A new rateless code with unequal error protection property

In our previous work, “robust transmission of scalable video stream using modified LT codes”, an LT code with unequal packet protection property was proposed. It was seen that applying the proposed code to any importance-sorted input data, could increase the probability of early decoding of the most important parts when enough number of encoded symbols is available at the decoder’s side. In this work, the performance of the proposed method is assessed in general case for a wide range of loss rate, even when there are not enough encoded symbols at the decoder’s side. Also in this work the degree distribution of input nodes is investigated in more detail. It is illustrated that sorting input nodes in encoding graph, as what we have done in our work, has superior advantage in comparison with unequal input node selection method that is used in traditional rateless code with unequal error protection property.     

基于IP无线网络FGS视频传输的多乘积码方案

研究基于IP无线网络中精细粒度可伸缩性(FGS)视频的传输。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。     

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。     

线性优先级不等差保护LT码的设计

LT码作为一种无码率的编码,能显著地提高网络数据吞吐量。在不同优先级的网络数据传输中,不等差保护（ UEP）是一种必要的方法。所以,设计一个性能良好的具有不等差错保护功能的LT码有很大的应用价值。文中设计了一类具有线性优先级不等差保护特性的LT码（ UEP-LT）。也就是说,对数据层的保护水平是线性分布的。提出的UEP-LT码能以极低的译码开销恢复大多数高优先级的数据。同时,这种UEP-LT码在合理的译码开销下具有比等差保护（ EEP）低的误码率,更好地满足了多媒体传输中对不等差错保护的要求。     

基于GA-BP的实时视频通信自适应前向纠错码

针对在动态的网络环境中,实时视频在基于数据报协议的传输中遇到大量丢包的问题,提出了一种基于遗传算法改进的BP神经网络自适应前向纠错码的方法。该方法通过设计自适应的前向纠错编码来恢复丢失的数据包。首先,设计一个基于帧级别的前向纠错的框架,主要包括视频编码解码器、RS前向纠错码编解码模块和前向纠错码冗余度计算模块,用来模拟一般视频传输的环境;然后,设计GA-BP模型,将其应用到RS-FEC的冗余度计算,实现一种帧级不均等的保护方案;最后,基于GE信道模拟网络,生成丢包数据,训练离线模型,进行实验验证。实验结果表明,相比StaticRS和DeepRS,所提方法能够在较低冗余度下较高地恢复丢失的数据包,得到更高质量的视频。     

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.     

联合H.264和多码率Turbo码的无线视频传输

提出了一种无线视频流联合信源信道编码传输的具体方案,结合H.264视频编码,对其进行合理数据分割后采用UEP技术,并联合信道设计了一个支持信道UEP的多码率Turbo编解码器,同时把Turbo编码与type-Ⅲ HARQ混合自动重传请求机制结合以达到更可靠的数据传输保证。通过仿真实验证明,这种设计方法可进一步优化系统在恶劣的无线信道下的链路吞吐量和取得更好的视频重建质量。     

Joint video adaptation and erasure code for video broadcast in wireless networks

Advances in wireless access technologies such as WiMax and LTE have accelerated the development of wireless video applications.Though existing erasure codes are designed for wireless data broadcasting,their potential can only be realized for wireless video broadcasting if the distortions associated with video packets and their complex decoding dependency are taken into consideration.In this paper,we propose the greedy video erasure code(GVEC)to minimize average video distortion by accounting for the temporal scalable decoding dependency among video frames e.g.I,P and B frames in MPEG.GVEC is a greedy algorithm and sufers from high computational complexity.For practical implementation,we have designed the joint video adaptation and erasure code(JVEC)with lower complexity,which can generate erasure codes on the fly to guarantee the decoding of important video frames.Simulation results show that the performance of JVEC is very close to that of GVEC,and is superior to that of existing erasure codes.Our results also show the existence of a performance tradeof between video distortion and video packet throughput.     

