H.263编码视频流的混合错误掩盖

当H．263编码视频流在因特网上传输时,易受错误的影响,错误不但会影响当前帧还会继续扩散到以后的解码帧,从而导致图像质量的严重恶化,目前消除错误影响的常用算法是空域掩盖和时域掩盖算法,但是单纯地使用空域算法会造成图像的钝化,而时域算法则无法处理大运动的图像区域,因此,建议了一种时域和空域混合掩盖算法,同时使用两类算法对发生错误的图像帧进行掩盖。模拟结果显示该算法能够达到可以接受的图像质量,适应于视频会议、远程教育等应用的要求。     

基于H．263视频解码的错误检测和掩盖

本文提出了一种应用于H．263视频编码传输的纠错方法,即基于H．263视频解码的错误检测和掩盖算法。这种算法可应用于公共交换电话网（PSTN）,Internet或移动信道的视频通信。模拟结果表明,这种纠错方法在不降低编码效率的前提下,使在有噪声干扰的信道上传输图像的质量有显著的改善。     

基于H.263视频解码的误码掩盖技术研究

本文提出了一种基于接收端像素域的误码掩盖算法,包括误码检测、重同步、误码定位和估计误码数据等四个环节。计算机模拟结果显示,经误码掩盖之后的图像质量有显著的改善     

Error concealment analysis for H.264/advanced video coding encoded video sequences

Error concealment methods have become very important in particular when transmitting video streams over error prone wireless links. Often a retransmission of corrupted sequences is not possible and thus the receiver has to make the best out of the received stream. The contributions of this article are the following: firstly, a performance comparison of various error concealment strategies (straight decoding, slice level concealment and macroblock level concealment) is presented based on the detection of errors, the exact location of which is unknown. Secondly, an analytical treatment of the slice level concealment, resulting in a precise mathematical model is provided. Finally, further improvements are proposed by subjective methods based on visual inspection and comparison of their performance by means of simulations.     

Error concealment via Kalman filter for heavily corrupted videos in H.264/AVC

Error concealment at the decoder side is an economical approach to ensuring an acceptable and stable video quality in case of packet erasure or loss, and thus it has attracted lots of research interest. Current techniques mainly employ the spatial or temporal correlation to predict the motion vectors (MVs) of the missing blocks, and interpolation, extrapolation or boundary matching schemes are usually effective. However, for heavily corrupted sequences, e.g., with macroblock loss rate beyond 50%, most methods might perform less satisfactorily. Inspired by the tracking efficiency of Kalman filter (KF), in the present work, we adopted it to predict the missing MVs, and the unpredicted ones (minority) were recovered complementarily using the bilinear motion field interpolation (MFI) method. Since the KF prediction is independent of the loss rate, the present framework is especially robust for heavily corrupted videos. Experimental results on typical sequences reveal that the proposed algorithm outperforms the boundary matching algorithm embedded in the H.264/AVC reference code, the MFI algorithm in the literature, and some other existing techniques by up to about 5.68 dB.     

Error concealment techniques for digital TV

Compressed video bitstreams are intended for real-time transmission over communication networks. Most of the video coding standards employ the temporal and spatial prediction structure to reduce the transmitted video data. Therefore, the coded video bitstreams are highly sensitive to information loss and channel errors. Even a single bit error can lead to disastrous quality degradation in both time and space. This quality deterioration is exacerbated when no error resilient coding mechanism is employed to protect coded video data against the error prone environments. Error concealment is a data recovery technique that enables the decoder to conceal effects of transmission errors by predicting the lost or corrupted video data from the previously reconstructed error-free information. Motion vector recovery and motion compensation with the estimated motion vector is a good approach to conceal the corrupted macroblock data. In this paper, we develop various error concealment algorithms based on motion vector recovery, and compare their performances to those of conventional error concealment methods.     

