The present invention discloses a method of injecting additional data in one or more image sensor frames in an image sensor device. The method comprises: providing (801) additional data in the form of a numeric sequence, controlling (802) the lengths of subsequent blanking intervals in one or more image sensor frames to represent the numeric sequence, and transmitting the one or more image sensor frames from the image sensor device. The one or more image sensor frames may be transmitted to an image processor (12, 72). Examples of image processors (12, 72) and a system (1, 7) comprising an image processor (12, 72) are also disclosed.