【作者】 钟凡；

【导师】 彭群生； 秦学英；

【作者基本信息】 浙江大学 ， 应用数学， 2010， 博士

【摘要】 最近几年,随着计算能力的提升,与视频相关的应用不断扩展,其中很多为实时系统,如增强现实系统,视频会议系统等。这些系统往往需要对视频中感兴趣的物体进行精确分割,以便对相关的区域进行特殊处理。与传统的离线视频分割不同,在线视频分割不仅要求速度快,而且在分割过程中不允许进行用户交互,因此对分割算法的性能和可靠性都有很高的要求,到目前为止还有很多问题有待解决。本文对在线视频分割所涉及的一系列关键问题进行了研究,其内容和创新工作主要有：(1)对在线视频分割已取得的成果进行回顾和总结,在此基础上提出了本文将要研究的四个问题,即静止背景场景的鲁棒分割、动态背景场景的实时分割、分割的自动初始化以及对分割结果的实时后处理。(2)提出了一种基于置信度的颜色分布模拟方法,以改善对静止背景场景视频分割的鲁棒性。该方法通过估计全局颜色模型和背景模型的置信度,使得二者在每个像素上都能达到最优组合,从而大大减少了前、背景包含的相似颜色所引起的错误。(3)提出了一种实时的递推式视频分割算法,将在线视频分割推广到视点移动的情况。其核心是一个基于时间连续性的的局部颜色模型,该模型不仅比全局颜色模型更精确,而且可以被实时构造。利用该模型可在没有背景信息的情况下,将上一帧的分割结果精确地传递到当前帧,从而使得对动态背景场景的实时分割成为可能。(4)提出了一种在线视频分割的自动初始化方法。传统的在线视频分割初始化要求提供背景图或第一帧的分割结果,或者需要针对特定的场景进行离线学习,在实际应用中显得很不方便。本文方法基于一种新的运动分割算法,该方法无需进行学习,即可在前景运动时从两相邻帧中提取出前景的完整分割。(5)提出了一种实时的分割后处理算法,以消除二值分割在边界附近的微小误差。二值分割的结果在边界附近容易出错,从而造成闪烁。传统的方法都通过对边界进行模糊来改善合成效果,但结果往往不够理想,而较复杂的方法又不能达到实时。本文所提出的后处理算法能够同时满足对精度和速度的要求,从而较好地解决了这个问题。(6)论文最后对全文的工作进行总结,提出了需要进一步深入研究的一些问题。更多还原

【Abstract】 In recent years, along with the development of hardware, the applications of video tech-nique have extended to many new areas, most of which are real-time systems, including augmented reality, teleconferencing, etc. Some of these systems need to know the accu-rate segmentation of the interested object(s) in order to be able to process correspond-ing regions in a special way. Compared with offline video segmentation, online video segmentation not only need to reach real-time speed, but also cannot involve user inter-action at online phase. Therefore, the segmentation algorithm should be very fast, and at the same time, very robust, which is very hard to be achieved in real environments.This dissertation studies a series of key problems and techniques related with on-line video segmentation, and includes the following contents:(1) A brief survey and discussion of previous works, based on which the four prob-lems are proposed, i.e. robustness in the scene of stationary background, real-time seg-mentation in dynamic scenes, automatic initialization and real-time post processing.(2) Presents a confidence-based color modeling method, which can greatly improve the robustness of segmentation methods in the scene of stationary background. By eval-uating the confidence of the global color models and the background model, the optimal combination can be achieved for individual pixels, in this way the errors introduced by ambiguous colors can be greatly reduced.(3) Presents a real-time transductive video segmentation method, which can be used for the cases of non-stationary background. The key is a novel local color mod-eling method combined with the temporal continuity, which is not only more accurate than the global color models but also can be constructed in real-time. By using this tech-nique the segmentation result can be propagated accurately without using background information.(4) Presents an automatic initialization method for online video segmentation. Tra-ditional initialization methods require either the background image or the segmentation result of the first frame, or need to be pre-trained in specific scene, which are very in-convenient in practice. The proposed initialization approach is based on a novel motion segmentation method, which does not need to be pre-trained, and can extract the fore-ground object from two adjacent frames when it is moving. (5) Presents a real-time post-processing algorithm, which can efficiently remove mi-nor errors around the boundary of binary segmentation. In order to suppress flicking, traditional methods usually simply smooth the boundary by feathering, which can not result in good effect in most cases. On the other hand, significant methods are hard to reach real-time speed. The proposed post-processing algorithm can meet the require-ment of accuracy and efficiency at the same time, and thus solves this problem very well.(6) Concludes the works of this dissertation, and presents some problems that can be studied further.更多还原