1、 STD-ITU-T RECMN H.297-ENGL 1998 m 4862593 Ob54328 339 INTERNATIONAL ITU=T TELECOMMUNICATION UNION TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU H.247 (09198) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Infrastructure of audiovisual services - Communication procedures Multipoint extension for bro
2、adband audiovisual communication systems and terminals ITU-T Recommendation H.247 (Previously CCITT Recommendation) STD-ITU-T RECMN H-2Li7-ENGL 1998 D 48b2592 Ob5Ll329 275 D ITU-T H-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS Characteristics of transmission channels used for other than
3、 telephone purposes Use of telephone-type circuits for voice-frequency telegraphy Telephone circuits or cables used for various types of telegraph transmission or Telephone-type circuits used for facsimile telegraphy H. 1 O-H. 1 9 H.20-H.29 H. 30-H .39 simultaneous transmission H.40-H.49 Characteris
4、tics of data signals CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS INFRASTRUCTURE OF AUDIOVISUAL SERVICES H.50-H.99 H.100-H.199 General H .200-H .219 Transmission multiplexing and synchronization H.220-H.229 Systems aspects H.230-H.239 Com Coding of moving video H .260-H .279 Related systems aspects H
5、 .28O-H .299 Systems and terminal equipment for audiovisual services Supplementary services for multimedia H. 300-H. 399 H ,450-H ,499 I Forfirther details, please refer to ITU-T List ofRecommendations. STD-ITU-T RECMN H-247-ENGL 1998 48b259L Db5Li330 T97 ITU-T RECOMMENDATION H.247 MULTIPOINT EXTENS
6、ION FOR BROADBAND AUDIOVISUAL COMMUNICATION SYSTEMS AND TERMINALS Summary This Recommendation describes and specifies the means by which three or more H.3 1 O audiovisual communication terminals operating in the native mode may communicate simultaneously over B-ISDN and/or customer premises ATM netw
7、ork, such communication being designated a “multipoint call“. It also covers conference configurations including other H-series terminals. Source ITU-T Recommendation H.247 was prepared by ITU-T Study Group 16 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 25th of Sept
8、ember 1998. STD-ITU-T RECMN H-21r7-ENGL 1798 = 48b257L Ob54331 723 FOREWORD IT (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (IT-T) is a permanent organ of the IT. The IT-T is resp
9、onsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by th
10、e ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the IT-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary stand
11、ards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibi
12、lity that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the
13、 Recommendation development process. As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest i
14、nformation and are therefore strongly urged to consult the TSB patent database. O ITU 1998 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from th
15、e ITU. I II Recommendation H.247 (09/98) STD-ITU-T RECMN H.ZLi7-ENGL 1998 48b2591 Ob54332 BbT CONTENTS Page 1 Scope 1 2 Nonnative references 3 3 Definitions 4 4 Abbreviations . 6 5 System descriptions Various VC connection configurations N-point tightly coupled connection case . A point-to-multipoin
16、t without return channels case 5.1 Multipoint Control Unit 5.2 5.2.1 5.2.2 5.2.3 N1-point tightly coupled and n2-point loosely coupled connection case . 5.2.4 A point-to-multipoint with return channels case . Initial VC connection directions . 5.3 6 6 7 7 7 8 8 10 6 Call signalling procedure 10 7 MC
17、U functions . 7.1 MC functions 7.2 MP functions 7.2.1 7.2.2 7.2.3 Video switching and mixing . Audio switching and mixing . Data broadcast procedures - Interactions with T.120 series protocols . 7.3 MR functions 7.4 Use of the H.245 control channel . 7.4.1 Masterklave determination . 7.4.2 Mode pref
18、erences 7.5 Clock synchronization. . STC generation in MP . 7.5.3 Transmission clock synchronization . 7.5.1 General 7.5.2 7.6 MCU-MCU interconnections . 10 10 10 11 11 11 11 12 12 12 12 12 13 14 14 8 Basic communication procedures using H.245 controls 14 8.1 General . 14 8.2 Procedure for determini
19、ng capabilities and selected communication mode 14 8.3 Initialization procedures for establishing communication between standard terminals and an MCU 14 8.3.1 First terminal added to conference 14 . Recommendation H.247 (09/98) 111 STD-ITU-T RECMN H.247-ENGL 1778 D 48b2591 Ob54333 7Tb D 8.4 8.5 8.6
