How+it+works

toc IP Videoconferencing speed is measured in Kbps (kilobits per second). Better audio and video quality is achieved at a higher speed. Frame rate can be adjusted to improve the video on slower networks. The closer the unit is to the core of the network the better for performance. Calls can be point-to-point (1 to 1) calls or multi-point calls.

=Main components=
 * 1) camera
 * 2) video display
 * 3) audio components (speakers)
 * 4) user interface (software or polycom unit)

=Protocol Standards= H.323. The H.323 protocol standard for multimedia communications (VoIP) was designed for real-time transfer of audio and video over IP networks. H.323 supports set-up, tear down and forwarding/transferring of calls. The component parts of H.323 are terminals, gateways, gatekeepeers and multi-point control units (MCU's). H.323 can run on TCP or UDP. It is the preferred standard for videoconferencing. Terminal - (codec) - unit that the user uses to place the call Multi-point Control Unit - bridge - mixes audio and video components of a multi-point call, enables participants to meet in a virtual meeting room Gateway - devices that allow H.323 equipment to "talk" to other equipment using different protocols Gatekeeper - optional device that can be used to register endpoints, resolve addresses (ie. you don't need to know my IP address just the gatekeeper and my extension), admission control, bandwidth control and manages calls.

SIP. SIP is Session Initialization Protocol, another protocol standard for VoIP. It also can be used to set-up, tear down and forward/transfer calls with one or multiple users. It uses port 5060 and applies text headers to the bodies of messages. H.245. The H.245 protocol standard establishes channels between end points when a call is made. It does not assign content to those channels. At least one channel will be split into an audio and video feed from end point to end point.

H.261, H.263 and H.264. These protocols are used to compress video during videoconferencing.

H.239. The H.239 protocol standard was patented by Polycom as their People + Content feature in 2000. Polycom offered free license versions of their protocol and in 2003 it was merged with Tandberg's standard as the industry standard. This protocol establishes one channel in the call to transmit data or an additional video signal.

=Types of systems=

Web-based

 * U-Stream - chat only
 * Yugma
 * Elluminate (Not H.323)
 * AIM, Skype (Not H.323)
 * iChat (Not H.323)

Desktop - software for PC or MAC, webcam, microphone, speakers

 * MAC - Xmeeting, iChat
 * PC - Microsoft NetMeeting
 * Both - Web X, Skype, AIM
 * Postives: low price, good audio
 * Negatives: poor video, only point to point

Desktop - Application sharing

 * PC - Netsharing

Mobile Room Units

 * Polycom
 * Tandberg

Room Units

 * Polycom
 * Tandberg

Testing Sites provided by Polycom

 * http://www.polycom.com/usa/en/support/documentation/video_test_numbers.html