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International audience; With the rapid emergence of various 360 video capturing devices and head-mounted displays, providing immersive experience using 360 videos is becoming a topic of paramount interest. The current techniques face motion sickness issues, resulting in low quality of experience. One of the reason is that they do not take advantage of the parallax between the divergent views, which may be helpful to provide the correct view according to the user's head motion. In this paper, we propose to get rid of the classical ERP representation, and to synthesize arbitrary views using different divergent views together with their corresponding depths. Thus, we can exploit the parallax between the divergent views. In this context, we assess the feasibility of the depth estimation and the view synthesis using state-of-the-art techniques. Simulation results confirmed the feasibility of such a proposal, in addition to possibility to achieve sufficient visual quality for a head motion up to 0.1m from the rig, when using generated depth map for view synthesis.

The coding efficiency of the new video coding standard, High Efficiency Video Coding (HEVC), is strongly associated with better use of spatio-temporal redundancies thanks to an increased number of competing coding modes. However, this competition involves a massive increase in signaling bitrate which becomes a possible limit for the next generation of encoder. Thispaperproposesa newcodingschemethat breakswith conventional approaches. It exploits a more complex decoder able to reproduce the choice of the encoder based on causal references, eliminating thus the need to signal coding modes and associated parameters. The general outline of this new codec and a proposed implementation are described in this paper. Experimental results under common test conditions report an average bitrate saving of 1.7% at the same quality compared to HEVC for a wide range of video sequences.

The up-and-coming extension of HEVC for 3D video (3D-HEVC) includes various tools to exploit different redundancies in a 3D video signal. Inter-view redundancies are in particular exploited using Inter-View Motion Prediction (IVMP) and Inter-View Residual Prediction (IVRP). Both of these tools compensate disparity-wise the current prediction unit (PU) in order to find its corresponding PU in a base view, from which some prediction information for the current PU is retrieved. The disparity vector (DV) used for disparity compensation is currently derived using a neighboring search process (NBDV) for a DV across spatial and temporal neighbors. The first DV found is selected as the final DV used in IVMP and IVRP, with no guarantee of optimality. In this paper, the NBDV derivation process is changed: all found DVs from different neighbors are stored in a list. Redundant vectors in this list are removed, and a median computation on the remaining vectors is performed. The resulting DV is set as the DV used for IVMP. Average bitrate reductions of 0.6% and 0.8% for the two dependent views and 0.2% on synthesized views are reported with only a slight increase in encoder and decoder runtimes.

International audience; Since the finalization of the H.264/AVC standard and in order to meet the target set by both ITU-T and MPEG to define a new standard that reaches 50% bit rate reduction compared to H.264/AVC, many tools have efficiently improved the texture coding and the motion compensation accuracy. These improvements have resulted in increasing the proportion of bit rate allocated to motion information. Thus, the bit rate reduction of this information becomes a key subject of research. This paper proposes a method for motion vector coding based on an adaptive redistribution of motion vector residuals before entropy coding. Motion information is gathered to forecast a list of motion vector residuals which are redistributed to unexpected residuals of lower coding cost. Compared to H.264/AVC, this scheme provides systematic gain on tested sequences, and 2.3% in average, reaching up to 4.9% for a given sequence.

Standard DCT -based video coding techniques perform good results in terms of data compaction, making feasible the use of digital video in several application frameworks. The price to pay is the introduction of annoying visual distortions/artefacts in the reconstructed video. The lower the encoding bit-rate, the larger the number of artefacts. Post-processing is a practical solution that achieves a visual enhancement of the compressed images after decoding. Some of the artefacts, such as blocking (tiled-effect aspect) and ringing (ghost effect) have already been widely studied.