20、8.7 9 10 11 8.3.2 Second terminal added to conference 8.3.3 Third terminal added to conference . 8.3.4 Fourth and subsequent calls added to conference . 8.3.5 Closure of conference Video processing 8.4.1 Video Switching . 8.4.2 Video mixing . Mode switching and data broadcast procedures . 8.5.1 Bit-
21、rate symmetry 8.5.2 Mode switching for data distribution in multipoint conferences MCU-MCU interconnections . Exceptional procedures . Advanced communication procedures using T . 120/T . 130 controls . Security considerations . Interoperability with other H-series terminals 8.4.3 Combination of vide
22、o switching and mixing Page 16 17 18 18 18 18 19 19 19 19 20 20 20 20 20 20 . 1 1.1 Interoperability with H.320M.321 terminals 20 Annex A . Point-to-multipoint audiovisual VC setup and release procedures based on Recommendation Q.297 1 . 20 A.1 Setup of the first party 21 A.2 Adding a party 21 A.3 D
23、ropping a party . 21 A.4 Information Elements for SETUP message 21 iV Recommendation H.247 (09/98) Recommendation H.247 MULTIPOINT EXTENSION FOR BROADBAND AUDIOVISUAL COMMUNICATION SYSTEMS AND TERMINALS (Geneva, 1998) 1 Scope This Recommendation concerns the system operation for a conference call be
24、tween three or more H.3 1 O terminals operating in the native mode. It also covers conference configurations including other H-series terminals. It is applicable to a single Multipoint Control Unit (MCU) that multicasts the multiplexed stream without any audio mixing nor video switching, and to a si
25、ngle MCU containing audio mixers and video switches. It is also applicable to an MCU containing video mixers, and to multiple MCUs. Recommendation H.3 1 O provides for communication between two audiovisual terminals connected point-to-point, using the multimedia multiplexer and network adaptation de
26、fined in Recommendations H.222.0 and H.222.1. Recommendation H.245 defines a number of Control and Indication signals, including those used in the multipoint communication procedures described in this Recommendation. Three or more native H.3 1 O terminals may be put into communication to form a conf
27、erence call, by means of one or more MCUs. It should be noted that the physical realization of an MCU may be such that two or more independent conferences are set up within the same unit; logically, however, there is no relationship between these conferences; the text herein refers to an MCU only as
28、 a logical entity pertinent to the particular call of concern. This Recommendation envisions providing: o a simple protocol stack that can support various applications (e.g. high-quality videoconferencing, distance learning and corporate TV broadcasting); mixture of bidirectional and multicast conne
29、ctions used in a panel discussion, and unidirectional connection like TV broadcasting); H.323, H.324; a support for various VC connection configurations (e.g. asymmetric bandwidth connection, o a conference configuration including other H-series terminals, i.e. H.320, H.321, H.322, an option support
30、ing continuous presence video display (video mixing); a multicast capability that significantly reduces the network traffic. o o For various VC connection configuration examples, the following are within the provision of this Recommendation: o n-point tightly coupled connection (e.g. multipoint vide
31、oconference); nl -point tightly coupled and n2-point loosely coupled connection (e.g. broadcast panel conference); a point-to-multipoint connection with some return channels (e.g. multipoint TV lecture). a a point-to-multipoint connection without return channels (e.g. broadcast conference); o o Reco
32、mmendation H.247 (09/98) 1 STD-ITU-T RECMN H-247-ENGL 1998 D 48b259L DI354335 577 D Figure 1 shows the general scope of H.247 conference configuration. There are two basic multipoint configurations: MCU-based multipoint vs. decentralized multi-party multipoint. In the interest of traffic load which
33、is significant in the broadband environments, this Recommendation specifies MCU-based multipoint configurations. Decentralized multi-party multipoint is for future study. H247 I- Tl4840-98 1 H.310 ROT 1 I“/ I I I I +-+ H.245 control VC (bidirectional) AV uplink VC (unidirectional) - AV VC (bidirecti
34、onal) 1111, AV multicast VC (point-to-multipoint) d-+ Other network channel Figure 1M.247 - General scope of H.247 conference configuration This Recommendation concerns the flow of signals along ATM virtual channel of B-ISDN or customer premises ATM network. The flow consists of a multiplex of audio