A rate control scheme using Kalman filtering for H.263

This paper proposes a rate control framework for H.263 video coding called the low-delay Kalman filtering rate controller (LKFrc), whose main part is the adaptive Kalman filter. In LKFrc, a low-delay two-stage selector is proposed to select the representative frames of video. The first stage can rapidly pre-select the relatively significant frames. The second selection stage is embedded in the prediction model of Kalman filter. By the prediction model, LKFrc can distribute a proper bit budget to the pre-selected frame or definitely skip this frame. The measurement model of Kalman filter exploits a rate–distortion (R–D) model to meet the given bit budget by selecting an appropriate picture-level quantization parameter (QP). From the picture-level QP, the subsequent macroblock-level QPs are rapidly yielded by a rapid offset model using the relative macroblock activity. In comparison with the TMN8 model, the LKFrc framework can obtain better PSNRs, higher motion continuities and lower flickering effects with lower computation cost.     

基于交互式抗误码技术的H.263编解码器

目前,在IP分组网中进行视频图像的传输正被日益广泛地应用。但是,由于IP分组网固有的特点,IP分组包丢失的现象不可避免并极大地影响了视频传输的服务质量。本文通过对一种使用连续更新来阻止差错传播（RESCU）的交互式抗误码技术进行改进,实现了一种新的交互式抗误码方法。同时,我们根据这种方法实现了一种具有良好差错恢复能力的H．263编解码器,从而改善了因分组包丢失对视频传输质量带来的影响。     

一种基于H.264的双二叉树GOP差错控制与错误隐藏方法

针对无线应均中的传输错吴和IP网络拥塞导致的视频数据包丢失,H.264采用了一系列的技术.介绍了H.264所使用的差错控制和错误隐藏技术,重点讨论了基于双二叉树GOP(double-binary tree GOP)的差错控制技术.实验结果表明该方案保证了更为有效的抗误码视频码流及良好的修复丢失帧性能.     

H.263抗误码技术存cdma2000 1X中的应用

随着第三代移动通信的发展,基于无线的视频抗误码技术成为近年来多媒体通信领域研究的热点之一。本文以H．263视频编码标准为基础．针对cdma2000 1X无线网络,分别对信源编码端的鲁棒熵编码和参考帧选择技术,信道编码所采用的非等重FEC技术,解码端的误码检测和差错隐蔽方法等进行了比较详细的阐述。     

Error concealment for shape in MPEG-4 object-based video coding.

In asynchronus transfer mode networks, cell loss or channel errors can cause data to be dropped in the channel. When digital images/videos are transmitted over these networks, one must be able to reconstruct the missing data so that the impact of the errors is minimized. In this paper, we present an error-concealment technique for shape in MPEG-4 object-based video coding. This method, which is based on using global motion estimation and compensation techniques for boundary recovery, consists of three steps: (1) boundary extraction from shape; (2) boundary patching using global motion compensation; and (3) boundary filling to reconstruct the shape of the damaged video object planes. Global motion parameters are inserted as part of the USER_DATA field in the compressed stream and are utilized in reconstructing the damaged boundaries of compressed video object planes.     

基于H.263视频码流的差错掩蔽算法

在H．263视频信号的传输过程中,由于采用了可变长编码,当发生比特错误时,很容易造成错误的扩散传播及图像质量下降。由于H．263为低速率传输模式,在进行错误恢复时不适于采用网络开销较大的前向纠错方式,所以采用了基于解码器端的差错掩蔽方法来消除错误的影响。使用的是自适应分类差错掩蔽方法,通过分析图像的运动剧烈程度,将图像分为三类进行掩蔽,既降低了运算复杂度,又取得了较好的掩蔽效果。     

Error concealment of multi-view video sequences using inter-view and intra-view correlations

An efficient error concealment algorithm for multi-view video sequences is proposed in this work. First, we develop three concealment modes: temporal bilateral error concealment (TBEC), inter-view bilateral error concealment (IBEC), and multi-hypothesis error concealment (MHEC). TBEC and IBEC, respectively, exploit intra-view and inter-view correlations in multi-view video sequences to reconstruct an erroneous block. MHEC finds a few candidate blocks based on the block matching principle and combines them for the concealment. We then propose a mode selection scheme, which chooses one of the three modes adaptively to provide reliable and accurate concealment results. Simulation results demonstrate that the proposed algorithm can protect the quality of reconstructed videos effectively even in severe error conditions.     

