Study On Improving The Coding Efficiency Of Multiview Video Coding

Multiview video captured by synchronized cameras, from different viewpoints, comprises rich 3-D information of a scene and is widely used as a signal of new types of visual media such as free viewpoint video/ free viewpoint TV and 3D Video/3D-TV. However, it results in a tremendous amount of data depending on the number of cameras. Thus, efficient compression of MVV is a key enabling factor for its widely application. Multiview video coding (MVC) has recently become an active research area, focused on compression for efficient storage and transmission of multiview video data. Currently, the standardization of MVC is being developed in the Joint Video Team (JVT) of ISO/IEC-MPEG and ITU-T-VCEG which will be an extension of H.264/AVC (Amendment 4).This dissertation deals with improving the coding efficiency of MVC, and the main research and contributions are listed as follows.1.Hierarchical B pictures are used as basic structure for temporal prediction in the reference prediction structure. Based on the analysis of the contribution of inter-view prediction to the coding gain in different temporal layer, a simplified prediction structure is proposed in which the inter-view prediction would be disabled if the picture redundancy is dominated by temporal dependency.2.The contribution of inter-view prediction to the coding gain decreases with the increase of temporal layer in each GOP. Motivated by this, the contribution of inter-view reference picture of current coding picture to the coding gain can be predicted by coded pictures. A flexible prediction structure is proposed in which only the temporal reference picture is used if the contribution derived from coded pictures is small.3.Different from the monoscopic video coding standard, both inter-view reference pictures and temporal reference pictures are used in MVC to explore the interview correlation and the temporal correlation. The reference picture selection mechanism of H.264/AVC spatial DIRECT mode is used for MVC. The spatial DIRECT mode in MVC can not work efficiently due to the variety of the reference picture list. A modified reference picture selection mechanism is proposed in the dissertation.4. Multiview video is captured by an array of cameras. Automatic white balance is one of the most important functions for each camera to provide high quality image. Color consistency among the multiple views can be achieved if each camera is white balanced. A new automatic white balance method is proposed using extracting gray color points in images, which has the advantage of robust convergence.5. The existence of color mismatch between views impairs the performance of the inter-view prediction in MVC. A novel color compensation method based on the color space conversion matrix is proposed. A color compensation model is developed in RGB channels and further extended to YCbCr channels which make the proposed method compatible to current video coding standards. The modified inter-view reference picture is more similar to the coding picture than the original inter-view reference picture, therefore the coding efficiency for MVC can be improved. Moreover, the color compensation factors can be derived both in encoder and decoder, therefore no additional data need to be transmitted to the decoder.