Content-based hybrid error concealment approach for packet video communication over the noisy channels

Video compression makes the encoded video stream more vulnerable to the channel errors so that, the quality of the received video is exposed to severe degradation when the compressed video is transmitted over the error-prone environments. Therefore, it is necessary to apply error concealment (EC) techniques in the decoder to improve the quality of the received video. In this regard, an Adaptive Content-based EC Approach (ACBECA) is proposed in this paper, which exploits both the spatial and temporal correlations within the video sequences for the EC purpose. The proposed approach adaptively utilizes two EC techniques, including new spatial-temporal error concealment (STEC) technique, and a temporal error concealment (TEC) technique, to recover the lost regions of the frame. The STEC technique proposed in this paper is established on the basis of non-Local Means concept and tries to recover each lost macroblock (MB) as the weighted average of the similar MBs in the reference frame, whereas the TEC technique recovers the motion vector of the lost MB adaptively by analyzing the behavior of the MB in the frame. The decision on temporally or spatially reconstructing the degraded frames is made dynamically according to the content of the degraded frame (i.e., structure or texture), type of the error and also block loss rate (BLR). Compared with the state-of-the-art EC techniques, the simulation results indicate the superiority of the ACBECA in terms of both the objective and subjective quality assessments.

     

H.264 video transmissions over wireless networks: Challenges and solutions

Multimedia video streaming is becoming increasingly popular. Using multimedia services, there are more and more users in end-system over wireless networking environment. H.264/AVC is now the standard for video streaming because of its high compression efficiency, robustness against errors and network-friendly features. However, providing the desired quality of service or improving the transmission efficiency for H.264 video transmissions over wireless networks present numbers of challenges. In this paper, we consider those challenges and survey existing mechanisms based on the protocol layers they work on. Finally, we address some open research issues concerning for H.264 video transmission in wireless networks.     

Control over noisy channels

Communication is an important component of distributed and networked controls systems. In our companion paper, we presented a framework for studying control problems with a digital noiseless communication channel connecting the sensor to the controller. Here, we generalize that framework by applying traditional information theoretic tools of source coding and channel coding to the problem. We present a general necessary condition for observability and stabilizability for a large class of communication channels. Then, we study sufficiency conditions for Internet-like channels that suffer erasures.     

Joint loss pattern characterization and unequal interleaved FEC protection for robust H.264 video distribution over wireless LAN

The recently adopted H.264 standard achieves efficient video encoding and bandwidth savings. Thus, designing communication protocols and QoS control mechanisms for H.264 video distribution over wireless IP networks is a topic of intense research interest. Delivering video streams to terminals via a wireless last hop is indeed a challenging task due to the varying nature of the wireless link. While a common approach suggests exploiting the variations of the wireless channel, an alternative is to exploit characteristics of the video stream to improve the transmission. In this paper, we combine both approaches through an efficient wireless loss characterization and a low-delay unequal interleaved FEC protection. Besides deriving new QoS metrics for FEC block allocation, the wireless loss characterization is as well used to adjust the interleaving level depending on the loss correlation exhibited by the wireless channel. This novel unequal interleaved FEC (UI-FEC) protocol allows graceful video quality degradation over error-prone wireless links while minimizing the overall bandwidth consumption and the end-to-end latency.     

A novel motion recovery using temporal and spatial correlation for a fast temporal error concealment over H.264 video sequences

Multimedia Tools and Applications - In this paper, we proposed an effective motion recovery method with low complexity for a fast temporal error concealment over H.264 video sequences. The proposed...     

H.264软件编码器的优化

为降低编码复杂度以满足实时应用的需求,以联合专家组（JVT）发布的H．264参考模型JM9．4为基础,分析H．264软件编码器的结构,指出影响编码速度的瓶颈所在,给出具体的优化方案,并结合MMX／SSE技术,对H．264软件编码器进行全面优化,其编码速度完全可以满足实时性应用的要求,而图像的重建质量基本不变。     

H.264的视频编码技术初探

H.264频编码是今年来多媒体信息技术领域出现的又一项关键技术,本文首先分析了H.264的分层结构和主要编码技术,并探讨了其在性能改进方面的研究成果,最后展望了其在多个领域中的应用前景。     

改进的H.264视频编码方案

提出了一种改进的H264视频编码方案。针对H264中具有7种不同块模式运动估值的特点,在帧间预测过程中使用一种扩展的变换编码概念——自适应块变换,把运动估值的块大小和变换块大小联系起来,通过限制最大的变换块尺寸对自适应块变换做了简化,以适应实际应用的需要;通过扩展帧内预测的块模式,将简化的自适应块变换也应用到帧内预测编码中：鉴于不同块尺寸的变换系数矩阵的概率分布不同,提出在熵编码过程中采用自适应通用变长编码对码表进行动态重组,以进一步提高编码效率。比较了与现有H．264视频编码方案的性能差异。     

Wireless transmission of HD video using H.264 compression over UWB channel

With the technological advancement, entertainment has become revolutionized and the high-definition (HD) video has become an integral feature of our modern amusement system. The demand for wireless transmission of HD video is rapidly rising for its ubiquitous nature, easy installation and relocation. Such wireless transmissions of HD video streams require very high bandwidth. The ultra-wideband (UWB) offers a large bandwidth, and short-range high-speed data transmission at low cost and low power consumption. In this paper, we present the feasibility study to transmit HD video wirelessly using H.264/AVC compression over the UWB communication channel. Simulations are carried out by controlling key H.264/AVC encoder parameters such as, in-loop deblocking filter, group of pictures, and quantization parameter. Based on the analysis, an optimum setting of these parameters is proposed for different bandwidth requirements, as well as acceptable video quality. The bandwidth achieved is restricted between 1.5 and 20?Mbps with a minimum reconstruction quality of 34?dB. The HD bit stream is then transmitted over the UWB communication channel and the demonstration shows that the overall encoder performance is satisfactory with the transmission bit-error-rate (BER) in the range of 10^?5?C10^?8.     

