Scene content driven FEC allocation for video streaming

Unequal error protection schemes applied on video data streams, considering varying importance of data packets over a group of pictures (GOP), are more efficient in terms of rate-distortion performance at different loss rates. Importance ordering policy adopted so far, mostly considered frame positions within a GOP. In the present work, we offer significant importance to the packets containing scene-transition frames, as these should be better error protected. We adopt a strategy of Forward Error Correcting (FEC) Code allocation, based on the minimization of end-to-end distortion up to the decoder, assuming that error concealment is adopted at the decoder. Two FEC allocation strategies are proposed within the Block of Packets (BOP) structure — one is an iterative modified hill climbing approach and the other is a reduced complexity heuristic approach. The Gilbert–Elliot model is used for the modeling of transmission channel. The proposed FEC allocation schemes outperform existing FEC allocation schemes in terms of PSNR for sequences with and without transitions, when transmitted over lossy channels.     

光传输网络性能与前向纠错

为了提高光传输网络性能,人们将前向纠错技术应用于高速光纤通信系统中。文章对同步数字系列/密集波分复用(SDH/DWDM)传输网络性能进行了简要分析,讨论了前向纠错技术以及它对系统误码率的改善。     

无线视频的一种码率控制方法

无线信道的高误码率对视频图像质量有很大的影响,前向纠错(FEC)和自动重发请求(ARQ)对于降低无线信道的误码率,提高图像质量有很好的效果。通过对FEC和ARQ方法的有效性分析,在TMN8的基础上提出一种简单的混合FEC/ARQ自适应模式选择码率控制方法。该方法首先预测报文丢失数量和纠错报文传输时延,从而选择合适的纠错编码模式,并为纠错编码分配比特数。实验结果表明该方法有效降低无线信道下报文丢失率,显著提高了图像质量。     

采用自适应FEC的卫星ATM网络的有效带宽估计

该文针对采用自适应FEC(AFEC)的卫星ATM网络,研究了两种用于接纳控制的有效带宽估计方法,由于AFEC码率的动态特性使业务实际的传输速率具有不固定性,因此估计有效带宽时要考虑AFEC的影响,作者首先针对一般卫星时变信道和多码率AFEC情况下的卫星ATM,应用流体近似方法分析了有效带宽的计算,然而该方法要求的条件及计算复杂度均比较高,应用中有局限性。以此方法为基础,作者又提出了采用修正因子的估计方法,数值结果表明采用修正因子的有效带宽估计方法比较简单可靠,适用面较广。     

Graceful Degradation FEC Layer for Multimedia Broadcast/Multicast Service in LTE Mobile Systems

This paper proposes an additional forward error correction (FEC) layer to compensate for the defectiveness inherent in the conventional FEC layer in the Long Term Evolution specifications. The proposed additional layer is called a graceful degradation (GD)‐FEC layer and maintains desirable service quality even under burst data loss conditions of a few seconds. This paper also proposes a non‐delayed decoding (NDD)‐GD‐FEC layer that is inherent in the decoding process. Computer simulations and device‐based tests show a better loss recovery performance with a negligible increase in CPU utilization and occupied memory size.     

A synchronous digital hierachy based dynamic error correction technique for wavelength division multiplexing networks

This paper proposes a new synchronous digital hierarchy (SDH) based forward error correction (FEC) scheme for wavelength division multiplexing (WDM) networks. In this scheme, a dedicated WDM channel is used to transport the FEC redundant bits. This paper also proposes the use of error location analysis of the FEC correctable bits to identify the pattern of errors, combined with the seriousness of errors obtained from B2-byte analysis to decide as to the suitable FEC code to be assigned to the payload channels. The proposed FEC scheme is studied not only under the typical Poisson errors but also the bursty errors. Simulation results show that the proposed FEC scheme performs significantly better than the existing FEC schemes. It is also shown that the performance of the proposed FEC scheme on bursty errors is independent of the line rates, whereas the existing FEC schemes either cannot support bursty errors or degrades with line rates.     

An ARQ/FEC coding scheme for land mobile communication

This paper describes the development of a laboratory test unit that implements a new Type I/II ARQ scheme for use on a land mobile forward satellite link. Investigation of channel characteristics showed that it was possible to use convolutional coding to combat random errors, but it was also necessary to employ an ARQ scheme in order to overcome fades due to signal blockage. The hardware development used commercial 68000-based VME cards as well as special-purpose cards to perform the functions of Viterbi decoding and packet synchronization. Results are presented for the hardware operating with Gaussian noise as time limitations excluded the use of satellite fading simulation. In order to ensure a high degree of data integrity error detection was applied to the data packets such that a residual error rate of less than 10^?11 should result. This was not able to be verified due to the limited time. However, long term tests did indicate that an error rate less than 10^?8 was achieved.     

