多描述编码

在Internet上传输视频有许多困难，其根本原因在于Internet的无连接每包转发机制主要是为突发性的数据传输而设计的，不适于对连续媒体流的传输。为了在Internet上有效而高质量地传输视频流，需要多种技术的支持。主要从压缩编码的角度分析了多描述编码方法是如何保证视频流高效稳定地传输。多描述编码属于差错复原技术的范畴，因此首先简单介绍了视频差错复原技术，接着介绍了多描述编码的基本原理，常用的视频多描述编码算法思想及面临的问题。     

基于多视点视频的差错控制技术

多视点视频数据量巨大,除了有效的压缩编码外,解决其在不可靠的信道如Internet和无线网络上传输的差错控制问题也是一个研究热点。针对多视点视频的三种编码结构,初步探讨了目前已经出现或正在研究中的多视点视频差错控制技术,主要集中在其编码端的差错复原编码和解码端的错误隐藏。     

视频编码新技术12题——第二讲 视频传输的差错控制

本文首先介绍了视频传输中三种常用的差错控制技术；然后着重介绍了其中的可分级编码技术，包括时间、空间、信噪比、精细可分级技术；最后介绍了多描述编码和信源信道联合编码技术。     

视频编码新技术12题第二讲视频传输的差错控制

本文首先介绍了视频传输中三种常用的差错控制技术;然后着重介绍了其中的可分级编码技 术,包括时间、空间、信噪比、精细可分级技术;最后介绍了多描述编码和信源信道联合编码技术。     

基于Internet的实时视频信号传输研究进展

随着Internet带宽和计算机处理能力的迅速提高,实时Internet视频传输在科研和工业领域引起了极大的研究兴趣。本文介绍了实时Internet视频传输的基本方法,针对Internet分组的丢失特性,讨论了具有差错复原能力的视频压缩与编码技术,详细介绍了Internet视频传输的信源／信道联方编码技术,并对今后的研究方向进行了概括的描述。     

多描述视频编码方法研究

稳健的视频编码压缩方法是实时网络视频传输的关键，多描述视频编码可为解决不可靠信道视频传输的丢包、误码和延时等所带来的视频质量严重降质问题提供一种新途径。本文介绍了面向网络传输的多描述视频编码的研究现状和一些典型的多描述视频编码器，并对其中的关键技术进行了分析、讨论。     

基于数据分割和可逆变长编码的数字视频传输差错复原技术

差错复原技术已成为易发生差错信道下视频编码的重要组成部分。本文实现了一个基于数据分割和可逆变长编码的具有差错复原性能的 H.2 63编解码器。通过利用数据分割、可逆变长编码、差错掩盖等技术 ,并利用第三代移动通信系统的信道差错模型对该编解码器的差错复原能力进行了实验。实验结果表明 ,在无线移动信道的恶劣环境下 ,在综合利用多种差错复原技术后 ,重建图像的主客观质量得到了明显的改善。     

基于3D视频的错误隐藏技术分析

随着3D视频产品的逐步问世,3D视频技术逐渐成为当前研究的热点。由于3D视频编码是利用多个视点的空间、时间及视点间的相关性进行压缩编码,导致当3D视频遭遇不可靠信道差错时,其受损的影响比传统的2D视频更严重。因此,研究基于3D视频的差错控制技术十分必要,针对3D视频的3种视频格式,初步探讨了目前已经出现或正在研究中的错误隐藏技术。     

无线视频传输容错算法研究新进展

视频信号经过压缩编码后通过Rayleigh衰减无线信道传输，容易受到突发性错误的影响，造成视频传输质量下降。容错(error resilience)是保证无线视频传输质量的重要措施。本文首先对几种无线信道模型进行了概括与比较，然后总结了各种容错算法的优缺点和最新研究进展情况。重点讨论了在传输层实施的前向纠错编码(FEC)和反馈差错控制，在编码器端根据不同的信道传输特性所采用的容错算法，包括帧内刷新、长期限存储、分层编码和多描述编码。本文还通过一种传输方案对容错策略的组合实施情况进行了分析。最后探讨了无线视频传输容错算法的发展趋势和挑战，提出了几个值得重视的发展方向。     

