The degree to which Videoconferencing software can compress and decompress the signals will affect quality and required bandwidth - and there will undoubtedly be future advances there. They can often utilise 384Kbs bandwidths, which enables large screen presentation using data or back-projection. Rollabout Systems are on wheels and can be plugged into ISDN and electricity sockets around a building as required. As with Room systems, a variety of peripherals can be used, for example second and third cameras, video and PC inputs. Desktop Systems are available as 'add-ons' to an existing PC, or as standalone units if only vision and voice are required.
Some systems allow a second camera to be added.
Many desktop systems also support real-time data communications and applications sharing, so that PC content can be shared. Less sophisticated MCUs provide 'voice activated' multipoint, which means that the location which is shown on screen is the one talking. Such conferences are difficult to manage effectively without clear protocols. More modern systems enable 'continuous presence', in which four locations can be heard and seen on screen at the same time, with further locations called up in one quarter of the screen as required. Multipoint Videoconferencing will allow far greater levels of innovation, but for the time being the cost is a considerable constraint.