面向立体视频传输的右视点图像错误隐藏

利用立体视频序列视点间相关性及单视点内相关性,提出了一种面向立体视频传输的错误隐藏算法.从基于H.264/AVC立体视频编码结构出发,推断出受损块的参考模式;然后基于出错块的内容特征,根据块视差活力度(TDA)或块运动活力度(TMA)的大小,内容自适应地选择恰当的视点间及时域错误隐藏方法对受损块进行错误掩盖.实验结果表...     

广播网络中基于补丁流的丢包恢复机制研究

现有的数字广播网络由于没有回传通道,发送端无法知悉传输过程中的丢包状况。接收端处在广播网络的不同位置,常常因处于小区边缘或受障碍物遮挡等原因造成信号减弱,从而导致丢包率提高。该文提出了一种基于pFEC (patching Forward Error Correction,补丁FEC)的丢包恢复机制,来解决单向广播网络的丢包问题。该方法利用蜂窝移动网络的双向信道来传输补丁流,提供自适应的FEC来降低丢包率。这种方式可以在广播业务中为不同位置的用户提供不同的丢包恢复能力。理论建模及仿真结果显示,在蜂窝移动网络丢包率不高的情况下,pFEC机制能够有效应对个别用户突发的丢包,从而提高广播业务整体的可靠性和服务质量。     

光通信系统中级联码性能分析

通过对光通信系统的发展趋势和级联码的理论进行分析后,对光通信系统中传统级联码、并行型级联码和交织型级联码三种级联码的性能进行了深入研究。通过理论分析与仿真结果表明:传统级联码冗余度过大,并行型级联码的译码实现过于复杂,而交织型级联码是一种纠错性能优良、冗余度适中、易于实现的码型,更适用于光通信系统。     

Robust spatio-temporal error concealment for packet- lossy H.264 video transmission

1 Introduction With the ubiquitous use of Internet and the deployment of next generation of networks, video communications are increa- singly becoming the major services in demand. Unlike data transmission, video communication is essentially time-sensitiv…     

Frame distortion estimation for unequal error protection methods in scalable video coding (SVC)

In many multimedia applications, coded video is transmitted over error prone heterogeneous networks. Because of the predictive mechanism used in video coding, transmission error would propagate temporally and spatially and would result in significant quality losses. In order to address this problem, different error resilience methods have been proposed. One of the techniques, which is commonly used in video streaming, is unequal error protection (UEP) of scalable video coding (SVC). In this technique, different independent layers of an SVC stream are protected differently and based on their importance by using forward error correction (FEC) codes. Accurately analyzing the importance or utility of each video part is a critical component and would lead to a better protection and higher quality of the received video. Calculation of the utility is usually based on multiple decoding of sub-bitstreams and is highly computationally complex. In this work, we propose an accurate low complexity utility estimation technique that can be used in different applications. This technique estimates the utility of each network abstraction layer (NAL) by considering the error propagation to future frames. We utilize this method in an UEP framework with the scalable extension of H.264/AVC codec and it achieves almost the same performance as highly complex estimation techniques (an average loss of 0.05 dB). Furthermore, we propose a low delay version of this technique that can be used in delay constrained application. The estimation accuracy and performance of our proposed technique are studied extensively.     

基于多视点视频整帧丢失的自适应错误掩盖算法

为解决多视点视频压缩(MVC)导致视频整帧丢失风险增大的问题,基于MVC的特点提出了一种4方向和多参考帧的错误掩盖算法。首先,在同一视点内,将相邻帧沿其各自运动矢量外推,得到视点内的最佳运动矢量;在视点间采用同样的方法,得到最佳视差;以外推的重叠面积为判断依据,在视点内错误掩盖和视点间错误掩盖之间选择较优的掩盖方式;最后,在MVC已有块模式的基础上引入新的块组合模式,合并具有相同错误掩盖方式、运动矢量的绝对差值小于阈值的相邻块,以减小图像的块效应。实验结果表明,与已有算法相比,本文算法有效利用了MVC的内部机制,改善了重建帧的客观指标,增强了主观质量。     

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。     

A combined multiple-candidate likelihood decoding and error concealment scheme for compressed video transmission over noisy channels

This paper presents a joint forward error correction (FEC) and error concealment (EC) scheme to enhance the quality of a compressed video signal transmitted over a noisy channel. A multiple candidate likelihood (MCL) channel decoding strategy is used in conjunction with redundancy in the compressed video (syntax validity and spatial discontinuity) to select the best-detected signal.

