1、 International Telecommunication Union ITU-T T.126TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (08/2007) SERIES T: TERMINALS FOR TELEMATIC SERVICES Data protocols for multimedia conferencing Multipoint still image and annotation protocol ITU-T Recommendation T.126 ITU-T T-SERIES RECOMMENDATIONS T
2、ERMINALS FOR TELEMATIC SERVICES Facsimile Framework T.0T.19 Still-image compression Test charts T.20T.29 Facsimile Group 3 protocols T.30T.39 Colour representation T.40T.49 Character coding T.50T.59 Facsimile Group 4 protocols T.60T.69 Telematic services Framework T.70T.79 Still-image compression JP
3、EG-1, Bi-level and JBIG T.80T.89 Telematic services ISDN Terminals and protocols T.90T.99 Videotext Framework T.100T.109 Data protocols for multimedia conferencing T.120T.149 Telewriting T.150T.159 Multimedia and hypermedia framework T.170T.189 Cooperative document handling T.190T.199 Telematic serv
4、ices Interworking T.300T.399 Open document architecture T.400T.429Document transfer and manipulation T.430T.449 Document application profile T.500T.509 Communication application profile T.510T.559 Telematic services Equipment characteristics T.560T.649 Still-image compression JPEG 2000 T.800T.849 St
5、ill-image compression JPEG-1 extensions T.850T.899 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. T.126 (08/2007) i ITU-T Recommendation T.126 Multipoint still image and annotation protocol Summary ITU-T Recommendation T.126 defines a protocol supporting the manag
6、ement of common multi-layer visual spaces and the multipoint exchange of graphical information directed to these spaces including images (hard and soft copy), pointers, and filled and unfilled parametric drawing elements (points, lines, polygons and ellipses). Support for rendering out-of-band video
7、 streams within T.126 workspaces is also included. In addition, keyboard and pointing device exchanges are specified to support basic user interaction. Protocol elements for creating and referencing archived visual spaces are defined to allow pre-stored or pre-distributed graphical materials to be r
8、eferenced. This protocol uses services provided by ITU-T Recommendations T.122 (MCS) and T.124 (GCC) and complies with the guidelines specified in ITU-T Recommendation T.121 (GAT). This revised version of ITU-T Recommendation T.126 introduces a number of clarifications to the previous version. Sourc
9、e ITU-T Recommendation T.126 was approved on 29 August 2007 by ITU-T Study Group 16 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. T.126 (08/2007) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunicat
10、ions. 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 them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunicatio
11、n 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 ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of info
12、rmation 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 used for conciseness to indicate both a telecommunication administration and a recognized operating age
13、ncy. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some
14、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 any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or im
15、plementation 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 Property Rights, whether asserted by ITU members or others outside of the Recommendation development proc
16、ess. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongl
17、y urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2008 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. T.126 (08/2007) iii CONTENTS Page 1 Scope 1 2 Normative references
18、 2 3 Definitions 4 4 Abbreviations and acronyms 5 5 Overview 5 5.1 SI application enrolment. 5 5.2 Capabilities and profiles. 5 5.3 Workspaces. 5 5.4 Hard copy devices 7 5.5 Bitmaps. 7 5.6 Pointers. 7 5.7 Video windows. 7 5.8 Text. 7 5.9 Drawn graphical elements 8 5.10 Remote events 8 5.11 Archives
19、8 5.12 Conducted mode behaviour 9 6 Use of MCS 9 6.1 Use of MCS service primitives. 9 6.2 Use of MCS tokens and channels. 10 6.3 Use of MCS data services. 11 7 Use of GCC 14 7.1 Use of GCC services 14 7.2 GCC unique handles. 14 8 Protocol specification . 14 8.1 Session initialization and management
