基于多方向自适应加权的空间错误隐藏算法

为了提高H.264/AVC压缩视频码流在无线信道传输过程中的抗误码性能,提出了一种基于多方向自适应加权的空间错误隐藏算法.该算法首先应用边缘算子检测受损宏块的相邻宏块信息,然后通过多方向自适应加权插值得到受损宏块像素近似值.实验表明,该算法相对传统空间错误隐藏算法,对于不同视频序列图像重构质量有很大的改善,具有较高的应用价值.     

SPATIAL ERROR CONCEALMENT BASED ON MOJETTE TRANSFORM

This letter presents a novel spatial error concealment algorithm for the H.264 video coding. The error concealment algorithm is based on directional interpolation. Mojette transform is used to estimate the orientation features of the damaged blocks,and the image is interpolated in the appro-priate directions. The proposed method is compared with bilinear interpolation algorithm in the ref-erence implementation of H.264 and all directional interpolation. Experimental results prove that the proposed algorithm has better subjective and objective image reconstruction quality.     

SPALTIAL ERROR CONCEALMENT BASED ON MOJETTE TRANSFORM

This letter presents a novel spatial error concealment algorithm for the H.264 video coding.The error concealment algorithm is based on directional interpolation.Mojette transform is used to estimate the orientation features of the damaged blocks,and the image is interpolated in the approDriate directions.The proposed method is compared with bilinear interpolation algorithm in the reference implementation of H.264 and all directional interpolation.Experimental results prove that the proposed algorithm has better subjective and objective image reconstruction quality.     

一种基于双域拉格朗日插值的视频错误隐藏方法

本文提出了一种基于双域拉格朗日插值的错误隐藏方法,编码采用H.264标准,分别在时域和空域进行插值获得两个运动矢量,通过建立插值系数表构造混合的插值模型,经过边缘匹配算法判断后获得最优的运动矢量作为丢失宏块的运动矢量.为了减小网络突发错误对插值效果的影响,本文在编码端提出了一种类交织的slice划分方法,实验证明本文方法由于充分利用了时域和空域的信息冗余,取得了较好效果,在15％网络丢包率的环境下平均PSNR比空域拉格朗日插值方法高0.5dB~1dB左右.     

基于拟合平面插值的时域错误隐藏算法研究

针对H.264/AVC压缩视频码流在无线信道传输过程中由于运动矢量失配导致图像重构质量下降的问题,本文提出了一种基于拟合平面插值的时域错误隐藏算法。该算法主要利用平面拟合算法对受损宏块运动矢量进行重建,同时采用外边界匹配算法选取最优运动矢量对受损图像进行恢复重建。实验表明,该算法不仅避免了原始算法产生的方块效应,而且在不同的RTP丢包概率下,该算法提升了峰值信噪比,恢复重建的图像质量在主观方面和客观方面都有很大的改善。     

Error Concealment Using Intra‐Mode Information Included in H.264/AVC‐Coded Bitstream

The H.264/AVC standard has adopted new coding tools such as intra‐prediction, variable block size, motion estimation with quarter‐pixel‐accuracy, loop filter, and so on. The adoption of these tools enables an H.264/AVC‐coded bitstream to have more information than was possible with previous standards. In this paper, we propose an effective spatial error concealment method with low complexity in H.264/AVC intra‐frame. From information included in an H.264/AVC‐coded bitstream, we use prediction modes of intra‐blocks to recover a damaged block. This is because the prediction direction in each prediction mode is highly correlated to the edge direction. We first estimate the edge direction of a damaged block using the prediction modes of the intra‐blocks adjacent to a damaged block and classify the area inside the damaged block into edge and flat areas. Our method then recovers pixel values in the edge area using edge‐directed interpolation, and recovers pixel values in the flat area using weighted interpolation. Simulation results show that the proposed method yields better video quality than conventional approaches.     

Motion field interpolation for temporal error concealment

When transmitted over practical communication channels, compressed video can suffer severe degradation. One approach to combat the effect of channel errors is error concealment. It is an attractive choice because it does not increase the bit rate, it does not require any modifications to the encoder, it does not introduce any delays and it can be applied in almost any application. Conventional temporal concealment techniques estimate one concealment displacement for the whole damaged block and then use translational displacement compensation to conceal the block from a reference frame. The main problem with such techniques is that incorrect estimation of the concealment displacement can lead to poor concealment of the whole or most of the block. Two novel temporal concealment techniques are presented. In the first technique, motion field interpolation is used to estimate one concealment displacement per pel of the damaged block and then each pel is concealed individually. In this case, incorrect estimation of a concealment displacement will only affect the corresponding pel. On a block level this may affect few pels rather than the entire block. In the second technique, multi-hypothesis motion compensation is used to combine the first technique with a boundary matching temporal concealment technique to obtain a more robust performance. Simulation results, within both an isolated error propagation environment and an H.263 codec, show the superior subjective and objective performance of the proposed techniques when compared with conventional temporal concealment techniques     

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.     

