基于H.263中PEI域的视频抗误码方法研究

本文提出利用H.263中PEI域自适应改变前向纠错能力,保护重同步信息进行误码掩盖,以及防止误码扩散的一种新颖的抗误码方法.实验结果表明,在信道变化和高误码率环境下,使用本文提出的抗误码方法大大提高了恢复视频的质量.另外,该算法与H.263标准兼容,且没有过多增加信道负担和运算复杂度,具有实用价值.     

视频通信抗误码方法研究的新进展

本文比较全面地总结了视频通信中抗误码方法的研究及其新进展.首先,详细评述了结合信源特点的前向差错控制、码流变换、解码端的误码掩盖和防误码扩散等视频抗误码新方法;然后,介绍视频编码标准H.263+/H.263++和MPEG-4中提出的抗误码算法;接下来,讨论多种视频抗误码系统的设计方案;最后,对视频抗误码今后研究的重点和方向提出了展望.     

低速率视频传输的抗误码技术

误码掩盖是在无线信道进行低速率视频传输的一种抗误码技术。本文在比较和分析了现有几种误码掩盖方法优劣势后,提出了一种混合误码掩盖法。该算法在没有过多增加解码端运算复杂度的同时,大大提高了恢复图像的质量。     

数据传输及可视数据业务

0322735拥塞高速数据通信网优化控制模型[刊]/朱刚//电波科学学报.—2003,18(3).—295～297(L)针对多信源——信宿高速数据通信网,引入 N 用户非零和微分对策优化控制路由模型。通信网中每个用户(决策者),通过决策瞬时队列、路由及通信流量速率,使优化指标(损耗函数)达到最小;给出了反馈Nash 平衡解的充要条件,并进行讨论。参60322736一种新颖实用的交互式视频抗误码方法[刊]/宋彬//电子学报.—2003.31(4).—556～559(L)本文提出一种新颖的交互式视频抗误码方法。首先.分析了块匹配运动补偿编码方法产生时域误码扩     

基于交互式抗误码技术的H.263编解码器

目前，在IP分组网中进行视频图像的传输正被日益广泛地应用。但是，由于IP分组网固有的特点，IP分组包丢失的现象不可避免并极大地影响了视频传输的服务质量。本文通过对一种使用连续更新来阻止差错传播（RESCU）的交互式抗误码技术进行改进，实现了一种新的交互式抗误码方法。同时，我们根据这种方法实现了一种具有良好差错恢复能力的H．263编解码器，从而改善了因分组包丢失对视频传输质量带来的影响。     

基于主观质量控制的数字视频综合抗误码技术

本文系统地提出了一套视频通信中的综合抗误码技术.本文针对窄带噪声信道,在H.263+编码的基础上,首先提出了视频主观质量控制策略;并在编码端根据视频信息的重要程度相应采用了非等重保护的前向纠错(FEC)算法,当恢复视频仍有误码时,则在解码端根据不同的帧编码类型使用相应的时/空误码掩盖方法提高恢复视频质量.计算机仿真结果表明,采用以视频主观质量控制策略为核心的综合抗误码技术,在高误码环境下,恢复视频信噪比可提高10-20dB,主观视频质量可提高1-2个等级.该综合抗误码方案已在实际中得到应用.     

一种基于对象几何形状的视频抗误码方法

针对压缩视频流中的误码,提出了一种新颖的基于对象几何形状的视频抗误码方法.首先,在编码端通过比较帧间编码帧内邻近宏块的运动向量差异获得粗略的对象几何形状信息,以对象标示图表示;再把它以与标准码流兼容的方式嵌入到压缩码流里去;最后,在解码端利用它帮助精确的构造错误宏块的运动向量.试验结果表明,该方法对于即使大量连续slice出错的情况仍能获得比较好的掩盖效果,而增加的运算复杂度和传输负载量都不大.     

一种面向Internet信道的H.26L率失真抗误码编码判决策略

从最新的H.26L视频压缩标准出发,提出了一个面向典型Internet误码信道的率失真宏块编码判决策略,通过在宏块编码判决层上引入优化的亮度率失真策略,从而在综合考虑视频编码质量和信道误码扩散导致的解码失真的条件下,使视频流具有更强的自适应误码抵抗能力.实际Internet误码信道下的测试结果充分证明了本率失真判决策略的抗误码优势.     

H．264后处理误码掩盖技术

数字视频通信中往往会由于信道不理想等原因而产生误码,而且误码在空间和时间上的扩散会导致重建图像质量不同程度的下降.而误码掩盖技术就是用来改进重建视频质量的重要方法之一.文章论述了国内外误码掩盖技术的现状及其典型算法,分析了误码掩盖技术的应用范围和性能,最后指出误码掩盖技术的发展前景.     