An Error Concealment Approach Based on H.263 Video Decoding in Pixel Domain

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低比特率通信的H.263视频编解码

本文介绍了国际电联组织ITU-T 于1995年2月起草并通过的 H.263建议草案中低比特率视频编解码的原理、实现流程和图像的数据结构,并对H.263建议的4个增强编解码模式以及 H.263建议与H.261建议编解码的不同之处进行了探讨。     

H.263: video coding for low-bit-rate communication

This article provides an overview of H.263, the new ITU-T Recommendation for low-bit-rate video communication. H.263 specifies a coded representation for compressing the moving picture component of audio-visual signals at low bit rates. The basic structure of the video source coding algorithm is taken from ITU-T Recommendation H.261 and is a hybrid of interpicture prediction to reduce temporal redundancy and transform coding of the prediction residual to reduce spatial redundancy. The source coder can operate on five standardized picture formats: sub-QCIF, QCIF, CIF, 4CIF, and 16CIF. The decoder has motion compensation capability with half-pixel precision, in contrast to H.261 which uses full-pixel precision and employs a loop filter. H.263 includes four negotiable coding options which provide improved coding efficiency: unrestricted motion vectors, syntax-based arithmetic coding, advanced prediction, and PB-frames     

Error concealment algorithms for robust decoding of MPEG compressed video

This paper provides some research results on the topic of error resilience for robust decoding of MPEG (Moving Picture Experts Group) compressed video. It introduces and characterizes the performance of a general class of error concealment algorithms. Such receiver-based error concealment techniques are essential for many practical video transmission scenarios such as terrestrial HDTV broadcasting, packet network based teleconferencing/multimedia, and digital SDTV/HDTV delivery via ATM (asynchronous transfer mode). Error concealment is intended to ameliorate the impact of channel impairments (i.e., bit-errors in noisy channels, or cell-loss in ATM networks) by utilizing available picture redundancy to provide a subjectively acceptable rendition of affected picture regions. The concealment process must be supported by an appropriate transport format which helps to identify image pixel regions which correspond to lost or damaged data. Once the image regions (i.e., macroblocks, slices, etc.) to be concealed are identified, a combination of spatial and temporal replacement techniques may be applied to fill in lost picture elements. A specific class of spatio-temporal error concealment algorithms for MPEG video is described and alternative realizations are compared via detailed end-to-end simulations for both one- or two-tier transmission media. Several algorithm enhancements based on directional interpolation, ‘I-picture motion vectors’, and use of MPEG-2 ‘scalability’ features are also presented. In each case, achievable performance improvements are estimated via simulation. Overall, these results demonstrate that the proposed class of error concealment algorithms provides significant robustness for MPEG video delivery in the presence of channel impairments, permitting useful operation at ATM cell-loss rates in the region of 10⁻⁴ to 10⁻³ and 10⁻² to 10⁻¹ for one- and two-tier transmission scenarios, respectively.     

Error control and concealment for video communication: a review

The problem of error control and concealment in video communication is becoming increasingly important because of the growing interest in video delivery over unreliable channels such as wireless networks and the Internet. This paper reviews the techniques that have been developed for error control and concealment. These techniques are described in three categories according to the roles that the encoder and decoder play in the underlying approaches. Forward error concealment includes methods that add redundancy at the source end to enhance error resilience of the coded bit streams. Error concealment by postprocessing refers to operations at the decoder to recover the damaged areas based on characteristics of image and video signals. Last, interactive error concealment covers techniques that are dependent on a dialogue between the source and destination. Both current research activities and practice in international standards are covered     

Best packetisation scheme for H.263 Internet video communication

The H.263 codec is an efficient way to stream variable bit-rate video sequences. It is proposed that, for equivalent bandwidth and frame rate, a two-slice packetisation scheme results in superior peak signal-to-noise ratio, rather than the conventional one-slice scheme, and that constant inter-packet gap rather than 'bursty' delivery is preferable.