An efficient retinex-like brightness normalization method for coding camera flashes and strong brightness variation in videos

Conventional hybrid video coding systems rely on the assumption that the brightness is constant. This does not take inter-frame brightness variations into consideration during motion estimation and compensation processes. Under the influence of inter-frame lighting variations like camera flashes, video motion activities are not accurately estimated and the pixel prediction is poor which directly increases the bits for prediction error coding. In this paper, we propose an efficient algorithm based on the retinex-like system which allows inter-frame brightness being normalized before applying the conventional motion estimation and compensation. Experimental results show that our approach is superior to all similar approaches in the literature and demonstrate that our proposed system is very robust against the inter-frame brightness variations. Further experimental works have been done using the verification models of the MPEG-4 and the H.264 on sequences with brightness variations, results of which show that our proposed system outperforms these coding systems, including the weighted prediction feature in H.264, which were specifically designed for this purpose.