Display-Camera Communication (DCC) is a unique form of Visible Light Communication that employs digital displays and cameras for optical free-space data transmission. Data is typically conveyed through 2D barcodes, which can be reconstructed and decoded from camera recordings. In DCC, synchronization challenges occur in the 2D space domain of the image signal. Optical projection introduces perspective distortion, causing the display's position in the camera image to vary frame by frame due to camera motion (frame-level spatial asynchrony). Additionally, lens distortion leads to nonlinear deviations of symbol positions in the received signal (symbol-level spatial asynchrony). To tackle frame-level spatial asynchrony, a Frame Position Recovery method is introduced to localize the display and compensate for camera motion, ensuring reliable detection of the display's position and rotation while minimizing visual impact on perceived video quality. For symbol-level spatial asynchrony, a novel Symbol Position Recovery approach is proposed, which estimates symbol positions based on the data pattern and compensates for lens distortion using a nonlinear model. This allows for accurate detection of sampling points even in small data blocks. Simulations and experiments with various hardware combinations demonstrate the excellent accuracy and reliability of these methods compared to existing techniques.
