一种基于H.264的快速多参考帧选择算法

H．264采用的多参考帧运动估计极大地增加了编码器的复杂度。文中分析了各参考帧在运动估计中的作用,提出一种快速多参考帧选择算法以降低运算复杂度。该算法利用已编码相邻块参考帧的相关性,对参考帧进行预选择和排序,以避免不必要的运动搜索。可以与其它多参考帧运动估计算法相结合。实验结果表明,与H．264参考软件JM9．6中的快速算法UMHexagonS相比,提出的算法在保持编码图像质量的同时,可以进一步降低多参考帧运动估计的运算量,能够节省约35％的编码时间。     

H．264帧内预测算法的研究与优化

H．264作为最新的视频编码标准,为了获得最佳的帧内和帧间预测,H．264采用了率失真优化（RDO）技术,提高了编码质量,降低了比特率。RDO技术对所有的帧内／帧间预测模式采用全搜索算法,导致了很高的计算复杂度。本文中,引入了一种新颖的快速帧内预测算法,改变模式选择的顺序,利用临块之间预测模式的相关性,通过阈值比较及绝对差值和排序的方式,对H．264帧内预测算法进行了优化。实验结果表明：与全搜索算法相比,快速算法降低了30％左右的编码时间,而信噪比、码流几乎不变。     

基于H.264多参考帧的运动搜索快速算法

提出了一种基于H.264多参考帧的快速整像素运动搜索算法,该算法通过建立多参考帧中的搜索起始点模型和基于多参考帧的六边形搜索,能够有效地降低运动搜索的计算量。实验结果表明,基于多参考帧的快速运动搜索算法在保持有较好编码质量的同时,能够在很大程度上减少H.264多参考帧的运动搜索时间。     

基于深度图像的H.264快速帧间模式选择算法

H.264编码标准的帧间模式选择算法采用全候选模式搜寻算法,为编码器带来了高运算复杂度。提出一种快速帧间模式选择算法,旨在降低H.264帧间编码的运算复杂度。算法利用深度图像信息从彩色图像中分割出背景区域和运动剧烈的区域,宏块根据所在的区域选择相应的编码策略,从而达到缩小候选模式范围,加快模式选择速度的目的。实验证明,该算法在图像质量基本不变的情况下编码时间平均节省23%以上。     

一种新的H.264多参考帧快速搜索算法

H.264/AVC是目前最新的视频编码国际标准.在H.264/AVC中,由于采用了多参考帧,运动估计部分的复杂度大大增加了.虽然JVT采用的快速运动估计(FME)提案能极大地提高搜索速度,但只是加快了一帧的搜索速度.本文在FME基础上提出了一种新的多参考帧快速搜索算法(FMRSA),它利用当前块周围的块信息来预测将要搜索的参考帧的范围,并在具体搜索过程中运用提前中断的方法加快整个搜索过程.实验证明本算法比标准快速搜索法搜索5个参考帧能在PSNR降低不超过0.05dB、码率增加不超过2.32%的情况下节省至少56.5%的时间.     

基于H.264的多参考帧快速选择算法

 H.264采用了多参考帧技术,大大提高了预测精度,改善了视频图像质量,然而这种特性同时也带来了很高的计算复杂度.为了降低H.264编码器的计算复杂度,本文提出了一种多参考帧快速选择算法.该算法充分考虑多参考帧中运动矢量的相关性以及中心偏置特性,通过对待选参考帧进行预选择,有效减少了需要进行全搜索的参考帧个数,提高了编码速度.实验结果表明,该算法在保持图像质量和码率变化很小的前提下,运动估计模块编码速度提高了30.91%.     

H.264中基于先验预测的帧间编码模式选择算法研究

帧间编码的模式选择算法是H.264视频编码器中计算量较大的部分。该文首先简要介绍了H.264帧间多模式编码原理,然后对帧间编码的最佳模式进行统计、分析,提出了一种基于先验预测的帧间编码模式选择快速算法。仿真实验结果表明该文提出的快速模式选择策略可以在保证视频编码质量的同时,很大程度上降低编码器的计算复杂度。     

基于空域特征的H.264快速多参考帧选择算法

提出了一种H.264快速多参考帧选择算法,它利用视频序列的空间相关特性,在运动估计之前判断当前宏块的Skip编码模式,实现在运动估计过程中快速选择编码模式,基于对Skip编码模式占用概率的统计分析,设置多模式下参考帧数量.实验结果表明,本算法在PSNR损耗与全搜索算法相比不超过0.07dB的情况下,平均节约72.5%的编码时间.     

