G．729标准码本搜索算法分析及优化

G.729用固定码本和自适应码本构成的激励通过合成滤波器恢复出较高质量的语音信号.由于算法复杂耗时过多,不能在DSP上实时实现,其中固定码本搜索和自适应码本搜索是最复杂的模块.介绍了码本搜索方法并进行了改进,使复杂度大大降低.结果表明语音质量没有明显下降.     

基于随机位置选择和矩阵编码的语音信息隐藏方法

针对低速率语音编码问题，该文提出基于G.723.1编码标准的信息隐藏算法。在基音预测编码过程中，通过控制闭环基音周期(自适应码本)的搜索范围，该文结合随机位置选择方法(RPS)和矩阵编码方法(MCM)，实现秘密信息的嵌入，在语音编码过程中实现了信息的隐藏。RPS方法的采用降低了载体码字之间的关联性，MCM方法的采用降低了载体的改变率。实验结果证明，该文算法下PESQ恶化率平均值最大为1.63%，隐蔽性良好。     

TETRA与G.729语音编码算法的比较研究

为了研究TETRA中的ACELP与ITU-TG.729中CS-ACELP两种语音压缩编码算法的异同,分别就以下几个方面对这两种算法进行了比较:预处理、线性预测分析(LPC)、自适应码本的搜索和固定码本的搜索.然后在VC++6.0环境下实现了这两种算法,并对算法的仿真结果进行了对比分析.最后采用ITU-TP.862.1标准感知语音质量评价(PESQ_LQO)对两种算法合成语音的质量进行客观测评,测试结果表明,G.729合成语音的质量比TETRA合成语音的质量要好.     

一种基于优先树脉冲取代的固定码本搜索方法

分析了G.722.2中的固定码本结构及其搜索方法,结合深度优先树与脉冲取代法各自的优点,提出了一种新的方法——基于优先树脉冲取代的固定码本搜索方法,该方法在基本保持语音质量的前提下,可使固定码本搜索计算复杂度降低,从而使G.722.2的编码运行时间进一步减少。实验结果表明,与G.722.2中采用的深度优先树搜索方法相比,基于优先树脉冲取代的固定码本搜索方法可以在不影响语音质量的前提下,使固定码本搜索复杂度降低85%以上。     

基于统计匹配的VoIP说话人特征补偿算法

在VoIP说话人识别中,当使用原始语音(未经过编译码处理)训练的说话人模型识别经过语音编译码处理的测试语音时,系统的识别性能会发生下降.本文给出了一种基于统计匹配和EM(期望最大化)算法的VoIP说话人特征(12阶的LPCC系数)补偿算法,其中对假设失真特征与未失真识别特征间符合非线性(二次函数型)和线性函数关系时的函数参数进行了估计,并使用得到的补偿函数对失真特征进行补偿.实验结果表明,该特征补偿算法对VoIP中广泛使用的G.729 8kb/s、G.723.1 6.3kb/s、G.723.1 5.3kb/s编译码所造成的识别性能下降有较大的改善,其性能也优于CMS(倒谱均值减)方法.     

一种基于G.729的CS-ACELP新算法

在G．729的基本框架下,码本搜索采用次最优部分码本快速搜索法,知觉加权滤波器使用基于声学心理模型的知觉加权滤波器,使得8Kb／s共扼结构代数码激励线性预测语音编码在不降低语音质量的情况下降低计算复杂度。次最优部分码本快速搜索方法虽然降低搜索准确度,但是大大减小了搜索时的数据处理量;声学心理滤波器考虑人耳对不同频率信号的不同敏感度,因而能获得更好的主观音质效果。仿真结果表明,该算法复杂度降低,并取得满意的合成语音质量。     

G.729自适应码书搜索算法的研究

G.729语音编码算法复杂,很大程度上要归因于码书搜索算法。为了降低码书搜索复杂度,G.729的简化版G.729A采用了自适应码书的偶样点开环基音搜索,使得编码复杂度大为降低,不过编码仍要花费很多的时间。通过对G.729码书搜索算法的研究,提出了对自适应码书的改进。改进了自适应码书搜索的G.729编码语音质量不低于G.729A的语音质量,但自适应搜索复杂度大大降低。     

高质量4kb/s FS-ACELP语音编码算法及性能

4kb/s有限状态代数码激励线性预测语音编码算法FS-ACELP是一种具有延时较短,合成语音质量高、算法复杂度较低的语音编码算法.在线性预测(LP)参数量化上,利用了语音帧内和帧间的相关性,对线谱对(LSP)参数使用预测式分裂式矢量量化,获得很高的量化效率.在自适应码本搜索上,采用了有限状态控制分数延时搜索的算法.在保证合成语音质量的同时,有效地降低了运算量.对于随机码本,采用了具有多模结构的代数码本,提高语音合成质量.对于激励码序列的增益,采用了预测式矢量量化,有效地提高了量化精度.经非正式听音测试,4kb/s FS-ACELP的合成语音质量超过了北美8kb/s VSELP,接近G.729 8kb/s CS-ACELP,MOS分约为3.9.     

