【作者】 戴宁赟；

【导师】 朱光喜；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2007， 硕士

【摘要】 H.264/AVC是由国际电信联盟(ITU)和国际标准化组织(ISO)共同制定的新一代视频编码标准。该标准采用了一系列先进的编码技术,在编码效率、网络适应性等诸多方面都超越以往的视频编码标准。因此受到业界的广泛关注。而且H.264/AVC等标准只规定了基本的框架对于细节的处理上尚有较大的发挥空间。将经过压缩的视频数据进行远程传输时,需要考虑网络拥塞、信道带宽及处理能力的影响。码率控制策略的目的就是通过调整编码端的编码参数,保证信道正常传输,同时尽可能达到高而平稳的图像质量。本文介绍了H.264/AVC的编码策略和技术特性,研究了现有的经典码率控制算法,探讨了其中关键技术及简要说明了各算法的不足之处,重点研究了场景切换下的码率控制策略。场景切换在视频的应用中极为常见,本文回顾了几种经典的检测场景切换算法并将它们分类。同时提出了一种利用DCT系数绝对值和,进行场景切换检测的方法并进行实验。实验结果中未发现有切换场景的漏检测和误检测的状况。针对H.264/AVC,由于其建议的码率控制算法在场景切换时未做相应的处理,因此存在一定的缺陷。对此,本文结合场景切换的检测提出一套包含场景切换的检测和相应切换帧调整的码率控制算法来改善场景切换时的编码质量。最后,本算法在JM8.6平台下实现,实验结果表明,使用改进后的算法,测试结果在序列平均PSNR和码率准确程度上均有改善。更多还原

【Abstract】 H.264/AVC video coding standard was developed jointly by the ITU-T and ISO/IEC. By adopting various advanced coding techniques, H.264/AVC gains a significant improvement in compression performance and network transmission while comparing to other ever existing standards before. So this standard obtains great attention from academic and industrial fields. And this standard, so as to others, only defined the main framework, many detail problems still need to be solved.When transmit compressed video data, network condition and bandwidth should be considered. The aim of rate control is to regulate the coded bit stream to satisfy the channel condition and improve the reconstructed video quality.In this dissertation, the coding strategy and techniques in H.264/AVC are explained. Research focus on rate control algorithm in scene change condition.Scene change happens frequently in video. Based on several classic scene change detection methods, a method by estimating the absolute sum of DCT coefficient to determine where scene change happens is proposed. In experiment the entire scene change frames have been found out.Based on the research of key technology and typical algorithms of rate control, as the rate control algorithm of H.264 lacks corresponding treatment in scene change condition, a rate control algorithm with scene change detection in frame level by estimating the absolute sum of DCT coefficient and corresponding adjustment after detection is proposed. This algorithm is implemented in JM86 (H.264/AVC),according to the test results, by using the improved algorithm, the average PSNR and actual bit rate of the test sequences is improved.更多还原