基于整数变换的全零块判决方法

H．263中的运动搜索和变换域编码是运算量很大的部分，也是影响系统实时性能的瓶颈，为了减少图像编码的运算量，在采用整数变换代替浮点DCT变换的基础上，提出了一种全局判决方法，即在运动搜索中和变换前进行全零块判决。该方法是根据整数变换和量化结果为零的特点，在运动搜索中，对差值块先进行全零块判决，如果找到全零块，就停止搜索，以省却以后的搜索运算和全零块的整数变换以及相应的量化运算，由于其可在基本保持H．263原有编码算法图像质量的同时，减少运算量和缩短码流，从而大幅度提高了编码器的编码效率。     

H.263自适应量化和可变长编码的最优化设计

该文首先概述了低码率图象编码标准H．263,然后着重讨论了自适应量化以及Huffman编码的联合优化设计,其中包括算法设计流程和相应的实现代码,最后给出了有关的实验结果和分析,结果表明该算法能有效地加快编码和解码器的运行速度,同时又能保证一定的图象质量。     

A region-based H.263+ codec and its rate control for low VBR video

This paper presents a region-based video codec, which is compatible with the H.263+ standard, and its associated rate control algorithm for low variable-bit-rate (VBR) video. The proposed region-based coding scheme is a hybrid method that incorporates traditional block DCT coding as well as object-based coding. To achieve this, we adopt H.263+ as the platform, and develop a fast macroblock-based segmentation method to implement the new region-based codec. The associated rate control solution includes rate control in three levels: encoding frame selection, frame-layer rate control and macroblock-layer rate control. The goal is to improve human visual perceptual quality at low bit rates. The efficiency of the proposed rate control algorithm applied to the region-based H.263+ codec is demonstrated via several typical test sequences.     

基于精细可扩展编码的多视角视频编码研究

多视角视频几倍于目前普通视频的数据量,如果不采用有效的压缩编码技术,其有效的传输和存储将是不可能的,也成为制约多视角视频广泛应用的瓶颈．因此,进行高性能多视角视频编码技术的研究是十分必要的．尤其是随着网络的发展,能提供交互的多视角视频技术越来越受到关注．如何有效地通过网络传输多视角视频信号的问题显得更加重要．针对这一问题,采用精细可扩展编码(FGS)的思想设计了多视角视频编码器．实验表明,方案在保证了高编码效率的同时能较好地解决多视角视频的网络传输问题．     

Scalable video transmission for the Internet

Information systems and distributed applications for the Internet show a growing demand for real-time audiovisual services. Support for those services within the Internet protocol layer will be widely available in the near future. Nevertheless, the heterogeneous structure of the Internet remains to be a great obstacle for establishing real-time video services. Scalable video codecs, generating bit-streams decodable at different rates, have been proposed to address the heterogeneity problem. In this article we present a scalable codec based on a spatio-temporal resolution pyramid combined with lattice vector quantization for efficient compression. With this approach additional lower bit-rate layers can be transmitted at the same overall bit-rate as needed by an H.263 single-layer transmission. The complexity of the codec is sufficiently low to allow software-only implementations of Internet video services. This is demonstrated on an Internet video server application.     

多解析度自适应零块判决算法

在视频会议等应用中,视频编码的速度是保证系统实时性的关键.为了减小视频编码的运算量并提高系统的整体性能,提出了多解析度的自适应零块发现判决算法.多解析度通过对图像的子采样从而大幅度降低了搜索最佳匹配块的次数;而自适应的零块判决算法使得运动搜索速度收敛的更快,在不影响图像质量的前提下提高了编码的效率,并且减少了后续模块(DCT、量化等)所占用的时间.利用H.263算法进行了测试,结果显示在图像主客观质量基本不变的前提下,编码时间最多减少了近40%.     

基于自动镜头分割的视频压缩编码算法

将镜头分割引入压缩编码,针对分割镜头特性确定适当的编码器及参数,能够提高视频压缩编码的效率．为此,提出了一种基于对分查找的镜头分割算法(VSSB)以及关键帧频率计算公式．其算法的核心是通过对分查找形成二叉树,同时通过广度优先搜索寻找分割点,具有O(log n)的时间复杂性．针对实时应用,采用了双阈值比较的镜头分割算法,能够较好地实现镜头切变和渐变的检测．基于镜头分割算法,建立并实现了并行方式的编解码系统模型．实验证明,基于镜头分割的编码方法能够提高压缩比,缩短压缩编码时间,有利于改善重建图像质量。     

