1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T H.239 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2014) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Infrastructure of audiovisual services Systems aspects Role management and additional media channels for ITU-T H.3
2、00-series terminals Recommendation ITU-T H.239 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.220H.229 Systems aspects H
3、.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 service architecture for
4、 audiovisual and multimedia services H.360H.369 Telepresence H.420H.429 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 service
5、s 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.559 Mobile multimedia collaborati
6、on inter-working procedures H.560H.569 BROADBAND, TRIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES Broadband multimedia services over VDSL H.610H.619 Advanced multimedia services and applications H.620H.629 Ubiquitous sensor network applications and Internet of Things H.640H.649 IPTV MULTIMEDIA SERVICES
7、 AND APPLICATIONS FOR IPTV General aspects H.700H.719 IPTV terminal devices H.720H.729 IPTV middleware H.730H.739 IPTV application event handling H.740H.749 IPTV metadata H.750H.759 IPTV multimedia application frameworks H.760H.769 IPTV service discovery up to consumption H.770H.779 Digital Signage
8、H.780H.789 E-HEALTH MULTIMEDIA SERVICES AND APPLICATIONS Interoperability compliance testing of personal health systems (HRN, PAN, LAN and WAN) H.820H.859 Multimedia e-health data exchange services H.860H.869 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T H.239 (1
9、0/2014) i Recommendation ITU-T H.239 Role management and additional media channels for ITU-T H.300-series terminals Summary Recommendation ITU-T H.239 defines the procedures for use of more than one video channel in ITU-T H.320-based systems, and for labelling individual channels with a “role“, whic
10、h indicates requirements for processing the channel and the role of the channel content in the call. Role labels are applicable to both ITU-T H.320 and ITU-T H.245 signalling-based systems. The defined procedures include control, indication and capability exchange mechanisms This revised version int
11、roduces a number of typographical corrections and clarifications to the previous version, primarily the description of MCU procedures. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T H.239 2003-07-14 16 11.1002/1000/6455 2.0 ITU-T H.239 2005-09-13 16 11.1002/1000/8563 3.0 IT
12、U-T H.239 2014-10-14 16 11.1002/1000/12235 Keywords AMC, capability exchange, commands, dual streams, ITU-T H.310, ITU-T H.320, ITU-T H.321, ITU-T H.322, ITU-T H.323, ITU-T H.324, multiple streams, roles, role labels, signalling, video channels, videoconferencing, videotelephony. _ * To access the R
13、ecommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T H.239 (10/2014) FOREWORD The International Telecommunication Union (ITU) is the United Nations
14、 specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on
15、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 Recommendations on these topics. The approval of IT
16、U-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 Recommendation, the expression “Administration“ is us
17、ed 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., interoperability or applicability) and compliance with th
18、e 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 compliance with the Recommendation is required of
19、 any party. INTELLECTUAL PROPERTY RIGHTSITU 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, validity or applicability of claimed Intellectual Pro
20、perty 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 to implement this Recommendation. However, imple
21、menters are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2015 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior writte
22、n permission of ITU. Rec. ITU-T H.239 (10/2014) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 2 4 Abbreviations and acronyms 3 5 Conventions 3 5.1 System terminology 3 5.2 Transport channel terminology . 3 5.3 Message names . 4 5.4 Requirement terminology . 4 6 Overview . 4 6
23、.1 Roles and role labels . 5 6.2 Additional media channels . 5 7 ITU-T H.239 capabilities exchange 5 7.1 ITU-T H.239 capabilities signals . 6 8 Control and indication (C users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Re
24、commendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T H.221 Recommendation ITU-T H.221 (200
25、9), Frame structure for a 64 to 1920 kbit/s channel in audiovisual teleservices. ITU-T H.224 Recommendation ITU-T H.224 (2005), A real time control protocol for simplex applications using the H.221 LSD/HSD/MLP channels. ITU-T H.230 Recommendation ITU-T H.230 (2009), Frame-synchronous control and ind
26、ication signals for audiovisual systems. ITU-T H.242 Recommendation ITU-T H.242 (2009), System for establishing communication between audiovisual terminals using digital channels up to 2 Mbit/s. ITU-T H.243 Recommendation ITU-T H.243 (2005), Procedures for establishing communication between three or
27、 more audiovisual terminals using digital channels up to 1920 kbit/s. ITU-T H.245 Recommendation ITU-T H.245 (2009), Control protocol for multimedia communication. ITU-T H.310 Recommendation ITU-T H.310 (1998), Broadband audiovisual communication systems and terminals. ITU-T H.320 Recommendation ITU
28、-T H.320 (2004), Narrow-band visual telephone systems and terminal equipment. ITU-T H.323 Recommendation ITU-T H.323 (2009), Packet-based multimedia communications systems. ITU-T H.324 Recommendation ITU-T H.324 (2009), Terminal for low bit-rate multimedia communication. ITU-T T.120 Recommendation I
29、TU-T T.120 (2007), Data protocols for multimedia conferencing. 2 Rec. ITU-T H.239 (10/2014) ISO/IEC 13871 ISO/IEC 13871:1995, Information technology Telecommunications and information exchange between systems Private telecommunications networks Digital channel aggregation. 3 Definitions This Recomme
