基于H．264的自适应可伸缩编码研究

为了更好地适应网络及终端的多样性,本文针对基于H．264的可伸缩编码,提出了一种基于运动区域的自适应可伸缩编码的优化方案。该方案根据基本层的运动信息及编码模式自动提取图像的运动感兴趣区域,并以独立片的形式对其进行时间、空间和质量上的可伸缩编码,实现选择性增强。实验结果表明,该方案不仅能大幅降低编码复杂度,而且使增强层码流集中包含运动区域信息,从而提高运动区域的重建质量及整幅图像的主观质量。     

一种室内视频监控图像序列编码方法

在实际高分辨率室内视频监控中,运动物体构成了视频监控的主要内容.本文基于感兴趣区域的检测与恢复,提出了一种高分辨率室内视频监控图像序列的编码新方法,通过对象提取实现基本层和ROI层双层码流传输,其中基本层实现低分辨率图像内容传输,而ROI层用以进行高分辨率图像恢复.新方法有效地降低了视频编码计算复杂度、提高了编码效率.     

嵌入掩膜的SPIHT任意形状ROI编码

感兴趣区域(ROI)编码可以在低码率条件下获得高质量的局部感兴趣区域,或在图像渐进传输中使感兴趣区域获得优先传输.本文在分析了当前各类ROI编码方法的基础上,基于SPIHT算法提出了一种支持多个任意形状感兴趣区域并生成可任意截断码流的ROI编码算法.该算法在SPIHT算法中嵌入了重要系数的ROI掩膜信息,使编码器同步地进行图像和ROI形状的编码,使得生成的码流具有任意可截断的特性.文中还就图像ROI编码的质量评价指标进行了讨论,并给出了一种充分考虑ROI和背景的重要性与面积比例差别的图像质量评价指标,称为重要性.面积加权峰值信噪比(WPSNR).实验结果表明,该算法支持有损到无损的多个任意形状ROI的图像编码,而且ROI优先级可调,能够生成具有嵌入式可截断性质的码流,在任意地方截断仍能保证解码器所需的图像信息和ROI掩膜信息,且计算复杂度和SPIHT相当,压缩效果高于BbB移位算法.适用于低码率应用或感兴趣优先渐进传输的应用.     

区域渐近增强与感受野结合的多核近似学习网

为充分提取图像中可辨识信息、提高分类正确率,提出多核近似学习网,该网络主要由2部分构成。在特征提取部分,利用二维高斯分布对原始图像进行区域渐进增强,局部感受野和全局感受野被用于充分提取原始图像和区域渐进增强图像中的局部和全局特征,并将其串联以组成代表图像的特征向量。在分类部分,提出多核近似算法,将近似核映射编码出的低秩特征矩阵作为网络的隐藏层,以求解网络的输出权重。为验证该网络的有效性,利用USPS、MNIST和NORB数据集进行实验,实验证明所提出的多核近似学习网能够在局部感受野极端学习机的基础上进一步提取出特征信息,有效提高了分类正确率。     

基于云模型编码算法的图像消噪研究

为了提高图像消噪的质量,采用云模型编码算法.首先通过正态云发生器产生云滴;接着正云滴映射为图像中大于平均灰度的像素,负云滴映射为图像中小于平均灰度的像素,不同云滴的编码则表示不同的像素的灰度特征;然后根据编码规则将图像子块分为平滑块和非平滑块,平滑块区域保持其增强质量;最后给出了基于云模型编码算法的图像消噪模型和算法流程.实验仿真显示该文算法对图像消噪效果最好,能以较大概率找到全局最优解.     

基于行内MPD极值的自适应灰度编码PDP画质提升方法

为改善动态伪轮廓(DFC)及其引起的灰度级损失,提出一种基于行内运动图像干扰(MPD)极值的自适应子场编码方法.该方法通过计算一行图像内出现的DFC极大值及其位置变化判断图像运动状态,再根据图像不同运动状选择DFC极小的灰度编码.对静态图像采用无灰度级损失的全灰阶编码方式,对动态图像采用DFC极小的关键灰度级编码.该方法的运动状态判断和关键灰度级选择均基于行图像的MPD极值完成,实验结果表明:静态图像显示细节丰富完整,动态图像DFC可减轻30％.     

视频图像的压缩传输技术研究

视频图像信号是信息间传递的主要内容之一。介绍视频图像信号的数字压缩传输技术,讨论几种压缩编码方法,给出基于MPEG-2编码的视频图像传输方案,论述JPEG2000编码系统总体流程,并对JPEG2000中感兴趣区域(ROI)算法对视频图像进行压缩的相关技术进行研究。     

支持ROI优先编码策略的自适应码率控制算法

在低码率视频通信中,感兴趣区(ROI)优先编码策略有助于图像主观质量的提高。本文提出了一种简单有效的ROI提取方法,并根据图像复杂度和运动信息给ROI和非感兴趣区(NROI)分别分配码流。对于ROI的编码范畴,文中推导出了高低码率的判断准则,使算法可以自适应地选择码率模型,减少了码率控制误差。另外,本文采用的宏块层编码顺序方案提高了图像的客观质量。实验结果表明,与TMN7和TMN8的算法相比,本文算法能将码率更稳定地控制在目标码率附近,减少了跳帧;图像的客观和主观质量都有了明显的提高。     

