CEPT T N 33-01 E-1987 International Digital Audiographic Teleconferencing《国际数字语音图文电话会议》.pdf

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1、. ._ CEPT T/N*33-OL*E 87 w 2326414 000bL3L O 33-01 Page E 1 Recommendation T/N 33-01 (Copenhagen 1987) INTERNATIONAL DIGITAL AUDIOGRAPHIC TELECONFERENCING Recommendation proposed by Special Group Integration (GSI) Text of the Recommendation adopted by the “Telecommunications” Commission: “The Europe

2、an Conference of Posts and Telecommunications Administrations, considering that there is a potential demand for audiographic teleconference services, nationally and internationally; such services having basic audiovisual facilities and a variety of optional facilities according to customers requirem

3、ents, and recognizing the need for interconnectability between audiographic teleconference terminals in different countries and in different customers premises, preserving not only the corsec electrical operation but also satisfactory acoustic conditions, recommends to the member Administrations tha

4、t they should implement an International audiographic teleconference service as described and defined in the attachment hereto.” e -7 Edition of February 10, 1988 CEPT T/N*33-O3*E 7 2326434 0006332 2 T/N 33-01 E Page 2 Contents 1 . Scope . 3 1.1. Introduction 3 1.2. Definition of audiographic teleco

5、nference 3 2 . Definitions and abbreviations . 3 3 . 3.1. 3.2, 3.3. 3.4. 3.5. 3.6, 3.7. 3.8. 3.9. 3.10. 3.11. 3.12. Services and facilities 3 Service description . 3 Basic facilities . 4 Other facilities . 4 Audiographic teleconference Terminals . 4 Controls and indications . 5 Quality of service 5

6、Network requirements 5 Operational aspects . 5 Geographical availability . 5 Tariffs and charging aspects . 5 The audiographic teleconferencing process . 5 List of service attributes . 7 Network 8 4. 4.1. Access 8 4.2. Transfer rate 9 4.3. Call 9 5 . Bitrate allocation, message channel, frame struct

7、ure . 9 5.1. Bitrate allocation 9 5.2. Message channel 9 5.3, Frame structure 10 5.4. Mode switching . 10 7 . Terminal specification 10 7.1 . Punctional description of an audiographic teleconference terminal . 12 7.2. Interconnection specifications for the audio system 13 7.3. Far-end quality specif

8、ications for the audio system 16 7.5. Meetingaids 20 8 . Multipoint audiographic teleconference . 21 8.1. General requirements 21 8.2. Configuration . 24 9 . Interworking 24 6 . Coding 10 7.4 . Near-end specifications for the audio system 18 Annex 1 . Annex 2 . Annex 3 . Annex 4 . Annex 5 . Annex 6

9、. Annex 7 . Annex 8 . List of definitions and abbreviations . Message channel specification (to be added later on) . . Frame structure at 64 kbit/s for multimedia applications Procedures for handling of Facsimile signals . Procedures for handling of SPTV signals . Procedures for handling of Telewrit

10、er signals . Procedures for handling of Telematic signals . Procedures and protocols to be performed by the MCU . 26 . 28 . 29 . 30 . 31 . 32 . 33 . 34 1 CEPT T/N*33-OL*E 87 232b414 OOObL33 4 1. 1.1. 1.2. 2. 3. 3.1. TIN 33-01 E Page 3 SCOPE Introduction A potential market for Audiographic Teleconfer

11、encing Service is now in evidence, resulting from tech- nological progress which makes possible satisfactory performance in a commercially viable way. Audiographic Teleconference is a means for teleconferencing, like telephoneconference and videocon- ference. It offers a conference facility of bette

12、r quality and more possibilities than telephoneconference although less than videoconference because of the lack of moving pictures, but is less expensive than videoconference. Information on human factor aspects is essential, but can only be obtained in the relevant context during a considerable pe

13、riod of experience. In order to open the new service on the basis of a European standard and to avoid any restraints on the service development the Recommendation set out here offers the basic elements for an international digital Audiographic Teleconference Service. Reference is made in the Recomme

14、ndation to compatibility with other related services, for example videoconferencing as described in CEPT Recommendation T/L 01-02, and visual telephony: at some time in the future it could be anticipated that distinctions between these three services will tend to disappear, and should then be covere