基于错误传播模型的非均等视频流丢失保护

提出一种适用于丢包网络、面向图像组（GOP）层的非均等视频流丢失保护方案。利用GOP中不同帧之间的非均等显著性,将不同数量前向错误校正包分配到GOP层的不同帧中。采用帧间包交错机制将突发包丢失分散到不同帧上,提高处理突发包丢失时的鲁棒性。仿真结果表明,在不同信道丢失模式下,该方案能提高视频接收质量。     

Error robust scalable audio streaming over wireless IP networks

Streaming high-fidelity audio over wireless Internet protocol (IP) networks is a challenging task because the networks present not only packet losses, but also residual bit errors. These losses and errors have severe adverse effect on the compressed audio bitstream. To solve this problem, this paper introduces error resilience in conjunction with error protection for scalable audio streaming over wireless networks. Specifically, error resilience is achieved by performing bitstream data partitioning and reversible variable length coding in the audio coder. Error protection is provided by layered product channel code to simultaneously handle packet losses and residual bit errors. Both the row and column codes of the product code provide unequal error protection for different layers of the audio bitstream by considering the characteristics of the scalable audio. Rate-distortion optimization is performed to determine the best source-channel coding tradeoff that minimizes the average expected end-to-end distortion. Simulation results demonstrate the effectiveness of our proposed approach.     

An unequal packet loss resilience scheme for video over the Internet

We present an unequal packet loss resilience scheme for robust transmission of video over the Internet. By jointly exploiting the unequal importance existing in different levels of syntax hierarchy in video coding schemes, GOP-level and Resynchronization-packet-level Integrated Protection (GRIP) is designed for joint unequal loss protection (ULP) in these two levels using forward error correction (FEC) across packets. Two algorithms are developed to achieve efficient FEC assignment for the proposed GRIP framework: a model-based FEC assignment algorithm and a heuristic FEC assignment algorithm. The model-based FEC assignment algorithm is to achieve optimal allocation of FEC codes based on a simple but effective performance metric, namely distortion-weighted expected length of error propagation, which is adopted to quantify the temporal propagation effect of packet loss on video quality degradation. The heuristic FEC assignment algorithm aims at providing a much simpler yet effective FEC assignment with little computational complexity. The proposed GRIP together with any of the two developed FEC assignment algorithms demonstrates strong robustness against burst packet losses with adaptation to different channel status.     

Adaptive unequal protection for wireless video transmission over IEEE 802.11e networks

Packet loss of video streams cannot be avoided at wireless links for limited wireless bandwidth and frequently changed environments. To provide differentiated Quality of Service (QoS) guarantees between multimedia and data services, IEEE 802.11e was proposed. However, its performance and flexibility need to be further improved. In this paper, after a survey on various modifications of IEEE 802.11e, we formulate the problem of video transmission over IEEE 802.11e networks to help scheme design and performance analysis. Then accompanied with in-depth analysis, an adaptive unequal protection schema is proposed, which is composed of three mechanisms: (1) Insert each video packet into the access category (AC) with the minimum relative queuing delay; (2) Assign each packet dynamically to a proper AC based on several parameters to guarantee the transmission of high priority frames; (3) Apply fuzzy logic controllers to adjust parameters so as to reply quickly to the variation of video data rate, coding structure and network load. Finally, regarding MPEG-4 codec as the example, we perform extensive evaluations and validate the effectiveness and flexibility of proposed scheme. Simulations are divided into WLAN and multihop parts, involving different video sequences and various traffic modes of data streams. Beside performance comparison between proposed scheme and other ones, influence of parameter setting and combination with routing algorithms are also evaluated.     

Packet loss resilience using unequal forward error correction assignment for video transmission over communication networks

Forward error correction (FEC) methods have been developed for packet loss resilience in application layer for real-time video transmission over communication networks. In this paper, an efficient packet loss resilience method is proposed using closed form solution for unequal FEC assignment based on a new packet distortion model. We first derive the packet distortion model by investigating the error concealment property and error propagation effect in H.264. To select the source and channel rate minimizing the overall distortion, we present a model-based rate allocation algorithm using the packet distortion model and rate-distortion function. Then we propose the closed form solution for unequal FEC assignment, which uses the packet distortion model and considers channel status information. Simulation results show that the proposed method gives substantial improvement for the received video quality in packet-lossy Internet and wireless network environments, while it requires much less computational complexity compared to the previous scheme.     