快速帧内预测模式选择新方法

为了提高编码性能,H.264采用了RDO(率失真优化),但与此同时带来的是计算复杂度的增加.本文着重分析了H.264中快速帧内预测模式选择的问题.为了降低帧内预测模式选择的计算复杂度,提出了一种高效的快速帧内预测模式选择算法.首先,对Pan的基于边缘方向直方图的快速算法进行了改进,同时提出了基于参考象素特征的4×4快速帧内预测模式选择算法,并将两者进行了结合.实验结果表明,本文算法和H.264校验模型JM61相比,I帧编码时间降低61%~69%,而PSNR基本保持不变,输出码率仅略有增加;与Pan的基于边缘方向直方图快速算法相比,本文算法的I帧编码时间降低12%~33%,PSNR和输出码率均基本保持不变.     

基于模式和时空相关性的运动估计快速算法

H.264标准中的多尺寸块运动估计,在显著提高编码性能的同时,大大增加了其计算量,使得H.264实时编码器的实现面临巨大挑战.本文充分利用视频图像的时空相关性和多尺寸块间的运动相似性,根据运动向量的中心偏置特性,提出了一种运动估计快速算法.该算法通过有效地预测搜索起点,自适应选择搜索模式以及采用二级终止搜索策略等方式,在编码性能相当的情况下,运动估计的速度比全搜索算法提高了95~247倍,比H.264推荐的快速算法提高了4.1~6.3倍.     

Fast multi-frame motion estimation for H264/AVC system

Advanced video compression standard, H264/AVC, with multi-frame motion estimation, can offer better motion-compensation than the previous coding standards. However, the implementation of real-time multi-frame estimation for an H264/AVC system is difficult due to heavy computations. In this paper, a fast algorithm is proposed in an effort to reduce the searching computation for motion estimation with five reference frames. The fast multi-frame motion estimation consists of the adaptive full-search, three-step search, and diamond search methods using the content adaptive control process. Efficient control flow is proposed to select the searching algorithm dependent on video features. The adaptive algorithm can achieve better rate-distortion and lower computation for H264/AVC coding. The experiments indicate that the speed-up is 6–15 times compared with the full search method, while the image quality slightly degrades.     

Fuzzy Logic Based Temporal Error Concealment for H.264 Video

In this paper, a new error concealment algorithm is proposed for the H.264 standard. The algorithm consists of two processes. The first process uses a fuzzy logic method to select the size type of lost blocks. The motion vector of a lost block is calculated from the current frame, if the motion vectors of the neighboring blocks surrounding the lost block are discontinuous. Otherwise, the size type of the lost block can be determined from the preceding frame. The second process is an error concealment algorithm via a proposed adapted multiple‐reference‐frames selection for finding the lost motion vector. The adapted multiple‐reference‐frames selection is based on the motion estimation analysis of H.264 coding so that the number of searched frames can be reduced. Therefore the most accurate mode of the lost block can be determined with much less computation time in the selection of the lost motion vector. Experimental results show that the proposed algorithm achieves from 0.5 to 4.52 dB improvement when compared to the method in VM 9.0.     

Improved motion estimation time using a combination of dynamic reference frame selection and residue-based mode decision

Motion estimation using multiple reference frames is widely used as the basis for recent video coding standards (eg. H.264/AVC) to achieve increased coding efficiency. However, this increases the complexity of the encoding process. In this paper, a new technique for efficient motion estimation is proposed. A combination of multiple reference frame selection and image residue-based mode selection is used to improve motion estimation time. By dynamic selection of an initial reference frame in advance, the number of reference frames to be considered is reduced. In addition, from examination of the residue between the current block and reconstructed blocks in preceding frames, variable block size mode decisions are made. Modified initial motion vector estimation and early stop condition detection are also adopted to speed up the motion estimation procedure. Experimental results compare the performance of the proposed algorithm with a state of the art motion estimation algorithm and demonstrate significantly reduced motion estimation time while maintaining PSNR performance.     

