Videoconferencing background: Other Technologies

This page is intended to provide background information regarding developments in the videoconferencing world.

The future of H.323

Most of the work on improving what we'd call "regular" videoconferencing appears to be going in the way of establishing H.239 as a replacement standard for H.323. Its importance lies in its ability to transmit simultaneously two image streams: one for standard video, and one for data. It is presumably a good idea to verify H.239 compliance when purchasing new hardware.


The company Skype has released a program for Windows, Mac, Linux and PocketPC which provides free Voice-over-IP (VOIP) service. The main advantage of this software is the incredible simplicity of its use: download, install, signup for a free account and you are ready to go. The software avoids all the complications of special firewall configurations, different codecs etc.

Video capabilities are currently only available for the Windows client but updates for the Mac and Linux clients to support video are expected soon. The software also allows up to 10 people to connect provided that the host machine uses an Intel CPU (this is due to a special deal with Intel and applies to both PCs and Macs). Other CPUs have a connection limit of 4.

Finally Skype also provides a service called Skypeout to dial ordinary telephones from your computer client. This service is currently free to call a Canadian or US phone from anywhere in the world and 2.4 cents (Canadian) a minute to call most of Europe.


AccessGrid is yet another videoconferencing software tool, with origins at Argonne National Laboratory. It is geared rather towards professional use. One noteworthy feature is that it uses multicasting rather than broadcasting: as a result, for large conferences, bandwidth can become a serious issue.


The Session Initiation Protocol or SIP is a project that is independent of the H.323 protocol. Inter-operability is however being worked on; and some clients (GnomeMeeting, as of version 1.3; and SeeVogh/Vidyo) are capable of dealing both with SIP and with H.323.

IP Telephony

With the advent of ubiquitous broadband IP connections, Voice Over IP (VoIP) tools in general are gaining momentum. For instance, Skype is a widely used, freely available (but closed-source) program allowing for IP telephony between computers. In addition, they sell software interfacing to ordinary telephones.

Technical information on IP telephony can be found in the IP Telephony cookbook.