Standards

A digital network uses bits per second (bps) as a measure of the capacity for transmitting data. One ISDN box contains two channels, where each of them handles up to 64 kbps. Videoconferencing has typically been using three ISDN boxes during the last years. This equals a maximum capacity of 384 kbps. By increasing the maximum capacity to at least 512 kbps or preferably at least 768 kbps, most movements, which enter into an educational setting, become smoothly. Thus, high quality connections in distance training should at least use 764 kbps as a minimum level, as this makes possible to use this learning environment for many hours in a distance-learning course.

At the beginning of the 90’s were expensive group based videoconferencing products developed. These systems were designed to transfer compressed audio and video through networks, which could guarantee a minimum transmission rate. It exists for the moment an “umbrella” of recommendations that set standards for entities that provide video communication over packet-based network. They are labelled H.3xx. The H.320 protocol (1990) was one of the first standards for how synchronously communication should be done. The International Telecommunication Union (ITU) has established a separate standard, H.323 (1996/1998), for audio and video communication through IP networks.

H.323 is a standard that describes the protocols, services and equipment necessary for multimedia communications including audio, video and data on networks without guaranteed Quality of Service (QoS). H.323 transfers a signal as a stream of packets. Various types of equipment, which are produced by different companies, should be interoperable in this network such that the different video terminals could communicate together. End-users should not need to think on compatibility when they start using video communication. The networks technologies may include Fast Ethernet, Ethernet, and Token Ring, and protocols like Integrated Packet Exchange (IPX) or Internet Protocol (IP). You can learn more about H.263 by selecting H.263 from menu.

The ITU did approve the H.264 video compression standard in July 2003. ITU is an international organization within the United Nations System that, among other things, works with private and public sectors to develop standards that benefit users of telecommunication systems worldwide. It is the highly efficient encoding and decoding of H.264 that enables organizations to communicate over both ISDN and IP networks with twice the video quality as compared to older standards, without any increase in network costs. Sharp video, which earlier did required 768 kbps of bandwidth, can now be achieved at only 384 kbps bandwidth. This new resolution-independent standard also enables better results for display devices and video capture, improving applications such as remote viewing of documents consisting of freeze-frames.

Universities, which are looking for reduced leaps in communications efficiency and effectiveness, can immediately take advantage of one of the latest developments in the history of collaboration technologies by selecting the H.264 video compression standard. If they carefully select the right video communications systems, users will manage to experience twice the video quality, with no increased network costs, and a reduced total cost of ownership. Systems capable of running H.264, i.e. they should have been produced no later that January 2003, are backwards compatible in such a way that they support both H.263 and H.261 endpoints.

The advent of the new and more powerful MCU (or bridges) and gateways allow H.261, H.263, and H.264 endpoints to coexist in the same conference. Furthermore, new software will enable most modern MCUs to support the H.264 algorithm. Organizations that plan to acquire new video communications systems for the first time or upgrading their existing installed base systems, should clearly only invest in H.264 compatible systems. Various producers are still not compatible on H.264, i.e. a multipoint conference containing Tandberg- and Polycom codecs at the endpoints, will automatically down speed to the old H.263 standard.