【 Weak current College 】 multimedia conferencing multipoint control units in the basic functions and testing methods---Power By 【 China power house network 】

Multimedia conferencing multipoint communication and Conference control in general there are two application types:
A circuit-switched networks to multipoint control unit (MCU) focus on the multiple points of control and management, based on H.320 proposed 64kbit/s s--1920kbit/is the use of multimedia conferencing MCU connect multiple Terminal and achieve more control, ITU-T this launched H.243, H.231 and T.120, and a series of related recommendations.
Another suitable mechanisms based on packet switching network environment (H.323), H.323 conferencing multipoint control and management of work can be used similar to H.320 systems, all Terminal via point-to-point (logical connection) and MCU, MCU in multipoint controller (MC) by H.245 realize multipoint control functionality, multiple point MCU processor (MP) for multi-point audio and video switching, synthesis, forwarding, etc.; other H.323 conferencing multipoint control and management of work can be distributed in multiple points of control and management, the management has no MCU, MCU function to MC and MP function module forms exist in the system of another device, place the network packet switching and Terminal from different terminal of group recognition function, realization of multicast capabilities.
64kbit/s s-1920kbit/H.320-based multimedia conferencing business by ISDN, DDN network to support its technology is more mature, China has a large number of inputs used, therefore, based on H.320 MCU of multi-point control method is currently in the implementation of the project multimedia conferencing and business operations in the us are concerned about a problem. This article on multipoint control unit of basic functions and testing methods.
MCU function models include: control module, the audio module, video modules, data module and ports and interfaces for conference control, such as call establishment, end the connection; implementation through the Exchange with the Terminal control and indicates that the signal to manage meetings; audio and video switching, synthesis, forwarding, etc. MCU transmission interface: PRI/BRI, G.703, E1, V.35 interface RS-449 or.
MCU for multimedia conferencing multipoint control consists of a series of communication procedures. Its multipoint communication of basic principles of the recommendation by H.321, multipoint communication and Conference control procedure recommended by H.243, H.243 recommendations is based on the recommendations set forth in H.221 bit rate allocation signals (BAS) to pass the proposed definition of control H.230 and indicates (C&I) signal for multipoint communication and Conference control. This is based on the BAS multipoint control mechanism in the present and multimedia conference wider application. In addition T120 recommends the use of multiple layer protocol (MLP) data channel to deliver the relevant control information with enhanced control function, can support multiple points of communication and Conference control. Here, mainly based on the BAS multipoint control mechanism. I. establishment of communication of the initialization process
For each meeting, the first in the MCU provides a selected communication model (SCM), including audio, video and data communication pattern, MCU in during a call, the SCM should be maintained.
If the MCU is set to dial-in session mode, the Terminal to the MCU dial; the MCU to support dynamically allocated or preset dial out, should also be able to establish a connection session. II. audiovisual conference control mode
Narrow-band multimedia conference-system for audio-visual Conference control, you can use voice control, forces the picture control, Chairman of the control, operation control Director mode. The first three models in line with the provisions and ITU-T H.231, the vast majority of manufacturers H.243 products also support the four modes. 1. the Chairman of the control mode
Chairman of the control mode is frequently used in multimedia conference to feature, support the President's control MCU should be able to assign a number to each terminal, each terminal is assigned a unique number MT, 1-191, (192-223 retention), M is assigned to a local MCU 8-bit number, T is the local MCU assigned to terminal of an 8-bit number. The control mode, the main venue of the exercise of the powers of the President, the President of the master "token" and control of the exercise session.
Provided to the Chairman of the controlling terminal information including: TM
The connected terminals and the assigned number MCU--Terminal number indicates the TIN, M, T, from the call to remove any Terminal number--Terminal disconnect indicates TID, M, T, and enter the video related terminal number--VIN, M, T;
Voice request--Terminal voice request indicates VIF, M, T.
Main MCU receives the TIN, M, T and TID, M, T after they forwarded; TM should send to the host MCU TCU to extract the current session of the Terminal code table.
