DCT域视频图像转码的下采样算法

研究了DCT域视频图像转码的下采样算法,包括DCT域帧内编码帧Ⅰ帧的两种下采样算法——线性内插法和DCT系数截断法,以及DCT域帧间编码帧P帧的下采样算法——DCT域反运动补偿和DCT域运动补偿算法。对stefan视频序列第一帧（Ⅰ帧）分别采用两种下采样算法进行转码下采样,通过峰值信噪比（PSNR）值的比较说明线性内插法转码下采样的效果要优于DCT系数截断法。采用DCT域反运动补偿算法实现在DCT域重构stefan视频序列第四帧（P帧）的帧内数据。     

压缩域内的视频图像处理算法

介绍了一些在压缩域内处理已压缩视频流的算法，主要关注如何对DCT系数直接进行处理的算法，对于带有运动估计的压缩系统(如MPEG视频压缩码)介绍了一些解码算法及相应压缩域内的重构操作，这些算法也应用于视频转码。     

DCT域中高清电视到标清电视转码技术及软件实现

随着数字电视的发展与普及，不同编码视频的转码变得越来越重要。研究DCT域中空间分辨率下采样的关键技术，包括DCT域图像尺寸下采样、DCT域的运动补偿、运动矢量重用等，并以软件方式实现了HDTV到SDTV的转码。     

DCT域中高清电视到标清电视转码技术及软件实现

随着数字电视的发展与普及,不同编码视频的转码变得越来越重要。研究DCT域中空间分辨率下采样的关键技术,包括DCT域图像尺寸下采样、DCT域的运动补偿、运动矢量重用等,并以软件方式实现了HDTV到SDTV的转码。     

DCT域中高清电视到标清电视转码技术及软件实现

随着数字电视的发展与普及,不同编码视频的转码变得越来越重要.研究DCT域中空间分辨率下采样的关键技术,包括DCT域图像尺寸下采样、DCT域的运动补偿、运动矢量重用等,并以软件方式实现了HDTV到SDTV的转码.     

HDTV到SDTV转码的关键技术及软件实现

研究了 DCT域中空间分辨率下采样的关键技术,包括DCT域图像尺寸下采样、DCT域的运动补偿、运动矢量重用等,并以软件方式实现了HDTV到SDTV的转码.     

DCT域快速下采样运动向量滤波器

目前的视频压缩标准多数采用DCT变换编码和运动补偿技术。运动估计约占整个编码时间的60％、运动补偿约占10％。所以在视频转码中，运动向量的再使用技术是十分重要的，目前较好的方法是欧氏最小距离方法，它的主要缺点是估计精度不高，本文对此进行了改进，提出了DCT、域快速下采样运动向量滤波器，其重建图像的峰值信噪声比Shanableh等人提出的方法平均高0．2dB。     

基于AVS的变换域帧内转码研究

根据MPEG-2与先进音视频编码（AVS,Advanced Coding of Audio and Video）标准在帧内预测中的不同点,介绍了一种基于变换域的帧内预测转码算法。新算法提出一种新的变换域转码结构,通过矩阵变换计算出AVS帧内预测的各种模式所对应的离散余弦变换（DCT,Discrete Cosine Transform）预测矩阵,推导出DCT域到AVS整数变换域的系数转换矩阵,同时给出DCT域内预测矩阵转换所需的运算量。实验结果表明,提出的帧内预测转换方法可以使计算复杂度降低50%,达到实时转码的要求。     

DCT域视频转码技术综述

随着数字视频技术的广泛应用,实现各种视频编码格式之间转码的要求越来越迫.视频转码是数字媒体网络网关的关键技术.本文从DCT域视频转码的体系结构、关键技术及最优转码策略三个方面,介绍了现有的各种算法,分析和总结了各自的特点,提出了DCT域视频下采样帧内刷新体系结构和最优视频转码策略解的概念,并指出了下一步的研究方向.     

