ITU-T H 243-2005 Procedures for establishing communication between three or more audiovisual terminals using digital channels up to 1920 kbit s (Study Group 16)《使用1920Kbit s以内的数字信道.pdf
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1、 International Telecommunication Union ITU-T H.243TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2005) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Communication procedures Procedures for establishing communication between three or more audiovisual terminal
2、s using digital channels up to 1920 kbit/s ITU-T Recommendation H.243 ITU-T H-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS H.100H.199 INFRASTRUCTURE OF AUDIOVISUAL SERVICES General H.200H.219 Transmission multiplexing and synchronization H.220
3、H.229 Systems aspects H.230H.239 Communication procedures H.240H.259 Coding of moving video H.260H.279 Related systems aspects H.280H.299 Systems and terminal equipment for audiovisual services H.300H.349 Directory services architecture for audiovisual and multimedia services H.350H.359 Quality of s
4、ervice architecture for audiovisual and multimedia services H.360H.369 Supplementary services for multimedia H.450H.499 MOBILITY AND COLLABORATION PROCEDURES Overview of Mobility and Collaboration, definitions, protocols and procedures H.500H.509 Mobility for H-Series multimedia systems and services
5、 H.510H.519 Mobile multimedia collaboration applications and services H.520H.529 Security for mobile multimedia systems and services H.530H.539 Security for mobile multimedia collaboration applications and services H.540H.549 Mobility interworking procedures H.550H.559Mobile multimedia collaboration
6、 inter-working procedures H.560H.569 BROADBAND AND TRIPLE-PLAY MULTIMEDIA SERVICES Broadband multimedia services over VDSL H.610H.619 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. H.243 (10/2005) i ITU-T Recommendation H.243 Procedures for establishing communicat
7、ion between three or more audiovisual terminals using digital channels up to 1920 kbit/s Summary This Recommendation concerns the system operation for a conference call between three or more audiovisual terminals conforming to ITU-T Rec. H.320. This revised version of ITU-T Rec. H.243 introduces a n
8、umber of enhancements and clarifications to the previous version, primarily the description on the usage of Unicode characters in H.320 systems. Source ITU-T Recommendation H.243 was approved on 7 October 2005 by ITU-T Study Group 16 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T
9、 Rec. H.243 (10/2005) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and
10、 tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Re
11、commendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Reco
12、mmendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interopera
13、bility or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that co
14、mpliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, valid
15、ity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required
16、to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2006 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without
17、the prior written permission of ITU. ITU-T Rec. H.243 (10/2005) iii CONTENTS Page 1 Scope 1 2 References. 2 3 Conventions 3 4 Capabilities and “selected“ communication modes 3 5 Initialization procedures for establishing communication between standard terminals and an MCU 5 5.1 First terminal added
18、to conference . 5 5.2 Second terminal added to conference. 6 5.3 Third terminal added to conference 7 5.4 Fourth and subsequent calls added to conference 7 5.5 Extension to multiple channels. 7 5.6 Other standard terminals. 8 5.7 MCU-MCU interconnections . 8 5.8 Closure of conference. 10 5.9 User-in
19、itiated connection establishment. 10 6 Video switching and mixing. 11 6.1 Video switching procedure. 11 6.2 Video mixing 12 6.3 Automatic switching and visualization-forcing 20 7 Numbering of terminals 23 7.1 Numbering method. 23 7.2 Terminal-MCU interconnection . 24 7.3 MCU interconnection . 26 7.4
20、 Terminal identity information 27 8 Mode switching and data broadcast procedures . 29 8.1 General mode switching. 29 8.2 Mode switching for data distribution in multipoint conferences 32 9 Chair-control procedure using BAS codes . 39 9.1 General . 39 9.2 Assignment, release and withdrawal of chair-c
21、ontrol token 40 9.3 Information available to the chair-control terminal 41 9.4 Video selection . 41 9.5 Terminal dropping by chair-control . 42 9.6 Withdrawal of data tokens by chair-control . 42 9.7 Request for floor. 42 9.8 Dropping the entire conference 42 10 BAS sequencing 43 11 Capability excha
22、nge during a call. 43 iv ITU-T Rec. H.243 (10/2005) Page 12 Procedure for loop detection at an MCU 43 13 Exceptional procedures. 44 13.1 A terminal connected does not indicate capability for the SCM 44 13.2 Contention resolution principle 44 14 MCU loopback procedures. 45 15 Interactions with T.120
23、control. 46 15.1 Chair-control interactions. 46 15.2 Interactions with passwording 46 15.3 Interactions with TIX/TIA 46 15.4 Interactions with SCM management 47 15.5 Rate matching in a cascade. 47 Appendix I C logically, however, there is no relationship between these conferences; the text herein re
24、fers to an MCU only as a logical entity pertinent to the particular call of concern. This Recommendation concerns only the flow of signals along the fixed digital paths, which may be at 64 kbit/s (56 kbit/s in certain networks) or multiples thereof up to 1920 kbit/s. The flow consists of a multiplex
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