MIMO系统中的H.264/SVC数据流抽取和重组算法

为了使H.264可分级视频编码(SVC)生成的数据流分割为多个子数据流,便于在多输入多输出(MIMO)无线网络的不同子信道上传输以提高视频传输速率,提出了一个SVC数据流抽取和重组算法.在发送端,该算法利用SVC数据流的分层结构,将其中的基本层和增强层抽取为多个子数据流,并保持基本层子数据流能够独立解码.在接收端,该算法将接收到的子数据流重组成可解码的SVC数据流.实验证明该算法能充分利用MIMO系统提供的高带宽,并具有较低的冗余度和较好的灵活性.     

基于H.264的误码隐藏技术

为了在高误码环境下提高视频通信质量,提出一种改进的基于H.264的误码隐藏技术。对于帧内编码图像,根据图像直方图信息计算图像的光滑特性,然后自适应地选择线性插值的方法。对于帧间编码图像,根据不同大小块编码类型和多参考帧的特性,能够更准确地估计出丢失的MV,进行时域误码隐藏。实验表明,此方法同H.264参考软件JM11.0方法相比,具有更好的主客观图像恢复质量。     

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.     

一种基于H.264的鲁棒视频水印算法

由于H.264标准视频的流行,对数字视频水的版权保护和认证的需求在不断增加。本文提出了一种基于H.264视频编解码标准的鲁棒视频水印算法。水印经过了增加帧同步信息,扩频编码和纠错编码的预处理后有着很强的鲁棒性。在嵌入过程中,选择了残差的DCT系数与参考块像素的DCT系数和作为嵌入载体,而不是通常的残差DCT系数,该处理可以很好的提高水印算法对视频攻击,如帧率攻击和码率攻击的鲁棒性,同时在嵌入的过程中,通过应用一个针对4*4的DCT的人类视觉系统来控制嵌入强度,使得水印算法对视频的视觉质量的影响降到最小。实验结果表明:本算法对多种攻击,如分辨率攻击、帧率攻击、码率攻击和重编码都有很好的鲁棒性,同时能保持很高的视觉质量。     

多路嵌入式H．264视频服务器的设计

介绍了一种基于Linux操作系统的多路嵌入式H．264视频服务器的设计方案。该方案给出了系统的硬件组成和软件设计框架．然后说明了发送端和接收端的实现过程，并对网络传输中利用RTP实现QoS机制做了说明。实验结果表明，上述设计的多路嵌入式视频服务器在不影响图象质量的前提下，能够比以往的视频服务器占用更低的带宽。     

Optimized H.264 compression of sign language video

In TV broadcasting deaf people are not able to get information from the audio content. In public television, some programs may be accompanied by a sign language interpreter as a part of the broadcasted signal. As a supplementary service, it would enable more programs to be accessible with a sign language interpreter to assist in comprehension. To be able to transmit such data flow separately, we define the parameters of compression of sign language interpreter image to ensure intelligibility and quality while maintaining low bitrate. This paper deals with specific video compression of Czech sign language interpreter based on regions of interest implemented to the ×264 open source library. The results of this approach are verified in subjective tests with the deaf and hearing evaluators. The experiments examine the intelligibility of sign language expressions containing minimal pairs for different levels of image compression and also evaluate the subjective quality of the final image.     

Suboptimal decentralized control over noisy communication channels

In this paper we present a technique for the design of decentralized controllers for mean square stability of a large scale system with cascaded clusters of subsystems. Each subsystem is linear and time-invariant and both system and measurement are subject to Gaussian noise. For stability analysis of this system we consider the effects of Additive White Gaussian Noise (AWGN) channels used for exchanging information between subsystems.     

H.264/AVC video error concealment algorithm by employing motion vector recovery under cloud computing environment

Network-based cloud computing has rapidly expanded as an effective way of video processing and transmission. Since packet losses or errors may frequently occur in cloud computing environment during the transmission of compressed video, error concealment is applied in the decoder to prevent significant degradation of image quality. Motion vector (MV) recovery is a widely-used temporal error concealment which shows satisfactory performance in practical application of video transmission. In this paper, a fast and effective temporal error concealment algorithm for H.264/AVC is presented, which efficiently utilizes the MVs of neighboring macroblocks (MB) which are adjacent to the lost MB under different circumstances. To ensure the precision of the MV recovery, a smallest division of \(4\times 4\) sub-block is applied, which will not bring too much complexity in the proposed algorithm. Each MV of sub-block is restored in individual method, and the recovery information is gathered from the nearby 20 sub-blocks. Simulation results under the virtual cloud environment show that our scheme can highly improve the quality of reconstructed video and obtain a gain of about 4 dB in PSNR, compared with other temporal error concealment methods in the condition of different packet loss rates and quantization parameters. The practical simplicity ensures that the proposed method can be readily applied to real-time video applications running under cloud computing environment.