Over-complete Signal Decomposition

CCR-9903368 ZakhorEfficient compression of image and moving video is becoming more more important in a wide range of emerging applications.这些应用可以根据它们所需的比特率进行分类。广播质量的视频点播系统可能需要每秒几兆比特，而商用视频会议系统可能仅使用每秒几百兆比特。在极低端的规模，视频电话和无线通信系统往往被限制在低于每秒20兆比特的速率。混合运动补偿离散余弦变换（DCT）结构是几乎所有现有视频编码标准（诸如H. 263和MPEG-1、2、4）和商业上可用的视频压缩系统的一部分。在将DCT应用于极低比特率视频编码时，块效应变得相当明显。本研究的重点是在现今的视讯编码系统中，以非区块导向分解技术取代离散余弦转换。Berkeley涉及基于Gabor字典的更大，更灵活的过完备基集上的信号分解。它使用的贪婪，匹配追踪算法从统计文献，以找到扩展系数。这种方法被发现导致显着的PSNR和视觉质量的改善基于DCT的计划。此外，由于对在其上执行信号分解的基函数的过完备集合没有约束，因此可以选择集合的元素以使其不受块伪影的影响，从而产生无伪影的重构帧，而不需要计算昂贵的后处理。本研究的主要目标是探讨信号分解沿着过完备字典与应用的视频编码。特别地，关于基于过完全信号扩展的视频编码系统要解决的问题包括：性能的基本界限、最佳幅度和位置编码算法、匹配基集的非块性质的基于非块的运动补偿技术、字典设计、分解和搜索策略，以及扩展到：（a）时空可分级性，（B）静止图像编码，（c）多描述编码和（d）合成视频/图像/图形。工作水平声明：在建议的支持水平下，PI将尽一切努力满足项目的原始范围和水平。

CCR-9903368ZakhorEfficient compression of image and moving video is becoming increasingly more important in a wide range of emerging applications. These applications can be classified by the bit rates they require. A broadcast quality video-on-demand system might require several megabits per second, while a commercial video conferencing system might use only a few hundred kilobits per second. At the extreme low end of the scale, video telephone and wireless communication systems are often restricted to rates below 20 kilobits per second. The hybrid motion-compensated Discrete Cosine Transform (DCT) structure is a part of nearly all existing video coding standards such as H.263 and MPEG-1,2,4, and commercially available video compression systems. In applying DCT to very low bit rate video coding, blocking artifacts become quite pronounced. This research is focused on non-block oriented decomposition techniques to replace DCT in today's video coding systems.One such scheme recently developed at the VIP group at U.C. Berkeley involves signal decomposition over a larger, more flexible over-complete basis set based on Gabor dictionary. It uses the greedy, matching pursuit algorithm from the statistics literature in order to find the expansion coefficients. This approach is found to result in significant PSNR and visual quality improvement over DCT based schemes. In addition, since there are no constraints on the overcomplete set of basis functions over which the signal decomposition is carried out, the elements of the set can be chosen to be free of blocking artifacts, resulting in artifact free reconstructed frames, with no need for compute expensive post processing. The main goal of this research is to investigate signal decomposition along overcomplete dictionaries with applications to video coding. In particular the issues to be addressed regarding video coding systems based on over complete signal expansion include: fundamental bounds on performance, optimum amplitude and position coding algorithms, non-block based motion compensation techniques to match the non-blocky nature of the basis set, dictionary design, decomposition and search strategies, and extension to: (a) spatio-temporal scalability, (b) still image coding, (c) multiple description coding and (d) synthetic video/imagery/graphics. Level of Effort Statement: At the recommended level of support, the PI will make every attempt to meet the original scope and level of the project.