1、 STD-ITU-T RECMN F.731-ENGL 1447 = 48b259L Ob37184 271 D INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU F.731 (07197) SERIES F: NON-TELEPHONE TELECOMMUNICATION SERVICES Audiovisual services Multimedia conference services in the ISDN ITU-T Recommendation F
2、.731 (Previously CCITT Recommendation) ITU-T F-SERIES RECOMMENDATIONS NON-TELEPHONE TELECOMMUNICATION SERVICES TELEGRAPH SERVICE Operating methods for the international public telegram service The gentex network Message switching The international telemessage service The international telex service
3、Statistics and publications on international telegraph services Scheduled and leased communication services Phototelegraph service Mobile services and multidestination satellite services TELEMATIC SERVICES Public facsimile service Teletex service Videotex service General provisions for telematic ser
4、vices MOBILE SERVICE MESSAGE HANDLING SERVICES DI RECTORY SERVICES DOCUMENT COMMUNICATION Document communication Programming communication interfaces DATA TRANSMISSION SERVICES AUDIOVISUAL SERVICES ISDN SERVICES UNIVERSAL PERSONAL TELECOMMUNICATION HUMAN FACTORS F.1-F. 1 O9 F.1-F.19 F.20-F.29 F. 30-
5、F.39 F.40-F.58 F.59-F.89 F. 90-F. 99 F. 100-F. 104 F. 105-F. 1 O9 F.110-F.159 F.l I O-F. 159 F. 160-F.399 F. 160-F. I99 F.200-F.299 F.300-F.349 F.350-F.399 F.400-F.499 F.500-F.549 F.550-F.599 F.550-F.579 F.580-F.599 F.600-F.699 F.700-F.799 F. 800-F.849 F. 850-F. 899 F.900-F.999 For further details,
6、please refer to ITU-T List of Recommendations. STD-ITU-T RECMN F.73L-ENGL 1777 W 48b2571 Ob3718b Cl44 D ITU-T RECOMMENDATION F.731 MULTIMEDIA CONFERENCE SERVICES IN THE ISDN Source ITU-T Recommendation F.731 was prepared by ITU-T Study Group 16 (1997-2000) and was approved under the WTSC Resolution
7、No. 1 procedure on the 10th of July 1997. STD-ITU-T RECMN F.731-ENGL 1777 1 Li8b2571 b37187 T8O 1 FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent
8、organ of the ITU. The ITU-T is responsible 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, est
9、ablishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within
10、 ITU-Ts purview, the necessary standards 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 Th
11、e ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The IT takes no position concerning the evidence, validity or applicability of claimed Intellectual Propery Rights, whether asserted by IT
12、U members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU had/had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned th
13、at this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 1997 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,
14、 without permission in writing from the ITU. 11 Recommendation F.731 (07/97) STD-ITU-T RECMN F.731-ENGL L797 4b2591 Ob37188 917 W CONTENTS Page 1 4.3 4.4 4.5 7.2 8 9 9.1 9.2 9.3 Introduction . Configuration Terminal aspects . 6.2.7 Conference management procedures . Roles of the participants . List
15、of service profiles Interworkinglintercommunication Attributes values . General . Service independent attributes Service specific attributes . Annex A . Multipoint Conference Units (MCUs) Recommendation F.731 (07/97) 1 1 2 2 2 3 3 3 4 5 . 111 STD-ITU-T RECflN F-732-ENGL 1777 = Li8b259L Ob37187 853 R
16、ecommendation F.731 MULTIMEDIA CONFERENCE SERVICES IN THE ISDN (Geneva, 1997) 1 Introduction This Recommendation describes the Multimedia Conference Services supported by an ISDN. It relies on Recommendation F.702 for the main body of the description, and only gives the specific complements relevant
17、 to the ISDN, which derive from its capabilities and its limitations. Thus when reading this Recommendation, it is necessary to refer back to Recommendation F.702. The numbers of the clauses are those of Recommendation F.702, and thus they do not form a continuous sequence because only a few clauses
18、 need a specific complement for the ISDN. In addition there is a new clause 9 on the attributes for the various profiles. 4.3 Configuration In the ISDN, all connections are bidirectional symmetric. When several B-channels are used, they are synchronized through the frame alignment process of Recomme
19、ndation H.221, so that a single composite channel is formed, where audio, video, data and control signals are multiplexed and are allocated specific subchannels. Data and enhanced control signals may be multiplexed in a common packet subchannel supporting the T.120-Series protocol (whereas basic con
