Adaptive reference filtering for bidirectional disparity compensation with focus mismatches
In this paper, we consider compensation of focus mismatches for frames that are encoded with inter-view bi-prediction (B-frames) in multiview coding (MVC). We start with an analysis of a multiview system with focus mismatches, to demonstrate that a B-frame may suffer from different types of mismatches with respect to the frames from different views used as references. As compared to our previous work for inter-view P-frames, filter estimation for B-frames has to consider not only the depth-dependency of focus mismatches, but also i) the possibility that the two predictors, from different directions, exhibit different types of prediction mismatches, and ii) the effect of bi-predictive search on the generation of filtered references. We show that, designing filters only for the averaged bi- predictors could lead to a suboptimal solution when combined with conventional bi-predictive search schemes. Instead, we propose a filter design approach that estimates two sets of depth-related filters, each set compensating for the focus mismatches exhibit in one of the two references used for bi-directional prediction. Simulation results shows that for views coded with inter-view bi-prediction, the proposed method provides up to 0.8 dB gain over current H.264/AVC in the sequences we tested.