Reversible video watermarking for plain and encrypted video based on recursive histogram modification

In this thesis, reversible video watermarking methods are developed for plain and encrypted video. In both cases, temporal correlation among frames in the video are exploited by using motion compensated frame interpolation and recursive histogram modification algorithm developed for images are used in watermarking. The recursive histogram modification can not be used directly for reversible plain video watermarking because of the important problems of ensuring reversibility for each frame and distribution of total capacity among frames. In this thesis, novel ideas are proposed to solve these two problems. The proposed method is tested on the video sequences commonly used in the literature. It is shown to give better performance than the existing reversible plain video watermarking algorithms in terms of capacity and distortion by means of computer simulations. In the method developed for encrypted video, room required for the watermark is created before encryption. The room creating process is achieved by embedding the original least significant bits of some pixels of the frame into the corresponding motion compensated interpolation errors through recursive histogram modification. Watermarking is carried out by replacing the least significant bits of the pixels in the room reserved encrypted frame by the watermark bits. The original video is encrypted with an encryption key and the encrypted video is watermarked with a data hiding key. Watermark decoding and video decryption operations can be performed independently. The original video can be restored and the watermark can be decoded without error from the watermarked encrypted video if both keys are known. The watermark can be decoded from the the watermarked encrypted video but video content can not be accessed when only the data hiding key is known. A video signal close to the original one can be obtained without having access to the watermark when only the encryption key is available. Computer simulations prove applicability of the method in encrypted domain reversible video watermarking applications.