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.     

Adaptive shape and texture intra refreshment schemes for improved error resilience in object-based video coding

Video encoders may use several techniques to improve error resilience. In particular, for video encoders that rely on predictive (inter) coding to remove temporal redundancy, intra coding refreshment is especially useful to stop temporal error propagation when errors occur in the transmission or storage of the coded streams, since these errors may cause the decoded quality to decay very rapidly. In the context of object-based video coding, intra coding refreshment can be applied to both the shape and texture data. In this paper, novel shape and texture intra refreshment schemes are proposed which can be used by object-based video encoders, such as MPEG-4 video encoders, independently or combined. These schemes allow to adaptively determine when the shape and texture of the various video objects in a scene should be refreshed in order to maximize the decoded video quality for a certain total bit rate.     

基于下抽样多描述视频编码及错误隐藏

采用基于空间下抽样方法实现多描述视频编码,避免了常用多描述视频编码过程的误匹配问题;系统实现了2种不同的多描述分解方案,适用于不同纹理特点的视频图像.为了提高多描述解码器的性能,解码过程中使用基于自适应的边缘保持插值方法进行后处理.仿真实验结果表明,本文提出的编码方法能有效地应用于视频在不同的网络环境下传输;经过解码的后处理过程后,视频图像的信噪比有了明显提高.     

High-frequency error concealment in wavelet-based image coding

A new algorithm for high-frequency subband error concealment in wavelet-based picture coding is presented. It is based on a wavelet patch repetition approach: the LBG algorithm, given by Linde et al., is used to generate a codebook of patches and, according to a boundary distance measure, one of these patches is selected to mask the damaged area. Experiments show noteworthy results.     

基于可伸缩视频编码的自适应误码隐藏方案

文中提出一种基于SVC的动态自适应误码隐藏方案。针对SVC码流增强层部分条带丢失情况,该方案结合散乱型灵活宏块排序功能,在宏块级别采用二阶差分边界匹配准则动态选择基本层和相邻条带信息恢复图像。实验表明,相对SVC标准参考平台JSVM的误码隐藏方案,文中提出方案在不同序列及丢包条件下,重建视频峰值信噪比均得到了一定提升。     

一种用于多视视频加深度联合编码的错误隐藏算法

ATM(AVC-based test model)测试模型实现了多视视频加深度(MVD)格式的联合编码,使得数据的压缩效率更高。然而,较高的压缩效率使得码流对传输错误非常敏感,极易产生错误扩散现象。针对ATM测试模型的编码顺序,提出一种用于MVD联合编码的错误隐藏算法。算法充分利用视点内、视点间及纹理视频与深度视频间的相关性,针对每个视点的不同特征提出了适应其视频特性的不同隐藏算法。实验表明,本文提出的算法可以在不增加算法复杂度的情况下,有效提高视频的主客观质量。     

Variable complexity motion compensated error concealment in video coding

Transmission of compressed video through a data network may involve loss of data owing to channel errors and/or congestion. To conceal the effect of such errors in perceived video quality, concealment schemes happen to be an important choice in terms of their pertinence to encoder-decoder models. This paper focuses on the scenario where error bursts do not extend to more than one frame of digital video. For this, there exist block-based and pixel-based concealment techniques and their applicability is often ruled by a trade-off between perceived video quality and computational complexity. The paper proposes a variable complexity concealment technique and compares the results with existing schemes qualitatively and quantitatively for a range of MPEG test sequences and macroblock loss rates.     

Residual motion coding method supporting error concealment in low bitrate video coding

A residual motion coding (RMC) method supporting error concealment (EC) in low bitrate video coding is proposed. In the RMC method, the residual motion vector (RMV) is interleaved into the bitstream at the encoder to improve the error resilience of MVs. Experimental results show that the EC using RMV performs better than conventional EC methods.     

Refreshment need metrics for improved shape and texture object-based resilient video coding

Video encoders may use several techniques to improve error resilience. In particular, for video encoders that rely on predictive (inter) coding to remove temporal redundancy, intra coding refreshment is especially useful to stop error propagation when errors occur in the transmission or storage of the coded streams, which can cause the decoded quality to decay very rapidly. In the context of object-based video coding, the video encoder can apply intra coding refreshment to both the shape and the texture data. In this paper, shape refreshment need and texture refreshment need metrics are proposed which can be used by object-based video encoders, notably MPEG-4 video encoders, to determine when the shape and the texture of the various video objects in the scene should be refreshed in order to improve the decoded video quality, e.g., for a given bit rate.     

Error concealment for SNR scalable video coding

This paper proposes an efficient error concealment method for SNR scalable coded video. The algorithm adaptively selects a proper concealment candidate from the base or the enhanced pictures to conceal the artifact of a lost enhancement block. To determine the best concealment candidate, we propose a trial process in which the concealment candidates are examined based on two criteria: (1) picture continuity at the border of concealed macroblocks, and (2) to satisfy the coding distortion bound of the base layer coefficients when they are available. For the latter, requantization of the concealed picture with the base layer quantizer step size and its dequantized pixels should result in zero distortion. We have implemented the method on a proposed SNR scalable H.264 video codec and compared the decoded video quality against just copying the base layer pixels into the enhanced picture. Simulation results show that the proposed method can achieve a considerable improvement by up to 3 dB especially in situations where the enhancement layer contains a large portion of the picture information. This will make scalable video transmission more successful over unreliable channels.     

