Low Complexity Mode Decision and Motion Estimation for H.264/AVC Based Depth Maps Encoding in Free Viewpoint Video

Within free viewpoint video, the 3-D reconstruction of the scene is created from a high number of viewpoints. Every viewpoint is represented by a traditional sequence, called texture, and its associated depth information. This is known as a View plus Depth environment. In this paper, a novel low complexity mode decision and motion estimation algorithm for the H.264/AVC based encoding of depth sequences is proposed. Given that a texture sequence and its associated depth represent the same scene from the same point of view, they should have similar motion characteristics. The complexity reduction of the depth encoding, in the proposed algorithm, is obtained by taking advantage of the texture motion information that has been previously processed by a traditional H.264/AVC encoder. The characteristics of depth and texture sequences are analyzed, focusing on similarities and differences that are properly managed to design an algorithm able to detect when the motion information of the texture might be usefully exploited in the encoding of the corresponding depth sequence. The proposed method is able to achieve the same objective quality, measured by means of the PSNR and the VQM, than a traditional H.264/AVC encoder with a reduction of up to 58% of the computational burden.