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。     

一种基于多描述编码的视频传输方案

论文提出一种基于多描述编码的视频传输方案。该方案将一个视频源编码为多个码流(称为描述),各描述分别经过Reed-Solomon编码后,通过多个独立的信道传输。该方案不仅利用了信道编码的纠错能力,又利用了多描述编码的鲁棒性,模拟结果表明新方案在有噪信道上表现出较好的性能。     

Unequal error protection under bitrate constraint for video streaming over internet

This article describes a simple packet-level FEC system suitable for unequal error protection of layered video streams, that we called TAPIOCA (in French, Transport Audiovisuel avec Protection Inégale des Objets et Contrôle d’Admission). It is designed in a way that the FEC overhead induced by redundant packets is perfectly controlled by the sender. In order to achieve that, TAPIOCA calculates on-the-fly the optimal erasure code to be used, video data unit by video data unit, under a given bitrate constraint. In addition, and contrary to the well-known PET (Priority Encoding Transmission) system, the video data units of each layer are encoded separately. This is especially useful when all layers are not output from the video coder at the same time. Simulation results for MPEG-4 video streaming show that the proposed FEC system can be very efficient even if packet losses are due to network congestion. Moreover, comparison with PET system shows that TAPIOCA exhibits better performance, considering criteria including the decodable frame rate, protection system efficiency and computational cost.     

RVLC decoding scheme for improved data recovery in MPEG-4 video coding standard

In this paper, we present a low-complexity ‘reversible variable length code’ (RVLC) decoding scheme for MPEG-4 video that recovers more blocks and sometimes more macroblocks (MBs) from error propagation region of corrupted video packets, as compared to the MPEG-4 scheme. The remaining blocks and MBs are concealed. Simulation studies have been carried out to show that the proposed scheme achieves better data recovery, both in terms of peak-signal-to-noise ratio (PSNR) and perceptual quality. In addition, we present more conditions for error detection than those suggested in MPEG-4, discuss properties of error propagation in corrupted video packets, and provide the RVLC codeword structure. The use of RVLC code structure will enable the decoding in both directions by using only one code table, instead of separate tables used for forward and backward decoding. Since the scheme is purely decoder based, the compliance with the standard is fully maintained. It is very simple for the decoder to keep track of the additional blocks/MBs recovered by the proposed scheme. Therefore, the data recovery scheme suggested in MPEG-4 can still be used as default scheme.     

用于H.264的Turbo码非均等译码保护策略

从最新的H．264视频压缩标准出发，提出一种基于H．264的数据分类和Turbo码的非均等译码保护的策略。针对Turbo码译码的特点译码迭代次数越多，纠错能力越强，但带来更多的译码复杂度和时延即消耗较多的功率。对于H．264三种数据分类，按照信息比特重要性的不同进行非均等译码保护，重要的数据给予更多的迭代次数的译码，次重要的数据给予较少的迭代次数的译码，以实现性能和功耗的折衷。仿真结果表明，本文算法不仅能提高解码质量，而且在实时中能减少时延和复杂度及功耗，特别适用于视频手机和手持设备业务。     

基于位置重排的视频不等纠错保护方法

针对基于DCT变换的视频压缩码流，该文提出了一种可有效改善其抗误码性能的收发交互不等纠错保护算法．主要思想是在宏块层对不同数据信息进行位置重排，使DCT系数按重要性重新排列，然后通过EREC算法提高宏块头等同步信息的抗误码性能．在信道编码部分，该算法依据译码端反馈的信道状态参数实时调整待传输的比特数和RCPC编码速率，从而实现收发交互的不等纠错保护(IUEP)．仿真结果表明，该文算法在高误码率信道下能较大程度地改善解码PSNR值，其性能明显优于UEP、EEP等方法．