Integrator's Reference Manual for Polycom HDX ... - 1 PC Network Inc

Integrator’s Reference Manual for Polycom HDX SystemsVideo Projection for Use in VideoconferenceMany installations make use of video projection devices. The most importantthing to remember in the planning of video projection for a videoconferencespace is that front projection is vastly inferior to rear projection. Frontprojection systems are less expensive and easier to implement, but theconflicting interest between the camera and the projection display makes thisform of display a very poor choice. Front projection setups operate best whenthe lighting in the room is dimmed or doused. When this is done, thevideoconference cameras can no longer operate, since they require even,bright, color-corrected light. A direct conflict between these two technologiesis clear. In the event that a rear projection room cannot be set aside,retro-projection units can be purchased from a number of manufacturers.These units normally are available in sizes ranging from 40” to 72” diagonalmeasure. To display high-quality video while maintaining optimum lightingfor interactive video meetings will require a projector of the “light-valve” orDLP class.Regardless of the exact type of projector selected and the exact nature of “frontversus rear,” there are certain essential rules for projector placement. The goalin projection is to get the image beam to aim directly into the audience’s eyes.In Western cultures the average distance from the floor to a seated person’s eyeis 4’. That distance becomes the target for the direct beam of the projector.Again keep in mind that front projection should be avoided except in the mostextreme cases. If it is employed at all it must be used with an extremely brightprojector (2,500 lumens or greater for any space smaller than 25’x40’).CamerasThere usually is a “main” or “local people” camera positioned on top center ofthe display, so that it can “see” the participants and anything necessary at thesides of the room, using pan and tilt features. If individual presentations maybe made from the side or “front of audience” area of the room, an additionalcamera should be located at the back of the room, also mounted to allow aview of the presenters when necessary. Some cameras contain an activecamera pointing system that also can be used effectively, given proper care inthe mounting of the camera assembly. The area immediately surrounding thecamera assembly needs to be acoustically “dead” to ensure that the voicetracking and pointing algorithms work correctly. This is another reason to payclose attention to the acoustic environment and acoustic treatment of anyspace intended for use with this type of camera system.If local presentation is blended with VC for any events, we must consider theneeds of the presenter who will not be “facing” the local image or inboundimage displays used by the main body of the local audience. One or twomonitors (and a camera) should be mounted at the back of the “audience-end”of the room, with the horizontal centerline at approximately 5’ from the floorfor ease of presentation interaction between the presenter and the group(s) atthe farend(s). Remember that, with the exception of PC-based information thatis not in a standard composite narrowband video format, any information weA - 12