基于H.264的具有抗分组丢失能力的视频通信系统

针对IP网络环境下实时视频通信的需要，提出了具有抗分组丢失能力的视频通信系统（PRVCS）。系统以H．264编解码算法为核心，在满足实时视频通信要求的同时，将前向分组保护，误码掩盖和交互式防误码扩散三种算法有机结合，在丢包环境下保证恢复视频的主客观质量。其中重点研究了PRVCS所使用的算法、体系结构以及系统的具体实现。     

Adaptive error-resilience transcoding using prioritized intra-refresh for video multicast over wireless networks

In this paper, we propose a two-pass error-resilience transcoding scheme based on adaptive intra-refresh for inserting error-resilience features to a compressed video at the intermediate transcoder of a three-tier streaming system. The proposed transcoder adaptively adjusts the intra-refresh rate according to the video content and the channel's packet-loss rate to protect the most important macroblocks against packet loss. In this work, we consider the problem of multicast of video to multiple clients having disparate channel-loss profiles. We propose a MINMAX loss rate estimation scheme to determine a single intra-refresh rate for all the clients in a multicast group. For the scenario that a quality variation constraint is imposed on the users, we also propose a grouping method to partition a multicast group of heterogeneous users into a minimal number of subgroups to minimize the channel bandwidth consumption while meeting the quality variation constraint. Experimental results show that the proposed method can effectively mitigate the error propagation due to packet loss as well as achieve fairness among clients in a multicast.     

一种用于H.264视频容错转码的帧内宏块刷新算法

无线网络信道具有误码率高、延时抖动等不稳定的特性。为了保证视频信息从有线网络到无线网络中传输的质量,需要对视频进行容错转码。基于H.264容错转码系统,利用转码结构中解码部分的运动矢量信息,自适应地在编码部分进行帧内刷新,以提高视频的抗误码能力。实验结果对比表明,该帧内刷新算法能够以较少的比特率为代价,有效地提高了接收端的视频质量。     

基于H．263视频解码的错误检测和掩盖

本文提出了一种应用于H．263视频编码传输的纠错方法,即基于H．263视频解码的错误检测和掩盖算法。这种算法可应用于公共交换电话网（PSTN）,Internet或移动信道的视频通信。模拟结果表明,这种纠错方法在不降低编码效率的前提下,使在有噪声干扰的信道上传输图像的质量有显著的改善。     

RD-optimized interactive streaming of multiview video with multiple encodings

This paper presents a rate-distortion (RD) optimized interactive streaming method for multiview video pre-compressed by H.264 Joint Multiview Video Model (JMVM). In the proposed method, multiple encodings are first used to facilitate the flexible server–client interaction. Second, a RD-optimized scheduling strategy is provided to guarantee the optimal view-dependent delivery of multiview video. In the RD-optimized scheduling strategy, a distortion model is proposed to estimate the expected end-to-end distortion by accounting for both coding and packet-loss-induced distortions, as well as rendering-induced distortion. With the end-to-end distortion model, the server can select the optimal encoding combination for transmission. Experimental results demonstrate that the proposed method can achieve a significant end-to-end RD performance improvement over the selective streaming methods with simulcast coding or scalable multiview coding. In addition, it has better error-resilience performance to combat with packet-losses over the Internet protocol (IP) networks.     

Error recovery for interactive video transmission over the Internet

Real-time interactive video transmission in the current Internet has mediocre quality because of high packet loss rates. Loss of packets in a video frame manifests itself not only in the reduced quality of that frame but also in the propagation of that distortion to successive frames. This error propagation problem is inherent in any motion compensation-based video codec. In this paper, we present a new error recovery scheme, called recovery from error spread using continuous updates (RESCU), that effectively alleviates error propagation in the transmission of interactive video. The main benefit of the RESCU scheme is that it allows more time for transport-level recovery such as retransmission and forward error correction to succeed while effectively masking out delays in recovering lost packets without introducing any playout delays, thus making it suitable for interactive video communication. Through simulation and real Internet experiments, we study the effectiveness and limitations of our proposed techniques and compare their performance to that of existing video error recovery techniques including H.263+ (NEWPRED). The study indicates that RESCU is effective in alleviating the error spread problem and can sustain much better video quality with less bit overhead than existing video error recovery techniques under various network environments     

Error-resilience improvement for block-transform video coders

An algorithm is presented to enhance the resilience of block-based video-coding algorithms against channel errors. The error-resilience algorithm described suggests the use of fixed length coding to alleviate the effect of Huffman coding on the synchronisation of the decode under erroneous conditions. The proposed mechanism modifies the order of transmission of the fixed-length video parameters to increase the chance of their arrival. Synchronisation words are sent at fixed-length intervals within the bit stream to reduce the possibility of the decoder falling on similar bit patterns within the bit stream. To limit the effect of error accumulation, the motion prediction process is halted and the differential coding of motion vectors is not applied. FEC techniques are applied on some error-sensitive segments of the reordered video bitstream. The effectiveness of the proposed error-resilience algorithm is evidenced by both subjective and objective results