LightSync

Abstract

A key challenge for smartphone based visual communication over screen-camera links is imperfect frame synchronization. The difficulty arises from frame rate diversity and variability due to camera capability, lighting conditions, and system factors. On the 4 smartphone cameras we tested, the frame rate varies between 8 and 30 frames per second. If the transmit frame rate is too high, the receiver might lose original frames or capture mixed frames, which are normally not decodable. Previous systems simply reduce the effective screen frame rate to be half the camera frame capture rate, to guarantee receiving a decodable frame every other frame. This under-utilizes the transmitter side capacity and is inefficient.