35、, video, control and indication signals, and optional user data as defined in Recommendation H.222.0 which should be handled by the MCU in a way which is satisfactory to the users. The signal multiplex on each path is fully in accordance with Recommendation H.222.0. Likewise, the basic procedures fo
36、r initialization and mode switching are fully in accordance with those defined in Recommendations H.3 10 and H.245 for point-to-point working. However, the composition of the multiplexed signal transmitted by each terminal and by the MCU is determined by terminai procedures and multipoint system pro
37、cedures, as follows: 4 terminal procedures are defined in service-specific system Recommendations, such as Recommendation H. 3 1 O for audiovisual communications systems and terminal equipment; b) multipoint system procedures are defined in this Recommendation, and are not of themselves service-spec
38、ific; c T.120/T.130: by making use of the T-series Recommendations, MCU and terminal procedures may be greatly enhanced, offering far more sophisticated specific applications to the user. Such enhancement is outside the scope of this Recommendation, although interactions with specific T. 120/T. 130
39、methods are described here. 2 Recommendation H.247 (09/98) STD-ITU-T RECMN H.ZLi7-ENGL 1778 48b2591 Ob5433b 405 The multipoint conferencing procedure and the MCU for H.320iH.321 interoperation mode of H.3 10 terminal are defined by Recommendations H.23 1 and H.243. 2 Normative references The followi
40、ng ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Rec
41、ommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. CCITT Recommendation G.711 (1988), Pulse Code Modulation (PCM)
42、 of voice fiequencies. ITU-T Recommendation H.221 (1997), Frame structure for a 64 to 1920 kbith channel in audiovisual teleservices. ITU-T Recommendation H.222.0 (1 995) I ISOAEC 138 18-1 : 1996, Information technology - Generic coding of moving pictures and associated audio information: Systems. I
43、TU-T Recommendation H.222.1 (1 996), Multimedia multiplex and synchronization for audiovisual communication in ATM environments. ITU-T Recommendation H.23 1 (1 997), Multipoint control units for audiovisual systems using digital channels up to I920 kbps. ITU-T Recommendation H.235 (1998), Security a
44、nd encryption for H-series (H.323 and other H. 245 based) multimedia terminals. ITU-T Recommendation H.243 (1 997), Procedures for establishing communication between three or more audiovisual terminals using digital channels up to I920 kbps. ITU-T Recommendation H.245 (1 998), Control protocol for m
45、ultimedia communication. ITU-T Recommendation H.26 1 (1 993), Video codec for audiovisual services at p x 64 kbith. ITU-T Recommendation H.262 (1 995), I ISOAEC 138 18-2: 1996, Information technology - Generic coding of moving pictures and associated audio information: video. ITU-T Recommendation H.
46、3 1 O (1 998), Broadband audiovisual communication systems and terminals. ITU-T Recommendation H.320 (1 997), Narrow-band ISDN visual telephone systems and terminal equipment. ITU-T Recommendation H.321 (1 998), Adaptation of H.320 visual telephone terminals to B-ISDN environments. ITU-T Recommendat
47、ion H.332 (1 998), H. 323 extended for loosely coupled conferences. ITU-T Recommendation 1.363.1 (1 996), B-ISDN ATM Adaptation Layer specification: Type I AAL. ITU-T Recommendation 1.363.5 (1 996), B-ISDN ATM Adaptation Layer specification: Type 5 AAL. ITU-T Recommendation 4.293 1 (1995), Digital S
48、ubscriber Signalling System No. 2 - User-Network Interface (UN4 layer 3 speciJication for basic caWconnection control. Recommendation H.247 (09198) 3 ITU-T Recommendation 4.2941.1 (1 997), Digital Subscriber Signalling System No. 2 - Generic identifier transport. ITU-T Recommendation 4.2961.1 (1 999
49、, Digital Subscriber Signalling System No. 2 - Additional trafic parameters: Additional signalling capabilities to support traflc parameters for the tagging option and the sustainable cell rate parameter set. ITU-T Recommendation 4.2961.2 (1 997), Digital Subscriber Signalling System No. 2 - Additional trafic parameters: Support of ATM transfer capability in the broadband bearer capability information element. ITU-T Recommendation 4.2971 (1995), Digital Subscriber Signalling System No. 2 - User- network interface layer 3 specijkation for point-t