20、trol signals are in the BAS channel of Recommendation H.22 1). The various possible configurations supported by these connections are as follows: a) point-to-point between two terminals; b) c multichannel multipoint for the continuous presence mode; shared channel around one or more MCUs: the audio
21、channels are mixed, the data signals are multiplexed (if present) in a common T.120 subchannel; this is the usual mode in the case of an audiographic conference or of CDH without video (see 7.1R.702); when video is present, the pictures from the different sources are combined into a single picture w
22、ith several windows; switched multipoint operation: the audio signals or the video signals or both are switched in the MCU(s); this is the usual mode for the videoconference service, with mixed audio and a single switched video picture; multiple switched video subpictures are for further study. d) 4
23、.4 Roles of the participants The basic control signals in the BAS channel allocate the roles of Chairman and controller jointly; they can only be separated inside the terminal equipment. The T.120-Series protocol allows separate allocation of call control, chair control and facility control. 4.5 Ter
24、minal aspects The normal audio mode for conferencing services is wideband audio conforming to Recommendation G.722. A G.711 codec should also be present for interworking purposes. G.728 coding may also be used in intenvorking or fallback situations, or temporarily to leave a larger bandwidth to the
25、video or to the data subchannels, e.g. while showing an object or transmitting a document. Recommendation F.731 (07/97) 1 Video codecs should conform to Recommendation H.261. The possible use of higher quality codecs is for further study. 6.2.7 Conference management procedures All terminals should c
26、onform to the procedures in Recommendation H.242. Multipoint procedures are those of Recommendation H.243. Media components other than audio and video should be transmitted on a common data subchannel supporting the T. 120-Series protocol. 7.2 List of service profiles The following service profiles
27、may be offered over an ISDN. Videoconference services - Profiles 1 a: Basic videoconference service on two B-channels; terminals should conform to Recommendation H.320; Profiles Ib: Standard videoconference service on six B-channels (or one HO-channel); terminals should conform to Recommendation H.3
28、20; Profile 1 c: Enhanced videoconference service; for further study; Profile 1 d: High quality videoconference service; for further study. - - - Audiographic conference services - Profiles 2: All audiographic conference services use wideband audio conforming to Recommendation G.722 and a data subch
29、annel supporting the T. 120-Series protocol. Cooperative document handling services - Profiles 3: All cooperative document handling services have audio to one or more of the Recommendations G.711, G.722, G.728; they have a data subchannel supporting the T.120-Series protocol, and in particular T.127
30、 for file transfer; other data functions are for further study; H.261 video is optional. Videophone conference supplementary services - Profile 4b: Basic videophone conference supplementary service; this supplementary service applies to basic videophone terminals on one or two B-channels, and does n
31、ot require any specific enhancements to the terminals; these terminals conform to Recommendation H.320, have G.728 and/or G.722 audio codecs (and G.711 for intenvorking purposes) and H.261 video codecs; on two B-channels, the profile is the same as Profile la except that G.722 coding is only optiona
32、l instead of mandatory. Interworking/intercommunication All terminals have the media component audio. The basic common audio mode is G.722. However, some videophone terminals (and possibly some CDH terminals) may not have that capability; in that case G.711 is used, or alternatively G.728 if all ter
33、minals in the conference have that capability. For the media component video, all terminals which support it use H.261 coding. They will always be able to communicate with this coding algorithm, by aligning the bit rate of the video subchannel on the lowest bit rate. If the resulting quality is not
34、sufficient, then a higher bit rate may be chosen, with some terminals relegated to secondary status and participating with sound (and possibly data) only. 2 Recommendation F.731 (07/97) For the other media components, all terminals using them have a common data subchannel with the T.120 protocol. Th
35、e bit rate of the subchannel will be aligned on the terminal with the lowest bit rate capability. However, this does not imply that all terminals will have a common media component. For instance a group of participants may be able to exchange facsimile while another group (overlapping or not) may ex