Spatial error concealment with sequence-aligned texture modeling and adaptive directional recovery

A spatial error concealment technique based on the sequence-aligned texture modeling and the adaptive directional recovery is proposed in this work. The sequence alignment technique captures the local variation and the global trend of image textures with surrounding uncorrupted pixels, and provides the best texture model under a given cost function. With the derived texture model, geometric interpolation is used to recover lost pixels adaptively based on pixel locations. There are four candidate modes of pixel sequences to recover lost pixels, and one of them is selected for the concealment purpose. The selection criterion is based on the texture pattern modes of surrounding uncorrupted blocks. The pixel sequences used for error concealment can be obtained from the computation of the decoder or the side information from the encoder. Extensive experimental results are given to demonstrate that our error concealment technique outperforms several benchmark methods in both objective and subjective tests.     

Interpolated Candidate Motion Vectors for Boundary Matching Error Concealment Technique in Video

The pertinency of error concealment (EC) schemes to the encoder-decoder model makes them an attractive choice to conceal the effects of transmission errors in a compressed video bitstream. Among various EC techniques, boundary matching (BM) has been the most popular due to its distortion measure criterion to select the most appropriate motion vector (MV) for damaged macroblock among a set of candidate MVs (CMVs). In a scenario where error bursts do not extend to more than one frame of digital video, the performance of BM can be highly enhanced if the CMVs depend upon an interpolation of surrounding MVs. This interpolation needs to be done, considering the change in their pattern from the reference to the current erroneous frame. This brief proposes a technique to build this novel set of CMVs and compares the results of BM with traditional CMVs qualitatively and quantitatively for MPEG test sequences     

Hybrid error concealment method combining exemplar-based image inpainting and spatial interpolation

This paper proposes an efficient error concealment method for the reconstruction of pixels that are lost in video communication. The proposed method is developed by combining exemplar-based image inpainting for patch reconstruction and spatial interpolation for pixel reconstruction using adaptive threshold by local complexity. By exemplar-based image inpainting, regions with regular structures are reconstructed. For complex regions with irregular structures, just one pixel is reconstructed using the proposed spatial interpolation method. The proposed spatial interpolation method performs reconstruction by selecting adaptively directional interpolation or neighbor interpolation based on gradient information. Simulation results show that the proposed hybrid method performs reconstruction with significantly improved subjective quality compared with the previous spatial error concealment and image inpainting methods. The proposed method also gives substantial improvements of PSNR compared with the previous methods.     

一种改进的H.264自适应帧内错误隐藏算法

提出了一种改进的H.264自适应帧内错误隐藏算法,使重建图像具有较好的平滑性,同时有效恢复了边缘信息。通过区域选择、亮度信号插值、块位置检测等方式,有效降低了解码运算量并解决了工程应用中的难点。在MATLAB和H.264标准测试平台JM86上分别进行验证,结果表明,该算法简单实用,适于实时处理,峰值信噪比高出一般传统方法 3 dB,改善了重建图像的主、客观质量,具有较高的应用价值.     

一种基于快速搜索的视频时域差错隐藏算法

为了克服视频传输中因传输差错引起的视频质量下降,提出一种基于快速搜索的边框匹配时域隐藏算法(CSBM)。该算法针对时域差错隐藏的运动矢量恢复问题,利用边框匹配算法改善被恢复的物体边缘模糊的情况;采用基于中心偏置的快速搜索样式得到最小边界匹配差值的候选运动矢量,减少了解码器差错恢复的计算复杂度。实验结果显示,针对不同性质的序列,该算法与边界匹配算法(SMA)、棱形搜索的边界匹配法(DSSM)等典型差错隐藏方法相比,平均搜索点数可减少12.5~19个点,亮度分量的峰值信噪比(PSNR)能改善0.93~1.55 dB,证明该算法能获得更好的差错隐藏效果,并减少了运算量。     

Joint estimation of forward and backward motion vectors forinterpolative prediction of video

A low-complexity iterative algorithm is introduced for joint estimation of forward and backward motion vectors in interpolative prediction of video. Starting from the initial values obtained by a commonly-used block matching independent search method, the motion vectors are iteratively refined until a locally optimal solution to the motion estimation problem for interpolative prediction is achieved. Each iteration consists of a series of two similar procedures. First, the backward motion vector is fixed and a new forward motion vector is searched to minimize the interpolation error. Then the forward motion vector is fixed and the backward motion vector is similarly refined by minimizing the interpolation error. This process is repeated until the interpolation error stops decreasing. Computer simulation results demonstrate that with this technique the prediction error in some scenes is significantly reduced.     