20、14 8.2 Interpretation of optional parameters . 15 8.3 SI capabilities . 15 8.4 Workspaces. 24 8.5 Bitmaps. 47 8.6 Pointers. 72 8.7 Video windows. 73 8.8 Text. 77 8.9 Drawn graphical elements 77 8.10 Remote events 88 8.11 Archives 93 8.12 Conducted mode operation. 96 9 SIPDU definitions. 101 iv ITU-T
21、 Rec. T.126 (08/2007) Page Annex A SI profiles 133 Annex B Object identifier assignments 134 Appendix I Deriving intermediate palettes for bitplane progressive transmission of palettized images 135 ITU-T Rec. T.126 (08/2007) 1 ITU-T Recommendation T.126 Multipoint still image and annotation protocol
22、 1 Scope This Recommendation defines a protocol supporting the management of common multi-layer visual spaces and the multipoint exchange of graphical information directed to these spaces including images (hard and soft copy), pointers, and filled and unfilled parametric drawing elements (points, li
23、nes, polygons and ellipses). Support for rendering out-of-band video streams within T.126 workspaces is also included. In addition, keyboard and pointing device exchanges are specified to support basic user interaction. Protocol elements for creating and referencing archived visual spaces are define
24、d to allow pre-stored or pre-distributed graphical materials to be referenced. This protocol uses services provided by ITU-T Recommendations T.122 (MCS) and T.124 (GCC) and complies with the guidelines specified in ITU-T Recommendation T.121 (GAT). The details of communication with the input and out
25、put devices and the user interfaces on the host terminal are considered out of the scope of this Recommendation and are left to the discretion of the implementer. Therefore, this Recommendation makes no assumption that these I/O devices are of any specific architecture. Figure 1-1 presents an overvi
26、ew of the scope of this Recommendation and its relationship to the other elements of the T.120 framework within a single node. 2 ITU-T Rec. T.126 (08/2007) Figure 1-1 Scope of T.126 2 Normative references The following ITU-T Recommendations and other references contain provisions which, through refe
27、rence 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; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most
28、 recent edition of the Recommendations 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 F.702 ITU-T
29、Recommendation F.702 (1996), Multimedia conference services. ITU-T H.221 ITU-T Recommendation H.221 (2004), Frame structure for a 64 to 1920 kbit/s channel in audiovisual teleservices. ITU-T H.245 ITU-T Recommendation H.245 (2006), Control protocol for multimedia communication. ITU-T T.4 ITU-T Recom
30、mendation T.4 (2003), Standardization of Group 3 facsimile terminals for document transmission. ITU-T T.6 ITU-T Recommendation T.6 (1988), Facsimile coding schemes and coding control functions for Group 4 facsimile apparatus. ITU-T Rec. T.126 (08/2007) 3 ITU-T T.35 ITU-T Recommendation T.35 (2000),
31、Procedure for the allocation of ITU-T defined codes for non-standard facilities. ITU-T T.42 ITU-T Recommendation T.42 (2003), Continuous-tone colour representation method for facsimile. ITU-T T.50 ITU-T Recommendation T.50 (1992), International Reference Alphabet (IRA) (Formerly International Alphab
32、et No. 5 or IA5) Information technology 7-bit coded character set for information interchange. ITU-T T.81 ITU-T Recommendation T.81 (1992) | ISO/IEC 10918-1:1994, Information technology Digital compression and coding of continuous-tone still images Requirements and guidelines. ITU-T T.82 ITU-T Recom
33、mendation T.82 (1993) | ISO/IEC 11544:1993, Information technology Coded representation of picture and audio information Progressive bi-level image compression. ITU-T T.120 ITU-T Recommendation T.120 (2007), Data protocols for multimedia conferencing. ITU-T T.121 ITU-T Recommendation T.121 (1996), G
34、eneric application template. ITU-T T.122 ITU-T Recommendation T.122 (1998), Multipoint communication service Service definition. ITU-T T.123 ITU-T Recommendation T.123 (2007), Network-specific data protocol stacks for multimedia conferencing. ITU-T T.124 ITU-T Recommendation T.124 (2007), Generic co
35、nference control. ITU-T T.125 ITU-T Recommendation T.125 (1998), Multipoint communication service protocol specification. ITU-T X.680 ITU-T Recommendation X.680 (2002) | ISO/IEC 8824-1:2002, Information technology Abstract Syntax Notation One (ASN.1) Specification of basic notation. ITU-T X.690 ITU-
