Research On Depth Map In3D Video Coding

With the development of3D display and interactive multimedia systems, new3D video applications, such as3DTV and Free Viewpoint Video, are attractingsignifcant interests. In order to enable these new applications, new3D dataformats(Multiview Video plus Depth, MVD) including captured multiview videosequences and corresponding depth maps have been proposed. This new videoformats can synthesize arbitrary virtual views by using depth image based rendering(DIBR). How to efficiently compress MVD data is a important issue in study of3Dvideo standard. Multiview video have been detailedly studied in Multiview VideoCoding(MVC) standard. This thesis mainly studys the coding and quality restorationof the depth data in MVD. The depth maps have different characteristics than videosignal. The value in depth map represents the distance between an object in a sceneand the camera. Depth maps are composed of many smooth regions and thosesmooth regions are separated by sharp edge, and the edge information is sensitive torender virtual views. Moreover, depth maps are not directly displayed but used inview rendering. Because of the physical limit of the depth sensor, the obtained depthmaps are blurring and noisy, so we should enhance the quality of the depth maps.Based on the characteristics of depth maps, the thesis proposed two technologies onthe coding of depth maps and a technology on the quality enhancement of depthmaps. The main content and novelties are listed below：1. Proposed a depth coding method based on the distortion estimation of therendered view.The thesis sufficiently analysed the relationship between the depth codingdistortion and the synthesized view distortion and proposed a new distortion modelin depth coding. The distortion model is used to estimate the distortion of renderedview caused by depth coding. We use the estimated distortion to replace thedistortion of depth in RD optimization mode selection process of depth coding.2. Proposed a disparity based depth coding methodThe thesis proposed to compress disparity maps rather than depth maps togreatly reduce the bitrate without significant quality degradation for synthesizedvirtual views. The method is used in a special situation that the virtual view positionis known before encoding. In current3D system, the virtual view position could beeasily derived by a feedback system, so the proposed disparity based depth codingmethod is meaningful.3. Proposed a sparse representation based depth enhancement method.The method uses the importance of the sparse representation in image inverse problem and combines the priors of the depth maps：most areas in depth maps aresmooth and the edges of depth maps and correspoding video have strong correlation,to enhance the quality of the depth maps.