基于无线信道的SVC数据误码保护方案

提出一种基于无线传输信道的分级视频编码数据误码保护方案。该方案通过综合分析空间增强层数据、时间增强层数据、信噪比增强层数据的相对重要性,按萤要性的不同将各增强层的数据归为3类,对不同级别数据采用不同冗余度的前向纠错保护方式。实验结果证明,该方案可以取得较好的传输效果,与传统的均匀误码保护及非均匀误码保护方案相比,可获得2dB和0．5dB的PSNR增益。     

SVC在无线信道传输中的非均衡差错保护

针对H.264的可伸缩视频编码扩展标准(SVC)在噪声信道中的传输,采用低密度奇偶校验码(LDPC)提出一种非均衡差错保护的方案。在所提的方案中,根据时间、分辨率和质量把原视频序列按重要性分成不同的层。由于不同层的数据对错误的敏感性不同,对其进行不同码率的LDPC信道编码,实现非均衡差错保护。根据视频流中每一帧不同层的PSNR增量不同,和不同信道码率下正确解码的概率不同,反复计算每一帧所有码率组合的PSNR增量值并找出最大组,从而进行信道编码并传输。实验表明,在相同的平均码率条件下,提出的方案相比其他方案的PSNR值增加了2.8 dB,更适合无线信道的传输。     

基于宏块的具有时域和SNR精细可伸缩性的视频编码

提出了一个高效灵活的视频编码方法，称为基于宏块的具有时域和SNR精细可伸缩性的视频编码方法（简称为PFGST视频编码方法），将原有的基于帧的渐进精细可伸缩的视频编码技术扩展为基于宏块的编码技术，即增强层编码中运动补偿和重建时所用的参考信息是基于宏块选择的而不是基于帧、然后将时域可伸缩特性引入到基于宏块的渐进精细可伸缩的视频编码中，从而实现了PFGST编码方案，在时域可伸缩的增强层编码中，根据运动补偿中使用的参考宏块的不同，提出了时域可伸缩增强层宏块编码的两种方法，由于在时域可伸缩的增强层编码中使用高质量的参考宏块不会造成任何误差传播，因此通过选用最佳的参考宏块，PFGST方法的编码效率得到了显著的提高，实验结果显示，同MPEG－4标准中的FGST编码方法相比，基于宏块的PFGST视频编码技术的编码效率提高了2．8dB，并且同样具有FGST的所有特性，即可以根据不同的通道，客户和服务器的需求来分别支持精细的SNR可伸缩特性，时域可伸缩特性和SNR－时域混合可伸缩特性。     

子带内运动补偿时域滤波的优化

在用提升算法实现子带内运动补偿时域滤波时,为了提高运动模型的有效性,探索了利用多假设预测技术以改善运动补偿。提出了更新算子的优化设计,以提高低码率下视频编码的可扩展性,并取得改善的重建视频质量。实验结果显示,优化的子带内运动补偿时域滤波,在保证运动估计精度下,通过合理选择时间滤波器,结合改善的提升实现中的更新操作,提高了编码系统的编码效率和可扩展性能。     

基于可伸缩视频编码的率失真优化编码算法*

可伸缩视频编码（SVC）可实现视频流空间、时间和信噪比的完全伸缩,但在差错信道上传输容易引起误差扩散,为此提出一种基于SVC的率失真优化编码算法。该算法在分析了差错信道下传输可伸缩视频流误差扩散失真的基础上,在率失真优化模型中引入时间和信噪比分级的误差分级参数,并根据信道状态自适应地确定宏块编码模式。该算法能够有效地抑制误码在各分层的扩散,提高了可伸缩视频流的鲁棒性。仿真结果表明,算法与以往的算法相比具有更好的抗误码性能,适合视频数据在差错信道上的传输。     