简支板振动无线主动控制及驱动器优化布置研究

推导光电层合简支板结构动力学方程及模态控制方程,以规格化后模态控制力指数作为遗传算法的适应度函数,基于二进制编码的遗传算法对用于简支板振动控制的单对、双对光致伸缩驱动器布局进行优化,计算机仿真结果表明优化后的驱动器布局方案可有效提高板结构振动控制的有效性。在此基础上进一步对板结构多模态振动控制进行探讨,提出适用于板结构多模态振动控制的驱动器布局优化方法及振动控制方案,仿真算例表明该方法可有效地对简支板前二阶模态进行振动无线控制。     

基于预测的多描述图像编码冗余插入的研究

为了研究图像、视频在不可靠网络上传输的鲁棒性问题,系统采用多描述编码方法,该方法通过去除冗余信息以达到数据的压缩,同时保留一部分冗余信息使得编码后的数据流在网络上传输具有一定的鲁棒性.本文针对采用多相下抽样实现的多描述编码,提出了一种新的基于预测的预处理和后处理方案,该方案能对多描述编码产生的数据流中冗余信息进行灵活插入,以达到多描述编码中的中央解码器与边沿解码器的效率进行拆衷控制.仿真实验结果表明该方法计算复杂度降低,冗余控制的灵活性大,编码后的数据流更能适应各种网络传输状况.     

Efficient bit‐plane coding scheme for fine granular scalable video coding

In this paper, we propose a new efficient bit‐plane coding method for fine granular scalable (FGS) video coding. The general structure of the proposed bit‐plane coding method is based on the traditional bit‐plane coding scheme in MPEG‐4 FGS. However, to enhance coding efficiency of bit‐plane encoding, we apply an efficient probability estimation scheme through employing the binary arithmetic coding. For probability estimation, various context models are designed to take advantage of the characteristics of each bit‐plane as well as the correlations of symbols among different bit‐planes. Experimental results show that the proposed FGS coding scheme provides better coding performance, compared to the well‐known FGS coding schemes in MPEG‐4 FGS and JSVM. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 16, 113–120, 2006.     

Selective and adaptive signal hiding technique for security of JPEG2000

In this article, we proposed a selective partial image encryption scheme of Secure JPEG2000 (JPSEC) for digital cinema or any other JPEG2000‐based applications. It makes a scalable encryption scheme possible on the basis of a trade‐off relationship between the encryption effect and the encryption cost. The encryption scheme was designed to activate during the image compression process, which is between quantization and entropy coding. Three data selection schemes were involved to select the parts of data to be encrypted: subband selection, data bit selection, and random selection of coefficients. The experimental results with over 3000 test images revealed that the PSNRs were between about 9.5 to 7.5 dB when the portion of the encrypted data by this scheme was between 1/4096 and 1/256. As the encryption effect is reasonably high with very low cost, the proposed scheme has high potential to provide secure communications in a variety of wired/wireless scenarios. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 277‐284, 2010     

Robust network coding against path failures

In this study, an approach for robust network coding is introduced for multicast in a directed acyclic network in the presence of network edge failures. The proposed designs aim at combating the resulting path failures, which result in interestingly scalable solutions. A robust network coding scheme (RNC1) is proposed that, devising a rate-path diversity trade-off for the receivers, attains the post-failure capacity of the network with high probability. The scheme is receiver based and can also be applied for correcting random erasures. Next, a rate-guaranteed robust network coding scheme (RNC2) is proposed. The code guarantees the maximum rate for a predetermined number of path failures. The scheme, of course, attains the refined Singleton bound for the edge failure model. A path failure may not necessarily reduce the network capacity, as the remaining intact edges within the network may still facilitate backup paths from the source to the sinks. We introduce RNC3 to employ such backup paths in addition to the original paths and guarantee multicast at a certain rate in the presence of all edge/path failure patterns that do not reduce the capacity below this rate. All the three proposed schemes for multicast are robust to a number of edge failures that may, in general, exceed the refined Singleton bound. Our analyses indicate that the design complexities and the required field sizes grow as a function of the number of network paths, as opposed to the number of network edges because of prior schemes.     

Dynamic selective information hiding based on search order coding with low bit rate

Abstract

A low bit rate information hiding scheme is important for efficient communication. According to our observation, in a search order coding based (SOC based) hiding method, the case distribution generated from different images and from different secret strings is different. Based on this characteristic, we designed a dynamic selective, SOC based, information hiding scheme to achieve a desirable compression effect. That is, depending on different case distributions, we used different coding modes to reduce the bit rate more effectively. The main concept of our design is to let the two cases that occur most frequently use one-bit indicators and to let the remaining two cases use four-bit indicators to indicate the following coding types. The experimental results showed that the proposed scheme has a lower bit rate than other SOC based information hiding schemes. As a result, the proposed information hiding scheme is more practical for real world applications.     