基于运动预测的Motion JPEG2000误码掩饰新算法

Motion JPEG2000(MJPEG2000)作为新兴的视频压缩标准,鲁棒传输控制是一个重要的应用需求,而误码掩饰技术是提高其鲁棒性的有效途径之一。充分利用压缩码流冗余信息,本文提出了一种基于运动预测的Motion JPEG2000视频传输误码掩饰新算法。首先利用相邻帧及帧内子带间的相关性进行小波域内的运动估计,以低频子带内码块的运动矢量来预测高频子带内丢失码块的运动矢量,再通过运动匹配修复丢失的码块。而低频子带内数据块的丢失可通过整个高频子带图像完成运动估计,得到预测信息对低频子带系数实施误码掩饰。仿真实验结果表明,提出的算法不管在低频还是高频子带进行误码掩饰修复,均能得到较好的图像帧重建效果。     

Fuzzy Logic Based Temporal Error Concealment for H.264 Video

In this paper, a new error concealment algorithm is proposed for the H.264 standard. The algorithm consists of two processes. The first process uses a fuzzy logic method to select the size type of lost blocks. The motion vector of a lost block is calculated from the current frame, if the motion vectors of the neighboring blocks surrounding the lost block are discontinuous. Otherwise, the size type of the lost block can be determined from the preceding frame. The second process is an error concealment algorithm via a proposed adapted multiple‐reference‐frames selection for finding the lost motion vector. The adapted multiple‐reference‐frames selection is based on the motion estimation analysis of H.264 coding so that the number of searched frames can be reduced. Therefore the most accurate mode of the lost block can be determined with much less computation time in the selection of the lost motion vector. Experimental results show that the proposed algorithm achieves from 0.5 to 4.52 dB improvement when compared to the method in VM 9.0.     

面向HBP编码格式的立体视频B帧整帧丢失分层错误隐藏算法

针对分层B帧(HBP)编码格式的立体视频B帧整帧丢失的问题,该文分析了双视点视频中存在的视点间运动矢量相关性,提出一种分层错误隐藏算法。该算法与当前主流的方法有两大不同:一是该算法采用分级隐藏,根据B帧的重要性等级不同采用不同的错误隐藏方法;二是该算法考虑了相邻视点序列之间的宏块运动矢量相关性。实验表明,该算法的性能优于当前常用的H.264多视点视频整帧丢失错误隐藏方法。     

Efficient error localization and temporal concealment based on motion estimation of enlarged block

We propose a modified motion estimation algorithm that is adequate for error localization and temporal error concealment in transmitting videos over unreliable channels. In order to achieve good error concealment performance, the proposed algorithm implicitly imposes spatial correlations on motion vectors by extending the block size and overlapping blocks in motion estimation. Thereby, the obtained motion vectors can be used to improve error concealment performance while keeping the encoding efficiency with negligible overhead. In addition, the proposed motion estimation can provide a new error detection measure so that we can maximally utilize uncorrupted data rather than simply discarding all data in a defected packet. Simulation results show that the proposed motion estimation scheme provides significant improvements in error concealment performance over the existing schemes and improves the bit utility over a wide range of error conditions.     

一种基于多参考帧的时域误码掩盖算法

视频压缩码流对于信道误码十分敏感,可导致重建图像质量严重下降,在接收端就要使用误码掩盖技术对损坏的视频进行掩藏。文中提出一种基于多参考帧的时域误码掩盖算法,首先计算受损宏块的相邻块的运动矢量的均值,然后遍历所有参考帧得到待选的误码掩盖宏块,最后用外边界匹配算法找出替代受损宏块的宏块。研究结果表明,该算法能更精确地恢复错误宏块的运动矢量,从而获得比传统的时域掩盖算法更好的视频质量。     

基于模糊聚类和网格变形的自适应时-空差错掩盖方法

当视频传输中出现不能恢复的误码或丢包时,在接收端就要使用差错掩盖技术对损坏的视频进行掩藏。该文提出了一种基于模糊聚类和网格变形的自适应差错掩盖方法,使得错误恢复效果提高。该方法首先用基于时-空的模糊聚类块匹配方法补偿平移运动场景中的块丢失,然后如果检测出丢失块所在的空间有旋转、缩放等复杂运动,则用基于网格变形的方法进行补偿。实验结果表明其PSNR值比Luigi(2001)的BMA-MBW方法平均提高约1.5dB,比传统的基于块匹配的方法平均提高约3.5dB。