MPEG-4的可伸缩视频编解码技术研究

回顾了目前的网络视频流服务，提出基于MPEG-4的可伸缩视频流服务。研究了其中的关键技术：利用MPEG-4的可伸缩码流，编程实现了MPEG的可伸缩解码。分析了在服务器端的MPEG-4的可伸缩编码依据时域可伸缩(即时域分辨率的变化)、空域可伸缩(即空域分辨率的变化)和对象的可伸缩(主要和次要对象的取舍)三个概念，对MPEG-4数据流进行分层，保证图像基本质量的为基本层数据，其它的则为各增强层数据，起着改善图像质量的作用。相应地，用户端也需要可伸缩解码器的支持，它能在收到完整的一层或几层数据后正确、快速地解码。     

Scalable Video Multicast Using Expanding Window Fountain Codes

Fountain codes were introduced as an efficient and universal forward error correction (FEC) solution for data multicast over lossy packet networks. They have recently been proposed for large scale multimedia content delivery in practical multimedia distribution systems. However, standard fountain codes, such as LT or Raptor codes, are not designed to meet unequal error protection (UEP) requirements typical in real-time scalable video multicast applications. In this paper, we propose recently introduced UEP expanding window fountain (EWF) codes as a flexible and efficient solution for real-time scalable video multicast. We demonstrate that the design flexibility and UEP performance make EWF codes ideally suited for this scenario, i.e., EWF codes offer a number of design parameters to be ldquotunedrdquo at the server side to meet the different reception criteria of heterogeneous receivers. The performance analysis using both analytical results and simulation experiments of H.264 scalable video coding (SVC) multicast to heterogeneous receiver classes confirms the flexibility and efficiency of the proposed EWF-based FEC solution.     

用于可分级视频编码的MCTF方法

提出用于可分级视频编码的3带小波提升与运动模型自适应结合的方法,将3带小波的提升步与运动补偿自适应相结合来实现时间域的小波变换,扩展了经典的运动补偿时域滤波,实现了时间分级的灵活性,同时又可以根据实际的视频序列选择适当的运动模型,从而达到更好的编码效果。仿真结果验证了该方法的有效性和性能的优越性。     

一种面向SVC的码率控制算法

H.264/AVC可伸缩性扩展视频编码系统(JSVM)提供了一种可伸缩视频编码(SVC)的解决方案,然而它本身并没有提供一种有效的码率控制算法.文中基于JSVM的分层预测结构,提出了一种全新的码率控制算法.首先在码率分配方面,考虑到分层B帧预测(或运动补偿时间域滤波(MCTF))结构,给出一种分层的码率分配方案;然后,针对不同类型和不同时间分解层各自的统计特性,分别为它们设计了不同的率失真(R-D)模型.实验结果表明,文中算法能够有效地控制码率,使得目标码率跟实际产生码率之间的偏差最大不超过2%;同时文中算法较大地提高了解码图像的质量,使得峰值信噪比(PSNR)在低码率端可提高1dB;另外,JSVM是通过不断调整量化参数(QP)使得实际产生的码率逐次逼近目标码率,较之这种尝试型的码率控制算法,文中基于模型的码率控制是在一次编码中产生最终的目标码率,从而大大降低了计算复杂度.     

Optimal adaptive channel scheduling for scalable video broadcasting over MIMO wireless networks

Video broadcasting is an efficient way to deliver video content to multiple receivers. However, due to heterogeneous channel conditions in MIMO wireless networks, it is challenging for video broadcasting to map scalable video layers to proper MIMO transmit antennas to minimize the average overall video transmission distortion. In this paper, we investigate the channel scheduling problem for broadcasting scalable video content over MIMO wireless networks. An adaptive channel scheduling based unequal error protection (UEP) video broadcasting scheme is proposed. In the scheme, video layers are protected unequally by being mapped to appropriate antennas, and the average overall distortion of all receivers is minimized. We formulate this scheme into a non-linear combinatorial optimization problem. It is not practical to solve the problem by an exhaustive search method with heavy computational complexity. Instead, an efficient branch-and-bound based channel scheduling algorithm, named TBCS, is developed. TBCS finds the global optimal solution with much lower complexity. The complexity is further reduced by relaxing the termination condition of TBCS, which produces a (1 − ε)-optimal solution. Experimental results demonstrate both the effectiveness and efficiency of our proposed scheme and algorithm. As compared with some existing channel scheduling methods, TBCS improves the quality of video broadcasting across all receivers significantly.     

