SIST ETS 300 177 E1:2003

SLOVENSKI STANDARD
01-december-2003
Terminalska oprema (TE) – Videotex – Fotografska skladnja
Terminal Equipment (TE); Videotex Photographic syntax
Ta slovenski standard je istoveten z: ETS 300 177 Edition 1
ICS:
33.160.99 Druga avdio, video in Other audio, video and
avdiovizuelna oprema audiovisual equipment
35.180 Terminalska in druga IT Terminal and other
periferna oprema IT peripheral equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 177
TELECOMMUNICATION September 1992
STANDARD
Source: ETSI TC-TE Reference: DE/TE-01006
ICS: 33.020, 33.040.40
Videotex, Photographic Syntax
Key words:
Terminal Equipment (TE);
Videotex
Photographic Syntax
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - secretariat@etsi.fr
X.400: Internet:
Tel.: +33 92 94 42 00 - Fax: +33 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 1992. All rights reserved.
New presentation - see History box

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ETS 300 177: September 1992
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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ETS 300 177: September 1992
Contents
Foreword.9
1 Scope . 11
2 Normative references . 11
3 Definitions, symbols and abbreviations . 12
3.1 Definitions. 12
3.2 Symbols and abbreviations . 14
4 Overview .15
5 ISO/IEC 9281, Part 1 syntax and switching structure . 16
5.1 Overall switching of coding environment. 16
5.2 Switching into the photographic mode. 18
5.3 ISO/IEC 9281, Part 1 syntax structure. 18
5.3.1 General use of the Length Indicator (LI). 19
5.3.2 Use of the Picture Identifier (PI) code . 19
6 Coding of the Picture Data Entity (PDE). 20
6.1 Introduction. 20
6.2 PDE data content identification mechanism . 20
7 Photographic header . 22
7.1 Introduction. 22
7.2 Header structure. 22
7.3 Header functionalities . 25
7.3.1 Parameter Status Attribute . 25
7.3.1.1 Reset To Default . 25
7.3.2 Picture Display Attributes . 25
7.3.2.1 Full Screen Display . 27
7.3.2.2 Source Aspect Ratio . 27
7.3.2.3 Photo-area LOCation . 27
7.3.2.4 Photo-Area Size . 27
7.3.2.5 Picture PLacement . 28
7.3.2.6 Clear Photo-Area . 30
7.3.3 Source Picture Attributes . 30
7.3.3.1 Source Picture Comments . 30
7.3.3.2 Source Picture Dimensions . 31
7.3.3.3 Source PIxel Density . 32
7.3.3.4 Source SWeep Direction . 33
7.3.3.5 DC Images . 33
7.3.4 Source Signal Attributes . 33
7.3.4.1 Source Component Description . 33
7.3.4.2 Source Component Data Precision . 34
7.3.4.3 Source Component Order . 34
7.3.4.4 Source Level Assignment . 34
7.3.5 Source Coding Algorithm Attributes . 35
7.3.5.1 JPEG Coding Mode . 35
7.3.5.2 Encoding Table Management . 37
7.3.5.3 Application Marker codes Assignment . 38
7.3.6 Transmission Channel Attributes . 38
7.3.6.1 Translation Mode Encoding . 38

