Television systems; Data transmission within Teletext

Specification of the use of Teletext to carry non-Teletext services. It includes the transportation of data which is intended to provide the means to carry an Electronic Programme Guide (EPG); see JTC work item DE/JTC-EPG (ETS 300 707).

Televizijski sistemi – Prenos podatkov v sistemu Teletext

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6060 - National Implementation/Publication (Adopted Project)
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ETS 300 708 E1:2003
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SIST ETS 300 708 E1:2003
Televizijski sistemi – Prenos podatkov v sistemu Teletext
Television systems; Data transmission within Teletext
Ta slovenski standard je istoveten z: ETS 300 708 Edition 1
33.050.30 Oprema za teleks, teletekst, Equipment for telex, teletext,
telefaks telefax
33.170 Televizijska in radijska Television and radio
difuzija broadcasting
SIST ETS 300 708 E1:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ETS 300 708 E1:2003

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SIST ETS 300 708 E1:2003
ICS: 33.020
Key words: Broadcasting, data, TV, Teletext
Union Européenne de Radio-Télévision
European Broadcasting Union
Television systems;
Data transmission within Teletext
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet:
Tel.: +33 4 92 94 42 00 - Fax: +33 4 93 65 47 16
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1997. All rights reserved.

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ETS 300 708: March 1997
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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Foreword .5
1 Scope .7
2 Normative references.7
3 Definitions and abbreviations .7
3.1 Definitions .7
3.2 Abbreviations .8
4 Page Format - Clear.8
4.1 General points.8
4.2 Advantages.8
4.3 Disadvantages .8
4.4 Coding of the packets .8
4.4.1 Page header.9
4.4.2 Packets 1 to 23 (in future up to 25) .10 Transmission order.11 The Structure Header (SH).11 Packing the data into the pages .11
4.4.3 Packet 28 .12
4.5 Providing a service according to Page Format - Clear .12
4.5.1 General points on Page Format - Clear .13
4.5.2 Encoding scheme for electronic data transmission.13
5 Page Format - CA .13
5.1 General points.13
5.2 Advantages.13
5.3 Disadvantages .14
5.4 Method of coding .14
5.4.1 Teletext page data.15 Scrambled Data Pages.15 Pages containing Reformatted Data.15
5.4.2 The Page Key Packet.16 Service Mode bits .16 Service Identification.17 Continuity and Repeat Indicators.17 Packet Flags.17 Data Length .17 Scrambling Method.18 The Cyclic Redundancy Check (CRC) word.18
5.4.3 Terminal Equipment Addressing Pages.19 System Key Packet.19 Shared User Packets.19 Unique User Packets.20 Service/Page Link packets .21 Link to Independent Data Line Services.21
5.5 Security of Page Format - CA.21
5.5.1 Cipher feedback algorithm .21
5.5.2 One-way function.22
5.5.3 Text scrambling.23
6 Independent Data Lines (IDL) .23
6.1 General points.23
6.2 Advantages.23
6.3 Disadvantages .23
6.4 Methods of coding.23

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6.4.1 Designation code . 23 Transmission multiplexing. 23
6.4.2 Data Channel addressing . 23
6.5 IDL Format A. 24
6.5.1 Format Type (FT) . 24
6.5.2 Interpretation and Address Length (IAL). 24
6.5.3 Service Packet Address (SPA). 25
6.5.4 Repeat Indicator (RI) . 25
6.5.5 Continuity Indicator (CI) . 25
6.5.6 Data Length (DL) byte. 25
6.5.7 User Data Group. 25 Dummy bytes . 26
6.5.8 Cyclic Redundancy Check (CRC) word. 26 Check word generation . 26
6.5.9 Transmission sequence. 27
6.6 Datavideo format. 27
6.6.1 Packet address. 27
6.6.2 Control Bytes (CB). 27 Packet Continuity Indicator (CI) . 27
6.6.3 Masking indicator. 27
6.6.4 Packet type indicator . 28
6.6.5 User data group. 28
6.6.6 Cyclic Redundancy Check (CRC) word. 28 Check word generation . 28 Check result . 28
6.7 Low bit-rate audio. 28
6.7.1 Method of coding . 29 Decoder action. 29
6.7.2 Programme-related audio service . 29 Service Byte (SB). 29 Control Byte (CB) . 29 Audio data. 30
6.7.3 Programme independent audio service. 30 Service Byte (SB). 30 Control Byte (CB) . 30 Audio data. 30
7 IDL - CA (type A) . 30
7.1 General points. 30
7.2 Advantages . 31
7.3 Disadvantages. 31
7.4 Methods of coding. 31
7.4.1 Block Separator . 31
7.4.2 Block Formats. 31
7.4.3 Block Format A . 31 Block Types. 31 Primary Block Key Messages . 32 Secondary Block Messages and Scrambled User Data . 32 System-Key Message Block . 32 Shared-User Message Block . 32 Unique User Message Block. 33 Service Address Message Block - Independent Data
Service . 33 Service Address Message Block - Link to Page Format -
CA . 33
History. 34