基于X264多线程并行编码研究

以X264编码器作为研究对象,着重研究片级多线程并行编码算法和帧间宏块级并行编码算法.帧间宏块级多线程并行编码算法需要对多帧图像进行并行编码,在系统中需保存与多帧图像编码有关的参考帧图像数据,所以占用大量的内存.但通过实验证明,在编码码率相对恒定的条件下,帧间宏块级多线程并行编码算法比片级多线程并行编码算法具有更高的编...     

Rate distortion optimization for H.264 interframe coding: a general framework and algorithms.

Rate distortion (RD) optimization for H.264 interframe coding with complete baseline decoding compatibility is investigated on a frame basis. Using soft decision quantization (SDQ) rather than the standard hard decision quantization, we first establish a general framework in which motion estimation, quantization, and entropy coding (in H.264) for the current frame can be jointly designed to minimize a true RD cost given previously coded reference frames. We then propose three RD optimization algorithms--a graph-based algorithm for near optimal SDQ in H.264 baseline encoding given motion estimation and quantization step sizes, an algorithm for near optimal residual coding in H.264 baseline encoding given motion estimation, and an iterative overall algorithm to optimize H.264 baseline encoding for each individual frame given previously coded reference frames-with them embedded in the indicated order. The graph-based algorithm for near optimal SDQ is the core; given motion estimation and quantization step sizes, it is guaranteed to perform optimal SDQ if the weak adjacent block dependency utilized in the context adaptive variable length coding of H.264 is ignored for optimization. The proposed algorithms have been implemented based on the reference encoder JM82 of H.264 with complete compatibility to the baseline profile. Experiments show that for a set of typical video testing sequences, the graph-based algorithm for near optimal SDQ, the algorithm for near optimal residual coding, and the overall algorithm achieve on average, 6%, 8%, and 12%, respectively, rate reduction at the same PSNR (ranging from 30 to 38 dB) when compared with the RD optimization method implemented in the H.264 reference software.     

一种多参考帧时域视频错误隐藏算法

提出一种自适应扩大搜索范围的多参考帧错误隐藏算法。该算法以视频序列的运动剧烈程度为基础,在多个参考帧中根据视频序列运动的剧烈程度的不同自适应地扩大搜索范围以寻找最优匹配块,用最优匹配块替换受损块。实验结果表明,与多帧恢复的时域错误隐藏算法相比,错误隐藏算法无论是在PSNR值上还是主观视觉效果上都有所提高。     

一种新型H.264/AVC多参考帧预测方法

在H.264/AVC视频压缩标准采用的几项关键技术中,使用多参考帧预测可以增加最佳匹配块的检索概率,进而大大提高了编码效率。受B帧直接(direct)预测模式的启发,提出了一种新的基于扩展帧的多参考帧预测方法,由多参考帧中的共同位置块及其参考块扩展得到一个新的抽取帧,增加了原始序列的时域分辨率,使得扩展帧更加接近当前帧,提高了运动估计中最佳匹配的检索概率,进而提升了编码效率。仿真结果证实该方法的编码性能好于H.264/AVC参考软件。     

Multiframe video coding for improved performance over wirelesschannels

We propose and evaluate a multi-frame extension to block motion compensation (BMC) coding of videoconferencing-type video signals for wireless channels. The multi-frame BMC (MF-BMC) coder makes use of the redundancy that exists across multiple frames in typical videoconferencing sequences to achieve additional compression over that obtained by using the single frame BMC (SF-BMC) approach, such as in the base-level H.263 codec. The MF-BMC approach also has an inherent ability of overcoming some transmission errors and is thus more robust when compared to the SF-BMC approach. We model the error propagation process in MF-BMC coding as a multiple Markov chain and use Markov chain analysis to infer that the use of multiple frames in motion compensation increases robustness. The Markov chain analysis is also used to devise a simple scheme which randomizes the selection of the frame (amongst the multiple previous frames) used in BMC to achieve additional robustness. The MF-BMC coders proposed are a multi-frame extension of the base level H.263 coder and are found to be more robust than the base level H.263 coder when subjected to simulated errors commonly encountered on wireless channels.