CONTENTS

1 Scope
2 Normative references
3 Definitions
4 Abbreviations
5 System descriptions
5.1 Multipoint Control Unit
5.2 Various VC connection configurations
5.2.1 N-point tightly coupled connection case
5.2.2 A point-to-multipoint without return channels case
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
5.3 Initial VC connection directions
6 Call signalling procedure
7 MCU functions
7.1 MC functions
7.2 MP functions
7.2.1 Video switching and mixing
7.2.2 Audio switching and mixing
7.2.3 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 Master/slave determination
7.4.2 Mode preferences
7.5 Clock synchronization
7.5.1 General
7.5.2 STC generation in MP
7.5.3 Transmission clock synchronization
7.6 MCU-MCU interconnections
8 Basic communication procedures using H.245 controls
8.1 General
8.2 Procedure for determining capabilities and selected communication mode
8.3 Initialization procedures for establishing communication between standard terminals and an MCU
8.3.1 First terminal added to conference
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
8.4 Video processing
8.4.1 Video switching
8.4.2 Video mixing
8.4.3 Combination of video switching and mixing
8.5 Mode switching and data broadcast procedures
8.5.1 Bit-rate symmetry
8.5.2 Mode switching for data distribution in multipoint conferences
8.6 MCU-MCU interconnections
8.7 Exceptional procedures
9 Advanced communication procedures using T.120/T.130 controls
10 Security considerations
11 Interoperability with other H-series terminals
11.1 Interoperability with H.320/H.321 terminals
Annex A Point-to-multipoint audiovisual VC setup and release procedures based on Recommendation Q.2971
A.1 Setup of the first party
A.2 Adding a party
A.3 Dropping a party
A.4 Information Elements for SETUP message