Recently, many interactive video display devices using body movement as input have been developed. However, their intrinsic latency before the resulting images are displayed creates a discrepancy between the visual information to the user and the physical sensation. This research aims to investigate the impact on user performance and latency perception when there is latency between the user's physical input to the system and the visual feedback. We developed a video latency control system to film the user's hand movements and control the latency when displaying the video (The standard deviation is 0.38 ms). The minimum latency of the system is 4.3 ms, hence this enables us to investigate the performance and latency perception in unknown low latency range. Using this system, we conducted experiments wherein 20 subjects performed a pointing task based on Fitts' law to clarify the effect of video latency, particularly for low latency. Experimental results showed that when the latency is over 24.3 ms, it begins to be sensed more easily by the user and the performance begins to decrease. This result will be applied to determine a standard limit for video latency in interactive video devices.