36、T Recommendation X.690 (2002) | ISO/IEC 8825-1:2002, Information technology ASN.1 encoding rules Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER), and Distinguished Encoding Rules (DER). ITU-T X.691 ITU-T Recommendation X.691 (2002) | ISO/IEC 8825-2:2002, Information techn
37、ology ASN.1 encoding rules Specification of Packed Encoding Rules (PER). ITU-R BT 601-6 ITU-R Recommendation BT 601-6 (2007), Studio encoding parameters of digital television for standard 4:3 and wide-screen 16:9 aspect ratios. ITU-R BT 709-5 ITU-R Recommendation BT 709-5 (2002), Basic values for th
38、e HDTV standards for production and programme exchange. CIE 15.2 CIE 15.2 (1986), Colorimetry, 2nd Edition. ISO/IEC 10646 ISO/IEC 10646:2003, Information technology Universal Multiple-Octet Coded Character Set (USC). ISO/IEC 13818-6 ISO/IEC 13818-6:1998, Information technology Generic coding of movi
39、ng pictures and associated audio information Part 6: Extensions for DSM-CC. 4 ITU-T Rec. T.126 (08/2007) 3 Definitions This Recommendation defines the following terms: 3.1 4:4:4: A notation that defines the relative horizontal resolution of a three-colour component raster to be equal. 3.2 4:2:2: A n
40、otation that defines the relative horizontal resolution of a three-colour component raster to have twice the horizontal resolution on the first channel than the other two. 3.3 4:2:0: A three-colour component raster having twice the horizontal resolution as well as twice the vertical resolution on th
41、e first channel. 3.4 annotation: Real-time drawings (freehand drawing, lines, rectangles, ellipses, etc.) and bitmaps (used for text and unsupported graphical elements, for example) shared between peer SICEs. 3.5 bitmap: A rectangular area described by a two-dimensional array of pixels. These pixels
42、 can be coded using a variety of encoding methods. 3.6 control points: A set of points defined in terms of the workspace coordinate system that define a drawing shape parametrically. 3.7 drawing: A type of annotation consisting of instructions for creating points, polylines, rectangles, ellipses or
43、non-standard drawing elements. 3.8 handle: A session-wide unique number used to identify an addressable item. 3.9 image: Photographic or document-oriented information which is transmitted in the form of an image bitmap. 3.10 non-standard capability: The capability is outside the scope of this Recomm
44、endation but it has been determined through negotiation that it is recognized among all session participants. 3.11 palette: A finite set of colours defined by at least three linearly-independent colour primaries. 3.12 palettized: A term used to describe visible objects (annotation bitmaps, drawing e
45、lements) comprised of palettized pixels. The colour of a palettized pixel is specified by the colour value at the location in a colour look-up table referenced by the pixel value. 3.13 plane: A virtual area defined to have the same pixel dimensions as the workspace with which it is associated. A pla
46、ne provides a canvas for the use of annotation tools such as drawing, erasing and text, as well as for bitmaps. 3.14 pointer plane: A virtual area defined to have the same dimensions as the workspace with which it is associated. This virtual area in front of all other planes houses all the pointers
47、referencing a given workspace. 3.15 pointer: A bitmap that is moveable over the workspace that is used by its creator as an indicator of position. 3.16 standard capability: The capability is defined within the scope of this Recommendation but is not required for all SICE implementation. Note that al
48、l standard capabilities must be negotiated before use. 3.17 still image conference entity: An application protocol entity that interacts with a user application above and with the local multipoint communication service (MCS) and local GCC provider below. Data are exchanged between peer SICEs using s
49、till image protocol data units (SIPDUs). 3.18 unicode: Multilingual text string format as defined in ISO/IEC 10646. ITU-T Rec. T.126 (08/2007) 5 3.19 workspace: A workspace is an area comprising N independent but coincident planes of the same pixel dimensions. The assembly of N planes forms the complete display. At a given workspace coordinate, data in any plane hides data present in underlying planes in the stack unless the pixel value at that plane is tr
