1、 I CEPT T/CD*Ob-OL*E 2326434 0004OL7 3 0 TCD06-01 Page 1 E Recommendation T/CD 06-01 (Innsbruck 1981, revised in Cannes 1983, in Montpellier 1984 and in Nice 1985) Edition of February 10. 1987 VIDEOTEX SERVICE Recommendation proposed by the Workig Group T/GT 10 “Data Communications” (CD) Revised tex
2、t of the Recommendation adopted by the “Telecommunications” Commission : The European Conference of Posts and Telecommunications Administrations, considering - the work undertaken within CEPT with a view to harmonising international telecommunication services as well studies carried out within the f
3、ramework of question CD 7, - the possible benefit to the expansion of the Videotex Service in providing a stable environment for the full the possibility that some Administrations require a lower cost basic service and others an enhanced service with - the need for a common standard which will enabl
4、e Administrations to confidently adopt the “harmonised - the need to leave the way open to add new facilities as technology progresses in a way which preserves investments as equipment, commercial exploitation of existing services already implemented, extra facilities, enhanced” service or up grade
5、a basic service to the “harmonised enhanced” service, in basic services or enhanced services, O recommends that 1. In order to facilitate international access between Videotex Services in Europe, 1.1. International access to national Videotex Services should be via PTT provided international gateway
6、s. 1.2. International gateways should intercommunicate using the communication protocols to be adopted by CEPT, the information being coded according to data syntax described in Annex A, with the range of information transmitted restricted to conform to the service reference model as described in An
7、nex B. 1.3. Administrations should ensure that the coded information is transcoded as necessary in order to provide the best possible display on the terminals in use in that country. In addition, Administrations may provide identification of user and billing. O 2. In order to recognise existing syst
8、ems and to harmonise further development of Videotex Services, 2.1. Systems offering a basic service shall be based on one of the four profiles described in Annex C (see Figure 1.a 2.2. An enhanced service of foreseen facilities is optional but where they are provided they shall conform to the 2.3.
9、New enhanced services which are either as yet unforseen or not yet defined in sufficient detail in Annex B (T/CD 06-01). standards referred to in Figure 1.b (T/CD 06-01). to make a recommendation at this stage shall be formulated such that they are (1) based on one of the four basic building blocks
10、and harmonised service or based on one of the four basic building blocks and be able to display informations generated by systems using the harmonised enhanced service standard; (2) able to be adopted without modifications to any parameters defined in the references given in Figure 1.b (T/CD 06-01).
11、 T/CD 06-01 E Page 2 2.4. New optional enhanced services which are either as yet unforeseen or not yet defined in Aufficient detail in annex B (see Figure 1.c (T/CD 06-01), shall: or not be added to a system providing the basic service without also including the “harmonised enhanced” service referre
12、d to in Figure 1.b (T/CD 06-01), CEPT T/CD*Ob-OL*E W 2326414 00040L8 5 W or may be adopted without also adopting the facilities of the “harmonised enhanced” service referred to in Figure 1.b (T/CD 06-01). In this case at least full compatibility with CEPT Recommendation T/CD 06-01 version Innsbruck
13、(May 81) shall be assumed. However it is preferable services for both (1 .b and 1 .c in Figure 1 (T/CD 06-01) to be adopted if maximum inter-working between services is to be achieved at the earliest possible time. 3. Studies should continue on - New enhanced services which are not yet defined in su
14、fficient detail in Annex B (geometric and photographic - International communication protocol. modes) so as to arrive at a common standard for them. 4. In order to harmonise the interface to “external computers” for communication between external computers and Videotex centres, Administrations shoul
15、d adopt the data syntax described in Annex A for the coding of informa- tion and common protocols for the other layers (possibly those referred to in l .2 above). Edition of February 10, 1987 CEPT T/CD*Ob-OL*E 232b414 00040l19 i M TlCD06-01 E Page 3 FUTURE HORIZON Figure 1.c (T/CD 06-01) Standard fo
16、r new enhanced services as yet unforeseen or not yet defined in services (optional) - must be based on one of the four basic building blocks and harmonised service, or - must be based on one of the four basic building blocks and be able to display information generated by systems - must be able to b
17、e adopted without modifications to any parameters defined in the references given in Figure 1 .b using the harmonised enhanced service standard, (T/CD 06-01). 1ST HORIZON Figure 1.b (T/CD 06-01) ff Standard for the “harmonised enhanced” service (optional) Annex B O. 6.1. 1.1.2. 6.2.2. 1.2.2. 8. 1.3.
