ITU-T H.243-2005
使用1920Kbit/s以内的数字信道在3个或以上视听终端间用于建立通信的程序.研究组16

Procedures for establishing communication between three or more audiovisual terminals using digital channels up to 1920 kbit/s Study Group 16

标准号

ITU-T H.243-2005

发布日期

2005年

实施日期

废止日期

无

中国标准分类号

M63

发布单位

IX-ITU

引用标准

ISO 639-1-2002 ISO/IEC 10646-2003 ITU-T G.711-1988 ITU-T G.722-1988 ITU-T G.728-1992 ITU-T H.221-2004 ITU-T H.224-2005 ITU-T H.230-2004 ITU-T H.231-1997 ITU-T H.233-2002 ITU-T H.242-2004 ITU-T H.261-1993 ITU-T H.262-2000 ITU-T H.263-2005 ITU-T H.320-2004

适用范围

This Recommendation concerns the system operation for a conference call between three or more audiovisual terminals. It is applicable to a single MCU containing an audio mixer and a video switch according to the provisions of ITU-T Rec. H.231, to calls involving two such MCUs, and to calls involving three or more MCUs in a star configuration. It is also applicable to MCUs containing a video mixer. ITU-T Recs H.233 and H.234 address issues concerning the use of the Encryption Control Signal (ECS). ITU-T Rec. H.242 provides for communication between two audiovisual terminals connected point to point, using the frame structure defined in ITU-T Rec. H.221. ITU-T Rec. H.230 defines a number of Control and Indication signals, including those used in the multipoint communication procedures described in this Recommendation. Three or more audiovisual terminals may be put into communication to form a conference call, by means of one or more Multipoint Control Units (MCU). The general principles of multipoint communication are described in ITU-T Rec. H.231. The means by which digital channels are established between terminals and MCUs, and between MCUs, is outside the scope of this Recommendation (see ITU-T Rec. H.200/AV.420). It should be noted that the physical realization of an MCU may be such that two or more independent conferences may be set up within the same unit; logically, however, there is no relationship between these conferences; the text herein refers 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 of audio, video, control and indication signals, and optional user data as defined in ITU-T Rec. H.221 which must 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 ITU-T Rec. H.221: the BAS commands define explicitly how the demultiplexer at the end of each link shall operate. Likewise, the basic procedures for initialization and mode switching are fully in accordance with those defined in ITU-T Rec. H.242 for point-to-point working. However, the composition of the multiplexed signal transmitted by each terminal and by the MCU is determined by terminal procedures and multipoint system procedures, as follows: a) Terminal procedures are defined in service-specific system Recommendations, such as ITU-T Rec. H.320 for visual telephony. b) Multipoint system procedures are defined in this Recommendation and are not of themselves service-specific. c) ITU-T Rec. T.120: by making use of the T series, 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 methods are described here. For definitions of terms used in this Recommendation, see ITU-T Rec. H.231; for definitions of SBE and MBE symbols, see ITU-T Rec. H.230.

谁引用了ITU-T H.243-2005 更多引用