A novel illumination compensation scheme for sprite coding

A novel illumination compensation scheme for sprite coding is presented in this paper. Inter-frame pixel discrepancy due to the effect of frustrating illumination conditions is one of the major challenges for most correlation-based global motion estimators. Our proposed system employs a lighting compensation technique, by means of some frame division operations, to eliminate the effect of illumination variation before motion estimation is conducted. The background information is then expressed in terms of our proposed mosaic based representation which can efficiently handle sequences involving frustrating illumination condition. This effectively increases the robustness of the global motion estimator. Meanwhile, this allows the normalization of the lighting conditions of each image in the sequence with respect to a particular base frame and gives rise to a sprite image characterized with global illumination homogeneity. Experimental results show that our proposed technique manages to increase the coding efficiency of video sequences which involve a strong variation of lighting conditions (up to 10 dB improvement), and is suitable for the sprite coding application in MPEG-4.