Scene-effect detection and insertion MPEG encoding scheme for video browsing and error concealment

For an MPEG coding scheme, the encoder can do more than video compression. In this paper, a novel MPEG codec embedded with scene-effect information detection and insertion is proposed to provide more functionality at the decoder end. Based on the macroblock (MB) type of information that is generated simultaneously in the encoding process, a single-pass automatic scene-effect insertion MPEG coding scheme can be achieved. Using the USER/spl I.bar/DATA of picture header, the video output bitstreams by our method still conform to the conventional MPEG decoding system. The proposed method provides a solution toward upgrading the existing MPEG codec with low complexity to accomplish at least two major advantages. Precise and effective video browsing resulting from the scene-effect extraction can significantly reduce the user's time to look up what they are interested in. For video transmission, the bitstreams containing scene-effect information can obtain better error concealment performance when scene changes are involved. Compared with the gain it achieves, the payout of our algorithm is very worthy with comparatively small efforts.     

基于图象内容的视频压缩方法

由于视频图像的知识冗余度,视频压缩可以采用基于图像内容的压缩方式。论文描述了基于内容的压缩系统的整体框架,并且对于视频对象的形状信息,运动信息和纹理信息的编码过程都进行了详细讨论,然后探讨了视频对象的Sprite编码和时间空间可分级编码,最后介绍了针对任意形状视频对象的形状自适应(SA)DCT变换编码,同时指出SA-DCT存在的缺陷并以此作为后继工作的基础。     

基于ARM11的H.264硬编解码视频传输系统设计

为了解决视频信息冗余、视频传输系统成本较高,视频编解码效率低等缺陷,研究了一种基于H.264硬编解码器的视频传输系统;该系统采用以ARM11为核心的,包含多媒体硬编解码器MFC的S3C6410作为处理器,使用CMOS摄像头采集实时视频数据;在嵌入式Linux操作系统上构建基于live555的RTSP服务器,监听客户端请求;重点阐述了多媒体硬编解码器MFC对视频数据进行的H.264硬件压缩编码,以及数据包的RTP封装,然后经由live555流媒体服务器转发至PC机;最后,在PC上对接收到的数据流进行解码播放,经实验测试证明,系统设计稳定可靠,具有可扩展性强、性能高、成本和功耗低等优点,图像质量和时延满足实际应用需求。     

基于H.264的复杂度-失真最优的运动估计算法

为了满足嵌入式、移动设备的实时视频编码应用，提出一种可分级的复杂度-失真最优的运动估计算法，通过调整复杂度控制参数来实现视频编码器计算复杂度的可分级性，确保视频质量达到最优，在编码效率最高和失真最小间取得相对最佳平衡。实验结果表明，随着处理器计算能力的变化，该算法能自动调整编码器的计算复杂度，大大减少运动估计的运算量，同时图像质量和码率变化不大。     

Statistical, DCT and vector quantisation-based video codec

The authors present a novel hybrid statistical, DCT and vector quantisation-based video-coding technique. In intra mode of operation, an input frame is divided into a number of non-overlapping pixel blocks. A discrete cosine transform then converts the coefficients in each block into the frequency domain. Coefficients with the same frequency index at different blocks are put together generating a number of matrices, where each matrix contains the coefficients of a particular frequency index. The matrix, which contains the DC coefficients, is losslessly coded. Matrices containing high frequency coefficients are coded using a novel statistical encoder. In inter mode of operation, overlapped block motion estimation / compensation is employed to exploit temporal redundancy between successive frames and generates a displaced frame difference (DFD) for each inter-frame. A wavelet transform then decomposes the DFD-frame into its frequency subbands. Coefficients in the detail subbands are vector quantised while coefficients in the baseband are losslessly coded. To evaluate the performance of the codec, the proposed codec and the adaptive subband vector quantisation (ASVQ) video codec, which has been shown to outperform H.263 at all bitrates, were applied to a number of test sequences. Results indicate that the proposed codec outperforms the ASVQ video codec subjectively and objectively at all bitrates.     

