AGOCG logo
Graphics Multimedia VR Visualization Contents
Training Reports Workshops Briefings Index
This report is also available as an Acrobat file.
Back Next Contents

Chapter 3

The University of Derby Video Conferencing System

As part of this project we established a six-node video conferencing network at the University of Derby based on the CUSeeMe video conferencing package (developed at Cornell University) and Apple Macintosh computers. The great advantage of using CUSeeMe is, of course, cost - the CUSeeMe compression/decompression system is software-based and the software is available as freeware, so the only expense needed to create a video conferencing workstation (in addition to that of the networked computer) is the cost of a video digitiser and video camera (see Appendix 1 for more information on how to obtain CUSeeMe).

CUSeeMe allows a suitably equipped computer (it can be a Mac or PC) to transmit a 16-greyscale video image via an IP network connection to another computer for point-to-point video conferencing, or to a video 'reflector' for multi-party conferencing (the CUSeeMe reflector allows up to to 8-way multi-party conferences). The transmitted frame-rate of the video image depends on the bandwidth of the intervening network, although a guide to its performance is that you can expect approximately 1-2 fps to be transmitted over a high-speed modem IP connection (PPP or SLIP) and between 10 and 20 fps over an unsaturated 10Mbit Ethernet link. As is discussed later, most of our video links took place over Ethane and microwave links - resulting in the transmission of moderately clear video images at about 5-7 fps.

There are a number of controls available when using CUSeeMe. The most important of these is the bandwidth control which puts an upper limit on the amount of network bandwidth used. It is recommended by the developers of CUSeeMe that this should not be set higher than 100Kbps. A CUSeeMe window and one of its control panel windows are shown in Figure 3.1.

Figure 3.1. The CUSeeMe window

Rather than use the audio transmission system built into CUSeeMe (based on a software package called Maven) - which is both bandwidth intensive and prone to loss of quality - all audio links used the University's standard telephone system. The University of Derby telephone system allows up to 6-way conference calls, hence multi-way CUSeeMe video sessions with multi-way audio were possible. Where available headset telephones were used.

Of the six video conferencing nodes established, four were located in the Britannia Mill building at the University of Derby and two were located in the Keddleston Road buildings approximately 1 mile away. Within each building the computers were connected via a 10Mbit Ethernet and the two buildings were connected by a 4Mbps microwave link. Some video conferencing sessions were also established via the University's 64Kbps JANET connection.

The Video Conferencing Workstations

Each workstation consisted of an Apple Macintosh (various 'flavours') with 8Mb RAM, a SuperMac VideoSpigot video digitiser and a video camera. It was found that at least 8Mb RAM was required if CUSeeMe was to be used as a 'background' application - any less than 8Mb and the user would typically have to quit all existing programs in order to make a CUSeeMe link with a colleague. The Video Spigot device was purchased primarily because it was the only suitable piece of video digitising hardware available at the time. Some compatibility problems were encountered with it, primarily to do with the version of the VDIG and QuickTime software used, although once these were settled the Video Spigot functioned adequately.

A variety of video cameras were used. Including camcorders, security cameras and - purchased especially for the project - two 'Peach' micro-CCD cameras. These tiny greyscale cameras are sold for 110 as electrical 'components' and require external power supplied and video cables, but are still extremely good value for. They also performed well and came in narrow- and wide-angle versions.

The CUSeeMe Video Reflector

The CUSeeMe video reflector (also developed by Cornell University) is freely distributed as 'C' program source and runnable code for various computer platforms. For our experiments we ran the reflector under UNIX on a Sun SPARCstation IPX. At its simplest, the reflector does just as its name suggests - it 'reflects' any incoming video stream back to any users connected to it, to allow multi-party video conferencing sessions. However, it is also possible to use the reflector to create video 'channels', some of which are private (restricted to certain IP numbers) and others of which are usable by anybody. The reflector can also be configured to display a 'Message of the Day' to anybody who connects to it.

The Layout of the Video Conferencing Network

The six video workstations and video reflector were oriented in the following configuration: one workstation in Sean Clark's office, one workstation in Prof. Scrivener's office, one workstation in the Research Office, one workstation in the CSCD Lab., one workstation in Computer Services (for a limited duration), one workstation for general use in the staff room and a second workstation in the CSCD Lab. (for a limited duration). The video reflector was running the SPARCstation located in the CSCD Lab. This layout is illustrated in Figure 3.2.

Figure 3.2. The layout of the video conferencing network.

Improving the Video Conferencing System

A number of more recent developments in Apple Macintosh technology have improved the cost-effectiveness and functionality of CUSeeMe as a video conferencing tool even further. Firstly, many Macintoshes now come complete with AV (audio-visual) capabilities. An AV facility removes the need for a add-on Video Spigot card and a version of CUSeeMe is available for AV Macs. This would have removed the need to solve the Video Spigot 'VDIG' compatibility problem experienced.

Secondly, a purely digital video camera is now available for the Apple Macintosh. The Connectix QuickCam (available from most Macintosh dealers) costs around 120 and is a greyscale camera that is able to deliver a video signal at approximately 15fps to the Macintosh's serial port. Since this device is purely digital, no video digitiser is needed. The frame rate and image quality is quite sufficient for CUSeeMe use and, again, a version of CUSeeMe is available that can use it.

Back Next Contents

Graphics     Multimedia      Virtual Environments      Visualisation      Contents