2002 - cesnet

22 Special VideoconferencesThis project was focused on high-quality videoconferences. Our goals can bedivided into two categories. The first one is to design a suitable testing methodologybased on findings achieved in 2001 and prepare appropriate testingmaterials for it. The second objective is to utilize these materials for the actualevaluation of selected devices. As a final consequence, our activities lead tobuilding of the infrastructure needed, which will allow expanding the spectrumof services provided by CESNET.As their name indicates, the special videoconferences are intended for a certain(special) category of users, which is delimited clearly enough in thesedays. This is given by the specific needs of this category of users and especiallythe technical requirements resulting from these needs. The devices involvedare not easily available or routinely used, but utilize state-of-the-art technologies.This brings both the corresponding technical demands for the operatorsand significant expenses for the equipment and for ensuring the actual videobroadcasts.Special videoconferences are currently applied mainly in the area of humanand veterinary medicine, biology, chemistry, pharmacology, etc. Their greatdemands are determined by several key parameters.The first parameter is the high resolution. The TV PAL standard is consideredto be the minimum, i.e., digital processing of 720 × 576 pixels at the frequency of50 frames per second according to CCIR 601. However, the required resolutionthat we have to take into account for the future corresponds more to the HDTVstandard.Another important parameter is the colour accuracy. A video recording orbroadcast with distorted colours is useless for medical diagnostics. The mostimportant is the dynamic behaviour of the entire video chain. In this type ofvideoconference, image degradation that would cause image disintegrationmust not occur. A video that becomes “pixelated” is, of course, unsuitable anduseless.The digitalized TV signal has high bandwidth demands. The transfer of raw datawould be very demanding for the network throughput. That is why the datahave to be compressed substantially. Lossy compression methods are used,which have a strong negative effect on the resulting quality of the video transferred.It is the most crucial modification of data throughout their path.The migration to new IP-based technology represented the essential problemfor operation of high-quality videoconferences and video broadcasts. The IPbehaviour, wide range of technologies in the market and definition of minimalparameters for specific ways of use influenced the selection of a suitable device.210 High-speed National Research Network and its New Applications 2002