可扩展视频编码中运动补偿时域滤波的改进

在基于小波变换的可扩展视频编码方案中,研究运动补偿时域滤波的优化方法.将有效的多相位子带内运动估计纳入分层运动估计策略中,用提升算法实现子带内运动补偿时域滤波,融入多假设预测以优化运动补偿技术;为了提高低码率下视频编码的可扩展性,提出更新算子的优化设计.实验结果显示,在保证运动估计精度下,合理选择时间滤波器,结合改善的提升实现中的更新操作,提高了编码系统的编码效率和可扩展性能.     

基于MPEG 4的无线视频传输方案的研究*

提出一种基于MPEG4的无线视频传输非等重误码保护方案。根据信道反馈的丢包率信息,自适应选择输出视频流的保护模式。在丢包信道中,对MPEG4码流中运动信息和纹理信息采取不同的保护力度,使用FEC重点保护运动信息数据提高其对误码的鲁棒性。在无丢包信道中,不对数据进行保护,降低打包开销,减少冗余数据。     

A new unequal error protection scheme based on FMO

This paper presents a novel scheme for video transmission over error-prone networks. The proposed scheme exploits the error resilient features of H.264/AVC and employs an unequal error protection (UEP) approach to protect effectively the streams. A novel algorithm is proposed to classify macroblocks into slice groups using the explicit mode of Flexible Macroblock Ordering (FMO). A rate distortion optimized algorithm is used to assign unequal amounts of FEC protection to the resulting slice groups according to their importance. In addition, a Converged Motion Estimation (CME) is proposed to further improve the proposed UEP scheme. The idea behind the CME is to make the macroblocks be referenced in a skewed manner, such that highly important macroblocks are converged on only a few and the use of redundancy for error protection is efficient. Simulation results show the superiority of the proposed method over other approaches for transmission of H.264/AVC streams.     

信源-信道联合编码的FGS增强层视频传输研究

研究了基于IP无线网络中精细粒度可伸缩性（FGS）视频的侍输。基于包交换的IP无线网络通常由两段链路组成：有线链路和无线链路。为了处理这种混合网络中不同类型数据包的丢失情况，对FGS视频增强层数据运用了一个具有比特平面间不平等差错保护（BPUEP）的多乘积码前向纠错（MPFEC）方案进行信道编码。对FGS增强层每一个比特平面（BP），在传输层，采用里德——索罗蒙码（RS）提供比特平面间的保护；而在链路层，则运用循环冗余校验码（CRC）串联率兼容穿孔卷积码（RCPC）提供数据包内保护。还提出了一个率失真优化的信源——信道联合编码的码率配置方案，仿真结果显示出该方案在提高接收端视频质量方面的优势。     

Scalable Joint Source and Channel Coding of Meshes

This paper proposes a new approach for joint source and channel coding (JSCC) of meshes, simultaneously providing scalability and optimized resilience against transmission errors. An unequal error protection approach is followed, to cope with the different error-sensitivity levels characterizing the various resolution and quality layers produced by the input scalable source codec. The number of layers and the protection levels to be employed for each layer are determined by solving a joint source and channel coding problem. In this context, a novel fast algorithm for solving the optimization problem is conceived, enabling a real-time implementation of the JSCC rate-allocation. An instantiation of the proposed JSCC approach is demonstrated for MeshGrid, which is a scalable 3-D object representation method, part of MPEG-4 AFX. In this context, the L-inflnite distortion metric is employed, which is to our knowledge a unique feature in mesh coding. Numerical results show the superiority of the L-inflnite norm over the classical L-2 norm in a JSCC setting. One concludes that the proposed joint source and channel coding approach offers resilience against transmission errors, provides graceful degradation, enables a fast real-time implementation, and preserves all the scalability features and animation capabilities of the employed scalable mesh codec.     