30、ndation defines the following terms: 3.1 bonding: Term referring to ISO/IEC 13871, which defines “Bandwidth ON Demand“ (BOND) mechanisms. 3.2 cap: Capability message. 3.3 channel: A transport mechanism for a stream of data, such as a video stream. Examples include an ITU-T H.245 Logical Channel, or
31、the ITU-T H.320 BAS and HSD channels. 3.4 control these include ITU-T H.310, ITU-T H.323 and ITU-T H.324 systems. 5.2 Transport channel terminology In this Recommendation, the traditional ITU-T H.320 video channel, and in the case of ITU-T H.245-based systems, the sessionID 2 video channel, is refer
32、red to as the “main“ video channel. The terminology used to describe these is given in Table 1. 4 Rec. ITU-T H.239 (10/2014) Table 1 Transport channel terminology ITU-T H.239 term ITU-T H.320 channels ITU-T H.245 based channels “control channel“ BAS LC 0 “main video channel“ Traditional ITU-T H.320
33、video channel LC with no role label “second video channel“ AMC LC with an explicit role “3rd video channel“ AMC2 (for future study) LC nn etc. AMC3, etc. (for future study) LC nn 5.3 Message names In this Recommendation signalling messages which are common to both ITU-T H.245 and ITU-T H.320 signall
34、ing systems are referred to by their names as given in Annex A of ITU-T H.245, except in cases where their use in the unique H.320 signalling environment is described. Message names are presented in bold font to distinguish them from the other text of this Recommendation. Table 2 provides a referenc
35、e for corresponding ITU-T H.245 and ITU-T H.242/H.230 messages mentioned in this Recommendation. Table 2 Corresponding ITU-T H.245 and ITU-T H.320 video signals ITU-T H.245 name ITU-T H.320/H.230 mnemonic cancelMultipointConference cancel-MCC cancelMultipointModeCommand cancel-MMS logicalChannelActi
36、ve VIA, VIA2, VIA3 logicalChannelInactive VIS multipointConference MCC multipointModeCommand MMS terminalYouAreSeeing VIN videoFastUpdatePicture VCU videoFreezePicture VCF NOTE ITU-T H.320 symbols VIA2 and VIA3 signal activity of alternate video sources (for example a document camera, VCR, or DVD pl
37、ayer) on a single video channel, as described in clause 4.4 of ITU-T H.320. They do not indicate activity on alternate video channels. Activity of the primary video source on any video channel should be signalled with VIA. 5.4 Requirement terminology In this Recommendation the following conventions
38、are used: “Shall“ indicates a mandatory requirement. “Should“ indicates a suggested but optional course of action. “May“ indicates an optional course of action rather than a recommendation that something take place. 6 Overview ITU-T H.245-based systems provide for multiple channels of video, while I
39、TU-T H.320 systems provide for only a single video channel. However, neither of these define a one-way transmission method, methods to label a video channels content as a presentation video stream, or methods to Rec. ITU-T H.239 (10/2014) 5 control presentation video in a multipoint conference. This
40、 Recommendation provides these extensions, as well as a means to add an additional video channel to ITU-T H.320. The mechanisms are designed for both one-way and two-way video transmission. One-way transmission is particularly advantageous for presentation video; it reduces computational complexity
41、in the devices, and it simplifies the distribution of the presentation stream in MCUs. 6.1 Roles and role labels The architecture of this Recommendation separates the idea of transport channels (logical channels in ITU-T H.245, BAS, main video, main audio, LSD, HSD, MLP, etc. in ITU-T H.320) from “r
42、oles“. Roles, which are indicated by “role labels“ on a channel, indicate both the purpose of the stream carried on a channel, and indicate how the stream should be presented at the end-user system and processed by an MCU. The general architecture is that a role label may be assigned to any channel
43、(audio, video, or data) where it is useful to establish policies for presentation, management, or distribution of the information on that channel. 6.2 Additional media channels While ITU-T H.320 has no provision for multiple video channels, it does provide a variety of data channels (LSD, HSD, MLP,
44、H-MLP), which could be used to transport a second video stream. However, these channels are commonly used for both ITU-T H.224 and ITU-T T.120 services. Permitting a second video stream to run over these channels would interfere with these services, and complicates the allocation of these channels i
45、n a multipoint conference. In addition, use of the existing data channels is not extensible. Therefore, for ITU-T H.320, a second video channel called the Additional Media Channel (AMC) is described. In principle, this framework could be extended to include more than one AMC channel (e.g. AMC2, AMC3
46、, etc.) but as applications for more than one AMC are not well defined, this functionality is for further study. The ITU-T H.320 AMC is described in Annex B. 7 ITU-T H.239 capabilities exchange The capabilities given in this clause are distinct from those given in Annex B for the AMC. ITU-T H.239 ca
47、pabilities use very similar structures for both ITU-T H.320 and ITU-T H.245-based signalling systems, to ease the implementation of gateways and MCUs. The h239ControlCapability indicates that the device supports ITU-T H.239 and the flowControlReleaseRequest and flowControlReleaseResponse messages de
48、fined in Table 7. A separate h239ExtendedVideoCapability message expresses video capabilities used with roles. The ITU-T H.239 capability signals permit a device to send capabilities that correspond to the following ITU-T H.245 capability structure: 1 or more capabilities for traditional video chann
49、el, 1 or more capabilities for second video channel, 1 or more capabilities for main video channel while second video channel is open The 1 or more capabilities for traditional video channel shall be sent via the normal capability exchange mechanism. The 1 or more capabilities for second video channel shall be sent via the h239ExtendedVideoCapability message as described below. 6 Rec. ITU-T H.239 (10/2014) The 1 or more capabilities for main video channel while sec
