No abstract

One of the key problems in distributed video coding is the generation of side information. This task consists of producing an estimate of an image with some neighboring ones, such as those taken by the same camera at different time instants, or, in the case of multiview setups, images taken at the same time instant by different cameras. If both estimates are available, a further problem arises, which is how to merge them in order to create a single side information. This problem is very relevant since a good estimate of the unknown image will require only a few bits to be corrected. Considering a multiview distributed video-coding setup, we propose a novel technique for inter-view interpolation based on occlusion prediction, a new fusion technique from multiple estimates, and finally an adaptive validation step for switching among the three possible side information images: temporal, inter-view, and fusion. We provide a comprehensive set of experimental results, which indicate bit rate reductions of more than 9% in average; moreover, we observe much more consistent results with respect to state-of-the-art techniques.

Multiple-views video is commonly believed to be the next significant achievement in video communications, since it enables new exciting interactive services such as free viewpoint television and immersive teleconferencing. However the interactivity requirement (i.e. allowing the user to change the viewpoint during video streaming) involves a trade-off between storage and bandwidth costs. Several solutions have been proposed in the literature, using redundant predictive frames, Wyner-Ziv frames, or a combination of them. In this paper, we adopt distributed video coding for interactive multiview video plus depth (MVD), taking advantage of depth image based rendering (DIBR) and depth-aided inpainting to fill the occlusion areas. To the authors' best knowledge, very few works in interactive MVD consider the problem of continuity of the playback during the switching among streams. Therefore we survey the existing solutions, we propose a set of techniques for MVD coding and we compare them. As main results, we observe that DIBR can help in rate reduction (up to 13.36% for the texture video and up to 8.67% for the depth map, wrt the case where DIBR is not used), and we also note that the optimal strategy to combine DIBR and distributed video coding depends on the position of the switching time into the group of pictures. Choosing the best technique on a frame-to-frame basis can further reduce the rate from 1% to 6%.

Abstract-Side information generation is a critical step in distributed video coding systems. This is performed by using motion compensated temporal interpolation between two or more key frames (KFs). However, when the temporal distance between key frames increases (i.e. when the GOP size becomes large), the linear interpolation becomes less effective. In a previous work we showed that this problem can be mitigated by using high order interpolation. Now, in the case of long duration GOP, state-ofthe-art algorithms propose a hierarchical algorithm for side information generation. By using this procedure, the quality of the central interpolated image in a GOP is consistently worse than images closer to the KFs. In this paper we propose a refinement of the central WZFs by higher order interpolation of the already decoded WZFs, that are closer to the WZF to be estimated. So we reduce the fluctuation of side information quality, with a beneficial impact on final rate-distortion characteristics of the system. The experimental results show an improvement on the SI up to 2.71 dB with respect the state-of-the-art and a global improvement of the PSNR on the decoded frames up to 0.71 dB and a bit rate reduction up to 15 %.

Three dimensional digital video services are gathering a lot of attention in recent years, thanks to the introduction of new and efficient acquisition and rendering devices. In particular, 3D video is often represented by a single view and a so called depth map, which gives information about the distance between the point of view and the objects. This representation can be extended to multiple views, each with its own depth map.Efficient compression of this kind of data is of course a very important topic in sight of a massive deployment of services such as 3D-TV and FTV (free viewpoint TV). In this paper we consider the application of distributed coding techniques to the coding of depth maps, in order to reduce the complexity of single view or multi view encoders and to enhance interactive multiview video streaming. We start from state-of-the-art distributed video coding techniques and we improve them by using high order motion interpolation and by exploiting texture motion information to encode the depth maps. The experiments reported here show that the proposed method achieves a rate reduction up to 11.06% compared to state-of-the-art distributed video coding technique.