Exploring CDMA for watermarking of digital video

Spread spectrum has been used as a technique for secure communications for a long time. For still image watermarking, spread spectrum has been the method of choice for some time. In this paper we argue that spread spectrum in the form of CDMA has a more natural application in the watermarking of uncompressed digital video. The reason for this sentiment is that digital video, by virtue of its time-space property, fits the direct sequence spread spectrum more readily. The problem, however, is that conventional CDMA achieves its data-hiding capability by a massive increase in bitrate. Successful implementation of CDMA for video watermarking, therefore, requires a reformulation of the concept. To this end, digital video is modeled as a bitplane stream along the time axis. Using a modified m-sequence, bitplanes of specific order are pseudorandomly marked for watermarking. Then, the desired watermark is mapped to a single bitplane and spread via another 2D m-sequence, not necessarily related to the first one, along a stream parallel to that of the video. The tagged planes are removed and replaced by the spread watermark. We show that the above approach resists noise as well as attacks on destroying synchronization at the watermark detector. Such attacks may include regular and/or random frame removal.