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ETS 300 177: September 1992
8 Coding rules.39
8.1 Purpose.39
8.2 General rules for coding the header.39
8.3 Photographic header code assignment.46
8.3.1 Attribute codes. 46
8.3.2 Parameter codes. 46
8.3.2.1 Parameter Status Attribute. 46
8.3.2.2 Picture display attributes .46
8.3.2.3 Source picture attributes .46
8.3.2.4 Source signal attributes.46
8.3.2.5 Source coding algorithm attributes .46
8.3.2.6 Transmission channel attributes .46
8.3.3 Sub-parameter codes .46
8.4 Encoding of photographic header parameters.47
8.4.1 Parameter Status Attribute: .47
8.4.1.1 Reset To Default . 47
8.4.2 Picture Display Attributes .47
8.4.2.1 Full Screen Display .47
8.4.2.2 Source ASpect Ratio .47
8.4.2.3 Photo-area LOCation . 47
8.4.2.4 Photo-Area Size .47
8.4.2.5 Picture PLacement .47
8.4.2.6 Clear Photo-Area .48
8.4.3 Source Picture Attributes .48
8.4.3.1 Source Picture Comments .48
8.4.3.2 Source Picture Dimensions .48
8.4.3.3 Source PIxel Density .48
8.4.3.4 Source SWeep Direction .49
8.4.3.5 DC Images . 49
8.4.4 Source Signal Attributes .49
8.4.4.1 Source Component Description .49
8.4.4.2 Source Component Data Precision .49
8.4.4.3 Source Component Order . 49
8.4.4.4 Source Level ASsignment .49
8.4.5 Source Coding Algorithm Attributes .50
8.4.5.1 JPEG Coding Mode . 50
8.4.5.2 Encoding Table Management .50
8.4.5.3 Application Marker codes Assignment .50
8.4.6 Transmission Channel Attributes .51
8.4.6.1 Translation Mode Encoding .51
9 Photographic data .51
9.1 Introduction.51
9.2 Translation modes.51
10 Defaults. 51
10.1 Default values for photographic header attributes.52
10.1.1 Default parameter status attribute.52
10.1.2 Default picture display attributes.52
10.1.3 Default source picture attributes .52
10.1.4 Default source signal attributes. 53
10.1.5 Default source coding algorithm attributes .53
10.1.6 Default transmission channel attributes.54
10.2 Default tables.54
10.2.1 Default quantisation tables .54
10.2.1.1 Default quantisation tables for CIF images. 54
10.2.1.2 Default quantisation tables for 2:1:1 images.55
10.2.1.3 Default quantisation tables for 4:2:2 images.55
10.2.2 Default Huffman tables.56
10.2.2.1 Default Huffman table for luminance DC differences.56

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ETS 300 177: September 1992
10.2.2.2 Default Huffman table for chrominance DC differences . 56
10.2.2.3 Default Huffman table for luminance AC coefficients . 57
10.2.2.4 Default Huffman table for chrominance AC coefficients . 59
11 Photographic profiles. 61
11.1 Compatible photographic profiles (P1 to P5) . 62
11.1.1 Profile P1 . 62
11.1.2 Profile P2 . 64
11.1.3 Profile P3 . 64
11.1.4 Profile P4 . 64
11.1.5 Profile P5 . 65
11.2 Private choice of photographic profile (Ppriv). 65
Annex A (informative): Photovideotex tutorial . 66
A.1 Introduction. 66
A.2 The present state of photovideotex. 66
A.3 Image representation. 67
A.4 The JPEG compression technique . 68
A.4.1 Lossy and lossless compression . 68
A.4.2 Modes of encoding. 69
A.4.3 The DCT-based coding. 70
A.4.3.1 The discrete cosine transform . 71
A.4.3.2 Quantisation. 72
A.4.3.3 Huffman coding [A8] . 73
A.4.3.3.1 PCM encoding of the DC coefficients . 74
A.4.3.3.2 Zigzag Ordering of AC Coefficients . 74
A.4.4 Lossless coding . 74
A.4.5 Source images and data interleaving. 75
A.4.6 Data organisation and signalling parameters. 75
A.5 The baseline system. 75
A.6 The extended system . 76
A.6.1 Coding model for successive approximation . 76
A.6.2 Coding model for spectral selection . 76
A.6.3 Hierarchical encoding. 76
A.7 Summary.77
A.8 Bibliography. 77
Annex B (informative): Implementation guidelines on display rendering. 78
B.1 Introduction. 78
B.2 Rendering of resolution . 78
B.2.1 Resolution independence . 78
B.2.2 Display rendering guidelines for Data Syntax II profiles . 80
B.2.2.1 Pixel alignment. 80
B.2.2.1.1 CCIR Recommendation 601, Part 1 4:2:2 resolution. 80
B.2.2.1.2 CCIR Recommendation 601, Part 1 2:1:1 resolution. 80
B.2.2.1.3 CIF format . 80
B.2.2.1.4 QCIF format. 81
B.2.2.2 Adjustment of horizontal resolution. 81
B.2.2.2.1 "Adding" pixels. 81
B.2.2.2.2 "Removing" pixels . 82