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ETS 300 708: March 1997
This European Telecommunication Standard (ETS) has been produced by the Joint Technical Committee
(JTC) of the European Broadcasting Union (EBU), Comité Européen de Normalisation ELECtrotechnique
(CENELEC) and the European Telecommunications Standards Institute (ETSI).
NOTE: The EBU/ETSI JTC was established in 1990 to co-ordinate the drafting of ETSs in the
specific field of broadcasting and related fields. Since 1995 the JTC became a tripartite
body by including in the Memorandum of Understanding also CENELEC, which is
responsible for the standardization of radio and television receivers. The EBU is a
professional association of broadcasting organizations whose work includes the
co-ordination of its Members' activities in the technical, legal, programme-making and
programme-exchange domains. The EBU has Active Members in about 60 countries
in the European Broadcasting Area; its headquarters is in Geneva *.
* European Broadcasting Union
Case Postale 67
Tel: +41 22 717 21 11
Fax: +41 22 717 24 81
Transposition dates
Date of adoption: 7 March 1997
Date of latest announcement of this ETS (doa): 30 June 1997
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 December 1997
Date of withdrawal of any conflicting National Standard (dow): 31 December 1997

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1 Scope
This European Telecommunication Standard (ETS) describes the various ways in which Teletext may be
used to carry non-Teletext services. It should be used in conjunction with ETS 300 706 [1]. An example is
fully described in ETS 300 707 [2]. This ETS includes additional practical information on implementing a
data service of this type.
Hooks into existing Teletext services may be provided from within the application which is carried as a
non-Teletext service. A data broadcast application may be pointed to from the Magazine Inventory Page
(MIP) or it may be allocated a specific page number. A Code of Practice (CoP) shall ensure that services
destined for the consumer may be found quickly by "low-end" Teletext decoders but this is outside the
scope of this ETS.
There are two methods available for carrying data services. The first method carries the data within
Teletext pages. The data in these pages is not sui for direct display by a Teletext decoder and shall
normally be allocated a special page number and/or have the display inhibited. The second method
carries the data within Independent Data Lines (IDL) and these are independent of the page service.
With both Page and IDL formats there exist versions which offer Conditional Access (CA).
There are other specific IDL data services which have been defined but it is beyond the scope of this ETS
to cover all of these.
2 Normative references
This ETS incorporates, by dated or undated references, provisions from other publications. These
normative references are cited at the appropriate places in the text, and the publications are listed
hereafter. For dated references subsequent amendments to, or revisions of, any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest
edition of the publication referred to applies.
[1] ETS 300 706: "Enhanced Teletext specification".
[2] ETS 300 707: "Electronic Programme Guide (EPG); Protocol for a TV Guide
using electronic data transmission".
[3] ETS 300 231: "Television systems; Specification of the domestic video
Programme Delivery Control system (PDC)".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of this ETS, the following definitions apply:
data stream: The sequence of bytes carried in a uniquely addressable data service.
encryption: The process whereby a sequence of data is made secret. See subclause 5.5 for further
network operator: The organization responsible for the compilation of the Teletext service for insertion
into the available Vertical Blanking Interval (VBI) lines.
scrambling: The process whereby a sequence of data is made unintelligible. See subclause 5.5 for
further information.
service provider: The organization responsible for the creation and supply of the data service application.