36、change still pictures. 1 9 Attributes values Attributes Values Transfer mode Circuit 9.1 General In the ISDN, only point-to-point independent channels can be established. When several B-channels are used in a connection, they are based on separate independent calls and synchronized in-band. Similarl
37、y, in a multipoint configuration, each connection between a terminal and an MCU or between two MCUs is an independent point-to-point connection. The same also applies for HO-channels. When two or more B- (or HO-) channels are needed to support a connection, one of them supports the audio and BAS con
38、trol subchannels; the call for establishing this channel is referred to as Call 1. Except when otherwise stated, the values of the attributes are the same for Call 1 and for the other calls involved in the connection. 3 4 9.2 Service independent attributes The following attribute values are applicab
39、le to all multimedia conference service profiles. 1) Low layer attributes Transfer capability Call 1 : unrestricted digital information with tonesannouncements Other calls: unrestricted digital information Structure 7 kHz integrity 5 6 1 2 1 Transfer rate 1 64 kbit/c I Establishment of communication
40、 Symmetry Bidirectional symmetric Demand or reservation 7 Configuration of call Point-to-point Recommendation F.731 (07/97) 3 STD.ITU-T RECMN F.731-ENGL 1997 m 48b2.572 b37L72 348 m Attributes 9.3 Values Access attributes 8 9.1 Access channel and rate D(16) or D(64) for signalling, B(64) for user in
41、formation Rec. 1.430/1.431 Signalling access protocol, Layer 1 9.2 9.3 Signalling access protocol, Layer 2 Signalling access protocol, Layer 3 Rec. 4.921 Rec. Q.93 1 9.4 9.5 Information access protocol, Layer 1 Information access protocol, Layer 2 Rec. H.221 Rec. H.230 Service specific attributes 9.
42、6 The following attribute values are applicable to the communication as a whole, even when two or more separate calls are established in the network to support the required connection. They are generally dependent upon the multimedia conference service profiles. Information access protocol, Layer 3
43、Rec. H.242, Rec. H.243 3) High layer attributes 10 11 12 13 14 Attributes Type of user information Layer 4 protocol functions Layer 5 protocol functions Layer 6 protocol functions Layer 7 protocol functions Values Audio (in Call 1 only) + video andlor data Rec. G.711, Rec. G.722 or Rec. G.728 for au
44、dio Rec. H.261 for video (profiles 1,4, optional for profile 3) T.120-Series for data (profiles 2,3, optional for profiles 1,4) 4 Recommendation F.731 (07/97) STDmITU-T RECMN F.731-ENGL 1977 4b2571 Ob37193 284 4) General attributes 15 16 17 18 Attributes Supplementary services provided Quality of se
45、rvice Intercommunicationlinterworking possibilities Operation and commercial aspects Values For further study Audio: 7 kHz telephony for profiles 1, 2 telephone quality for profiles 3,4 Video: see 5.3.2.2F.702 Synchronization of audio and video: no subjectively discernible delay between sound and im
46、age Data: for further study With other multimedia conference services with videophone service with telephony with other services: for further study For further study ANNEX A Multipoint Conference Units (MCUs) MCUs shall conform to Recommendation H.23 1 and use the procedures of Recommendation H.243.
47、 In a conference, all connections have the same overall bit rate and the same allocation of bit rates to the audio, video and data subchannels, whether between a terminal and an MCU or between MCUs. The exception to this is the connection to a terminal with secondary status, which cannot use all the
48、 subchannels and may thus be connected at a smaller bit rate. The possibility of additional or broader subchannels on inter-MCU connections is for further study. Recommendation F.731 (07/97) 5 STD-ITU-T RECMN F-73L-ENGL 1997 W 48b257L Ob37194 110 Series A Series B Series C Series D Series E Series F
49、 Series G Series H Series I Series J Series K Series L Series M Series N Series O Series P Series Q Series R Series S Series T Series U Series V Series X Series Z ITU-T RECOMMENDATIONS SERIES Organization of the work of the ITU-T Means of expression: definitions, symbols, classification General telecommunication statistics General tariff principles Overall network operation, telephone service, service operation and human factors Non-telephone telecommunication services Transmission systems and media, digital systems and networks Audiovisual and multimedia
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