A method of encoding data in the visible portion of a transmitted video
signal without degrading display of the received video
signal, and for decoding the data in the received video
signal. Each group of
data bits to be transmitted, referred to a data symbol, is associated with one of a number of longer predetermined sequences of chips. Each
chip sequence is divided into a multiplicity of lines of chips, and each line of chips together with its inverse are embedded, in pairwise fashion, in respective pairs of line scans of the video signal prior to its transmission. Received pairs of line scans are operated upon to detect the lines of chips they represent, and each of the number of
chip sequences is correlated with the detected line of chips to derive a correlation magnitude. The
chip sequence with the largest correlation magnitude is selected as the chip sequence whose data symbol was transmitted. The number of
data lines exceeds the number of video lines required to define a video framer. In addition, each line has an amplitude which is modulated in accordance with a data carrying parameter determined by analyzing spatial and / or temporal characteristics of the video signal.