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。     

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.     

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.     

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。     

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.     

多路PSK/FSK视频信号的光纤传输设计

介绍了多路PSK/FSK调制的视频信号经过A/D转换后,通过现场可编程门阵列(FPGA)进行复用,经并串转换、电光转换后通过光纤进行传输的设计方法,为了监测光线路通信质量情况,另设计了误码检测电路.     

Rate-distortion optimized unequal loss protection for video transmission over packet erasure channels

Video transmission over networks often suffers from packet loss due to network congestions and stringent end-to-end delay constraints. In this paper, we develop a Rate-Distortion optimized Unequal Loss Protection (RD-ULP) scheme to combat packet loss. Based on packet-level transmission distortion modeling, we estimate the amount of contribution of each video packet to the reconstructed video quality, which defines the priority level of each packet. Unequal amounts of protection are then allocated to different video packets according to their priority levels and the dynamic channel conditions. The proposed RD-ULP resource allocation problem is formulated as a constrained nonlinear optimization problem. An optimization algorithm based on Particle Swarm Optimization (PSO) is then developed to solve the optimal resource allocation problem. Our extensive experimental results demonstrate the effectiveness of the proposed RD-ULP scheme, which outperforms existing methods by up to 2 dB in the reconstructed video quality.     

基于H.264 SVC无线视频传输的自适应差错保护方法

提出了一种针对H.264可分级编码(H.264 SVC)的自适应前向纠错编码保护方案.通过比较不同的纠错方案,提出了划分丢包率区间的概念,并根据不同区间的丢包率自适应地选择最佳的纠错方案.仿真结果表明,与单一保护方法相比,所提自适应方法能够取得更好的保护效果,更适于在无线信道中进行视频传输.     

Improved interview video error concealment on whole frame packet loss

An improved DIBR-based (Depth image based rendering) whole frame error concealment method for multiview video with depth is designed. An optimal reference view selection is first proposed. The paper further includes three modified parts for the DIBRed pixels. First, the missing 1-to-1 pixels are concealed by the pixels from another view. The light differences between views are taken care of by the information of the motion vector of the projected coordination and a reverse DIBR procedure. Second, the generation of the many-to-1 pixels is improved via their depth information. Third, the hole pixels are found using the estimated motion vectors derived efficiently from a weighted function of the neighboring available motion vectors and their distance to the target hole pixel. The experimental results show that, compared to the state-of-the-art method, the combined system of the four proposed methods is superior and improves the performance by 5.53 dB at maximum.     

Robust adaptive transmission of images and video over multiple channels

Reliable transmission of images and video over wireless networks must address both potentially limited bandwidths and the possibilities of loss. When bandwidth sufficient to transmit the bit stream is unavailable on a single channel, the data can be partitioned over multiple channels with possibly unequal bandwidths and error characteristics at the expense of more complex channel coding (i.e., error correction). This paper addresses the problem of efficiently channel coding and partitioning pre-encoded image and video bit streams into substreams for transmission over multiple channels with unequal and time-varying characteristics. Within channels, error protection is unequally applied based on both data decoding priority and channel packet loss rates, while cross-channel coding addresses channel failures. In comparison with conventional product codes, the resulting product code does not restrict the total encoded data to a rectangular structure; rather, the data in each channel is adaptively coded according to the channel's varying conditions. The coding and partitioning are optimized to achieve two performance criteria: maximum bandwidth efficiency and minimum delay. Simulation results demonstrate that this approach is effective under a variety of channel conditions and for a broad range of source material.     

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。     

Key-frame-based depth propagation for semi-automatic stereoscopic video conversion

In this paper, we propose a key-frame-based bi-directional depth propagation algorithm for semi-automatic 2D-to-3D stereoscopic video conversion. First, key-frames are identified from each video shot based on color motion-compensation errors to prevent high-motion content between any pair of consecutive key frames. Depths for key-frames are manually assigned or rendered by popular computer tools, and then bi-directionally propagated to non-key-frames there between. Our depth propagation algorithm is featured of a multi-pass error correcting procedure for each frame to prevent depth artifacts from being further propagated to adjacent frames. Our proposed algorithm is advantageous in solving the background occlusion/dis-occlusion problem that degrades the performances of traditional depth propagation algorithms. Experimental results show that our scheme is capable of achieving better results against three prior algorithms in view of the qualities of the estimated depth map (e.g., dis-occluded background and object boundaries) and the synthesized stereo views.     

长电缆数字化传输系统的可靠性设计

纠错编码被广泛应用在各种数字通讯、数字广播和数据存储系统中。随着单片机、DSP和FPGA等器件的快速发展,越来越容易在各种通用硬件平台上实现纠错编码。在长电缆的地震数据数字化传输中,采用单片机和FPGA实现Reed Solomon编码和交织编码,保证恶劣传输条件下可靠的高速数据传输,就此传输系统的功能结构以及编解码方案做简要介绍。     

一种H.264视频编码码率控制方法

根据视频编码线性率失真函数和对H．264整数变换量化方法分析，提出一种适合于H．264编码算法的码率控制算法。先验证线性率失真函数对H．264编码算法的适用性，再通过将H．264整数变换的量化分解为系数校正和统一量化两个步骤实现了线性率失真函数在H．264码率控制中的应用。实验证明，与JVT—G012码率控制算法相比，码率控制的准确性和信噪比均有所提高。