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。     

基于H.264/AVC的时空域差错隐藏方案

为了减小视频传输中的错误对解码端重建视频质量的影响,提出了一套结合时空域差错隐藏算法的方案。针对错误宏块在视频图像中呈随机分布的情况,首先将编码端帧内预测编码的思想引入到解码端,提出了一种方向性插值的空域差错隐藏算法;然后提出了一种基于8×8块的增强型时域差错隐藏算法来改善运动剧烈区域的质量;最后,提出了一种根据相邻宏块编码模式来选择时域或空域差错隐藏算法的切换策略。实验证明,提出的差错隐藏方案无论是在客观质量上,还是在主观质量上,都优于H.264/AVC的效果。     

基于PN序列自相关的双门限自适应DTMB频谱感知

对于地面电视的模数转换产生宝贵的广播电视“白频谱冶资源,频谱感知与检测技术是高效有序地利用频谱资源的基础。在数字电视地面多媒体广播( DTMB )传输系统中,针对传统的基于信号特征的感知算法在检测性能、计算复杂度与灵活性上的不足,提出了一种自适应的DTMB频谱感知算法。该算法以双门限感知检测为基础,在双门限之外采用基于伪随机( PN )序列自相关的算法,在双门限之内采用不等间隔PN序列累积自相关的算法,同时自适应地调整双门限的取值,平衡算法复杂度、感知性能与信道环境的需求。仿真结果表明,该算法在不同的信道条件下能自适应且快速地调整参数,有效提高频谱检测性能,降低算法复杂度。     

H.264和AVS编码在地面数字电视广播系统的应用

介绍了H.264和AVS两种先进信源编码方式在地面数字电视广播系统中的应用,提出了一种在现有的MPEG-2编码系统中同时实现H.264和AVS码流混合传输的方法,并实现了终端接收.     

多视点立体视频传输系统与错误隐藏算法设计

针对多视点立体视频数据量大、网络带宽受限等问题,提出了一种分组传输多路复用的多视点立体视频实时传输系统。系统将多视点数据通过H.264/AVC压缩编码后,在两个IP链路中进行分组复用,实现了立体视频在带宽受限网络中的实时传输;同时,为了解决IP网络传输中的丢包问题,提出一种联合时域视点间预测的错误隐藏算法。最后通过实验表明,本文错误隐藏算法可以提高多视点立体视频的解码质量。     

高效的H.264空域错误隐藏算法

在视频传输过程中视频质量会受到受损宏块的影响而导致视频质量下降,针对此问题并兼顾错误隐藏效果和算法复杂度,提出了一种高效的空间域错误隐藏算法.首先根据设定的阈值判断当前帧中出错宏块是否满足时域替代条件,若满足就利用前一帧同一位置宏块替代出错宏块,否则就对出错宏块进行基于边缘检测的方向性内插.实验结果表明,该算法与JM测试模型中的方法相比,具有较好的错误隐藏效果且没有增加运算量.     

一种适合国标DTMB系统的载波恢复新方法

针对数字电视地面多媒体广播(DTMB)接收机申多数传统载波恢复算法估计范围较小,且没有考虑定时误差的影响,提出了一种粗偏调整结合扫频的低复杂度载波恢复算法.该算法兼容不同的发送制式以降低接收端的实现复杂度.为了保证估计性能,算法先利用PN的时域特性进行粗频偏调整,然后用变步长扫频估计剩余大频偏.理论分析和计算机仿真表明...     

地面数字电视传输系统测试

随着地面数字电视的发展,世界各国开始部署和实施地面数字电视广播系统.为了客观评估地面数字电视系统的整体性能,必须研究制定相应的地面数字电视传输系统测试方法和技术.本文主要介绍了国际国内开展地面数字电视测试相关技术.     

单频网组网优化方法及复杂度分析

首先介绍了单频网覆盖的判定准则,其次针对地面数字电视广播单频网的组网优化问题,提出了一种基于遗传算法的优化方法,并分析了算法的复杂度,着重探究算法参数对算法性能的影响,从而确保在得到最佳优化结果的同时付出最小的代价.     

短波通信中的低复杂度时域均衡

提出了一种基于Chase算法的低复杂度时域均衡技术.首先通过传统的自适应均衡器获取软值,再利用Chase算法计算可信度找到不可靠位,同时构造测试序列,然后进行滑动窗搜索和逐比特译码.此算法在减小计算量的同时消除了译码时延,并且误码率逼近最大似然序列估计,实现了复杂度和性能的折衷.     

