Two-dimensional reversible data hiding-based approach for intra-frame error concealment in H.264/AVC

Highly compressed video bit-stream is extremely sensitive to transmission error. A novel two-dimensional reversible data hiding-based approach for intra-frame error concealment is proposed, which aims at improving video quality at decoder when video bit-stream incur transmission errors. The scheme involves embedding the motion vector (MV) of a macroblock (MB) into other MB within the same intra-frame, and extracting the embedded MV from the received video frame for reconstruction of the corrupted MB. Based on the distribution of the motion vector data and the characteristic of histogram shifting, a specific two-dimensional reversible data hiding mechanism is designed. Consequently, the distortion of the marked video can be controlled at a low level. Experimental results show that the damaged macroblocks can be recovered with a higher quality using the reversible data hiding methodology, as compared to the non-reversible data hiding method. Furthermore, experimental results demonstrate that the proposed algorithm outperforms some state-of-the-art reversible data hiding error concealment schemes in improving the perceptual quality.     

Error resilience of multireference motion compensated prediction in video coding

Standard coded video is vulnerable to transmission errors when transmitted over unreliable channels. The authors propose using multireference motion compensated prediction (MCP) to provide resilience to transmission errors. Both the concealment error and propagation error can be reduced in multireference MCR. First, using the multiple motion vectors associated with each coded block, a concealment scheme of low complexity with small concealment error is proposed. Then the theoretical performance limit of propagation error and coding efficiency in multireference MCP is analysed. Through a numerical solution based on the theoretical performance limit, it is found that a multireference MCP scheme can achieve greater propagation error attenuation than the traditional single-reference MCP scheme. The numerical solution also demonstrates that the performance of the multireference MCP average scheme approaches the theoretical performance limit, with coding efficiency higher than the traditional single-reference MCP scheme. Finally, results of a simulation under the assumed packet loss environment typical of the Internet are given. Simulation results demonstrate that video coding with multireference MCP performs much better than the conventional H.263 coding scheme in a lossy environment.     

Temporal shape error concealment by global motion compensation with local refinement.

This paper presents an original temporal shape error concealment technique based on a combination of global and local motion compensation. For this technique, which is especially useful for object-based video applications in error-prone environments (e.g., mobile networks), it is assumed that the shape of the corrupted object at hand is in the form of a binary alpha plane and some of the shape data is missing due to channel errors. To conceal the corrupted shape, the decoder first assumes that a global motion model can describe the shape changes in consecutive time instants. This way, based on locally estimated global motion parameters, the decoder attempts to conceal the corrupted alpha plane by global motion compensating the shape data from the previous time instant. Afterwards, since a global motion model cannot perfectly describe all alpha plane changes, a local motion refinement is applied to improve the concealment in areas of the object with significant local motion.     

Data partitioning and coding of DCT coefficients based on requantization for error-resilient transmission of video

In this paper, we propose an efficient data partitioning and coding algorithm for an error-resilient transmission of DCT coefficients in error prone environment. In the typical data partitioning for Inter-coded frames, motion and macroblock header information is separated from the texture information. It can be an effective tool for the transmission of video over the error prone environment. For Intra-coded frames, however, the loss of DCT coefficients is fatal because there is no other information to reconstruct the corrupted macroblocks by errors. Conventional data partitioning algorithm for DCT coefficients is to separate a fixed number of the significant DCT coefficients from the remaining coefficients, called the spectral separation. While the spectral separation can guarantee an error resilient transmission with small overhead, the main drawback is a significant decrease in the image quality of the high priority partition, compared with that of the bitstreams without data partitioning for an equivalent bit-rate. In the proposed scheme, the quantized DCT coefficients are partitioned into an even-value approximation and the odd remainder part. We also propose a simple and efficient coding algorithm for the odd remainder part. It is shown that the proposed algorithm provides a better image quality than the conventional methods with a little overhead.     

