基于信息隐藏的图象数据恢复

本文针对JPEG2000基本编码系统,提出一种基于信息隐藏的图象数据恢复方法.首先依据JPEG2000码流的特点设计容错信息,然后对量化前的小波系数进行非线性处理,估算出量化以后各个小波系数上存在冗余的相对大小,根据估算的冗余对各个嵌入点处的嵌入强度进行图象自适应调整,最后将容错信息嵌入到图象的高频分量中,实现对码流的非均等差错保护.     

JPEG2000小波域隐写算法

针对JPEG2000基本压缩编码系统,提出一种基于冗余估算的小波域隐写算法(RE-WDS)。利用JPEG2000标准扩展部分中规定的对量化前小波系数的非线性处理方法,以及人眼的亮度敏感性特点,对每个小波系数的量化冗余进行估算,做到隐写算法与人眼掩蔽特性紧密结合。通过自适应地选择嵌入点并对嵌入强度进行调整,来提高压缩图像的信息隐藏容量,仿真实验证明了算法的可行性和有效性。     

一种实现指纹隐藏的自适应位替换算法

考虑小波变换的多分辨率特性和JPEG2000码流分层的结构,对隐藏的指纹图像生成的比特流按重要性进行排序,再按其排序依次嵌入到小波变换分解后从低到高的各频率子带中,嵌入时根据各系数的冗余度不同自适应地选择嵌入强度,最后根据不可见性和鲁棒性的折衷考虑进行幅度补偿和设置保护区域,实现了一种应用JPEG2000进行指纹隐藏的自适应位替换算法.     

JPEG2000的重要性编码

讨论一种利用图像重要性测度实现静态图像压缩标准JPEG2000编码方法。JPEG2000编码器的技术核心是离散小波变换和：EBCOT，而EBCOT是由两个编码引擎T1，T2组成的，其中T2编码主要是完成码流的组织，其方法是灵活多变的，用户可以根据特殊要求组织码流，只要码流的格式符合JPEG2000的格式即可。本文根据编码图像小波域的系数和时域的像素值计算该系数的重要性，并利用重要性组织完全符合JPEG2000格式的码流。可以利用标准JPEG2000解码器对本算法形成的码流进行解码。     

一种JPEG2000图像传输中位平面错误修复算法

JPEG2000图像的编、解码是逐个位平面进行的,因此码流中任何的数据丢失都会影响最后的位平面及对应的小波系数.为了解决这一问题,JPEG2000标准中将错误的小波系数以零替换,但这一替换将影响很多非零系数,造成某些高频成分丢失.本文结合JPEG2000码流的特点提出一种新的错误修复算法.该算法将根据子带间和未损坏的位平面信息来修复损坏的位平面数据.试验结果表明所提出算法比现有算法的信噪比改进1~3个dB.     

基于JPEG XR的半脆弱数字水印技术研究

研究并实现基于JPEG XR图像稳定性和内容认证的半脆弱数字水印技术。对JPEG XR图像的频率结构和码流结构进行了分析和研究,提取码流中每个分割块的DC系数和LP系数构造基于图像的二值信息,作为数字水印置乱后嵌入到原图像对应像素点YUV色彩空间的Y分量的最低有效位中,然后再对含有水印的图像进行JPEG XR再编码实现水印嵌入。通过比较基于图像的二值信息和嵌入在图像的二值水印信息,进行篡改定位。对含水印图像进行压缩、噪声、剪切等常见攻击实验,结果表明具有较好的稳定性和内容认证能力。     

基于抗差错算术编码的不等差错保护图像传输方法

JPEG2000图像的分层特性要求采用不等差错保护方法以实现高效传输,本文提出了一种新型的不等差错保护方法,对不同位平面采用不同码率的抗差错算术码进行编码.与基于信道编码的不等差错保护方法相比,该方法保持了压缩码流的结构,避免了复杂的信道成帧过程.与已有的基于抗差错算术码的等差错保护方法相比,该方法提高了传输图像的质量.     

一种在JPEG2000中隐藏指纹图像的方法研究

根据JPEG2000码流分层结构及其渐进传输性能,通过对指纹图像生成特征点数据按重要性在空间域位平面排序,结合小波系数的冗余度不同,把指纹信息自适应地从低到高嵌入到各频率子带中,实现了一种应用JPEG2000进行指纹图像隐藏的通信方法。结果表明,在不同压缩因子条件下,该方法提高了信息的隐藏效率并具有较高的不可见性。     

JPEG2000无线标准JPWL性能分析及应用研究

对JPEG2000标准第11部分印JPEG2000无线传输(JPWL)进行了系统描述和性能分析,结合实例提出了具体的应用方法:根据错误敏感度描述符提供的码流错误敏感度,利用错误保护块对码流执行头保护的基础上进行不等错误保护;在解码时利用残余错误描述符提供的码流残余错误信息进行错误隐藏.仿真结果表明,和常用方法相比,该方法能够保持码流中的重要信息,有效地纠正传输误码,显著地提高了解码能力和恢复图像的质量.     

一种基于JPEG2000的小波域信息隐藏算法

针对JPEG2000基本压缩编码的特点,提出了一种应用于隐蔽通信的基于小波域统计特征的隐写算法.该算法首先利用置乱变换对待隐藏图像进行变换处理,并对载体图像进行多分辨率小波分解,然后根据人类视觉系统的掩蔽特性选择重要小波系数,将隐秘信息分别嵌入到重要小波系数的不同频率域中.实验结果表明,算法提高了信息隐藏的容量,较好地...     

