AVS-M解码在BREW平台上的实现

介绍了AVS-M标准的参考代码移植到BREW平台的方法和要解决的问题,并针对AVS-M标准的参考代码给出几种优化方法,实现了AVS-M在三星W109上解码QCIF格式达到10fps以上.     

AVS移动视频标准及其产业化

本文首先介绍了我国具有自主知识产权的移动视频编解码标准AVS-M制定的背景及标准的特点,然后分析了标准的专利收费优势及产业化优势,最后介绍了AVS-M当前产业化发展状况,并对AVS-M前景进行了探讨.     

移动数字多媒体电视广播编码器的研究

提出了一种"AVS-M DAB"的DMB编码器实现方案,通过DSP和FPGA软硬件平台实现了AVS-M DAB方式的DMB编码器,并最终用接收机成功接收和验证.     

AVS-M中的错误恢复技术

介绍了AVS-M中采用错误恢复技术对误码进行控制和隐藏的方法,实验结果显示,目前AVS-M中的错误恢复技术明显提高了视频码流抗误码的能力,可满足无线和实时应用.     

一种适用于AVS_M的改进型交叉搜索算法

针对于移动视频编码标准(AVS-M)中运动估计模块的计算,本文提出了一种适用于AVS-M的改进型交叉搜索算法。该算法以传统的交叉算法为基础,通过对AVS-M运动矢量的研究和分析,针对传统优秀算法的不足,引入灵活的搜索窗口,有效的降低了运动估计的运算量。实验结果表明,该算法显著降低了复杂度,大大减少了搜索点数,具有较好的鲁棒性。     

基于NVDK的AVS-M视频解码器的实现与优化

研究了AVS-M视频编码技术特点和NVDK C6416的体系结构,设计了一种基于NVDK C6416硬件平台的AVS-M视频解码器.阐述了AVS-M视频解码器的硬件实现和软件优化方法,经优化后的解码器能实现AVS-M视频的实时解码,具有可靠性高、体积小、功耗低和易于升级等特点.     

基于视频时空相关性的帧内预测模式抉择

提出了一种帧内预测模式抉择方法,利用视频图像的时间相关性和空间相关性,选择部分预测模式对图像块进行帧内预测处理和编码,减少编码的计算复杂度,保持其原有的编码效率。同时提出了一种复杂度分级方法,通过准确控制帧内预测的复杂度,以匹配通信终端有限的计算资源。该方法在AVS-M平台中进行了验证。     

AVS-M视频解码器设计和实现

设计实现了新的国家视频压缩标准AVS-M的软件解码器,介绍了程序设计流程和方法,在奔腾4代CPU计算机上实现了352×288 CIF图像的实时解码.     

一种适用于AVS-M的自适应快速运动估计算法

为了减小移动视频编码标准(AVS-M)中运动估计模块的复杂度,提出了一种快速、有效的块匹配运动估计算法.该算法充分利用了视频图像中运动矢量场的中心偏置特性和时空相关性,根据运动类型自适应的选择搜索起点和搜索策略,结合改进的搜索模板和高效搜索中止准则,有效地降低了运动估计的运算量.实验结果表明,该算法在保证搜索精度的同时,大大减少了搜索点数.     

基于移动平台的AVS-M主观视觉评价方法

提出了一套覆盖AVS-M主要模块的测试方案,根据测试结果可以分析不同模块对主客观评价实验的影响,为简化或屏蔽措施提供了依据.     