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ETS 300 177: September 1992
B.3 The concept of normalised colour space.82
Annex C (informative): Solutions for common compatible photovideotex databases serving different
resolution terminals .83
C.1 Introduction.83
C.2 Hierarchical mode.83
C.2.1 Coding.83
C.2.2 Decoding .85
C.2.3 Example for a "resolution pyramid" for hierarchical build-up.85
C.2.3.1 Advantages of the suggested technique .86
C.2.3.1.1 Independence of transmission, decompression and
display.86
C.2.3.1.2 Independence of image resolution from the terminal
resolution. .86
C.2.3.1.3 Storage gain in the database host through the pyramidal
database.86
C.2.3.2 Disadvantages .86
C.3 Special spectral selection.87
C.3.1 Coding.87
C.3.2 Decoding .88
Annex D (informative): Coding examples.90
D.1 Introduction.90
D.1.1 Example 1 .90
D.1.2 Example 2 .92
D.1.3 Example 3 .94
D.2 Image positioning examples.96
D.2.1 Example 1: 640 X 480 picture inside DDA .96
D.2.2 Example 2: 720 X 576 picture full screen.96
D.2.3 Example 3: 720 X 346 picture covering upper 60% of full screen.97
D.3 Example for Source Picture Comments (PCT) .98
D.3.1 An application scenario .98
D.3.2 Sample logical record of a Source picture: .98
Annex E (informative): ETSI/CCITT Cross-reference list.100
Annex F (normative): Encoding parameters values for the 2:1:1 derived from CCIR
Recommendation 601, Part 1.101
F.1 Introduction.101
F.2 Encoding parameters for 2:1:1 .101
F.2.1 Main body of CCIR Recommendation 601, Part 1.101
F.2.2 Annex I of the CCIR Recommendation 601, Part 1.101
F.2.3 Annex II of the CCIR Recommendation 601, Part 1.101
F.2.3.1 Relationship of active line to analogue synchronisation reference.101
F.2.3.2 Definition of the digital signals Y, C , C , from the primary (analogue)
R B
signals E' , E' and E' .101
R G B
F.2.4 Annex III of the CCIR Recommendation 601.102
Annex G (normative): Translation modes.106
G.1 Mode 0 (No translation, full transparency) .106

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G.2 Mode 2 (3-in-4 coding) . 106
G.3 Mode 4 (Shift scheme - 7 bits) . 106
Annex H (informative): Huffman tables for the "special spectral selection" . 108
H.1 Introduction. 108
H.2 Spectral bands. 108
H.3 Luminance DC differences . 108
H.3.1 List of codelengths . 108
H.3.2 List of values . 108
H.4 Chrominance DC differences. 109
H.4.1 List of codelengths . 109
H.4.2 List of values . 109
H.5 Luminance AC coefficients . 109
H.5.1 List of codelengths . 109
H.5.2 List of values . 109
H.6 Chrominance AC coefficients. 112
H.6.1 List of codelengths . 112
H.6.2 List of values . 112
History. 115

