MCU Videoconferencing

A guide to multipoint conferences using the H.323 protocol

 

Introduction

With currently existing hardware and software, internet users can participate in multi-user conferences with full motion video and high quality audio.  This guide will show you how to set up and take part in one of these conferences.

 

Basic Setup

        In order to hold a videoconference with n members, n+1  computers are needed.  Each participating member of the conference needs his/her own computer, and one must be a dedicated server.  This server will run the software that controls and manages the conference, known as a Multipoint Control Unit, or MCU.  From now on, this computer will be referred to as computer M for MCU.  The other computers (known as terminals or endpoints) will be called T for terminal.  So, if three people would like to hold a conference, there must be three T computers, and one M computer.

 

Requirements

          Before the conference can take place, certain computer requirements must be met.  The following table shows the specifications for all computers participating.  The table also includes multimedia hardware.

 

Component

Required

Recommended

M computer (dedicated server)

PIII 1Ghz

128MB RAM

Win95 or above

PIV 1.5Ghz+

256MB+ RAM

Win2000

T computers (endpoints)

PII or above

64MB RAM

Win95 or above

PIII

128MB RAM

Win2000 or WinXP

Video Cameras* (on T computers)

Any USB or Parallel Port digital video camera

FireWire digital video camera

Microphones* (on T computers)

Any PC microphone

High quality microphone (for better noise cancellation)

Speakers (on T computers)

Any PC speakers

High quality speakers

Additional Software

WinZip

WinZip, Functioning Web Browser (IE or Netscape)

 

*Although the table states that a video camera and microphone are necessary on each T computer, this is not entirely true.  If a user wants to speak to the group, he/she requires a microphone, and if the user needs to be seen by the group, he/she requires a video camera.  If neither of these components are present, the user will simply be able to listen and watch the other users.

 

Preliminary Setup

Before setting up the videoconferencing software, each T computer must be properly configured to work with its multimedia hardware.  Follow the instructions of the hardware vendor in order to install the proper drivers for the video camera, microphone, and speakers.  Then, test the hardware to make sure that they operate properly; this can save the user from much future aggravation.

 

Software Installation

          The proper software for conferencing must first be installed on the M computer, then on the T computers.

 

M software

The M computer must run the following programs: OpenGK and OpenMCU.  Both of these programs are available for free from www.OpenH323.org.  To install them, follow this procedure:

 

  1. Using Internet Explorer or Netscape (or any other web browser), go to www.OpenH323.org. 
  2. On the left side of the page, click on “Download” (the first link under “Home”)
  3. Under “Download an executable for Linux or Windows”, click on the “Windows” link.
  4. Download the following four files by clicking on the “Win32” link to their right:
    1. PWLib DLL libraries
    2. OpenH323 DLL libraries    
    3. OpenMCU
    4. OpenGK
  5. If prompted, choose “Open this file from its current location”
  6. After each file finishes downloading, a WinZip window should appear.
    1. Click the “Extract” button on the menu bar of WinZip
    2. Choose the location in which you would like to install the software
    3. Create a new folder in that location by clicking the “New Folder” button in the lower right hand corner of the WinZip Extract window.  Call this folder “OpenH323”.
  7. Extract all four files to this folder.

 

T Software

The T computers must each run an H.323 compatible client.  The easiest one to use, Windows Netmeeting, is available for free from www.microsoft.com.  Certain versions of windows (such as XP) come with it already installed; before trying to download it, check that it is not already present on your computer.  If it is not, follow this procedure:

 

  1. Using a web browser, go to www.microsoft.com/windows/netmeeting/download
  2. Click on the “Windows Netmeeting 3.01” link.
  3. Follow the “How to download” instructions in order to install the program.
  4. Run the program after it is installed, following the on screen instructions to properly configure it.

 

If you would like to use a client other than Netmeeting, feel free.  Simply follow the link on the Client Table page and follow the installation information on the client’s site.

 

Setting up a Conference

            Now that the proper software has been installed, a conference can be held.  The proper software must be run on the M machine, then the T machines can log in.  To set up the conference, follow this procedure:

 

M programs

The M computer must run OpenGK and OpenMCU in order to host the conference.

