H.264码率控制论文：基于H.264的码率控制算法研究

H.264码率控制论文：基于H.264的码率控制算法研究【中文摘要】视频压缩编码的主要目标就是在带宽、比特率受限的条件下,尽量使编码失真最小。为了获得最优的压缩效率,确保编码数据在信道上成功传输,同时在接收端得到最佳的视频质量,编码过程中就少不了率失真优化和码率控制技术。码率控制的就是调整编码输出码流,保证信道带宽的充分利用,同时尽可能达到高平稳的图像质量。本文首先介绍了H.264编码器的结构及原理。与以往的编码标准相比,H.264采用了多种新技术,主要包括:帧内/帧间预测、整数变换与量化、熵编码及去方块滤波,使得其编码效率有所提高。其次探讨了码率控制的原理,并分析了当前经典的码率控制算法TM5、TMN8和VM8。最后对H.264的码率控制算法JVT-G012进行深入研究,在此基础上发现其存在的几点不足之处:初始QP的选取仅仅取决于每像素的比特数(bpp)或是根据经验估计,没有考虑帧的复杂度,不够精确;图像复杂度MAD的估计仅仅利用了相邻帧或宏块间的时间相关性,即在进行预测时只考虑到了图像的全局运动,而忽略了其局部运动;在进行目标比特分配时只是简单的平均分配,完全没有考虑到当前帧或宏块的复杂度。对此,本文作了如下改进:提出了基于bpp和I帧复杂的初始量化参数的选取算法。该方法在原算法根据bpp计算出来的初始量化参数的基础上,引入了不同序列的第一个I帧的复杂度对最佳初始量化参数的影响,通过大量实验统计,得出初始量化参数与bpp及I帧复杂度的函数关系。改进算法使得初始量化参数的选取更加合理,编码后得到的图像PSNR值及码率控制两方面均优于原算法。提出了结合MAD和反映图像位置信息的梯度来估计图像复杂度的算法,使得图像复杂度能够有效地反映出其全局运动和局部运动。实验证明,改进后的算法使得在相同的编码质量下,码率控制更加精确。在新的图像复杂度估计的基础上,根据编码帧的相对复杂度进行目标比特数的分配。实验表明,与原算法中的平均分配剩余比特数相比,该算法在使码率控制更加准确的同时也使得编码后图像的PSNR值波动较小。【英文摘要】The main target of video compression code is to limit the distortion of code under the condition of bandwidth and restricted rate. In order to get the most optimized compression efficiency, ensure the coded data transfer in the channel successfully, and obtain the best video quality. The distorted optimization and the rate control are necessary in the encoding process. The purpose of rate control is to adjust the output code stream, ensure make use of the bandwidth effectively, and achieve the high steady image quality at the same time.The paper first discusses H.264s encoding system. Compared with the previous coding standards, H.264 adopts many new technologies, including intra-frame and inter-frame prediction, integer transform and quantization, entropy coding and deblocking filter, which make the coding efficiency increase.Secondly,discuss the principle of rate control are, and analyze the classic rate control algorithms TMN8 and TM5, VM8.Finally, study the rate control algorithm JVT-G012 that is usually sued in H.264 deeply, and find some deficiencies in JVT-G012, mainly including: Initial QP selection just depends on the bits per pixel (bpp) or accords to experience estimates, without considering the complexity of frame, is not precise enough; MAD estimation of image complexity only makes use of the temporal correlation that exists between the adjacent frames or macro blocks, namely, the estimation only considers global motion of images, while ignoring their local motion; Average distribution is used in the allocation of target bits, without considering the complexity of current frame or the macro block. This paper presents the following improvements for these deficiencies:Put forward a selection algorithm of initial quantization parameter based on bpp and the complexity of I-frame. The algorithm introduces the influence of the first I-frames complexity of different sequencesto the best initial quantization parameter, on the basis of the initial quantization parameter computed by the original algorithm. Then get the initial quantization parameter as a function of bpp and the complexity of I-frame through a lot of experiments statistics. The improved algorithm makes the initial quantization parameter selection more reasonable, the PSNR of coded images and bit rate control are better than the original algorithm.An algorithm to estimate the image complexity is proposed, combining MAD and gradient, the image complexity can be effectively reflect its global motion and local motion. The experiments show that the improved algorithm can control rate more accurately in the same coding quality.Based on the new image complexity, allocate the number of target bits according to relative complexity of encoding frame. Experiment results show that rate control is more accurate, and the fluctuation of PSNR is small.【关键词】H.264码率控制 JVT-G012 图像复杂度 MAD预测【英文关键词】H.264 rate control JVT-G012 image complexity MAD prediction【目录】基于H.264的码率控制算法研究论文摘要3-5Abstract5-7第一章 绪论11-181.1 研究背景及意义111.2 视频编码的基本原理11-131.3 视频编码技术的发展及现状13-151.4 码率控制概述15-161.5 论文研究内容及结构安排16-171.5.1 论文研究内容161.5.2 论文结构安排16-171.6 本章小结17-18第二章 H.264 视频压缩编码标准18-282.1 H.264 视频编码标准的产生背景及应用18-192.2 H.264 的编码结构及其原理19-202.3 H.264 编码技术分析20-272.3.1 多模式的帧内预测20-222.3.2 精细的帧间预测22-242.3.3 整数变换和量化24-252.3.4 熵编码25-262.3.5 去方块滤波26-272.4 本章小结27-28第三章 码率控制算法研究28-483.1 码率控制的原理28-293.2 常用的码率控制算法模型29-373.2.1 MPEG-2 测试模型TM5 码率控制算法29-333.2.2 MPEG-4 VM8 码率控制算法33-343.2.3 H.263 TMN8 码率控制算法34-373.3 H.264 的码率控制算法37-473.3.1 率失真模型37-383.3.2 拉格朗日优化算法38-393.3.3 JVT-G012 码率控制算法39-473.3.3.1 基本概念39-403.3.3.2 算法流程40-413.3.3.3 GOP 层码率控制41-423.3.3.4 帧层码率控制42-453.3.3.5 基本单元层码率控制45-473.4 本章小结47-48第四章 基于 H.264 的码率控制算法研究及改进策略48-634.1 H.264 码率控制算法研究48-494.2 初始 QP 选取的改进策略49-544.