压缩域H.264视频转换编码及其关键技术分析

在分析最新的视频编码标准H.264与以前的编码标准差异基础上,针对压缩域的H.264视频转码,系统地研究了其关键技术的进展,并按DCT到HT的系数变换、运动矢量快速重估计、修正和帧内/间编码模式和速率控制等4个方面进行了分类归纳,还对未来本领域值得研究的问题进行了展望和预测。     

Motion analysis in 3D DCT domain and its application to video coding

Global, constant-velocity, translational motion in an image sequence induces a characteristic energy footprint in the Fourier-transform (FT) domain; spectrum is limited to a plane with orientation defined by the direction of motion. By detecting these spectral occupancy planes, methods have been proposed to estimate such global motion. Since the discrete cosine transform (DCT) is a ubiquitous tool of all video compression standards to date, we investigate in this paper properties of motion in the DCT domain. We show that global, constant-velocity, translational motion in an image sequence induces in the DCT domain spectral occupancy planes, similarly to the FT domain. Unlike in the FT case, however, these planes are subject to spectral folding. Based on this analysis, we propose a motion estimation method in the DCT domain, and we show that results comparable to standard block matching can be obtained. Moreover, by realizing that significant energy in the DCT domain concentrates around a folded plane, we propose a new approach to video compression. The approach is based on 3D DCT applied to a group of frames, followed by motion-adaptive scanning of DCT coefficients (akin to “zig-zag” scanning in MPEG coders), their adaptive quantization, and final entropy coding. We discuss the design of the complete 3D DCT coder and we carry out a performance comparison of the new coder with ubiquitous hybrid coders.     

基于量化系数均方误差准则的运动估计算法

提出了一种基于量化系数均方误差匹配准则的DCT域运动估计视频编码算法.算法中采用了一种新的运动估计匹配准则,该准则在DCT域内计算逆量化的残差均方误差值.由于该准则已考虑到量化噪声对运动残差能量的影响,因此与传统编码算法相比较,在图像质量基本不变的前提下码率更低.仿真结果显示,基于量化系数均方误差准则的DCT域运动估计算法具有较高的编码效率.     

Variable temporal-length 3-D discrete cosine transform coding

Three-dimensional discrete cosine transform (3-D DCT) coding has the advantage of reducing the interframe redundancy among a number of consecutive frames, while the motion compensation technique can only reduce the redundancy of at most two frames. However, the performance of the 3-D DCT coding will be degraded for complex scenes with a greater amount of motion. This paper presents a 3-D DCT coding with a variable temporal length that is determined by the scene change detector. Our idea is to let the motion activity in each block be very low, while the efficiency of the 3-D DCT coding could be increased. Experimental results show that this technique is indeed very efficient. The present approach has substantial improvement over the conventional fixed-length 3-D DCT coding and is also better than that of the Moving Picture Expert Group (MPEG) coding.     

DCT-based motion estimation

We propose novel discrete cosine transform (DCT) pseudophase techniques to estimate shift/delay between two one-dimensional(1-D) signals directly from their DCT coefficients by computing the pseudophase shift hidden in DCT and then employing the sinusoidal orthogonal principles, applicable to signal delay estimation remote sensing. Under the two-dimensional (2-D) translational motion model, we further extend the pseudophase techniques to the DCT-based motion estimation (DXT-ME) algorithm for 2-D signals/images. The DXT-ME algorithm has certain advantages over the commonly used full search block-matching approach (BKM-ME) for application to video coding despite certain limitations. In addition to its robustness in a noisy environment and low computational complexity, O(M(2)) for an MxM search range in comparison to the O(N(2).M(2)) complexity of BKM-ME for an NxN block, its ability to estimate motion completely in DCT domain makes possible the fully DCT-based motion-compensated video coder structure, which has only one major component in the feedback loop instead of three as in the conventional hybrid video coder design, and thus results in a higher system throughput. Furthermore, combination of the DCT and motion estimation units can provide space for further optimization of the overall coder. In addition, the DXT-ME algorithm has solely highly parallel local operations and this property makes feasible parallel implementation suitable for very large scale integration (VLSI) design. Simulation on a number of video sequences is presented with comparison to BKM-ME and other fast block search algorithms for video coding applications even though DXT-ME is completely different from any block search algorithms.     