18、2. 1 o. 1.4.1. and 1.4.2. (simultaneously) 1.4.3. to 1.4.6. 1.5. to 1.9. 4. 5. ii II II II II see section 2.4. Il II II II A / JJ Figure 1.a (T/CD 06-01) FLEXIBLE INITIAL BUILDING BLOCKS (ALTERNATIVE9 . -, - / ./ / I I I BASIC SERVICE LEVEL 1 Figure 1 (T/CD 06-01). CEPT Recommendation on enhanced Vi
19、deotex Service and its relationship with existing basic Videotex Service systems and new as yet undefined facilities. Edition of February 10, 1987 CEPT T/CD*Ob-OL*E = 232b4L4 0004020 3 T/CD 06-01 Page 5 VIDEOTEX PRESENTATION LAYER DATA SYNTAX ANNEXA PART O. GENERAL 1. Introduction 2. References 3. D
20、efinitions PART 1. ALPHA MOSAIC DISPLAYS 1. Description 2. Repertory 3. Coding structure PART 2. GEOMETRIC DISPLAYS 1. 2. 3. 4. 5. 6. 7. 8. 9. 1 o. Introduction Scope and field of the application References Definitions and abbreviations General description Description of the primitive Encoding princ
21、iples Encoding of the primitives Defaults Conformance PART 3. PHOTOGRAPHIC DISPLAYS 1. Introduction 2. 3. 4. Photographic table header unit 5. Photographic table transfer unit Appendix A3A. DPCM image coding - one dimensional Appendix B3B. Cosine transform - two dimensional DEFINE DYNAMICALLY REDEFI
22、NABLE CHARACTER SETS 1. Introduction 2. DRCS Header units 3. Pattern transfer units 4. Coding methods 5. 6. Applicability of attributes Photographic pixel header unit (PPHU) Photographic pixel transfer unit (PPTU) PART 4. Designation and invocation of DRCS PART 5. DEFINE COLOUR 1. Introduction 2. Co
23、lour system extension 3. Coding of redefinable colours PART 6. DEFINE FORMAT 1. Introduction 2. Coding 3. Defaults PART 7. TRANSPARENTDATA 1. Introduction 2. Protocol Edition of February 10, 1987 CEPT T/CD*Ob-OL*E 232bYl14 OOOLi02L 5 TfCD 06-01 E Page 6 ANNEXA PART 8. (Continued) PART 9. PART 10. PA
24、RT 11. RESET 1. Introduction 2. Coding structure 3. Functional descripl in ani coding TELESOFWARE (for further study) TERMINAL FACILITY IDENTIFIER 1. Introduction 2. Coding structure 3. Coding 4. Defaults TIMING CONTROL 1. Introduction 2. Wait ANNEX B ANNEX C ANNEX D List of abbreviation. Service Re
25、ference Model: Conformance to Data Syntax II Service Reference Model: Profiles of terminals applying to Data Syntaxe II Edition of February 10, 1987 c CEPT T/CD*Ob-l*E W 232b414 0004022 i TjCD06-01 E Annex A, Part O, Page 1 PART O. GENERAL Contents 1. INTRODUCTION . 3 1.1. Coding Principles 3 1.1.1.
26、 Ident$cation of Datu Types. . 3 1.1.2. Use of Default Vulues 3 1.2. Display Principles 4 1.2.1. Defined Display Area 4 1.2.2. Display Structure 4 2. REFERENCES. 4 DEFINITIONS. 4 3. Edition of February 10, 1987 CEPT T/CD*Ob-OL*E 232b414 0004023 i T/CD 06-01 E Annex A, Part O, Page 3 1. INTRODUCTION
27、O VIDEOTEX systems are text communication systems with the capability of a given level of pictorial representation and a repertoire of display attributes. The text and the pictures obtained are intended to be displayed using the current television (TV) raster standards of the different countries. Vi
28、deotex Services will be provided in different ways in different countries. The Videotex Services may be a distributed network of independent computers or a hierarchy of computers with external databases or a mixture of both. It is probable that in all countries Videotex terminals will primarily acce
29、ss the Videotex Services via the switched telephone network, over which data is transmitted to a terminal which generates displays. Three types of display have been identified and are described and defined in this recommendation: Part 1. Alphamosaic. Part 2. Geometric. Part 3. Photographic. Notes: O
30、ther types of display may be defined in the future. Each type of display may be used simultaneously, though data for each type of display is separated during transmission. The way in which data is used to generate a display may be modified by “management data”. Management data may affect more than o
31、ne type of display. 1.1. Coding Principles 1.1.1. Identijication of Data Types Different types of display data and management data are separated into different “Videotex Presentation Data Elements” (VPDEs) during transmission. “Videotex Presentation Data Elements” (VPDEs) are made up of two parts: “
32、Videotex Presentation Control Element” (VPCE) which identifies the type of data and “Videotex Service Control Element” (VSCE) which contains the data itself. I VPCE 1 VSCE 1 VPCE I VPCEs are coded in the form us x where X is a character from: columns 4-7 for alphamosaic data, column 2 for management
33、 data, column 3 for other data. The following VPCEs have been provisionally assigned : Define DRCS US 213 Define COLOUR US 216 Define FORMAT US 2/13 RESET US 2/15 ALPHAMOSAIC display data US GEOMETRIC display data (2D) US 310 GEOMETRIC display data (3D) US 311 PHOTOGRAPHIC pixel data US 314 PHOTOGRA
