Video-Conferencing
From BingWiki
Video-conferencing is a means to communicate via live video and audio with a remote location. Video phones and video chat clients can also be considered video-cnferencing. Two users must be using the same or compatible protocols in order to communicate. For a multi-point video-conference, a Multi-point Control Unit (MCU) is needed to mix the various video and audio streams together. Each user participating runs a client known as an endpoint. This can be software program or a specialized hardware device. Software endpoints require separate Web Cams in order to send video, but none are required to receive and display video. Many users will also require a microphone or headset in order to send their voice.
There are several standard protocols used for video-conferencing. ISDN endpoints typically use H.320, and are usually hardware-based. Internet (and especially Internet2) video-conferencing often uses H.323, which is a standard that encompasses many technologies. To be considered H.323 compliant, the endpoint must support a minimum subset of those technologies, which include video and audio encoders which compress the data size and allow for more efficient use of bandwidth. This translates into smoother video and audio for the session. Session-Initiated Protocol is also used for video-conferencing, but it is most popular for audio-conferencing alone, and it is the dominant protocol used by Voice over Internet Protocol (VoIP). Services such as Vonage, Earthlink's Vling, Time Warner Digital Phone, and AT&T CallVantage all use SIP-based VoIP to deliver calls from a digital phone (a hardware audio endpoint) to the regular phone system.
There are many program which can be used for video-conferencing, and some of the most popular ones can be found below:
NetMeeting is the venerable video-conferencing endpoint developed by Microsoft. It is already installed on most Windows computers and support features like Application Sharing and a Whiteboard. Unfortunately Microsoft has officially stopped development of this project because it competes directly with Microsoft Live Office, which allows for video-conferencing and real-time collaboration, but unlike NetMeeting is not free to downlaod or use. As a result it only supports some of the older, more basic protocols of H.323 which are now becoming rapidly out-dated.
Ekiga is a fast and flexible video-conferencing endpoint, developed initially for Linux users, but work has been done to port the endpoint to other operating systems. The program used to be called GnomeMeeting, a reference to its similarity to and compatibility with NetMeeting. The change in name reflects the fact that while NetMeeting has stagnated and no new features have been added to it, Ekiga has kept up with current standards and now supports both H.323 and SIP. Currently the project has clients available for Linux and Windows.
XMeeting is a Macintosh video-conferencing endpoint and it is based upon the same powerful codebase that Ekiga is developed from. As a result, they interoperate extremely well. Older Macitoshes must use the OhPhoneX program, which is similar to GnomeMeeting and also borrows code from OhPhone, which was developed by the OpenH323 project.
Other Endpoints
Other popular endpoints include Polycom PVX and vPoint HD. While neither of these are free, they provide support for a very rich set of compression standards and features which make them premier endpoints for high quality video-conferencing. Both are only available for Windows. Currently, Polycom PVX provides the best image and sound quality available for a software-based endpoint.
Many instant messenger programs, such as Trillian Pro, Yahoo! Messenger, MSN Messenger, and AOL Instant Messenger include support for video cameras. Yahoo! Messenger also supports VoIP audio-conferencing. Google Talk and Gaim are working on adding these capabilities to their programs, but they are currently not available. Apple iChat AV also supports video-conferencing and even provides multi-point capabilities without an MCU. However, it is only available for Macintosh and requires a firefire camera like the Apple iSight. To use USB Web Cams with iChat, you will need iChatUSBCam which costs about 10 dollars, but the trial version is free for 30 days.
Other non-standard video-conferencing programs inlcude Skype and Sony IVE (Instant Video Everywhere), which use proprietary protocols that are not compatible with any other programs. Currently both of these programs are free to download and use.