An improved 3D wavelet-based scalable video coding codec for MC-EZBC

With the rapid growth of modern multimedia applications, 3D wavelet-based scalable video coding (SVC) codec has received considerable attention lately because of its high coding performance and flexibility in bitstream scalability. It combines the motion-compensated temporal filtering (MCTF) together with the spatial decomposition to produce an embedded bitstream offering various levels of video quality over the heterogeneous networks. However, in the existing 3D wavelet-based SVC schemes, where the block types for block matching algorithms are limited, weighting matrices for block-wise motion compensation are fixed, and variations in activities of temporal subbands are not considered in the selection of the Lagrange multiplier for mode decision. In this paper, our major contribution is to provide some recent extensions to the well-known scalable subband/wavelet video codec Motion-Compensated Embedded Zero Block Coding (MC-EZBC) using three novel and content adaptive algorithms. Firstly, the enhanced hierarchical variable size block matching (Enhanced HVSBM) algorithm is proposed for the variable block size motion estimation. Then, the rate-distortion optimization (RDO) based adaptive Lagrange multiplier selection model for mode decision is presented. Finally, we introduce the adaptive weighting matrices design for overlapped block motion compensation (OBMC). Experimental results show that all the three proposed algorithms significantly improve the overall coding performance of MC-EZBC. Comparisons with other popular wavelet-based SVC codecs demonstrate the effectiveness of our improved codec in terms of both video quality assessment and computational complexity.     

基于长支集小波的可伸缩视频编码及其并行实现

离散小波变换由于具有良好的时空频率局域性和多分辨率特性，已经成为可伸缩视频编码的理想工具．可伸缩视频编码只需编码一次就可产生完全可伸缩的嵌入式码流，对码流的一部分解码可以得到不同质量和时空分辨率的视频、本文在MC-EZBC的基础上，通过采用提升型长支集小波进行亚像素精度的运动补偿时间滤波和空间分解实现了对MC—EZBC的改进，在中高码率时的性能可与H、264／AVC相比较．在南开之星上实现了并行编码，取得了较高的加速比．     

Concealment of Whole-Picture Loss in Hierarchical B-Picture Scalable Video Coding

H.264/AVC scalable video coding (H.264/AVC SVC), as the scalable extension of H.264/AVC, offers the flexible adaptivity in terms of spatial, temporal and SNR scalabilities for the generated bitstream. However, such compressed video still suffers from the bad playback quality when packet loss occurs over unreliable networks. In this paper, we present an error concealment algorithm to tackle the whole-picture loss problem in H.264/AVC SVC when hierarchical B-picture coding is used to support temporal scalability. In the proposed algorithm, by taking advantage of the temporal relationship among the adjacent video pictures, the motion information of the lost picture is derived simply and efficiently based on the principle of temporal direct mode. Utilizing the derived motion information, the lost picture is concealed by performing motion compensation on the correctly received temporally previous and future video pictures. The experimental results demonstrate that as a post-processing tool, the proposed error concealment algorithm is able to significantly improve both the objective and subjective qualities of the decoded video pictures in the presence of packet losses when compared to the error concealment algorithm used in H.264/AVC SVC reference software. The proposed method can also be applied to H.264/AVC with hierarchical B-picture coding for error concealment.     

一种无线信道多描述图像编码算法

提出了一种新的图像多描述编码算法，给出了多描述分解的算法和规则，并结合运动补偿时间域滤波(MCTF)进行多描述间的编码，针对无线信道的特点提出了多描述间分层的概念，以适应无线信道传输。实验结果表明，提出的空域分层多描述图像编码(spatial-layer multiple image coding, SL-MDIC)算法有效地利用了MCTF编码的特点，提高了中央信道的编码性能，同时对于收到单个描述或部分描述，解码的图像仍能获得较好的重构图像。     

FGS码流在Internet上的鲁棒性传输研究

研究了在存在丢包的Internet环境下FGS(精细粒度可分级)码流的鲁棒性传输。分析了应用于网络视频流的FGS视频编码方案在存在丢包环境下的鲁棒性，并与不分级编码方案比较；利用FGS的分级特点，设计合适的数据包保护策略来增强它的传输鲁棒性，实验结果表明使用不等数据包保护策略，FGS比不分级编码方案有更好的传输鲁棒性。