| Title | Multiscale Recurrent Pattern Matching Approach for Depth Map Coding |
| Author | Danillo B. Graziosi (UFRJ, Brazil), Nuno M. M. Rodrigues (IT, Portugal), Carla L. Pagliari (IME, Brazil), Eduardo A. B. da Silva (UFRJ, Brazil), Sérgio M. M. de Faria (IT, Portugal), Marcelo M. Perez (IME, Brazil), Murilo B. de Carvalho (UFF, Brazil) |
| Page | pp. 294 - 297 |
| Keyword | Depth Maps, 3D Image Coding, Recurrent Pattern Matching |
| Abstract | In this article we propose to compress depth maps using a coding scheme based on multiscale recurrent pattern matching and evaluate its impact on depth image based rendering (DIBR). Depth maps are usually converted into gray scale images and compressed like a conventional luminance signal. However, using traditional transform-based encoders to compress depth maps may result in undesired artifacts at sharp edges due to the quantization of high frequency coefficients. The Multiscale Multidimensional Parser (MMP) is a pattern matching-based encoder, that is able to preserve and efficiently encode high frequency patterns, such as edge information. This ability is critical for encoding depth map images. Experimental results for encoding depth maps show that MMP is much more efficient in a rate-distortion sense than standard image compression techniques such as JPEG2000 or H.264/AVC. In addition, the depth maps compressed with MMP generate reconstructed views with a higher quality than all other tested compression algorithms. |
| Title | Sparse Representation of Depth Maps for Efficient Transform Coding |
| Author | Gene Cheung (National Institute of Informatics, Japan), Akira Kubota (Chuo University, Japan), Antonio Ortega (University of Southern California, U.S.A.) |
| Page | pp. 298 - 301 |
| Keyword | Depth-image-based rendering, transform coding, sparse representation |
| Abstract | Compression of depth maps is important for "image plus depth" representation of multiview images, which enables synthesis of novel intermediate views via depth-image-based rendering (DIBR) at decoder. Previous depth map coding schemes exploit unique depth characteristics to compactly and faithfully reproduce the original signal. In contrast, given that depth maps are not directly viewed but are only used for view synthesis, in this paper we manipulate depth values themselves, without causing severe synthesized view distortion, in order to maximize sparsity in the transform domain for compression gain. We formulate the sparsity maximization problem as an l0-norm optimization. Given l0-norm optimization is hard in general, we first find a sparse representation by iteratively solving a weighted l1 minimization via linear programming (LP). We then design a heuristic to push resulting LP solution away from constraint boundaries to avoid quantization errors. Using JPEG as an example transform codec, we show that our approach gained up to 2.5dB in rate-distortion performance for the interpolated view. |
| Title | A Novel Approach for Efficient Multi-View Depth Map Coding |
| Author | Jin Young Lee, Hochen Wey, Du-Sik Park (Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd., Republic of Korea) |
| Page | pp. 302 - 305 |
| Keyword | Multi-view video plus depth format, Depth map coding, Video coding |
| Abstract | Multi-view video plus depth (MVD) format, which consists of texture and depth images, has been recently presented as video representation to support depth perception of scenes and efficient view generation at the arbitrary positions. In particular, a depth image has been one of the significantly important issues for successful services of highly advanced multi-media video applications, such as three-dimensional television (3DTV) and free-viewpoint television (FTV). In this paper, we present a novel approach for efficient multi-view depth map coding. We assume that a texture image in the MVD format is first encoded and then the corresponding depth image is encoded. According to an analysis of inter-view correlation between the previously encoded texture images, the proposed method skips some blocks of the depth image without encoding. The skipped blocks in the depth map are predicted from the neighboring depth images at the same time instant. Experimental results demonstrate that the proposed method reduces the coding bitrate of up to 74.8% and improves PSNR of up to 3.51dB in P and B views. |
| Title | Diffusion Filtering of Depth Maps in Stereo Video Coding |
| Author | Gerhard Tech, Karsten Müller, Thomas Wiegand (Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, Germany) |
| Page | pp. 306 - 309 |
| Keyword | diffusion filtering, noise reduction, stereo video, video plus depth coding |
| Abstract | A method for removing irrelevant information from depth maps in Video plus Depth coding is presented. The depth map is filtered in several iterations using a diffusional approach. In each iteration smoothing is carried out in local sample neighborhoods considering the distortion introduced to a rendered view. Smoothing is only applied when the rendered view is not affected. Therefore irrelevant edges and features in the depth map can be damped while the quality of the rendered view is retained. The processed depth maps can be coded at a reduced rate compared to unaltered data. Coding experiments show gains up to 0.5dB for the rendered view at the same bit rate. |