Adaptive nonlocal range filter in depth map coding

In this paper, we present a novel depth map coding scheme to improve coding efficiency. For this purpose, we develop an adaptive nonlocal range filter that restores the coded depth map by the noise suppression. Unlike the previous works that adapted the original nonlocal means algorithm or the original bilateral filter to the depth data, our approach is fundamentally different in that the nonlocal principle in the color data and the range filter in the depth map are taken into account, respectively. Furthermore, the optimal fall-off parameters that control the smoothing strength are determined at the encoder and the restoration is performed with the optimal fall-off parameter at the decoder. This technique allows for the strong slope restoration at the boundary and the noise smoothing near the boundary. Finally, the depth map coding that performs the new approach is implemented and this results in 9.71%(rate-distortion evaluation) and 8.71%(rate-quality evaluation) BD-bitrate reduction on average when compared with 3DV HEVC.