基于运动特性分析的立体视频差错掩盖

传统的视频差错掩盖技术在处理含有剧烈或复杂运动的丢失宏块时效果不理想,该文在对立体视频编码预测方式统计分析的基础上,利用丢失宏块周围正确接收块和已掩盖块的运动和视差信息,将当前丢失宏块进行判别分类,根据不同类别做不同的处理,这就对丢失宏块的恢复更具有针对性,进而提高差错掩盖的质量和效率。实验结果表明,所提方法能够改善视频剧烈或复杂运动区域的掩盖质量。     

Recovery of motion vectors for error concealment based on an edge-detection approach

A new approach to error concealment is presented which exploits both spatial and temporal information from the current and previous frames. The technique consists of two stages, motion vector estimation and enhancement of the estimated motion vector. In the first stage the proposed method estimates a replacement for the corrupted motion vector by applying dynamic weights to related motion vectors from the top, bottom, left and right sub-macroblocks. The estimated motion vectors are then enhanced using a new approach based on edge detection in the second stage. The experimental results for several test video sequences are compared with conventional error concealment methods and higher performance is achieved in both objective peak signal-to-noise ratio measurements and subjective visual quality.     

Multiframe error concealment for MPEG-coded video delivery over error-prone networks

Compressed video sequences are very vulnerable to channel disturbances when they are transmitted through an unreliable medium such as a wireless channel. Transmission errors not only corrupt the current decoded frame, but they may also propagate to succeeding frames. A number of post-processing error concealment (ECN) methods that exploit the spatial and/or temporal redundancy in the video signal have been proposed to combat channel disturbances. Although these approaches can effectively conceal lost or erroneous macroblocks (MBs), all of them only consider spatial and/or temporal correlation in a single frame (the corrupted one), which limits their ability to obtain an optimal recovery. Since the error propagates to the next few motion-compensated frames in the presence of lost MBs in an I or P frame, error concealment should simultaneously minimize the errors not only in the current decoded frame but also in the succeeding B and P frames that depend on the corrupted frame. We propose a novel multiframe recovery principle which analyzes the propagation of a lost MB into succeeding frames. Then, MPEG-compatible spatial and temporal error concealment approaches using this multiframe recovery principle are proposed, where the lost MBs are recovered in such a way that the error propagation is minimized.     

A video error concealment method using data hiding based on compressed sensing over lossy channel

The video error concealment with data hiding (VECDH) method aims to conceal video errors due to transmission according to the auxiliary data directly extracted from the received video file. It has the property that can well reduce the error propagated between spatially/temporally correlated macro-blocks. It is required that, the embedded information at the sender side should well capture/reflect the video characteristics. Moreover, the retrieved data should be capable of correcting video errors. The existing VECDH algorithms often embed the required information into the corresponding video frames to gain the transparency. However, at the receiver side, the reconstruction process may loss important information, which could result in a seriously distorted video. To improve the concealment performance, we propose an efficient VECDH algorithm based on compressed sensing (CS) in this paper. For the proposed method, the frame features to be embedded in every video frame are generated from the frame residuals CS measurements and scrambled with other frame features as marked data. The marked data is embedded into the corresponding frames by modulating color-triples for its least impacts on the carriers. For the receiver, the extracted data is used to reconstruct residuals to conceal errors. Error positions are located using the set theory. Since the CS has the ability to sample a signal within a lower sampling rate than the Shannon–Nyquist rate, the original signal could be reconstructed very well in theory. This indicates that the proposed method could benefit from the CS, and therefore keep better error concealment behavior. The experimental results show that the PSNR values gain about 10 dB averagely and the proposed scheme in this paper improves the video quality significantly comparing with the exiting VECDH schemes.     

A Hybrid Frame Concealment Algorithm for H.264/AVC

In packet-based video transmissions, packets loss due to channel errors may result in the loss of the whole video frame. Recently, many error concealment algorithms have been proposed in order to combat channel errors; however, most of the existing algorithms can only deal with the loss of macroblocks and are not able to conceal the whole missing frame. In order to resolve this problem, in this paper, we have proposed a new hybrid motion vector extrapolation (HMVE) algorithm to recover the whole missing frame, and it is able to provide more accurate estimation for the motion vectors of the missing frame than other conventional methods. Simulation results show that it is highly effective and significantly outperforms other existing frame recovery methods.     

Spatial error concealment with edge related perceptual considerations

Video transmission over error-prone networks can suffer from packet erasures which can greatly reduce the quality of the received video. Error concealment methods reduce the perceived quality degradation at the receiving end by masking the effects of such errors. They accomplish this by exploiting temporal and spatial correlations that exist in image sequences. Spatial error concealment approaches conceal errors by making use of spatial information only which is necessary in cases where motion information is not available or reliable. The performance of such methods can be greatly increased if perceptual considerations are taken into account as, e.g., the preservation of edge information. This paper proposes a spatial error concealment method that uses edge-related information in order not only to preserve existing edges but also to avoid introducing new strong ones by switching to a smooth approximation of missing information where necessary. A novel switching algorithm which uses the directional entropy of neighbouring edges chooses between two interpolation methods, a directional along detected edges or a bilinear using the nearest neighbouring pixels. Results show that the performance of the proposed method is better compared to both ‘single interpolation’ and to edge strength-based switching methods.     

