With the rapid growth of images database and computer networks broadcasting, the legal issues of multimedia copyright protection have become very important. In this paper, a method for video object watermarking using GVF snake and HU moments is proposed, providing copyright protection of the semantic content. To achieve this goal, the contour of the objects of an image is initialised by the user and then using a GVF snake the real position of the video objects contours are retrieved. Next, an invariant watermark is designed using invariant Hu moments of each video objects. The proposed algorithm is tested against various attacks such as JPEG lossy compression, blurring, filtering and cropping. Experimental results on real life images indicate the efficiency and robustness of the proposed scheme.