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...     

Motion compensated shape error concealment.

The introduction of Video Objects (VOs) is one of the innovations of MPEG-4. The alpha-plane of a VO defines its shape at a given instance in time and hence determines the boundary of its texture. In packet-based networks, shape, motion, and texture are subject to loss. While there has been considerable attention paid to the concealment of texture and motion errors, little has been done in the field of shape error concealment. In this paper we propose a post-processing shape error concealment technique that uses the motion compensated boundary information of the previously received alpha-plane. The proposed approach is based on matching received boundary segments in the current frame to the boundary in the previous frame. This matching is achieved by finding a maximally smooth motion vector field. After the current boundary segments are matched to the previous boundary, the missing boundary pieces are reconstructed by motion compensation. Experimental results demonstrating the performance of the proposed motion compensated shape error concealment method, and comparing it with the previously proposed weighted side matching method are presented.     

结合视觉感知的对象基嵌入式图像编码中的码率控制方法

结合人眼视觉感知特性,提出一种面向对象基嵌入式编码的码率控制算法.首先结合人眼视觉感知特性估计各对象的重要性并确定其编码优先级;然后依据优先级对视觉对象进行位平面建模和熵编码,得到各自独立的码流;最后基于率失真优化理论在给定码率下对对象码流进行优化截取和重装.仿真实验结果表明,所提算法可以对不同重要对象进行差异化编码和传输,与基于PCRD算法的码率控制方法相比,新算法能提高重构图像的整体视觉效果     

卫星视频帧内自适应误码掩盖新算法

在易发生错误的卫星信道的传输过程中,视频会产生误码和丢包.根据视频的边缘特征,将丢失块分成平坦块、边缘块和纹理块.然后,自适应地选择双线性内插、方向内插或者新方向加权内插作为内插方法,提高重构视频质量,加速误码掩盖过程.为了减少梯度计算量,将噪声像素从候选预测像素列表中剔除.为了准确地呈现图像的方向信息以及抑制噪声,选择Prewitt算子作为梯度滤波器.另外,使用分数像素内插来提高插值精度,适应高清视频应用.客观评价结果显示,在解码时间稍微增加的情况下,峰值信噪比大约提升了3 dB.主观比较结果显示,提出的算法能够获得更高的视觉质量.     

用于多视视频加深度的错误隐藏算法

提出了一种针对多视视频加深度(MVD)的错误隐藏( EC)算法。算法充分利用MVD特有的深度 信息及当前丢失宏块周围正确解码的宏块信息,将丢失宏块分为3类不同属性的宏块。针对3类宏块的特 点,分别提出了基于候选运动矢量修正(CMVR)、基于深度的外边界匹配(DOBMA)以及自适应 权 值的EC(AWEC)等模式。实验表明,本文提出的算法在保证相同的视频主客观质量情况下, 能够快速有效地实现EC。     

立体视频右视点图像宏块丢失错误隐藏算法

根据宏块的运动特性,提出了一种立体视频右视 点图像宏块丢失的错误隐藏算法。根 据视点内时域相邻帧及 视点间相邻帧的相关性估计丢失宏块的运动静止特性,将丢失宏块分为运动块和静止块。对 于静止块,直接使用时 域帧拷贝的方法恢复;对于运动块,使用外边界匹配准则选择候选块并赋予相应的权重得到 加权候选块,根据最优 候选块和加权候选块的边界匹配值自适应地选择最优块或空域插值方法恢复丢失信息。实验 表明,本文算法提高了 隐藏图像的主客观质量。在不同量化参数(QP)和不同宏块丢包率(PLR) 的情况下,经本文算 法恢复后图像的峰值信噪比(PSNR)与普通JM算法相比,平均提高0. 77～3.22dB。     

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。     

一种低复杂度立体视频错误隐藏新方法

针对立体视频流传输中右视 点整帧丢失,提出 了一种低复杂度的错误隐藏算法。首先,为了高效地感知立体视频的时域质量和视点间质量 ,定义了时域相似尺度(TSM)、 视间相似尺度(ISM)的概念;将前一时刻右视点图像进行时域和视点间匹配,分别求取 其以像素为单位的TSM和 ISM映射图;然后,计算前一时刻右视点图像当前宏块的TSM和ISM值,通过比较得 到当前宏块的预测模式;最后,根据视频序列的时域一致性,将前一时刻右视点图像宏块 的预测模式作为丢失图像宏 块的预测模式,从而使用运动补偿预测(MCP)或者视差补偿预测(DCP )的方法恢复丢失信息。研究结果表明,与已有错误隐藏 算法相比,本文算法获得更好主客观视觉效果;同时与基于图像结构相似度(SSIM)的错误隐藏算法相比,在保持主观视觉质量情况下,错误隐藏时间节省20%左右。