Robust Digital Terrestrial TV Broadcasting System with Error-Resilient Schemes

In this paper, error-resilient schemes are proposed to support robust video transmission for digital terrestrial TV broadcasting (DTTB). In particular, a temporal error concealment incorporated with a low-complexity block-matching is developed, achieving an effective reception of predictive pictures in harsh terrestrial environment. Special algorithms are also designed for isolated I-pictures. Moreover, combined with an intra/inter case prediction, an adaptive error concealment scheme is further contrived to fit for different error conditions. Extensive simulations have been conducted under various DTTB channel conditions, even with a very high packet error rate, to verify the effectiveness of the proposed schemes.     

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.     

基于多方向边界匹配的视频误码掩盖算法

视频压缩码流对于信道误码十分敏感,可能导致重建图像质量严重下降.误码掩盖技术利用图像在时间和空间上的相关性,可以有效地降低误码对视频图像的影响.文中提出了一种基于多方向边界匹配的时域误码掩盖算法.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.     

Robust spatio-temporal error concealment for packet- lossy H.264 video transmission

1 Introduction With the ubiquitous use of Internet and the deployment of next generation of networks, video communications are increa- singly becoming the major services in demand. Unlike data transmission, video communication is essentially time-sensitiv…     

Mixture Model- and Least Squares-Based Packet Video Error Concealment

A Gaussian mixture model (GMM)-based spatio-temporal error concealment approach has recently been proposed for packet video. The method improves peak signal-to-noise ratio (PSNR) compared to several famous error concealment methods, and it is asymptotically optimal when the number of mixture components goes to infinity. There are also drawbacks, however. The estimator has high online computational complexity, which implies that fewer surrounding pixels to the lost area than desired are used for error concealment. Moreover, GMM parameters are estimated without considering maximization of the error concealment PSNR. In this paper, we propose a mixture-based estimator and a least squares approach for solving the spatio-temporal error concealment problem. Compared to the GMM scheme, the new method may base error concealment on more surrounding pixels to the loss, while maintaining low computational complexity, and model parameters are found by an algorithm that increases PSNR in each iteration. The proposed method outperforms the GMM-based scheme in terms of computation-performance tradeoff.     

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.     

A joint encoder–decoder error control framework for stereoscopic video coding

Stereoscopic video coding (SSVC) plays an important role in various 3D video applications. In SSVC, robust stereoscopic video transmission over error-prone networks is still a challenge problem to be solved. In this paper, we propose a joint encoder–decoder error control framework for SSVC, where error-resilient source coding, transmission network conditions, and error concealment scheme are jointly considered to achieve better error robustness performance. The proposed joint encoder–decoder error control framework includes two parts: an error concealment algorithm at the decoder side and a rate–distortion optimized error resilience algorithm at the encoder side. For error concealment at the decoder side, an overlapped block motion and disparity compensation based error concealment scheme is proposed to adaptively utilize inter-view correlations and temporal correlations. For error resilience at the encoder side, first, the inter-view refreshment is proposed for SSVC to suppress error propagations. Then, an end-to-end distortion model for SSVC is derived, which jointly considers the transmission network conditions, inter-view refreshment, and error concealment tools at the decoder side. Finally, based on the derived end-to-end distortion model, the rate–distortion optimized error resilience algorithm is presented to adaptively select inter-view, inter- or intra-coding for SSVC. The experimental results show that the proposed joint encoder–decoder error control framework has superior error robustness performance for stereoscopic video transmission over error-prone networks.     

High‐Performance Spatial and Temporal Error‐Concealment Algorithms for Block‐Based Video Coding Techniques

A compressed video bitstream is sensitive to errors that may severely degrade the reconstructed images even when the bit error rate is small. One approach to combat the impact of such errors is the use of error concealment at the decoder without increasing the bit rate or changing the encoder. For spatial‐error concealment, we propose a method featuring edge continuity and texture preservation as well as low computation to reconstruct more visually acceptable images. Aiming at temporal error concealment, we propose a two‐step algorithm based on block matching principles in which the assumption of smooth and uniform motion for some adjacent blocks is adopted. As simulation results show, the proposed spatial and temporal methods provide better reconstruction quality for damaged images than other methods.