15、d by a single Recommendation covering a range of bitrate options. This document presents the Recommendation, including definition and description of the services and facilities offered, technical specifications for equipment, and alignment and operating procedures. A number of sections are included

16、as headings only for completeness of the structure of the Recommendation, but in fact require further study. Although this Recommendation contains references to both point-to-point and multipoint applications, for the time being only point-to-point working has been specified. Also the envisaged mess

17、age channel has not fully been specified yet and will be added to this Recommendation later. Definition of audiographic teleconference Real time conferencing among individuals or groups of individuals at separate Iocations by means of audioterminals together with the possibility of transmission of n

18、on-moving visual information, telematic information and control and indications (speaker identification, floor request, etc.). DEFINITIONS AND ABBREVIATIONS See Annex 1. SERVICES AND FACILITES This section provides descriptive infoimation concerning the Audiographic Teleconference Service from the p

19、oint of view of customers and marketing organisations. Further details, including technical specifications, are considered in later sections of the Recommendation. Service description A service for real time communication between groups of users in different locations, combining a good audio facilit

20、y with optional auxiliary facilities such as still pictures, facsimile, telewriting, character or graphic format, etc. The service is applicable to companies private audiographic teleconference rooms, as well as to public-access audiographic teleconference rooms for hire on an occasional basis; it i

21、s applicable to a variety of types of audiographic teleconference terminals, including multi-purpose committee rooms used only part-time for audiographic teleconference as well as dedicated studios; it is applicable also to “mobile” or “site-transferable” audiographic teleconference facilities and e

22、ven desk top terminals. The service is bidirectional via public switched or private telecommunication networks, and provides for interconnection of two or more terminals on an equal basis. In the case of switched calls, the user must be assured of availability (the probability of successfully dialli

23、ng up the connection must be high), and may also require an assurance of condentiality. Edition of February 10, 1988 CEPT T/N*33-01*E 87 E 2326434 0006334 6 E T/N 33-01 E Page 4 3,2. 3.2.1. 3.2.2. 3.2.3. 3.3, 3.3.1. 3.3.2. 3.3.3. 3.3.4. 3.4. Basic facilities The basic facilities consist in the prima

24、ry means for audiovisual communication, namely an audiochannel together with transmission capability for additional control and telematic data and messages. Audio System By the design of the room and/or the equipment participants should be allowed to listen and speak simultaneously; speech transmiss

25、ion is of 7 kHz bandwidth. Data Transmission The basic service provides for a data port for the use of the customer in any way he wishes. Additional data channel An additional data channel is permanently included which may be used to provide for the control and management of the audiographic telecon

26、ference system and for user messages (see section 5.2.). Other facilities Since practical experience of audiographic teleconferencing is still very limited, there is no clear consensus as to which auxiliary facilities must be provided; the audiographic teleconference system specification therefore s

27、eeks to avoid constraints upon the users by providing for a wide range of possibilities, leaving to the customer the choice as to which should be implemented. Here follows a (non-exhaustive) list of the facility options which a potential user may consider. Subjectively the quality of the audio shoul

28、d not be greatly affected by providing this meeting aids. Ergonomic reasons suggest that the number of display screens be reduced to a minimum. The following auxiliary facilities may be provided by use of a data transmission channel as in 3.2.2. above: Still Picture TV System As for videoconferencin

29、g, a display camera can be used to capture pictures of objects (charts/diagrams, documents, solid objects). The nature of a still picture TV codec is such that indefinite retention and display of the still picture at the remote end is possible. Facsimile Facsimile documents may be transmitted at any

30、 time on a point-to-point call, using a digital facsimile machine. X- Y Devices (including Telewriter) Several proprietary devices are available which can be used for remote pointing (cursor function) or remote writing, or both. Input devices include writing tablet, light pen, mouse, ball and joysti

31、ck. The resulting information can be displayed independently, or superimposed on another picture. Still Pictures of Participants In the case where a company possesses a videoconference the videoconference type terminal may be used for audiographic teleconferencing, transmitting only still pictures.