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Foreword
This European Telecommunication Standard (ETS) has been prepared by the Terminal Equipment (TE)
Technical Committee of the European Telecommunications Standards Institute (ETSI) in order to specify a
new common data syntax for transmitting photographic images to be used by Videotex terminal equipment.
This ETS is part of a series of ETSs which describe the Videotex presentation layer data syntax.
This ETS defines a data syntax to be used for conveying photographic data in a Videotex environment. The
necessary tools are provided for the transfer of photographic data, typically from a Videotex Host to a
Videotex terminal. This data syntax is equally applicable to either storage or communication applications
and is independent of physical device or transmission media.
This ETS does not deal with the visible appearance of the displayed pictures, however all the necessary
source image information is provided to make the proper physical adaptation at the receiving side. The
specification of post-processing techniques is left to the implementors and is, therefore, outside the scope
of this ETS.
More precisely, this ETS defines the syntax and semantics of image data and image attributes for
photographic Videotex interchange purposes. In particular, it addresses the various aspects of image
dimensionality such as spatial, amplitudinal, temporal and spectral content, it provides some basic tools for
positioning photographic images within a defined area, it also addresses the structure and organisation of
the data and uses standardised compression schemes. In particular, the ISO-Joint Photographic Experts
Group (JPEG) compression algorithm [13], based on the Discrete Cosine Transform (DCT) is used. In this
ETS the algorithms or compression techniques themselves are not described, references are provided.
The intention of this ETS is primarily to provide Videotex application developers with a sufficient set of
photographic transfer tools which are independent of the equipment used to implement/provide them. This
ETS is intended to support operations on and display of, various classes of images from a wide variety of
imaging applications. However, to ensure that compatibility can be achieved between various Videotex
services supporting photographic mode, some realistic and specific characteristics are chosen and defined
in the Clause on profiles (Clause 11). In the future, other selections might be made allowing the definition
of new recommended profiles.
This ETS closely follows the concepts and coding techniques as described in ISO/IEC 9281, Part 1 [11]
for the identification of pictorial information and for switching between picture environments and coding
systems according to ISO 2022 [10].

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ETS 300 177: September 1992
1 Scope
This ETS specifies the data syntax to be used by Videotex services for conveying photographic data.
In general, it applies to the interchange of photographic data via storage or transmission media.
The ETS is applicable to Videotex terminals connected to various types of telecommunication networks
including; a Public Switched Telephone Network (PSTN), a Public Switched Packet Data Network (PSPDN)
or an Integrated Services Digital Network (ISDN). For the ISDN case, these terminals will typically support
"ISDN Syntax-based Videotex" (see ETS 300 079 [3]).
The syntax allows for some private extensions beyond the transmission of still pictures. For example, a
provision has been made for the transmission of a "difference" image to allow a slow scan television type
of application.
2 Normative references
This ETS incorporates by dated or undated reference, 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 300 072: "Terminal Equipment (TE); Videotex presentation layer protocol,
Videotex presentation layer data syntax".
[2] ETS 300 076 (1992): "Terminal Equipment (TE); Videotex, Terminal Facility
Identifier (TFI)".
[3] ETS 300 079 (1991): "Integrated Services Digital Network (ISDN); Syntax-based
Videotex, End to end protocols".
[4] CCITT Recommendation F.300 (1988): "Videotex service".
[5] CCITT Recommendation T.101 (1988): "International interworking for Videotex".
[6] CCITT Recommendation H.261 (1988): "Common intermediate format".
[7] CCITT Recommendation T.51 (1988): "Coded Character sets for Telematic
services".
[8] CCITT Recommendation T.61 (1988): "Character repertoire and coded
character sets for the international teletex service".
[9] CCIR Recommendation 601-1 (1986): "Encoding Parameters of Digital
Television For Studios".
[10] ISO 2022 (1986): "Information Processing - ISO 7-bit and 8-bit coded character
sets - Code extension techniques".
[11] ISO/IEC 9281-1 (1990): "Information technology - Picture coding methods- Part
1: Identification".
[12] ISO/IEC 9281-2 (1990): "Information Technology - Picture coding methods -
Part 2: Procedure for registration".
[13] ISO/IEC DIS 10918/CCITT Recommendation T.81: "Digital compression and
coding of continuous-tone images".

