Videoconferencing Standards

The International Telecommunications Union (ITU) (formerly: Consultative Committee on International Telegraphy and Telephony (CCITT)) has three umbrellas of standards for videoconferencing
ITU H.320 is known as the standard for public switched telephone networks (PSTN) or videoconferencing over integrated services digital networks (it is accessible to anyone with a high speed Internet connection, such as DSL).
H.264 SVC (Scalable Video Coding) is a compression standard that enables video conferencing systems to achieve highly error resilient IP video transmission over the public Internet without quality of service enhanced lines. This standard has enabled wide scale deployment of high definition desktop video conferencing and made possible new architectures which reduce latency between transmitting source and receiver, resulting in fluid communication without pauses.
In addition, an attractive factor for IP videoconferencing is that it is easier to set-up for use with a live videoconferencing call along with web conferencing for use in data collaboration. These combined technologies enable users to have a much richer multimedia environment for live meetings, collaboration and presentations.
The Unified Communications Interoperability Forum (UCIF), a non-profit alliance between communications vendors, launched on May 19, 2010. The organization's vision is to maximize the interoperability of UC based on existing standards. Founding members of UCIF include HP, Microsoft, Polycom, Logitech/LifeSize Communications and Juniper Networks.
ITU V.80: videoconferencing is generally compatibilized with H.324 standard point-to-point video telephony over regular phone lines.

source:Wikepedia