34、PHIC table data US 31.5 US is the UNIT SEPARATOR control and is coded 1/15. Where data fields are used to describe parameters of the following data (e.g. the DRCS header) default values for these fields have been assigned. If the data field is not transmitted then the terminal will apply the default
35、 value. TRANSPARENT data us 3/15 1.1.2. Use of Default Values Edition of February IO. 1987 T/CD 06-01 E Annex A, Part O, Page 4 1.2. 1.2.1. 1.2.2. 2. 3. CEPT T/CD*Ob-Ol*E 2326434 0004024 O O It is anticipated that some terminais will only be able to process data which conforms to these default value
36、s, to simplify their operation these terminals may ignore such data, unless the parameters describing that data are omitted (implying that the data conforms to the default). It is therefore recommended that when a parameter is equal to the default value that field is not transmitted, if it is transm
37、itted then the response of the terminal is not guaranteed. Display Principles Defined Display Area The defined display area is a rectangular area of the screen within which the text and pictorial information is displayed. The ratio of the width to the height (aspect ratio) of this area should be 4:3
38、. For the alphamosaic display this area is composed of a defined number of rows each with a defined number of character positions. The default is 24 rows of 40 character positions. For the geometric display the bottom lefthand corner of the defined display area is addressed as (O, O) and the upper r
39、ighthand corner is defined as (1, 0.75). The photographic display area also maps to the same area. The top lefthand pixel of the photographic display area is addressed as (1, 1). The possibility of defining different aspect ratios is for further study. Display Structure The theoretical structure of
40、the display consists of the following layers in order of precedence: 1. Alphamosaic character foreground and background layers (see Part l., Section 1.2.), 2. Geometric layer or layers (see Part 2.), 3. Photographic layer (see Part 3.), 4. Full screen background layer (see Part l.), 5. Any other vid
41、eo source. Changing the display structure is for further study. REFERENCES This document is intended to be as closely compatible as possible with the following recommendations and standards: CCITT Recommendation V.3 International alphabet No. 5. CCITT Recommendation F.300 Vidotex Service. CCITT Reco
42、mmendation S. 1 O0 International information exchange for interactive Videotex. IS0 Standard 2022 Code Extension Techniques for use with the IS0 7-bit coded character set. IS0 Standard 6937 Information processing - coded character sets for text communication. IS0 Standard 6429.2 Draft standard - add
43、itional control functions for character imaging devices. DEFINITIONS BIT-COMBINATION Bit-combination is an ordered set of bits that represents a character. BORDER AREA Border area is that part of the display screen (visible display) which is outside the defined display area. (See Note and Figure 1 b
44、elow.) CONTROL CHARACTER Control character is a control function, the coded representation of which consists of a single bit-combina- tion. Edition of February IO, 1987 CEPT T/CD*Ob-OZ*E 2326414 0004025 2 T/CD06-01 E Annex A, Part O, Page 5 CONTROL FUNCTION Control function is an action that affects
45、 the recording, processing, transmission or interpretation of data. The coded representation of a control function consists of one or more bit-combinations. DEFINED DISPLAY AREA The defined display area is a rectangular area of the screen within which the text and pictorial information is displayed
46、(see Figure AO-1 (T/CD 06-01) and Section 1.2.1.). Full Visible Display Border Area Defined Display Area i) Figure AO-1 (T/CD 06-01). Full Visible Display, Border Area and Defined Display Area. Note: The default format of defined display area for the alphamosaic option is given in Part i., Section 1
47、.1.2. GRAPHIC CODE EXTENSION Graphic code extension is the method of encoding graphic characters in excess of those which may be represented by the code combinations of the basic code table. Alternative sets of 94 characters may be designated by means of shift functions. Edition of February 10, 1987
48、 CEPT T/CD*Ub-OL*E 2326434 0004026 4 = T/CD 06-01 E Annex A, Part 1, Page 1 PART 1. ALPHAMOSAIC DISPLAYS Contents 1. 1.1. 1.1.1. 1.1.2. 1.1.3. 1.1.4. 1.1.5. 1.1.6. 1.2. 1.2.1. 1.2.2. 1.2.3. 1.2.4. 1.3. 1.3.1. i .3.2. 1.3.3. 1.3.4. 1.3.5. 1.3.6. 1.3.7. 1.3.8. 1.3.9. 1.3.10. 1.3.11. 1.3.12. 1.4. 1.5.
49、1.5.1. i .5.2. 1.5.3. 1.5.4. 1.5.5. 1.5.6. 2. 2.1. 2.1.1. 2.1.2. 2.2. 2.3. 2.3.1. 2.3.2. 2.3.3. 2.3.4. 2.3.5. 2.3.6. 2.3.7. 2.3.8. 2.3.9. 2.3.10. 2.3.11. 2.3.12. 2.3.13. O DESCRIPTION . 5 Introduction . 5 Definitions 5 Format 5 Characters 5 Format Eflectors . 5 Attributes 6 Device Control Functions 6 Theoretical Terminal Model. 6 . 6 Description. 6 . Operation of ?Parallel? and ?Serial? Mode Controls Layered Structure . 7 Action of Attributes on Layers . I 8 Defined Attributes and Qualified Areas 8 Foreground Colour 8 Background Colour Lined 8 Size . 8 Flash 8 Conceal 8 Invert 9
