MPEG-4 emphasizes on coding efficiency and allows for content-based access and transmission of arbitrary shaped object. It addresses the encoding of video object using shape coding, motion estimation, and texture coding for interactivity, high compression ratio, and scalability. In this letter, an advanced object-adaptive vertex-based shape coding method is proposed for encoding the shape of video objects. This method exploits octant-based representation to represent the relation of adjacent vertices and that relation can be used to improve coding efficiency. Simulation results demonstrate that the proposed method may reduce more bits for closely spaced vertices.

A wavelet-based vector quantization scheme for image compression is introduced here. The proposed scheme obtains a better compression efficiency by the following three methods. (1) Utilizing the correlation among wavelet coefficients. (2) Placing different emphasis on wavelet coefficients at different levels. (3) Preserving the most important information of the image. In our experiments, simulation results show that this technique outperforms the recent SMVQ-ABC [1] and WTC-NIVQ [2] techniques.

An adaptive data hiding scheme capable of hiding considerable quantities of secret data while preserving acceptable visual quality for cover images is proposed. The major idea of this scheme is to hide secret data into the compressed codes of cover image during the encoding process of side-match vector quantization (SMVQ) such that the interceptors will not capture the secret information. Based on the experimental results, it is confirmed that the proposed scheme is better than earlier works. Moreover, the receiver can efficiently receive both the compressed cover image and the hidden secret data at the same time.