Pseudo-Sequence-Based 2-D Hierarchical Coding Structure for Light-Field Image Compression

In this paper, we propose a pseudo-sequence-based two-dimensional (2-D) hierarchical coding structure for light-field image compression. In the proposed scheme, we first decompose the light-field image into multiple views and organize them into a 2-D coding structure according to the spatial coordinates of the corresponding microlens. Then, we mainly develop three algorithms to optimize the 2-D coding structure. First, we propose a 2-D hierarchical coding structure with a limited number of reference frames to exploit the intercorrelations among various views. To be more specific, we divide all the views into four quadrants, and all the views are encoded one quadrant after another to reduce the reference buffer size as much as possible. Inside each quadrant, all the views are encoded hierarchically in both horizontal and vertical directions to fully exploit the correlations among different views. Second, we propose to use the distance between the current view and its reference views instead of the picture order count difference as the criterion for selecting better reference frames for each inter view. The distance-based criterion is also applied to the motion vector scaling process to obtain more accurate motion vector predictors. Third, an optimal bit allocation algorithm taking the influence of the various views on the following encoding views into account is proposed to further exploit the intercorrelations among various views and improve coding efficiency. The entire scheme is implemented in the reference software of high efficiency video coding. The experimental results demonstrate that the proposed novel pseudo-sequence-based 2-D hierarchical structure can achieve maximum 28.4% bit-rate savings compared with the previous pseudo-sequence-based light-field image compression method.