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ETS 300 177: September 1992
[14] ISO 646 (1990): "Information processing - ISO 7-bit coded character set for
information interchange".
[15] ISO 6937-1 (1991): "Information processing - coded character sets for text
communication: Part 1 General introduction".
[16] ISO 2375 (1991): "Data Processing - Procedure for registration of escape
sequences".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purpose of this ETS the following definitions apply.
Aspect ratio: the ratio of the width to the height of a rectangular area, such as the defined display area.
Attribute: a particular property or quantity defined in this syntax and described by a number of parameters
(e.g. the source picture specifications).
Baseline: the basic sequential DCT-based encoding and decoding process specified in ISO/IEC DIS
10918 [13].
Continuous tone image: an image comprised of data which exhibits a first order continuity in the
analogue domain and requires, when digitised, more than one bit to describe each sample contained in one
or more of its components (monochrome (grey scale) or colour pictures) e.g., a monochrome image needs
at least 6 bits/picture element (64 grey levels) to appear "continuous" to the eye.
Data syntax I: term used within CCITT for one of the recommended world-wide Videotex data syntaxes
originating from the Japanese Character And Pattern Telephone Access Information Network (CAPTAIN)
system.
Data syntax II: term used within CCITT for one of the recommended world-wide Videotex data syntaxes
originating from the European CEPT Videotex syntax.
Data syntax III: term used within CCITT for one of the recommended world-wide Videotex data syntaxes
originating from the North American Presentation Layer Protocol Syntax (NAPLPS).
Defined Display Area (DDA), Physical (Physical Defined Display Area (DDA)): a rectangular area of
the full screen area where photographic data, text etc. shall be displayed.
Defined Display Area (DDA), Logical (Logical DDA): a unit square, the length of all sides being one unit,
co-ordinates being defined as fractions of unity (unit screen concept). The origin is coincident with the
bottom left corner of the physical DDA and one side is coincident with the longest side of the physical
DDA.
Defined Display Area, Source (Source DDA): the virtual display space where the source image was
encoded and which is to be mapped for display either to the full screen area or to the physical DDA.
Discrete Cosine Transformation (DCT): see ISO/IEC DIS 10918 [13].
Full screen area: the part of a display screen where photographic data can be displayed, it normally
means a display with no borders.
Forward DCT: see ISO/IEC DIS 10918 [13].
Inverse DCT: see ISO/IEC DIS 10918 [13].
Image attribute: the various properties of a continuous tone image described by a number of parameters.

