An improved VLC mapping method with parameter optimization for reversible data hiding in JPEG bitstream

Abstract

The typical reversible data hiding (RDH) method for JPEG bitstream is conducted by building the mapping between the used VLCs and the unused VLCs, and will not modify the standard coding conventions. So, it can ensure not only the perfect decoding after data embedding but also preserve the file size well. However, the capacity is limited. One reason is that the variable length codes (VLC) are not fully utilized. Moreover, there lacks of an efficient optimization for the mapping design, and the existing solution is to examine various possible choices. In this paper, we propose an improved VLC mapping design and devise a method for the parameter optimization. The proposed mapping design is motivated by taking more alternative solutions into account to find the optimal mapping and increase the capacity. We redefine the optimization objective and introduce some optimization rules to prune the solution space. We investigate the mapping results and use a more flexible parameter setting to reduce the complexity. The experimental results show that, the proposed method can increase the capacity and cost a relatively low time complexity.