分布式视频编码中关键帧编码方式的改进

在分布式视频编码中关键帧间的时间相关性没有被利用, 据此提出一种基于频带划分的关键帧编码模式的选择方法。关键帧经过DCT后得到的系数带划分为低频带和高频带, 低频带部分采用Wyner-Ziv编解码, 然后对高频带进一步进行编码模式的选择, 分别进行Wyner-Ziv编解码和传统的帧内编解码, 且在解码端完成编码模式的选择, 通过反馈信道向编码端传送编码模式的选择。仿真结果表明, 在不增加编码端复杂度的情况下, 所提出的方法改善了解码后视频的质量, 使系统的峰值信噪比（PSNR）提高约1~5 dB。     

Scalable video coding using motion-compensated temporal filtering and intra-band wavelet based compression

Scalable video compression is a crucial task that allows for high flexibility of video streams to different networks in various applications. Current video coding techniques exploit temporal correlation using motion-compensated predictive or filtering approaches. Particularly, motion-compensated temporal filtering (MCTF) is a useful framework for scalable video compression schemes. In this paper, we propose a new scalable video coding method that combines open-loop motion-compensated prediction with an embedded intra-band wavelet based compression. Our major objective is to provide a wavelet based video coding system that circumvents the drawbacks of conventional closed-loop prediction systems, without sacrificing compression performance. To improve the coding efficiency, we adaptively weight the target bitrate according to the temporal frame position in the temporal pyramid. Comparisons with state-of-the-art scalable video coding solutions confirm an overall coding efficiency gain of the proposed method specially at high bitrates.     

基于TMS320C6211的H.263编码器设计

依据H．263视频编码标准,在一颗DSP芯片上完成视频编码器的设计工作,以实现高质量的视频流的传输。该编码器是视频服务器的重要组成部分,其硬件平台选用TI公司的基于TMS320C6211DSP芯片的图像采集装置,软件开发环境采用CCS2．20．18。编码器不仅可以实时处理视频信号,而且还满足了高压缩比的要求,并且降低了系统成本。设计结果表明：在一棵DSP芯片上实现实时的H．263编码方案,并且满足高质量、低带宽传输的系统要求是完全可行的。     

Multiresolution,perceptual and vector quantization based video codec

This paper presents a novel Multiresolution, Perceptual and Vector Quantization (MPVQ) based video coding scheme. In the intra-frame mode of operation, a wavelet transform is applied to the input frame and decorrelates it into its frequency subbands. The coefficients in each detail subband are pixel quantized using a uniform quantization factor divided by the perceptual weighting factor of that subband. The quantized coefficients are finally coded using a quadtree-coding algorithm. Perceptual weights are specifically calculated for the centre of each detail subband. In the inter-frame mode of operation, a Displaced Frame Difference (DFD) is first generated using an overlapped block motion estimation/compensation technique. A wavelet transform is then applied on the DFD and converts it into its frequency subbands. The detail subbands are finally vector quantized using an Adaptive Vector Quantization (AVQ) scheme. To evaluate the performance of the proposed codec, the proposed codec and the adaptive subband vector quantization coding scheme (ASVQ), which has been shown to outperform H.263 at all bitrates, were applied to six test sequences. Experimental results indicate that the proposed codec outperforms the ASVQ subjectively and objectively at all bit rates.     

基于RDWT-子带运动补偿的可扩展视频编码方法

随着技术的发展，视频编码方法要求的不再仅是压缩效率，还包括码流的可扩展性．本文提出了一种基于RDWT-子带运动补偿的可扩展视频编码方法．首先对输入帧组进行空域DWT分解，在其后集成运动补偿过程的时域分解步骤中，使用冗余离散小波变换（RDWT）分解得到的各相位子带作为候选，选取一个最佳相位子带作为预测，提高运动补偿效率；在编码阶段，提出基于子带扫描顺序的改进3DSPIHT技术，保障码流的扩展特性．实验表明，所提出的方法获得较高编码效率的同时，提供了码流的高度可扩展特性。     

Statistical motion learning for improved transform domain Wyner-Ziv video coding

Wyner-Ziv (WZ) video coding is a particular case of distributed video coding (DVC), the recent video coding paradigm based on the Slepian-Wolf and Wyner-Ziv theorems which exploits the source temporal correlation at the decoder and not at the encoder as in predictive video coding. Although some progress has been made in the last years, WZ video coding is still far from the compression performance of predictive video coding, especially for high and complex motion contents. The WZ video codec adopted in this study is based on a transform domain WZ video coding architecture with feedback channel-driven rate control, whose modules have been improved with some recent coding tools. This study proposes a novel motion learning approach to successively improve the rate-distortion (RD) performance of the WZ video codec as the decoding proceeds, making use of the already decoded transform bands to improve the decoding process for the remaining transform bands. The results obtained reveal gains up to 2.3 dB in the RD curves against the performance for the same codec without the proposed motion learning approach for high motion sequences and long group of pictures (GOP) sizes.