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.     

基于MV自适应选取的帧间隐藏算法

数字视频通信在多媒体通信系统中占据重要的地位,但视频帧传输错误将导致接收视频质量的下降.视频帧传输错误不仅会破坏当前的解码帧,还会在时间上扩散造成对后续帧的预测错误.为减少视频帧传输错误对视频质量的影响,设计了一种基于运动矢量自适应选取的错误隐藏算法,算法充分利用相邻宏块间运动矢量的空间相关性来自适应地恢复受损宏块的运动矢量.仿真实验结果表明,相对于典型的错误隐藏算法,所述算法在主观视觉质量和客观评价指标上都有一定的提高.     

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

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Adaptive Pixel Interpolation for Spatial Error Concealment

Error concealment techniques are widely used as efficient ways to recover the lost information at the decoder. This paper proposes an adaptive pixel interpolation technique for spatial error concealment in the block based coding system. For a missing pixel in a corrupted block, its value is derived from four neighborhoods of the block through interpolation using multiple prediction strategy. The weighting rules of these four neighborhood blocks are carefully designed with regard to three factors, the distance to the missing pixels within the given corrupted block, the percentage of uncorrupted pixels, and the similarity to the given corrupted block. The proposed method works effectively in consecutive block loss situation, which is common in real applications of video transmission. Experimental results show the proposed technique gains more accurate recovery of the missing pixels than the existing schemes.     

An improved reversible data hiding-based approach for intra-frame error concealment in H.264/AVC

As H.264/AVC video streams are highly compressed, they become sensitive to errors caused by unreliable transmission channels. In order to address this issue, an improved version of Chung et al.’s reversible data hiding-based approach for intra-frame error concealment is proposed for H.264/AVC codec. By using the histogram shifting technique, the original work reversibly embeds the motion vector (MV) of a macroblock (MB) into other MB within the same intra-frame. If an MB is corrupted at the decoder side, the embedded MV can be extracted from the corresponding MB for the recovery of the corrupted MB. However, Chung et al.’s work did not fully exploit the number of coefficients which need to be modified in order to reversibly hiding data, and did not consider many extra nonzero residual blocks produced by data hiding. These two issues could reduce the visual quality of the stego-video. This paper adopts MV data pre-processing, the selection of most suitable embedding region, and the minimum possible amount of histogram modification, which lead to higher PSNR of the stego-video for a given payload. Experimental results further reveal that the proposed method offers stego-video with better visual quality over Chung et al.’s work.     

An error resilient video coding and transmission solution over error-prone channels

With the rapid development of network and multimedia technology, the error control in video coding and video transmission over error-prone channels has become increasingly important. The DCT based predictive coding and VLC based entropy coding greatly increase the coding efficiency, but make the compressed video stream very sensitive to transmission errors. Therefore, this paper proposes a reliable error resilient video coding and video transmission framework. In order to improve the robustness to packet loss errors, an error resilient video coding algorithm named Z-FMO is proposed. Some channel may bring random bit errors, an adaptive error concealment algorithm based on macroblock boundary gradient namely ECMBG is proposed aiming at such problem. As the indispensable part of a video transmission system, we implement an adaptive video transmission control algorithm JCBAF. Experimental results show that the proposed framework performs well both in R-D performance and subjective quality.     

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。     

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.     

An integrated temporal error concealment for H.264/AVC based on spatial evaluation criteria

Owing to error-prone transmission networks, the compressed video bit stream is prone to packet loss in the transmission channel. This loss causes serious distortion and the distortion will propagate to successive frames, especially in highly compressed video coding standard. Therefore, it is very important to efficiently enhance the restored result. In this paper, an integrated temporal error concealment technique for H.264/AVC is proposed. The technique could effectively restore the corrupted data by adaptively integrating error concealment approaches with the adaptive weight-based switching algorithm. The integrated mechanism is based on spatial evaluation criteria, judged by boundary distortion estimation and texture intensity. Experimental results show that the technique could effectively enhance the performance of error concealment.