSB Least Significant Bit
MJD Modified Julian Date
MPEG Moving Picture Experts Group
MSB Most Significant Bit
OSI Open Systems Interconnection
PES Packetized Elementary Stream
PID Packet Identifier
PMT Program Map Table
RFC Internet Requests for Comments
RPCHOF Remainder Polynomial Coefficient, Higher Order First
SDT Service Description Table
TS Transport Stream
UIMSBF Unsigned Integer Most Significant Bit First
URL Uniform Resource Locator
UTC Universal Time Coordinated
VBI Vertical Blanking Interval
4 Delivery profiles
There are several ways in which a TeleWeb application can be delivered (see Figure 1 in
IEC 62298-1). For the purposes of this document, a delivery profile specifies layers 1 to 4 of
the OSI seven-layer model.
4.1 TeleWeb delivered via Teletext packets in VBI lines
Figure 1 shows layers 1 to 4 of the OSI seven-layer model for delivering a TeleWeb service
via Teletext packets. The application files are formed into a DSM-CC data carousel at the
transport layer, as defined in 5.1. The components of the carousel are then encapsulated in
independent Teletext data packets (see 6.3). These are transmitted in the VBI lines of an
analog TV signal as described in ETSI EN 300 708.

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62298-2  IEC:2005(E) – 9 –

Layer  Generic content  TeleWeb specific content
Layer 4: Arranging the data in a suitable way for transport DSM-CC data carousel:
Transport Blocks and modules
Descriptors
Groups and supergroups
Delimiting between messages
Forward error correction
Layer 3: Logical functions related to the multiplexing and Format B independent data line as defined in
Network demultiplexing of data packets belonging to ETSI EN 300 708 (“Packet 31”)
different communications flows:
Data channel addressing
Data packet sequencing
Layer 2: Logical functions related to data transmission: Normal Teletext packet format as defined in ETSI
Link EN 300 706
Byte synchronization
Error control (framing, misdirection and
 false detection)
Data formatting
Layer 1: Electrical transmission of the data signal Normal Teletext parameters as defined in ETSI
Physical EN 300 706
IEC  679/05
Figure 1 – Delivery method for TeleWeb using Teletext packets in VBI lines
4.2 TeleWeb delivered via PES packets in an MPEG-2 TS
Figure 2 shows layers 1 to 4 of the OSI seven-layer model for delivering a TeleWeb service
via Teletext packets. The application files are formed into a DSM-CC data carousel at the
transport layer, as defined in 5.1. The components of the carousel are then encapsulated in
independent Teletext data packets (see 6.3). These are transmitted in an MPEG-2 transport
stream using PES packets as described in ETSI ETS 300 472.
NOTE The data is prepared as it would be for transmitting in 4.1, added to a transport stream and treated as an
analog Teletext service.

Layer  Generic content  TeleWeb specific content
Layer 4: Arranging the data in a suitable way for transport Embedding in DSM-CC data carousel as specified
Transport in this standard

Layer 3: Logical functions related to the multiplexing and Embedding in Format B independent data line as
Network demultiplexing of data packets belonging to defined in ETSI EN 300 708 (“Packet 31”)
different communications flows:
Data channel addressing
Data packet sequencing
Layer 2: Logical functions related to the data transmission: Embedding in an MPEG-2 transport stream using
Link PES packets ETSI ETS 300 472
Byte synchronization
Error control (framing, misdirection and
 false detection)
Data formatting
Layer 1: Electrical transmission of the data signal Multiplexing and transmission according to DVB-T
Physical ETSI EN 300 744, DVB-C ETSI EN 300 429 or
DVB-S ETSI EN 300 421
IEC  680/05
Figure 2 – Delivery method for TeleWeb using PES packets in an MPEG-2 TS

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– 10 – 62298-2  IEC:2005(E)
4.3 TeleWeb delivered via DSM-CC sections in an MPEG-2 TS
Figure 3 shows layers 1 to 4 of the OSI seven-layer model for delivering a TeleWeb service
via DSM-CC sections. The application files are formed into a DSM-CC data carousel at the
transport layer, as defined in 5.1. The components of the carousel are then encapsulated in
DSM-CC sections in an MPEG-2 transport stream as described in ISO/IEC 13818-6.