At least three meetings a session state television Terminal, as in the figure of T1, T2 and T3. 
1 President control mode: President control gets command (CCA) and the Chairman of the control indicates that the token (CIT). From the Terminal T1 for President token, testing was successful. Then, the President of the token, T1 release check other terminal can obtain control of the President. Terminal T1 application is successful, the President of the token from the MCU to recover control of the token, the President should immediately stop the President T1, and send to the MCU. CIS when President token control is released or recover, video switching control should turn voice prompting. 
2 President control mode: Terminal indicates the layer requests (TIF). Chairman of the Terminal T1 owned by token, T2 and T3 for venue, check the T1 is approved, the decision whether the Terminal Hall broadcast out. 
3 President control mode: broadcast video instruction (VCB). Chairman of theTerminal T1 has a Terminal token T2 site broadcast out, checkedCheck other terminal of the video source is the venue for the T2. 
4 President control mode: President video selection (VCS) (optional). In the Terminal T1 has a Chairman, elected at the token Terminal T2, check the Terminal T3 video source is a President-T1, and the Chairman-T1 video source to be elected at the Terminal T2 meeting.
(5) the removal of the Terminal (CCD). Chairman of the Terminal T1 has, from the session token, removing a terminal connection test was successful.
(6) recover data token (DCR). In the Terminal T1 has, after the President of the token data transmission status to terminate the data transfer.
(7) the removal of the entire Conference (CCK). In the Terminal T1 owned after the removal of the President of the token to the participation of relevant connection (last removal of the Chairman of the Terminal). 2. mandatory Imaging control mode-point directive Visual force (MCV)
Any venue forced to MCU sends the site MCV signals to other broadcasting Terminal, at the same time, the MCU sends to the Hall Terminal "play", so to speak at know its image and voice received by another site, and then the venue Terminal release force Imaging control, check is successful. 3. speech excitation mode
At the meeting of the State's three videoconferencing terminals are located at the sound of three rooms, respectively in T1, T2 and T3 venue, check on the venue is broadcast out.
In speech excitation mode, the check can be above describes the VCB, VCS, MCV, control mechanisms beyond. 4. the operator control mode
In the absence of the President by MCU console T1, T2, respectively, broadcasting and T3, inspection other terminal of the video source is to be broadcast venue. Third, the voice function
At least two conferences in the State television Terminal session.
1. echo cancellation
At the meeting of the State's two Conference TV Terminal is located in the noise of thetwo rooms, speaker, speaking at the end, check in the side speakers can hear in their own speech voice.
2. mute function
The client himself is muted, speaking in a different terminal, check whether the local terminal can hear other sounds of the terminal's statement, unmute after they hear. Through operator control so that the end is muted, press the above method checks the local terminal of the mute function.
3. mute audio function
This side is mute the sound, and then speak, check whether the other terminal can hear the voice of the end-to-speak, cancel the mute tone can be heard. Through operator control so that the end is mute the sound, press the above method checks the local terminal of the mute audio features. Fourth, video features
1. multi screen display (split)
MCU video composite enable video conferencing terminal can also see a point in the image above (may also include local image, four separate H221 multimedia bit stream into the MCU, is divided into single media streaming, video mix it several video stream combination that creates a composite image.
MCU appear composite image, it is sent to all Terminal video combination indicates (VIC) M, where M is the combination:.
When the end image combination MCU operation, it should be available to all terminals send VIN that returns video switching.
At least three meetings a session state television Terminal, as T1, T2 and T3. By MCU worktop broadcasting all over the screen, check the T1, T2 and T3 are able to see more pictures of cutting.
2. screen time sequencing switch
Check the MCU worktop can switch each venue regularly take turns. 5. data
The system consists of two levels with a MCU and three terminals, one of the top MCU, MCU as acting as a data conference top of GCC and top MCS.