32、The “split-screen allows the combination of the outputs from two cameras, each viewing up to three people, into a single video signal; similarly, at the remote end, the two half-height pictures can be separated for display on two adjacent screens. Audiographic teleconference Terminals In general, it

33、 is not possible to standardise completely all aspects of audiographic teleconference rooms and equipment: much will depend on the size and shape of the accommodation which the customer has at his disposal, and on the choice of optional facilities. Furthermore, considerable scope can be allowed to e

34、quipment, suppliers in the styling and detailed facilities of their products, which will not materially affect the international service itself. To ensure correct interworking of terminals on the international service, it is only necessary to ensure complete adherence to the electrical interface spe

35、cifications and observance of the audio and video align- ment procedures, as described in this Recommendation and in the Videoconference Recommen- dation T/L 01-02. Edition of February 10, 1988 3.5. 3.6. 3.6.1. 3.6.2. 3.6.3. 3.6.4. 3.6.5. 3.7. 3.8. 3.9. 3.10. 3.11. 3.11.1. T/N 33-01 E Page 5 Control

36、s and indications In general, the controls to be operated by the user are kept to a minimum. Apart from call set up, audio mute and volume control, further controls will depend on the optional facilities present. Normally one person (“the conductor”) at each terminal may be appointed to operate thes

37、e controls, though this is not essential. The system itself does not require the appointment of a conductor but provides the facilities whereby this may he done. Quality of service Transmission Peiformance The worst-case transmission assumed in the above paragraphs is of an error rate of 1 : lo4. Th

38、e networks to be used for the audiographic teleconference service are assumed to be so specified that such an error rate may only occur extremely rarely. Routing The choice of the routing should ideally not influence the quality of service. If satellite transmission is employed, the delay thus intro

39、duced affects the quality of service. More than two satellite hops should hence be avoided. Conjden tiality Must be guaranteed. Adio Quality The basic service provides for an audio channel 7 kHz bandwidth. For the case of interworking with telephony, videoconference and videophone details are given

40、in chapter 9. Data transmission The data channel provided offers a worst-case bit error rate of 1 : lo4. Network requirements Service offerings are based on digital access at 64 kbit/s or 2x64 kbit/s. Further details are given in section 5.1. Operational aspects Subject to study. Geographical availa

41、bility The service will be available wherever 1 or 2 x 64 kbit/s transparent links are provided. Tariffs and charging aspects Each connection of the conference contributes to the charge. An additional charge must be paid for providing the Multipoint Control Unit, MCU(s) (and tesminal if applicable).

42、 Normally the convenor has to pay for the whole conference. The option should be provided that each participant will be charged for his connection to the MCU(s) and the convenor additionally for the MCU(s). The audiographic teleconferencing process One can distinghish several phases in the overall p

43、rocess of an audiographic teleconference: 1. reservation 2. Set-up 3. session 4. recovery and reconguration 5. disconnection Reser va tion In order to ensure the performance of an audiographic teleconference service for an appointed time reservation will be required at least for the MCU(s). Normally

44、 reservation will be handled by the customer as the service will be an automatic one, Administrations may provide also a manual version of a reservation system. This process is normally left to each Administration, however general guidelines for an harmonized operation of the International Audiograp

45、hic Teleconference Service follow. Edition of February 10, 1988 - T/N 33-01 E Page 6 The reservation is performed through the operator service. The following information must be given by the convenor: - list of participating terminals, - starting time of the session, - closing time of the session, -

46、 symbolic name of the session, - symbolic names of the terminals. It will be possible for a convenor to get access to the Reservation Centre (RC) through an ordinary telephone connection to register a reservation for a conference. A data terminal can be used in an automatic system, alternatively it

47、can be performed by voice in a manually operated system. The RC determines which MCU(s) and which connections are required for the meeting and subsequently reserves these facilities. It modifies each terminal to what MCU it has to connect. During a conference session the conductor may have the possi

48、bility to get access to the reservation diary by using his control and indicators device. In this way it will be possible during a conference meeting to agree on a following conference. Set-up of the conference session The start of a conference is decided by the conductor. There are two possibilitie

49、s in switched networks: the connections are established from the terminal or the connections are established from the MCUs. For the case that a terininal is to be added during a meeting initiation from the terminal should be possible. In the case that more MCUs are connected the RC notifies the MCUs which MCU establishes the connection(s) to the other MCU(s). In order to avoid ambiguity each conference session may have a symbolic name which is given in the reservation phase. As soon as the connection between a terminal and its MCU is established, the terminal enters the S