A power-based unequal error protection system for digital cinema broadcasting over wireless channels

This paper deals with the efficient and robust wireless broadcasting of JPEG2000 digital cinema (DC) streams from studios to theatres. Several unequal error protection (UEP) techniques have been proposed in literature for the transmission of JPEG2000 images. Some are based on variable forward error correction (FEC) coding applied to different parts of the stream according to their importance. Alternatively, UEP can be achieved by means of unequal power allocation (UPA) schemes based on differentiated transmission power over the stream. On the other hand, in DC applications UPA achieves weak performance if considered as the only protection strategy, unless high-power budget is assigned to transmission. This work proposes a novel hybrid FEC–UPA system adopting the resilience tools of the JPEG2000 wireless (JPWL) standard. The JPWL stream is partitioned into a certain number of packet groups to which “light” FEC coding is applied. Groups are then transmitted through separate wavelet packet division multiplexing (WPDM) sub-channels at different power. Both stream partitioning and UPA are driven by the sensibilities of the JPWL packets to the channel errors. The novelty of the proposed technique relies on the use of JPWL error resilience tools for the codestream partitioning, on optimized UPA among JPWL packets based on genetic algorithms (GA) and supported by “light” FEC channel coding. The proposed system is compared to the state of the art UEP techniques on JPEG2000 transmission. The performance is evaluated in case of transmission over wireless channels with both sparse and packet error statistics. Experiments show that the proposed approach allows achieving an average peak signal-to-noise ratio (PSNR) on the reconstructed frames compliant to the standard quality required by DC applications (40 dB) for bit error rate (BER) up to 10⁻⁴.     

Error-resilient image and video transmission over the Internet using unequal error protection

This paper presents a new bit-plane-wise unequal error protection algorithm for progressive bitstreams transmitted over lossy networks. The proposed algorithm protects a compressed embedded bitstream generated by a 3-D SPIHT algorithm by assigning an unequal amount of forward error correction (FEC) to each bit-plane. The proposed algorithm reduces the amount of side information needed to send the size of each code to the decoder by limiting the number of quality levels to the number of bit-planes to be sent while providing a graceful degradation of picture quality as packet losses increase. We also apply our proposed algorithm to transmission of JPEG 2000 coded images over the Internet. To get additional error-resilience at high packet loss rates, we extend our algorithm to multiple-substream unequal error protection. Simulation results show that the proposed algorithm is simple, fast and robust in hostile network conditions and, therefore, can provide reasonable picture quality for video applications under varying network conditions.     

A vector set partitioning noisy channel image coder with unequalerror protection

A vector enhancement of Said and Pearlman's set partitioning in hierarchical trees (SPIHT) methodology, named VSPIHT, has been proposed for embedded wavelet image compression. A major advantage of vector-based embedded coding with fixed length VQs over scalar embedded coding is its superior robustness to noise. We show that vector set partitioning can effectively alter the balance of bits in the bit steam so that significantly fewer critical bits carrying significant information are transmitted, thereby improving inherent noise resilience. For low noise channels, the critical bits are protected, while the degradation in reconstruction quality caused by errors in noncritical quantization information, can be reduced by appropriate VQ indexing, or designing channel optimized VQs for the successive refinement systems. For very noisy channels, unequal error protection to the critical and noncritical bits with either block codes or convolution codes are used. Additionally, the error protection for the critical bits is changed from pass to pass. A buffering mechanism is used to produce an unequally protected bit stream without sacrificing the embedding property. Extensive simulation results are presented for noisy channels, including bursty channels     

On multirate optimality of JPEG2000 code stream.

Arguably, the most important and defining feature of the JPEG2000 image compression standard is its R-D optimized code stream of multiple progressive layers. This code stream is an interleaving of many scalable code streams of different sample blocks. In this paper, we reexamine the R-D optimality of JPEG2000 scalable code streams under an expected multirate distortion measure (EMRD), which is defined to be the average distortion weighted by a probability distribution of operational rates in a given range, rather than for one or few fixed rates. We prove that the JPEG2000 code stream constructed by embedded block coding of optimal truncation is almost optimal in the EMRD sense for uniform rate distribution function, even if the individual scalable code streams have nonconvex operational R-D curves. We also develop algorithms to optimize the JPEG2000 code stream for exponential and Laplacian rate distribution functions while maintaining compatibility with the JPEG2000 standard. Both of our analytical and experimental results lend strong support to JPEG2000 as a near-optimal scalable image codec in a fairly general setting.     

Progressive transmission of images over memoryless noisy channels

An embedded source code allows the decoder to reconstruct the source progressively from the prefixes of a single bit stream. It is desirable to design joint source-channel coding schemes which retain the capability of progressive reconstruction in the presence of channel noise or packet loss. Here, we address the problem of joint source-channel coding of images for progressive transmission over memoryless bit error or packet erasure channels. We develop a framework for encoding based on embedded source codes and embedded error correcting and error detecting channel codes. For a target transmission rate, we provide solutions and an algorithm for the design of optimal unequal error/erasure protection. Three performance measures are considered: the average distortion, the average peak signal-to-noise ratio, and the average useful source coding rate. Under the assumption of rate compatibility of the underlying channel codes, we provide necessary conditions for progressive transmission of joint source-channel codes. We also show that the unequal error/erasure protection policies that maximize the average useful source coding rate allow progressive transmission with optimal unequal protection at a number of intermediate rates