video over IP

For many years,video telephony and video conferencing were limited to circuit-switched networks. It was not until the advent of packet-switched IP networks and the use of powerful routers that provide differentiated support for quality of service( QoS) at OSI layers 2 and 3 that the transmission technology requirements for packet-switched video transmissionsarose. The influence of quality of service on video transmission is considerably higher than that for Internet telephony( VoIP).

Technically, Internet telephony created the prerequisites for IP-based video conferencing, with the provision of higher bandwidth being the minor problem. The ITU recommendations of the H.320 series and the IP-oriented Session Initiation Protocol( SIP), as high- performance transmission protocols for moving image transmission in circuit- and packet-switched data networks, were co-decisive for the realization. Transmission security can be provided via Virtual Private Networks ( VPN) with tunneling and encryption of video data, as in Internet telephony(VoIP). In addition, Secure Realtime Transport Protocol( SRTP) can be used for secure transmission and authentication.

As far as image quality is concerned, there are various approaches from the International Telecommunication Union (ITU) with H.261, H. 263 and H.264, but also from the Joint Video Team( JVT), which developed the high-performance video compression H.26L with MPEG, which is officially designated H.264.