 

1.  Close all running programs – they can slow down the conference.

2.  In the Start Menu, choose “Run” and type “command”, then click “OK”.

  1. In the DOS window that appears, go to the directory in which the programs were extracted.  To do this, type “cd\”, then “cd <directory name>” where <directory name> is the name of the folder in which the files have been extracted*.  *For example, if the files were extracted to c:\windows\desktop\openh323, type “cd\”, then “cd windows\desktop\openh323”.
  2. At the prompt, type the following commands, in order:
    1. “opengk install”
    2. “opengk debug”
    3. “openmcu –v”  (Modifiers can be added to this line; they will be discussed later)
  3. Minimize all windows
  4. In the Start Menu, choose “Run” and type “command”, then click “OK”.
  5. At the prompt, type “ipconfig”.
    1. Three numbers will be displayed in the command window.  The topmost one (on the line labeled “IP Address” is the IP address of the M computer.  Write this down, it will be used later.

 

T programs

The T computers each use a client program (assumed here to be Windows Netmeeting) to connect to the conference.  In order to log onto the conference server, follow this procedure:

 

  1. Close all running programs, then run Windows Netmeeting.
  2. Go to the “Tools” menu and select “Options”
  3. On the “General” tab, click on “Advanced Calling”.
    1. Check the box next to “Use a Gatekeeper to place calls” and in the “Gatekeeper” box, type the IP address of the M computer.
    2. Check the box next to “Log on using my account name” and in the “Account Name” box, enter a name that you’d like to be identified by during the conference.
  4. Click “OK”.
  5. On the “Video” tab, make sure that both “Automatically send video at the start of each call” and “Automatically receive video at the start of each call” are enabled (unless the terminal does not have a video camera attached).
  6. Click “OK”.
  7. Go to the “Call” menu and select “New Call”.
    1. In the “To” box, enter “<roomname>@<IP>” where <roomname> is the name of the conference room (this can be anything, but make sure all participants enter the same room name) and <IP> is the IP address of the M computer*.  For example, if the room name were “conference” and the M computer had IP address 100.20.30.40, “conference@100.20.30.40” would be entered.
    2. Make sure that the “Using” box says “Automatic”
    3. Click “Call”
  8. The T computer should now be connected to the conference.

 

Options

There are various options that can be changed to customize your videoconference.  When running the OpenMCU program, different modifiers can be added.  A table of options follows:

 

String

Description

Comments

--videolarge

Causes each user to transmit and receive a larger video picture

Can be used if there is sufficient available bandwidth on the LAN, but may affect audio and video quality adversely.

--videotxfps n

Sets the frame rate of the conference video to n frames per second.

n must be between 2 and 30.  A higher framerate means smoother video, but too high a framerate can affect audio and video quality adversely.

--videotxquality n

Changes the quality of the conference video

n must be between 1 and 31.  A lower value for n means better quality.  Too low an n can affect audio and video quality adversely.

--defaultroom name

Changes the default room name to name.

name is the new default room name.  In order to enter the default room, the T computer users simply enter the M computer’s IP address when making a call.

 

In order to use these options, when running OpenMCU, simply add the desired string after the “OpenMCU –v” command.  For example, if a conference with large video were needed, the command “OpenMCU –v --videolarge" would be entered at the command prompt.  To get the best possible conference quality, these settings should be tested to find the highest possible frame rate at the desired video quality without sacrificing conference stability or smoothness.

 

Remarks

There are several limitations of these procedures that must be mentioned.  First, a conference cannot support more than four participants at one time.  Second, the system is not 100% stable.  In the event of the conference freezing, simply restart the conference, following the same procedure that was used to initially start it.

 

Sources

          For more information on internet videoconferencing and on the programs recommended by this guide, please see:

         

  1. www.openh323.org
  2. www.packetizer.com
  3. www.videnet.gatech.edu/cookbook

 

 

 

 

 

 

 

Guide by Jeremy Medow with help from Alex Wong