Layer  Generic content  TeleWeb specific content
Layer 4: Arranging the data in a suitable way for transport Embedding in DSM-CC data carousel as specified
Transport in this standard

Layer 3: Logical functions related to the multiplexing and Embedding in DSM-CC sections as specified
Network demultiplexing of data packets belonging to in this standard
different communications flows:
Data channel addressing
Data packet sequencing
Layer 2: Logical functions related to the data transmission: Embedding in TS packets as specified in ISO/IEC
Link 13818-6
Byte synchronization
Error control (framing, misdirection and
 false detection)
Data formatting
Layer 1: Electrical transmission of the data signal Multiplexing and transmission according to DVB-T
Physical ETSI EN 300 744, DVB-C ETSI EN 300 429 or
DVB-S ETSI EN 300 421

IEC  681/05
Figure 3 – Delivery method for TeleWeb using DSM-CC sections in an MPEG-2 TS
4.4 TeleWeb delivered via other methods
This standard will be amended when necessary with other transport methods.
5 Transport layer protocols
This clause defines protocols for implementing the transport layer.
5.1 DSM-CC data carousel
5.1.1 Overview
The files of a TeleWeb service are organized in DSM-CC data carousels according to the
general principles defined in ISO/IEC 13818-6 and adapted for DVB applications as described
in ETSI EN 301 192 and ETSI TR 101 202. The DSM-CC data carousel specification
embodies the cyclic transmission of data to receivers. The data transmitted within a carousel
is first organized into “modules”, which are then subdivided into “blocks”. All the blocks of all
modules within the data carousel are of the same size, except for the last block of each
module, which may be of a smaller size. Each individual file in a TeleWeb service is treated
as a module. Modules can be clustered together to form a “group”. Likewise, groups can be
clustered to form “supergroups”.
The data carousel specification defined here uses three messages from the full data carousel
specification defined in ISO/IEC 13818-6. The data blocks are carried in DownloadDataBlock
(DDB) messages, while control over the modules is provided by DownloadInfoIndication (DII)
and DownloadServerInitiate (DSI) messages. Other DSM-CC messages listed in ISO/IEC
13818-6 are not used in the TeleWeb application and should be ignored by receivers
2
designed to this edition. All messages begin with the generic DSM-CC Message Header.
———————
2
ISO/IEC 13818-6, Clause 2.

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62298-2  IEC:2005(E) – 11 –
This header contains information about the type and size of the message. The maximum size
of any DII, DSI or DDB message shall be 4 084 bytes (including the message header).
A receiver shall ignore message fields marked “reserved” (ISO-designated) or “reserved for
future use” (ETSI-designated), noting that such fields may be variable in size.
A data carousel can have one or two layers of control information as shown in Figure 4. The
service provider is free to choose the most appropriate type. A receiver shall be able to work
with both types.

One-layer data carousel Two-layer data carousel
DSI TransactionId
gi gi
DII TransactionId DII TransactionId DII TransactionId
mi mi mi mi mi mi mi mi mi
DDB DDB DDB DDB DDB DDB DDB DDB DDB
DDB DDB DDB DDB DDB DDB DDB DDB DDB
DDB DDB DDB DDB
DDB
DDB
Block
DDB DDB DDB
Block
Module
Module
Group
Group
SuperGroup
DSI: DownloadServerInitiate message
DII: DownloadInfoIndication message
DDB: DownloadDataBlock message
gi: Group Information bytes
mi: Module Information bytes
IEC  682/05

Figure 4 – Structure of one-layer and two-layer data carousels
A one-layer carousel defines a single group. The top-level control message is a DII message.
This describes all the modules in the carousel. The module description includes a descriptor
loop that carries the attributes (for example, type, theme) of each module.
A two-layer carousel comprises a number of one-layer carousels. The top-level control
message is a DownloadServerInitiate message (DSI), 5.1.2.2. This describes th
...