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ETS 300 177: September 1992
Image data: the data which represents a continuous tone image in digital form, it contains photographic
header data and photographic data.
JPEG compression algorithm: a general term for referring to any one of the possible modes of encoding
defined in ISO/IEC DIS 10918 [13].
Normalised co-ordinate: a co-ordinate specified in a device independent co-ordinate system, normalised
to some range (usually to 1).
Parameter: a quantity which is described using one or more sub-parameters.
Photographic data: pixel based pictorial information usually in compressed digital form; the data includes
any tables which are necessary to decode and decompress the data.
Photographic data syntax: the rules by which the photographic header data and the photographic data
are formatted.
Photographic header data: coded data containing the values of the attributes and parameters used for
describing the photographic image.
Photographic image: a continuous tone image, e.g. an image represented with 256 shades of grey.
Photographic mode: the mode of operation of a Videotex terminal while it is receiving photographic
header data and photographic data.
Photographic profile: a collection of attributes with parameters set to a given value to represent a type of
source image and define a mode of photographic image coding and photographic image transfer.
Photo Videotex: neologism used for Videotex photographic mode.
Physical device: any tangible piece of equipment (e.g., personal computer, display monitor, etc).
Pixel, picture element: it is the minimum displayable element of an image (see ISO/IEC DIS 10918 [13]).
Pixel density: expresses the number of pixels per physical unit (e.g. pixels/mm) in the horizontal and
vertical directions.
Post-processing technique: image processing which is performed (e.g. for display) after the image has
been decoded and decompressed.
Spatial resolution: definition of the size of the image, expressed in the number of pixels per horizontal line
and the number of lines per image.
Storage media: a type of physical means to store data.
Sub-parameter: a quantity to which a value can be assigned.
NOTE: Example of the use of attribute, parameter and sub-parameter. Consider the ISDN, it
has the following attributes, it is digital and supports data transmission with a speed of
64 kbit/s. For the ISDN the parameter network speed is assigned the value 64 kbit/s.
Two sub-parameters can represent this quantity, "numerical speed" i.e., 64 and "unit of
measure" i.e., kbit/s.
Spectral content: a physical quantity that measures the frequency content i.e., the amplitude and phase
of each frequency contained in a given physical item. It generally refers to the fourier analysis. For the
Discrete Cosine Transformation (DCT) it relates to the amplitude of each DCT basic function (Discrete
Cosine) or sub-image. In simple terms, for the image, it gives an idea on the "level of detail" of the source
image.
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ETS 300 177: September 1992
Transmission media: the type of physical means to transport data (e.g., coaxial cable, optical fibre, radio
link).
Videotex system: text communication system, hardware and software, with the capability of running a
Videotex service or application.
Videotex application: see CCITT Recommendation F.300 [4].
Videotex host computer: see CCITT Recommendation F.300 [4].
Videotex service: see CCITT Recommendation F.300 [4].
Videotex terminal: see CCITT Recommendation F.300 [4].
NOTE: Reference should also be made to ISO/IEC DIS 10918 [13] for definitions of terms
related to image coding which are used in this ETS but not included in this Clause.
3.2 Symbols and abbreviations
For the purpose of this standard the following abbreviations and symbols apply.
AM Alphamosaic
C Chrominance colour difference, Blue
B
C Chrominance colour difference, Red
R
CAPTAIN Character And Pattern Telephone Access Information Network
CCIR International Radio Consultative Committee
CCITT International Telegraph and Telephone Consultative Committee
CD Committee Draft
CEPT Commission Européenne des Postes et Télécommunications
CIF Common Intermediate Format
CMI Coding Method Identifier
CMYK Cyan, Magenta, Yellow, Black
DCT Discrete Cosine Transformation
DDA Defined Display Area
DPCM Differential Pulse Code Modulation
E' , E' , E' Primary (analogue) signals (red, green, blue)
R G B
ESC ESCape
ETS European Telecommunication Standard
ETSI European Telecommunications Standards Institute
F "Final character" registered by ISO 2022 registration authority
IEC International Electrotechnical Committee

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ETS 300 177: September 1992
ISDN Integrated Services Digital Network
ISO Organisation for International Standardization
JPEG Joint Photographic Experts Group
LI Length Indicator
NAPLPS North American Presentation Layer Protocol Syntax
P1 to P5 Compatible Photographic Profiles, numbered 1 to 5
P Private Photographic Profile
priv
PCD Picture Coding Delimiter
PCE Picture Control Entity
PDDA Physical Defined Display Area
PDE Picture Data Entity
PE Picture Entity
PI Picture Identifier
PM Picture Mode
PSPDN Public Switched Packet Data Network
PSTN Public Switched Telephone Network
RGB Red, Green, Blue
SDDA Source Defined Display Area
US Unit Separator
VPCE Videotex Presentation Control Element
Y Luminance
4 Overview
The photographic data syntax allows for the transmission and display of an image consisting of individually
defined Picture elements (Pixels) with many grey/colour levels. Digital signal processing techniques are
used to compress the image for storage and transmission.
The photographic data syntax allows, in principle, the specification of a wide variety of different modes of
photographic images for use in Videotex systems. However, to cater for the foreseen requirements of
users and to aid compatibility, some recommended application profiles are specified, they are based on
CCIR Recommendation 601, part 1 [9] and CCITT Recommendation H.261 [6], which describes the
Common Intermediate Format (CIF).
This photographic data syntax is basically unidirectional; the photographic data shall be transported from a
Videotex Host computer to a Videotex terminal using the syntax.
In Videotex photographic mode the size of a file containing an encoded photographic image can be rather
large. One picture may be transmitted in several PEs. The use of several PEs could facilitate the
termination of the transmission of a picture by the user.