Video transmission over mobile satellite systems

Mobile satellite communication channels are characterized by long transmission delays, variation of these delays, high bit‐error‐rates, shadowing and the multipath effect which severely reduce the quality of video services. Error control techniques including feedback mechanisms, error concealment methods, forward error correction techniques and error resilience schemes are examined in this paper for achieving a high‐integrity video transmission over a mobile satellite channel. The application of three different error resilience algorithms, namely Turbo codes, error‐resilient entropy codes and two‐way decoding using reversible codes is presented. Their joint performance is also examined. Furthermore, a low‐delay and low‐complexity video transcoding algorithm which fully interconnects two very low bit rate video communication standards: MPEG‐4 and H.263 is also elaborated. This transcoder works as a gateway tool which links two heterogeneous multimedia networks, such as a mobile satellite network and a land‐based network, with negligible processing delay and complexity. Copyright © 2000 John Wiley & Sons, Ltd.     

基于L∞最小搜索和陪集码的高光谱图像无损及近无损压缩

 分布式信源编码(DSC)由于其较低的编码复杂度及较高的抗误码性被应用于高光谱图像压缩.在典型的基于陪集码的分布式高光谱图像无损压缩算法s-DSC(scalar coset DSC)框架下,本文指出最优的预测准则应为无穷范数最小,提出了基于L_∞最小搜索的预测方法来逼近最优准则,并将框架推广到近无损压缩.实验表明,和原有的s-DSC相比,本文算法无损压缩的平均码率降低了大约0.25bpp,近无损性能也明显优于JPEG-LS,本文算法具有较低的计算复杂度、较高的压缩性能,且具有一定的抗误码能力,适用于星上压缩.     

Efficient error resilient algorithm for H.264/AVC: mobility management in wireless video streaming

The H.264/AVC standard introduces enhanced error robustness capabilities enabling resilient and reliable transmission of compressed video signals over wireless lossy packet networks. Those robustness capabilities are achieved by integrating some new error resilience tools that are essential for a proper delivery of real-time video services. Those tools include the Intra Refreshing (IR), Arbitrary Slice Ordering (ASO), Sequence Picture Parameter Sets (PPS), Redundant Slices (RS) tools and Flexible Macroblock Ordering (FMO). This paper presents an error resilient algorithm in wireless H.264/AVC streaming. The proposed method merges Reference Frame Selection (RFS), Intra Redundancy Slice and Adaptive Intra Refreshment techniques in order to prevent temporal error propagation in error-phone wireless video streaming. The coding standards only specify the decoding process and the bitstream syntax to allow considerable flexibility for the designers to optimize the encoder for coding performance improvement and complexity reduction. Performance evaluations demonstrate that the proposed encoding algorithm outperforms the conventional H.264/AVC standard. Both subjective and objective visual quality comparative study has been also carried out in order to validate the proposed approach. The proposed method can be used and integrated into H264/AVC without violating the standard.     

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。     

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.     

Phase error resilience to I/Q mismatch of a simplified CPM receiver

A low complexity receiver which was devised in previous papers proved there to be quasioptimum over additive gaussian noise and also showed low power penalty with flat Rayleigh fading, i.e., with random phase, and despite the fact that one of three reduced complexity blocks of that receiver relies on symmetries on signal's phase transitions. This letter analyzes the origin of that error resilience during the derivation of the metrics.     

一种甚低速率语音编码的抗误码算法

为满足在高误码率的窄带信道上进行语音通信的需求，本文研究了一种适用于甚低速率语音通信的抗误码参数估值算法。在一定的解码状态下，声码器通过计算最小均方误差（MMSE）估计的方法估计最优参数，充分降低信道误码对重建语音质量的影响。对于解码状态参数，通过计算最大后验转移概率的方法作最佳估计，并给出了一种简化的计算方法。这种抗误码算法复杂度低。计算机仿真结果表明，在不同误码率下该算法恢复出的语音的平均谱失真（ASD）低于帧删除方法的谱失真最大可达0.4dB。     

基于DM642的AVS-M视频编码器的设计与优化

设计了一种基于DM642实现的4路AVS-M实时视频编码器,给出了系统的软硬件设计和优化方法;提出了编码器关键模块的优化策略。经优化后能实现4路AVS—M视频的实时编码,具有功能强、可靠性高、体积小、功耗低和易于升级等特点。