DETECTING CODED LIGHT

A series of frames is captured by a rolling-shutter camera, each frame capturing an image of a light source which has a periodic message embedded in its light. With a rolling-shutter camera, each line captures a respective sample of the message and each frame captures a respective fragment of the message made up of a respective subsequence of the samples, wherein the message can be reconstructed from the fragments captured over multiple frames. Further, the frame rate of the rolling-shutter camera is dependent on a region of interest (ROI), and the method further comprises evaluating a metric indicative of how long will be required to accumulate enough fragments to reconstruct the message at the current frame rate, and adapting the ROI in dependence on this metric in order to change the frame rate and thereby reduce the number of subsequent frames required to complete the reconstruction of the message.