Simulation results on both objective and subjective performance measures indicate a significant improvement provided by the proposed scheme.     

基于区域划分的立体视频整帧丢失错误隐藏新算法

针对立体视频传输中右视点整帧丢失,提出了一种基于区域划分的立体视频整帧丢失错误隐藏新算法。首先通过丢失帧视点内和视点间相邻帧的运动信息,估计丢失帧的运动区域与静止区域;然后利用视点间的全局视差,将丢失帧运动区域进一步划分为遮挡边界区域和非遮挡边界区域,并对遮挡边界区域和非遮挡边界区域分别采用运动补偿预测和视差补偿预测进行恢复,而对静止区域则直接采用帧拷贝的方法恢复丢失信息。实验结果表明,本文算法有效提高了所恢复的立体视频丢失帧图像的主客观质量。     

Interleaved coding and sequential transmission scheme for packet‐level forward error correction over burst loss channels

Burst packet loss is a common problem over wired and wireless networks and leads to a significant reduction in the performance of packet‐level forward error correction (FEC) schemes used to recover packet losses during transmission. Traditional FEC interleaving methods adopt the sequential coding‐interleaved transmission (SCIT) process to encode the FEC packets sequentially and reorder the packet transmission sequence. Consequently, the burst loss effect can be mitigated at the expense of an increased end‐to‐end delay. Alternatively, the reversed interleaving scheme, namely, interleaved coding‐sequential transmission (ICST), performs FEC coding in an interleaved manner and transmits the packets sequentially based on their generation order in the application. In this study, the analytical FEC model is constructed to evaluate the performance of the SCIT and ICST schemes. From the analysis results, it can be observed that the interleaving delay of ICST FEC is reduced by transmitting the source packets immediately as they arrive from the application. Accordingly, an Enhanced ICST scheme is further proposed to trade the saved interleaving time for a greater interleaving capacity, and the corresponding packet loss rate can be minimized under a given delay constraint. The simulation results show that the Enhanced ICST scheme achieves a lower packet loss rate and a higher peak signal‐to‐noise‐ratio than the traditional SCIT and ICST schemes for video streaming applications.     

Performance modeling of FEC‐based unequal error protection for H.264/AVC video streaming over burst‐loss channels

Unequal error protection systems are a popular technique for video streaming. Forward error correction (FEC) is one of error control techniques to improve the quality of video streaming over lossy channels. Moreover, frame‐level FEC techniques have been proposed for video streaming because of different priority video frames within the transmission rate constraint on a Bernoulli channel. However, various communication and storage systems are likely corrupted by bursts of noise in the current wireless behavior. If the burst losses go beyond the protection capacity of FEC, the efficacy of FEC can be degraded. Therefore, our proposed model allows an assessment of the perceived quality of H.264/AVC video streaming over bursty channels, and is validated by simulation experiments on the NS‐2 network simulator at a given estimate of the packet loss ratio and average burst length. The results suggest a useful reference in designing the FEC scheme for video applications, and as the video coding and channel parameters are given, the proposed model can provide a more accurate evaluation tool for video streaming over bursty channels and help to evaluate the impact of FEC performance on different burst‐loss parameters. Copyright © 2014 John Wiley & Sons, Ltd.     

Comparison of video protection methods for wireless networks

An experimental comparison of video protection methods targeted for wireless networks is presented. Basic methods are the data partitioning, reversible variable length coding, and macroblock row interleaving as well as macroblock scattering for packet loss protection. An implementation is described, in which scalable video is protected unequally with forward error correcting codes and retransmissions. Comparisons are performed for simulated wideband code division multiple access channel, and measurements are carried out with wireless local area network, Bluetooth as well as with GSM high speed circuit switched data. For the measurements, point-to-point connections are used. The achieved video quality is examined in our real-time wireless video demonstrator. The performance is measured with peak-signal-to-noise-ratio of received video, data overhead, communication delay, number of lost video frames, and decoding frame rate. Results show that the quality of decoded video can be improved by 1 dB with transparent connections compared to connections designed for general packet data. As a conclusion, a video coding subsystem must have access to the error control in a wireless link for the best quality in varying conditions.