In this paper, an information hiding method using decimal expansion of irrational numbers to generate random phase mask is proposed. Firstly, the decimal expansion parts of irrational numbers generate pseudo-random sequences using a new coding schemed, the irrational number and start and end bit numbers were used as keys in image information hiding. Secondly, we apply the coding schemed to the double phase encoding system, the pseudo-random sequences are taken to generate random phase masks. The mean square error is used to calculate the quality of the recovered image information. Finally, two tests had been carried out to verify the security of our method; the experimental results demonstrate that the cipher image has such features, strong robustness, key sensitivity, and resistance to brute force attack.
Motion estimation plays an extremely important role in video coding. The objective of the motion estimation is to remove the temporal redundancy between video frames so that the video sequences can be coded efficiently. In this paper, an improved fast motion estimation algorithm, based on the successive elimination algorithm (SEA) of Li and Salari, is studied. This fast motion estimation algorithm results in the same displacement vectors as the exhaustive search algorithm (ESA) with a reduced computational load. An improved fast motion estimation algorithm, introducing further computational load reduction with negligible distortion, is proposed, and a transform coder based on the improved algorithm is developed. Implementation issues are discussed and compared. Experimental results show that the number of searching operations can be reduced dramatically with the help of the fast motion estimation algorithm.