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The paper presents a new method of depth estimation, dedicated for free-viewpoint television (FTV) and virtual navigation (VN). In this method, multiple arbitrarily positioned input views are simultaneously used to produce depth maps characterized by high interview and temporal consistencies. The estimation is performed for segments and their size is used to control the trade-off between the quality of depth maps and the processing time of depth estimation. Additionally, an original technique is proposed for the improvement of temporal consistency of depth maps. This technique uses the temporal prediction of depth, thus depth is estimated for P-type depth frames. For such depth frames, temporal consistency is high, whereas estimation complexity is relatively low. Similarly, as for video coding, I-type depth frames with no temporal depth prediction are used in order to achieve robustness. Moreover, we propose a novel parallelization technique that significantly reduces the estimation time. The method is implemented in C++ software that is provided together with this paper, so other researchers may use it as a new reference for their future works. In performed experiments, MPEG methodology was used whenever possible. The provided results demonstrate the advantages over the Depth Estimation Reference Software (DERS) developed by MPEG. The fidelity of a depth map, measured by the quality of synthesized views, is higher on average by 2.6 dB. This significant quality improvement is obtained despite a significant reduction of the estimation time, on average 4.5 times. The application of the proposed temporal consistency enhancement method increases this reduction to 29 times. Moreover, the proposed parallelization results in the reduction of the estimation time up to 130 times (using 6 threads). As there is no commonly accepted measure of the consistency of depth maps, the application of compression efficiency of depth is proposed as a measure of depth consistency.

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We propose a new coding technology for 3D video represented by multiple views and the respective depth maps. The proposed technology is demonstrated as an extension of the recently developed high efficiency video coding (HEVC). One base views are compressed into a standard bitstream (like in HEVC). The remaining views and the depth maps are compressed using new coding tools that mostly rely on view synthesis. In the decoder, those views and the depth maps are derived via synthesis in the 3D space from the decoded baseview and from data corresponding to small disoccluded regions. The shapes and locations of those disoccluded regions can be derived by the decoder without any side information transmitted. To achieve high compression efficiency, we propose several new tools such as depth-based motion prediction, joint high frequency layer coding, consistent depth representation, and nonlinear depth representation. The experiments show high compression efficiency of the proposed technology. The bitrate needed for transmission of two side views with depth maps is mostly less than 50% than that of the bitrate for a single-view video.

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