1. more static images and annotations Exchange features (T.126)
In established data session, the endpoints are started T.126 application:
(1) a still image exchange. In an endpoint on open a bitmap file, and add that file to send out meeting all Terminal should receive the file, and display on the screen. Bitmap files can be uncompressed, T.4 (G3), T.6 (G4), T.81 (JPEG) or T.82 (JBIG) format.
(2) text callout. In an endpoint on open a bitmap file in the file comment text (including text editors, such as font, color, size, etc.) and to send the file out, meeting all Terminal should receive the file, and display on the screen.
(3) the drawing. Open the Whiteboard in the whiteboard to create some graphics, such as points, lines, circle, rectangle, color, alignment, etc., other Terminal in local Whiteboard should appear above created graphics.
(4) editing features. A Terminal on the creation of graphics editing (copy, paste, delete, select, etc), other Terminal in local Whiteboard should appear appropriate graphics editing.
(5) keyboard and mouse event Exchange and remote operation. A terminal using the mouse and keyboard in a local build path and storage/open file, and participating in other Terminal in local should appear the same action.
(6) multiple page Whiteboard. Participants terminal building multiple page whiteboard, one Terminal in different Whiteboard created different graphics or text, and other participating Terminal in local should appear and the creation of graphics or text the same content.
2. more binary file transfer (T.127) established data session, the endpoints are started T.127 application:
(1), multicast a binary file. In a Terminal pre-selection an arbitrary file formats, the file is sent to the participants a terminal shall receive the file compare before and after the transfer; the file size and content are there should be no different.
(2) multipoint simultaneous transmission of two or more binary files. In aA Terminal pre-selection of two or more arbitrary file formats, these files are sent at the same time, the participants receive terminal should be; compare transport these files before and after the file size and content are there should be no different. Sixth, the MCU management-session parameter settings
By MCU control desk set session parameters, such as: participating terminal list, transfer rate, voice and image Protocol and data communication rate and so on, check whether you can successfully set. VII. management of the MCU on the Terminal
At least three meetings a session state television Terminal.
1. the Conference process monitoring in the MCU appear at each venue console has joined the Conference, a meeting is being broadcast, President and LSD token belong to which venue, etc.
2. public capacity set becomes a venue console comes through MCU appear at the remote site's ability to set.
3. channel status monitor in the MCU appear at each venue console or from the central State. VIII. PTZ control functions. At least two conferences in the State television Terminal session.
1. control remote camera movement during the end-to-use remote control to adjust the remote camera around campaigns, check the remote camera and image are as far remote command and movement.
2. controlling a remote camera focal length at the distal end-to-use remote control to adjust the camera's focal length, check the remote camera focal length is as far remote commands. 9. multiple group meeting
Make a MCU and at least four Terminal is in two different set of meetings, check whether the two group meeting, do not disturb each other independently. 10. rate matching function
At least three terminals in the same group meeting State, examine whether the different rate of terminal can be joined by MCU to the same session, and the image quality is good. 11, exception handling and belt electric plug
The switch type MCU, at least three terminals in the same group session state, disable the master during a meeting with the Board, check whether the spare board can immediately switch-boards. 12. two-stage cascade-cascade MCU.
If the MCU is E1 interface, two MCU through E1 connections, so that at least two MCU and three terminals in the same group meeting State, in either Terminal Executive Chairman application (CCA, CIT), Chairman of the video selection (VCS) and video broadcasting (VCB), check whether you can successfully complete.
If the MCU is BRI interfaces, from ISDN MCU M2 by M1 call main MCU, so that at least two MCU and three terminals in the same group meeting, in either Terminal Executive Chairman application (CCA, CIT), Chairman of the video selection (VCS) and video broadcasting (VCB), check whether you can successfully complete.
Multipoint communication and Conference control technology is the key technology of multimedia Conference, due to the specification for control based H.243 consume less than the rate, and more flexible, is the multimedia conferencing equipment should have basic skills. As a user on meeting the functional requirements and continuous improvement, multipoint communication and Conference control technology is also more complex.