The 4 types of AV conferencing systems are categorized by how their transmission operates. The H.32x standards are defined by the International Telecommunication Union.
1. H.324 - Transmission over analog telephone line.
2. H.320 - Transmission over ISDN telephone line.
3. H.323 - Transmission over TCP/IP ethernet.
4. MBone - de facto standard for multicast over computer network.
Point-to-point connection - 2 participants.
15 frames per second.
Very easy to set up and use. Calling rates apply.
http://www.dlink.com/products/?pid=302 videophone $375
http://picturephone.com/products/vialta_beamer_tv.htm TV set top box $150
2 participants on basic units, 4 participants on multiple control units.
ISDN charges apply. http://gnrt.terena.nl/content.php?section_id=228
PPL operates H.320 teleconferences from conference rooms with ISDN connections.
Each participant connects to the conference using an H.323 client. The client is a combination of hardware and software that can receive and transmit audio and video. One approach is to use a computer with a-v accessories and conferencing software.
USB video camera, headset, microphone - Logitech under $100
If the audio is output on speakers then the microphone may need echo cancellation preprocessing. Otherwise the audio from the speakers will be picked up by the microphone and sent back to its original source. Some combined camera, speaker microphone units have echo cancellation - Polycom viaVideo II - USB; $600; Mac isight - $150. A speakerphone with a computer interface box can also broadcast the audio and provide echo cancellation.
Netmeeting - Windows XP, free download, 2 participants
OhphoneX - Mac OS, free download, 2 participants; uses Mac iSight camera and audio hardware.
VRVS - XP, Mac, Linux; free download, multiple participants, web browser access
MSN Messenger - XP, free download, 2 participants, pay per use
Polycom pvx software - XP, $150
Webex - central server, subscription fee
Polycom WebOffice conferencing portal - subscription fee
Microsoft live communications server
iChat - Mac, included in OS X, 4 participant video, 10 person audio; is not compatible with H.323 clients.
Similar hardware environment as H.323, uses computers plus audio/video accessories. Data is multicast for more efficient transmission to multiple sites. Network must support multicast and pass through firewall. The software for handling the video is a program called vic which can send and receive multiple video windows. The audio software is called rat. These programs can be used by themselves for conferencing. They have also been integrated into the Access Grid software which has collaborative presentations and a meeting framework of virtual rooms. All the software is public domain.
H.323 conferencing on existing computers with Internet access. USB camera, audio headset with attached microphone. Echo cancellation not required because audio is not broadcast out loud.
VRVS software because it runs on XP, Mac, and Linux. It is widely used and is controlled through a web browser interface. The video windows could be displayed on the NSTX Display Wall. VRVS is free to download and free to operate from a browser interface. Parts of it must be installed on the user's computer and the user must register. ESnet endorses VRVS for conferencing.
Some integration of hardware and software is required.
Other H.323 programs, such as netmeeting and iChat, may be able to connect to VRVS. This is something to test.