基于H.264和双树小波的多描述视频编码

本文针对互联网和无线信道等不可靠网络的视频传输问题,提出一种基于H.264和双树小波变换的多描述视频编码解决方案.采用分层的多描述视频编码框架,实现H.264和双树小波编码的有机结合.基本层用H.264编码器对视频信号进行低码率编码后,复制到各个描述;增强层用三维双树小波变换对原视频和基本层重建视频的差值进行编码,将产生的四棵三维小波树经噪声整形后两两组合,编码送到不同描述.在解码端,若能够接收到两个描述,则通过中心解码器实现高质量的视频重建;若丢失一个描述,则通过边解码器解码仍可保证一定质量的视频重建.实验结果表明在相同码率下,本算法的视频中心解码和边解码质量优于现有的多描述视频编码算法.     

面向移动的视频编码标准AVS-M

对AVS-M标准技术要点作了全面介绍,并与其他视频编码标准进行了性能比较.AVS-M的目标是在移动网络环境下,提供高压缩、高差错恢复、低复杂度和网络界面友好操作方便等性能,特别在降低复杂度和提高容错能力上有了很大的改进.     

无线视频传输的容错编码研究

基于无线视频监控传输技术进行无线信道视频图像传输的过程中,经常面临数据传输错误、带宽变化、网络拥塞导致的视频数据丢失问题,严重影响了图像质量。Joint Video Team(JVT)of ISO/IECMPEG and ITU-T VCEG提出了可伸缩视频编码(SVC),可实现视频空间、时间和图像质量的完全伸缩,本文结合率失真优化算法将可伸缩编码作为容错工具,引入了不同层数据,根据B-D代价函数决定自动重传机制,降低了视频数据丢失对图像质量的影响。仿真结果表明,该方法大大提高了视频码流的抗误码能力和传输的鲁棒性。     

一种新的视频数据差错控制算法

文中提出了无线信道下视频数据的一种新的组合式差错控制算法.该算法主要针对以下三个方面提出了创新,首先在信源的数据划分上,针对不等差错防护技术进一步提出了交错式控制思想.然后从信道编码方面针对现有前向纠错技术多采用多参数RS编码方式的复杂性和局限性,提出了一种UEP型RS十CRC差错控制算法.最后在不同的信道状态,保证一定的失真度情况下,提出采用合理的帧长及组包算法,使得传输功耗能够得到降低.最后根据实时媒体特性,对不同的数据丢包率进行了仿真,从仿真结果表明,该算法可以在降低失真度的同时,节省传输功率,其中在信道编码上可以降低50%左右的功耗.因此可达到最佳端到端功耗控制的效果.     

Video transmission over mobile satellite systems

Mobile satellite communication channels are characterized by long transmission delays, variation of these delays, high bit‐error‐rates, shadowing and the multipath effect which severely reduce the quality of video services. Error control techniques including feedback mechanisms, error concealment methods, forward error correction techniques and error resilience schemes are examined in this paper for achieving a high‐integrity video transmission over a mobile satellite channel. The application of three different error resilience algorithms, namely Turbo codes, error‐resilient entropy codes and two‐way decoding using reversible codes is presented. Their joint performance is also examined. Furthermore, a low‐delay and low‐complexity video transcoding algorithm which fully interconnects two very low bit rate video communication standards: MPEG‐4 and H.263 is also elaborated. This transcoder works as a gateway tool which links two heterogeneous multimedia networks, such as a mobile satellite network and a land‐based network, with negligible processing delay and complexity. Copyright © 2000 John Wiley & Sons, Ltd.     

可分级视频编码差错控制技术综述

H.264/AVC视频压缩标准相比于H.263和MPEG-4,H.264,其压缩性能提高了近一倍,但H.264/AVC局限于传统的单层编码模式,即便在编解码两端添加差错控制措施,仍不足以达到在高丢包率信道下流畅清晰观看视频的要求。分析了SVC(可分级视频编码)在高丢包率信道下的容错性,较为详细地介绍了目前SVC中提出的一些容错编码以及差错掩盖的方法,并介绍了SVC差错控制技术的发展。     