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3.2 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
AUDETEL AUdio DEscription of TELevision
BL Block Length
BP Block Pointer
BS Block Separator
BT Block Type
CA Conditional Access
CI Continuity Index
CoP Code of Practice
EPG Electronic Programme Guide
FB Filler Bytes
IDL Independent Data Lines
LSB Least Significant Bit
MIP Magazine Inventory Page
MSB Most Significant Bit
RI Repeat Indicator
SH Structure Header
VBI Vertical Blanking Interval (fully defined in this ETS)
4 Page Format - Clear
4.1 General points
A page number which includes at least one hexadecimal digit should be chosen for this type of service.
For an Electronic Programme Guide (EPG) service this will generally be page 1DF as fully described in
ETS 300 707 [2]. The value nFF is not permitted for any data service, where n can take the value from
1 to 8 inclusive. The page number is defined in the Magazine Inventory Page (MIP), ETS 300 706 [1].
The user data is divided into blocks, each of whose length is defined. An additional check of where the
block boundaries are located is provided by means of a block pointer placed in the first byte in each
packet. The data stream is further identified by means of additional data provided in the page header. It is
possible to carry several independent data services within the same page number.
4.2 Advantages
This mode is appropriate for reception by all existing Teletext decoders. A default coding method is
defined in order that services may be offered using existing Teletext systems. Synchronization of the user
data blocks is assured by means of a simple robust method of dual pointing to each block start location.
Future possibilities exist by providing an additional packet 28 which will further define the coding system in
use. It is left up to the service provider to apply any additional protection to those parts of his service which
require it. It is possible to sub-divide the service into those parts which will be required by all decoders and
those parts which will only be required by the more sophisticated decoders.
4.3 Disadvantages
This mode is not efficient for sending a small amount of data as there is always the overhead of including
a page header and the optional, but useful, packet 28. Another disadvantage of this mode is that the data
transmission efficiency is further reduced when the Teletext broadcaster wishes to send the data in a
fragmented way in order to interleave the data service with his primary Teletext service.
4.4 Coding of the packets
In order to provide greater flexibility for the network operator it is not necessary to fill each data page.
Several separated headers, each with some data packets, may be required to provide the data service
and this technique is covered fully in ETS 300 706 [1]. In the case of a data service it is possible to send
full but fragmented pages as well as to simply send shorter pages.

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Fragmented pages are usually interleaved with one or more other pages. Each fragmented page contains,
in row order, parts of a full page. Fragmented pages transmitted in stream 1 shall obey the 20 ms rule for
each fragment.
4.4.1 Page header
This is necessary but shall not generally contain any of the application data. It may be identical to all
others in the same magazine. The use of the Teletext page sub-code is defined as shown in figure 1.
S4 S3 S2 S1
(2 bits) (4 bits) (3 bits) (4 bits)
Number of packets Transmission Rule Continuity Index (CI)
1 to 23 normally but 25 LSB = 0 then 20 ms 0 to 15
possible in future
rule applies else it does
(see table 1)
Figure 1: The use of the Teletext page sub-code
The default valid range for the number of packets is 1 to 23 where this value provides the last row
which is being transmitted for the page with this particular value for the Continuity Index (CI). The packets
of the page are transmitted in ascending address order. There are no missing rows and where a new
header is required to complete the page then this shall be provided with the same CI. The maximum
number of packets per page is 25 and as a result S2 and S4 will never have values of 7 and 3
simultaneously. Thus the reserved sub-code value of 3F7F defined in ETS 300 706 [1] can never occur.
As expected the Least Significant Bit (LSB) of each parameter in the page sub-code is transmitted first.
S2 contains least significant 3 bits of the "Number of packets".
The 20 ms rule requires that the header packet 0 is sent during a previous field. This rule shall be
followed when the LSB of S3 is set to 0. When this bit is set to 1 then the header may be followed
immediately by the packets associated with this header. The following values have been defined in
table 1.
Table 1: Values of S3
Hex value of S3 Interpretation
0 20 ms rule applies - data stream 1
1 no 20 ms rule - data stream 2
2 20 ms rule applies - data stream 3
3 no 20 ms rule - data stream 4
4, 6, 8, A, C & E 20 ms rule applies - data stream 5, 7, 9, 11, 13 & 15 respectively
5,7,9,B & D no 20 ms rule - data stream 6, 8, 10, 12 & 14 respectively
F reserved for future use, no 20 ms rule applies
In each stream the CI value increments modulo 16 for each page which contains different application
Page control bytes C4 to C14; their action is as follows:
The values for C5, C6, C7, C8, C11, C12, C13 and C14 depend upon the type of service which the
network provider is offering and have the same meaning as for normal Teletext pages. The following
control bytes in table 2 have a recommended value.

