VIDEO DISPLAY

摘要

Video display of a sequence of advertisements is provided by display units (10) in shopping centres (1-4) in accordance with video signals supplied via a wide-area network (6) . Each display unit (10) includes a sub-unit (12) for adding a marker signal into the network-supplied video signals, and a photo-sensor (25) is used to verify display of the marker, and thus of the advertising, on the screen (13) of the display unit (10) . If display of the marker is interrupted, a signal identifying the respective display unit (10) and its centre (1-4) is transmitted via the network (6) to trigger remedial action and/or logging. The added marker signal is synchronised to the input video signal to appear in a fixed screen-location, and enhanced verification of integrity of the video display includes checking whether there is correspondence between encoding detected in the displayed marker and encoding of the marker signal added to the video signals.