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ETS 300 177: September 1992
This draft ETS clearly separates the functionalities, the syntax (the formatting rules i.e., structuring the
data) and the coding rules (i.e. coding of the header, coding of the photographic data, etc.). The ISO
9281, Part 1 [11] syntax structure used to introduce the photographic header is encoded using 7 bits only.
For coding in an 8 bit transfer environment the most significant bit (bit 8) is set to zero.
The photographic data is encoded and represented using 8 bits. For transmission, allowance is made for
both a 7 bit and an 8 bit channel.
5 ISO/IEC 9281, Part 1 syntax and switching structure
5.1 Overall switching of coding environment
ISO/IEC 9281, Part 1 [11] describes a technique for identifying picture coding methods. The Videotex
photographic mode is one of the picture coding methods identified by ISO/IEC 9281, Part 1 [11]. The
diagram in figure 1 gives an overview of the relationship between the Videotex data syntaxes and ISO/IEC
9281, Part 1 [11] picture coding environments.
From an ISO 2022 [10] environment, a Videotex data syntax can be explicitly entered using an ESC 2/5 F
code. This is also the mechanism used for entering from an ISO 2022 environment [10] into an ISO/IEC
9281 [11] environment. The F code ("final byte") is allocated and registered, according to ISO 2022 [10],
by the registration authority ISO 2375 [16]. According to ISO 2375 [16], Annex B, the Videotex data
syntaxes are regarded as "coding systems different to that of ISO 2022 [10]". The F codes are 4/3 for
CCITT data syntax I, 4/4 for CCITT data syntax II and 4/1 for CCITT data syntax III.

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ETS 300 177: September 1992
ESC 2/5 4/0
ISO 2022 Environment, Default = ISO 646
Data Syntax I
(DI)
Alpha Photo
ESC 7/0 CMIp
ESC 2/5 4/3 Rank
Photographic
ESC 7/0 CMIa
Audio
Data Syntax II
US 2/0 . 3/15
Other
US 3/4 US 3/5
Old photo
(P1 - 4)
ESC 2/5 4/4
US 4/0 . 7/15
AM display
ESC 7/0 CMIp
Photographic
ESC 7/0 CMIa
Audio
ASCII
Data Syntax III
other
Alpha geo
ESC 2/5 4/1 ESC 7/0 CMIp
Photographic
ESC 7/0 CMIa
Audio
ESC 2/5 F
Any ISO/IEC 9281 registered coding method
Figure 1: Global switching mechanism

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ETS 300 177: September 1992
Key to figure 1:
DI: is data syntax I specific
P: is a profile in data syntax II
F: is a final code assigned by the ISO 2022 [10] registration authority
CMI : is any CMI for Videotex audio data
a
CMI : is any CMI for Videotex photographic data
p
Rank: is data syntax I specific
Since a Videotex terminal usually begins operation, by default, in one of the data syntaxes, it shall not be
mandatory to first send an ESC 2/5 F code (F is 4/1, 4/3 or 4/4). The diagram shows how these codes
can be used to switch a Videotex terminal supporting more than one data syntax from one data syntax to
another.
5.2 Switching into the photographic mode
A Videotex terminal operating within one of the data syntaxes (i.e., a coding system other than that
described by ISO 2022 [10]) can enter the ISO/IEC 9281, Part 1 [11] environment of the photographic
mode according to their own rules. In the case of Videotex for switching into the ISO/IEC 9281, Part 1 [11]
environment of the photographic mode the Picture Code Delimiter (PCD) of the first Picture Element (PE)
is used. The Coding Method Identifier (CMI) is used to distinguish between picture coding methods. In the
case of Videotex this shall be, for example, a distinction between audio and photographic data.
5.3 ISO/IEC 9281, Part 1 syntax structure
The high level st
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