Reversible Data Hiding Based on Run-Level Coding in H.264/AVC Video Streams

This paper presents a reversible data hiding (RDH) method, which is designed by combining histogram modification (HM) with run-level coding in H.264/advanced video coding (AVC). In this scheme, the run-level is changed for embedding data into H.264/AVC video sequences. In order to guarantee the reversibility of the proposed scheme, the last nonzero quantized discrete cosine transform (DCT) coefficients in embeddable 4×4 blocks are shifted by the technology of histogram modification. The proposed scheme is realized after quantization and before entropy coding of H.264/AVC compression standard. Therefore, the embedded information can be correctly extracted at the decoding side. Peak-signal-noise-to-ratio (PSNR) and Structure similarity index (SSIM), embedding payload and bit-rate variation are exploited to measure the performance of the proposed scheme. Experimental results have shown that the proposed scheme leads to less SSIM variation and bit-rate increase.     

Efficient secure channel coding based on quasi-cyclic low-density parity-check codes

A secure channel coding (joint encryption-channel coding) scheme provides both data security and reliability in one combined process to achieve faster processing and/or more efficient implementation. The issue of using quasi-cyclic low-density parity-check (QC-LDPC) codes in a symmetric-key secure channel coding scheme is addressed. A set of this class of LDPC codes has recently been recommended by the NASA Goddard Space Flight Center for near-earth and deep-space communications. The proposed scheme provides an efficient error performance, an acceptable level of security and a low-complexity practicable implementation. The results indicate that the proposed scheme can efficiently employ large QC-LDPC codes to achieve a relatively smaller secret-key size to be exchanged by the sender and the receiver, and higher information rates in comparison with the previous symmetric-key McEliece-like schemes. Simulation results indicate that there is no trade-off between the error performance and the security level of the proposed scheme unlike that of the previous ones. These characteristics make the proposed scheme suitable for high-speed communications, such as satellite communication systems.     

基于小波包分解复杂度可分级的音频编码算法

提出了一种基于小波包分解的复杂度可分级的音频编码算法。该算法对信号进行复杂度可分级的不完全不波包分解,并充分利用人耳的听觉特性和不同子带间小波系数的相关性对系数进行零树编码,不仅可在低码率上获得透明质量的重构信号,而且具有复杂度可分级编,解码和多码率可分级编码的功能,可在具有不同计算能力的计算机上实时实现音频编码的解码。     

Multispectral plasmon induced transparency in coupled meta-atoms

We introduce an approach enabling construction of a scalable metamaterial media supporting multispectral plasmon induced transparency. The composite multilayered media consist of coupled meta-atoms with radiant and subradiant hybridized plasmonic modes interacting through the structural asymmetry. A perturbative model incorporating hybridization and mode coupling is introduced to explain the observed novel spectral features. The proposed scheme is demonstrated experimentally by developing a lift-off-free fabrication scheme that can automatically register multiple metamaterial layers in the transverse plane. This metamaterial which can simultaneously enhance nonlinear processes at multiple frequency domains could open up new possibilities in optical information processing.     

Optimization of wireframe model adaptation and motion estimation in a rate-distortion framework

A rate-distortion framework is used to define a very low-bit-rate coding scheme based on wireframe model adaptation and optimized selection of motion estimators. This technique achieves maximum reconstructed image quality under the constraint of a target bit rate for the coding of the vector field and the wireframe representation information. First, a complete scheme is proposed for hybrid two-dimensional (2D) and 3D motion estimation and compensation. The wireframe adaptation and updating is optimized for hybrid motion estimation in the rate distortion sense. A more sophisticated technique, adapted to the requirements of a very low-bit-rate coder is also proposed which considers also the transmission of the prediction error corresponding to the particular choice of the motion estimator for each object in the scene. Experimental results illustrating the performance of the proposed techniques in very low-bit-rate image sequence coding application areas are presented and evaluated. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 238–247, 1998     

Image coding based on wavelet feature vector

In this article, an efficient image coding scheme that takes advantages of feature vector in wavelet domain is proposed. First, a multi‐stage discrete wavelet transform is applied on the image. Then, the wavelet feature vectors are extracted from the wavelet‐decomposed subimages by collecting the corresponding wavelet coefficients. And finally, the image is coded into bit‐stream by applying vector quantization (VQ) on the extracted wavelet feature vectors. In the encoder, the wavelet feature vectors are encoded with a codebook where the dimension of codeword is less than that of wavelet feature vector. By this way, the coding system can greatly improve its efficiency. However, to fully reconstruct the image, the received indexes in the decoder are decoded with a codebook where the dimension of codeword is the same as that of wavelet feature vector. Therefore, the quality of reconstructed images can be preserved well. The proposed scheme achieves good compression efficiency by the following three methods. (1) Using the correlation among wavelet coefficients. (2) Placing different emphasis on wavelet coefficients at different decomposing levels. (3) Preserving the most important information of the image by coding the lowest‐pass subimage individually. In our experiments, simulation results show that the proposed scheme outperforms the recent VQ‐based image coding schemes and wavelet‐based image coding techniques, respectively. Moreover, the proposed scheme is also suitable for very low bit rate image coding. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 123–130, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20045