基于预测式错误恢复机制的多描述视频编码研究

该文提出一种基于预测式错误恢复机制的多描述视频编码方法。在编码端通过预测单路解码可能产生的错误影响,为每个描述分配必要的冗余信息。考虑到视频编码压缩的效率问题,设计了不同的编码模式来处理冗余信息。解码端可以充分利用冗余信息,从而实现丢失视频帧的高质量恢复。实验表明,与传统时域采样方法相比,该方法具有更好的率失真性能。     

Image/video communications: joint source/channel coding

Transmission of image/video messages over communication networks is becoming a standard way of communication due to very efficient compression algorithms that reduce required channel capacity to an acceptable level. However, all compression standard techniques are strongly sensitivitive to channel disturbances and their application is suitable only for practically noiseless channels. In standard noisy channels, the effect of errors on a compressed data bit stream can be divided into two categories: systematic errors defined by the structure of data blocks, and random errors caused by amplitude changes of transmitted components. A systematic error can be detected at the receiver through control of the data stream structure and corrected by error concealment methods or by automatic repeat request (ARQ) procedures. Random errors, noise and burst‐like errors, as well as impulse noise, should be controlled through channel coding. It is reasonable that an integrated source and channel coding methods should be preferred and should give better coding performance. In this paper, a new framework for an image/video coding approach has been presented in which the source and channel coding is integrated in a unique procedure. Image compression is performed in a standard way of the JPEG algorithm based on discrete cosine transform (DCT) and error control coding is based on the real/complex‐number (N,M) BCH code using discrete Fourier transform (DFT) specified with zeros in the time domain, i.e. with roots in the frequency domain. Efficiency of the proposed method is tested on two examples, an one‐dimensional real‐valued time sequence coded by real‐number (20,16) BCH code using DFT, and an example of an image coded by complex (10,8) BCH code using DFT with the correction ability of up to 8 impulses per transmitted 8×8 block. In addition, two decoding methods based on Berlekamp–Massey algorithm (BMA) and the minimum‐norm algorithm (MNA) have also compared. Copyright © 1999 John Wiley & Sons, Ltd.     

分布式视频编码技术研究

建立在Slepian-Wolf和Wyner-Ziv编码理论基础上的分布式视频编码是一种全新的编码框架。与传统视频编码方案相比,其突出的特点决定它可为未来无线视频信号编码与传输提供具有极大竞争力的解决方案。首先详细介绍了分布式视频编码的理论基础和特点,然后讨论了分布式视频编码的关键技术,最后给出了今后的研究方向。     

On the importance of error resilience in visual communications over noisy channels

This paper presents the importance of error resilience tools in visual communications. Error resilience tools provide a mechanism enabling transmission of visual information over channels with residual random bit errors in the received bit stream. The benefits of using error resilience tools are proven by devising the analytic relationship between the time delay in a transparent channel using automatic repeat request (ARQ) and the equivalent residual bit error rate in a nontransparent channel. The error resilience tools make it possible to achieve an acceptable visual quality even in the presence of these residual errors. Our work is related and compared to the standardization work of the next-generation still image compression system JPEG2000.The results show that partial and complete substitution of the quantization and symbol encoding in visual compression systems by robust error resilience tools provides a significant increase in robustness. Three error resilience tools are discussed: (1) substitution of the quantization and symbol encoding by a fixed length coding scheme, (2) substitution by a mixed fixed length coding and variable length coding scheme, and (3) substitution of the variable length coding by reversible variable length coding.     

网内编码：无线视频传感网中分布式编码速率控制机制

Wyner-Ziv Video Coding (WZVC) is considered as a promising video coding scheme for Wireless Video Sensor Networks (WVSNs) due to its high compression efficiency and error resilience functionalities, as well as its low encoding complexity. To achieve a good Rate-Distortion (R-D) performance, the current WZVC paradigms usually adopt an end-to-end rate control scheme in which the decoder repeatedly requests the additional decoding data from the encoder for decoding Wyner-Ziv frames. Therefore, the waiting time of the additional decoding data is especially long in multihop WVSNs. In this paper, we propose a novel progressive in-network rate control scheme for WZVC. The proposed in-network puncturing-based rate control scheme transfers the partial channel codes puncturing task from the encoder to the relay nodes. Then, the decoder can request the additional decoding data from the relay nodes instead of the encoder, and the total waiting time for decoding Wyner-Ziv frames is reduced consequently. Simulation results validate the proposed rate control scheme.