A Motion Picture Coding Algorithm Using Adaptive DCT Encoding Based on Coefficient Power Distribution Classification

A motion picture coding algorithm using motion-compensated interframe prediction and the adaptive discrete cosine transform (DCT) encoding technique is proposed. High coding efficiency is obtained by the adaptive DCT encoding technique in which encoding parameters are fitted to widely varying characteristics of the interframe differential signal. Segmented DCT subblocks of interframe prediction error are classified into categories based on their coefficient power distribution characteristics. The adaptation gain results from using a suitable variable word length code set designated by the above classification for encoding each quantization index of DCT coefficients. In addition, a new coding parameter control method is introduced based on the information rate estimation of the current frame. This classification promotes high stability because good estimation accuracy of bits consumption for each DCT subblock is obtained by utilizing the category indexes. Simulation results show that the proposed algorithm has enough coding efficiency to transmit videoconferencing motion pictures through a 384 kbit/s channel.     

基于DCT变换的快速分形编码方法

本文提出了一种基于DCT变换加速相似块匹配的分形编码方法.通过图像块与相似块在DCT变换域少数低频系数的比较,来确定匹配的相似块.并根据DCT变换的性质,方便的确定对比度因子和亮度偏移量.并采用将图像块与相似块的DCT变换系数预制成查找表的方法减少重复运算.结果表明,编码时间大幅度减少,而PSNR只是略有下降.     

WHT-based composite motion compensated NTSC interframe directcoding

The motion compensated interframe differential pulse code modulation (DPCM) and discrete cosine transform (DCT) hybrid (MC DCT) coding was nominated as a standard scheme for component TV signals by ISO and ITU-R. However, in cases where an NTSC composite TV signal is used such as the United States and Japan, applying the MC DCT scheme with its luminance/chrominance separating and composing process causes unavoidable quality degradation. The reason for this additional process required for MC DCT is that a composite TV signal presents a “color subcarrier phase shift problem” in which the color subcarrier phase varies between a coding block and reference block according to the motion vector. In this paper, we propose a Walsh Hadamard transform (WHT)-based composite motion compensated NTSC interframe direct coding scheme. In this scheme, phase shifts of a color subcarrier and modulated chrominance components between a coding block and reference block can be effectively compensated by a simple process of coefficient permutation and polarity changes of several pairs of WHT coefficients to which 100% of the subcarrier energy and most of the modulated chrominance component's energy are packed. In the motion compensated DCT scheme, however, the energy of the color subcarrier and modulated chrominance components are spread over too many coefficients and a pair-based coefficient handling rule is not given to solve this problem. This paper demonstrates that the proposed scheme provides higher coding performance for a composite NTSC signal than does the motion compensated DCT scheme with its luminance/chrominance separating and composing process     

Vector-scalar classification for transform image coding

This paper introduces vector-scalar classification (VSC) for discrete cosine transform (DCT) coding of images. Two main characteristics of VSC differentiate it from previously proposed classification methods. First, pattern classification is effectively performed in the energy domain of the DCT subvectors using vector quantization. Second, the subvectors, instead of the DCT vectors, are mapped into a prescribed number of classes according to a pattern-to-class link established by scalar quantization. Simulation results demonstrate that the DCT coding systems based on VSC are superior to the other proposed DCT coding systems and are competitive compared to the best subband and wavelet coding systems reported in the literature.     

Fast Inverse Motion Compensation Algorithms for MPEG and for Partial DCT Information

In prior work, we developed a fast inverse motion compensation method that can be implemented directly on the DCT domain representation derived from the compressed bitstreams conforming to MPEG, H.261, and H.263 standards. That work was restricted to compressed-domain representations wherein the motion-vectors have integer pel accuracy. Here, we extend this work to fractional-pel accurate motion-vectors. We also extend the prior work to speed up the inverse motion compensation process in the DCT domain by explicitly exploiting the sparseness of the DCT domain representation. Using partial DCT information, we show that the DCT domain method has substantially lower operation count than the conventional spatial domain approach which requires decompression followed by inverse motion-compensation.     

结合视频压缩编码的动态图像水印方案

本文提出了一种新的、结合视频压缩编码的动态图像水印方案。在嵌入水印时，充分考虑动态图像压缩编码的特性，对帧内编码帧(I帧)，将水印信息嵌入到DCT低额系数中；面对帧间编码帧(P、B帧)，结合动态补偿/离散余弦变换(MC/DCT)混合编码，把水印信息嵌入到运动补偿后的残差图象的直流成分中。同时，在水印嵌入时，采用扩频技术与多维水印相结合的方法，并通过相关检测的方法判断水印的存在。由于水印的检测是对视频码流直接实施的，不需要对压缩数据进行完全解码，从而大大降低了计算量，提高了视频数据水印的适用性。