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Table 2: Page Control Bits
C4 C9 C10
Erase Page Interrupted Sequence Inhibit Display
01 1
The next 24 bytes should normally match those of the other pages in the same magazine. This is to avoid
possible display problems with viewers of the normal Teletext service which shares this Magazine.
The last 8 bytes of the header shall be used in a way which takes account of the rest of the Teletext
service. Where the time can be the same as that on the normal Teletext service it shall be presented in
the same format. Where this is not possible these 8 bytes should be filled with spaces. In the case where
there is no other Teletext service then the local time shall be placed in these 8 bytes according to the
Enhanced Teletext Specification ETS 300 706 [1].
4.4.2 Packets 1 to 23 (in future up to 25)
These packets may carry the data service. The page sub-code indicates to the decoder how many
packets to expect. The default maximum number of packets is 23 although future services may be able to
use up to 25. Each Teletext packet is constructed in the manner shown in figure 2.
Structure Header (SH) comprises the Block Type (BT)
Block Separator (BS)
followed by the Block length (BL)
Hamming 8/4 coded
Hamming 8/4 coded 4 bytes = 16 data bits
C hex = A1 hex
5 LSB provide BT, 11 MSB provide BL (see figure 3)
Packet 0
8 bytes 24 bytes text (normal magazine contents) 8 bytes (see text)
Packet 1
Points to BS
Packet 2
last -1
Block Pointer (BP) Hamming 8/4 coded Possible Filler Bytes (FB) Hamming 8/4
See text below for options & meaning coded 3 hex = 5E hex. See text below
Figure 2: Example of a page according to Page Format - Clear

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ETS 300 708: March 1997 Transmission order
This follows the normal Teletext format where the LSB is transmitted first. For example in the Structure
Header (SH) the least significant 4 bits of the Block Type shall be placed in the byte which is transmitted
first. The most significant bit of BT shall be placed in the least significant position of the next byte.
The Hamming 8/4 coding is carried out in the same way as fully described in ETS 300 706 [1]. The bytes
defined above are all transmitted in the same way. It is up to the data service provider how he codes
the bytes which constitute the "user data". The values for BP are given in table 3.
Table 3: Values for Block Pointer (BP)
Hex value for BP Interpretation
0 to C point to BS in byte position (BP x 3) + 1
D means that there is no BS in this packet
E and F reserved for future use The Structure Header (SH)
The SH comprises four Hamming 8/4 coded bytes. This is put in by the data service provider and the 16
available data bits are used in the following way.
Shown in transmission order from left to right. LSB transmitted first. Only the data bytes are shown.
Figure 3: The Structure Header
The first 5 bits (BT) provide the Application ID. This gives the data application provider the possibility of
providing up to 31 different categories of data within one page service. This is addition to the separation
into a number of streams which is possible by means of the page sub-code value for S3. The actual value
for the Application ID is up to the application provider. When the Application ID has the value 0 this is used
to provide the system with information about which services are carried in this data channel. This is fully
covered in ETS 300 707 [2].
The remaining 11 bits define the block length which permits block lengths of up to 2 048 bytes long. Packing the data into the pages
The network operator packs the available data into the Teletext packets. He has to read the block
lengths in order to put in the Block Pointer (BP) values. The BP may point to 1 of 13 locations in a Teletext
packet according to table 3. Where a data block does not fill up to 1 of the 13 possible start locations the
free bytes are filled with Filler Bytes (FB). Filler bytes are also used to pad out the end of a packet if the
broadcaster has no data available to fill it. The benefit of this process is that each block start is not only
pointed to from the previous block length but also from the BP. It provides a robust method of
synchronizing the application data stream. Block Pointer (BP), Block Separator (BS) and Block Length

(BL) are all Hamming 8/4 coded. Even with bit errors it should be possible for the reception device to have
a high confidence that it is in correct synchronization. The BL may not point precisely to the next BS as
these may only be placed in every third byte, when pointed to from the BP. The existence of the FB
informs the decoder to look forward to find the next BS.

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Where the Service Operator provides very short data blocks it is possible that 2 blocks may commence in
the same Teletext Packet. Where this occurs the BP shall point to the first BS. The

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