高质量4kb/s FS-ACELP语音编码算法及性能

4kb/s有限状态代数码激励线性预测语音编码算法FS-ACELP是一种具有延时较短、合成语音质量高、算法复杂度较低的语音编码算法.在线性预测(LP)参数量化上,利用了语音帧内和帧间的相关性,对线谱对(LSP)参数使用预测式分裂式矢量量化,获得很高的量化效率.在自适应码本搜索上,采用了有限状态控制分数延时搜索的算法,在保证合成语音质量的同时,有效地降低了运算量.对于随机码本,采用了具有多模结构的代数码本,提高语音合成质量.对于激励码序列的增益,采用了预测式矢量量化,有效地提高了量化精度.经非正式听音测试,4kb/s FS-ACELP的合成语音质量超过了北美8kb/s VSELP,接近G.729 8kb/s CS-ACELP,MOS分约为3.9.     

8Kb/s脉冲自适应码本激励(PACELP)-一种新的数字移动通信用语音编码方案

数字移动通信近几年来得到长足的发展,而语音低码率编码是其中一项关键技术.本文提出一种脉冲自适应码本激励编码方案.该方案将规则脉冲激励算法和码本激励算法有机地相结合,采用新的有效码本结构,降低码字的维数,提高码字的效率,另外,在最佳激励搜索上采用了脉冲自适应搜索方式,避免了全寻的工作方式,使得码本搜索的计算量大大降低。通过计算机模拟结果表明,该编码方案和美国EIA公布的编码算法相比具有计算量小,所占储存空间少而合成音质几乎不下降等优点.在8Kb/s PACELP能够合成出令人满意的语音质量。而这一切又保证了PACELP算法可以在一块TMS320 C25上实现。     

LPC parameters substitution for speech information hiding

Information hiding techniques adopted in secret communication should meet the requirements of high hiding capacity, real-time and high robustness. For the purpose of real-time speech secure communication, an information hiding algorithm based on the analysis-by-synthesis (ABS) speech coding scheme is presented in this article. This algorithm substitutes secret speech data bits for linear predictive coefficients (LPCs) in linear predictive coding (LPC). Statistics show that the change of voiced signal track is slow and the codebook for LPCs vector is large in ABS coding scheme. Therefore, a new concept, filter similarity, is proposed to determine the LPC parameters for substituting with secret speech information, and to generate multi-codebook for saving storage space to store secret speech information. To achieve the best effects of information hiding, a dynamic threshold is built to make an optimal trade-off among hiding-capacity, security, robustness, transparence and real time. Experiments show that the proposed approach meets the requirements of information hiding and secret communication speech quality. The test results indicate that this approach reaches high hiding capacity with an excellent speech quality and complicating speakers'recognition.     

基于分块最佳预测的可逆数据隐藏

为了提高嵌入算法的性 能,提出一种基于分块最佳预测和直方图平移的灰度图像可逆数据隐藏算法。根据嵌 入阈值,统计 每一图像块中4种预测方案的嵌入容量,选择最大容量对应的预测方案作为该图像块的最佳 预测方案。嵌 入算法充分利用像素值局部相关性,自适应地选择最佳预测方案,有效提高嵌入容量。实验 结果表明,本 文算法在保证图像质量的同时有效提高嵌入容量,算法的整体性能比其它同类算法更优。     

基于帧内预测模式的H.264/AVC视频信息嵌入算法

提出了一种基于帧内预测模式的H.264/AVC视频信息嵌入算法.在秘密信息进行嵌入时,根据人类视觉特性的掩蔽效应,筛选出I帧中纹理密集区域的4×4亮度块,确定为嵌入块.通过秘密信息调制4×4亮度块的预测模式最低有效位,完成秘密信息的嵌入.通过对算法进行仿真实验,证明本算法计算量小,能够实时处理.对视频载体影响小,有一定的嵌入容量,能够保证秘密信息的有效传输.     

Enhanced hybrid image security algorithms for high definition images in multiple applications

Protection of multimedia information from different types of attackers has become important for people and governments. A high definition image has a large amount of data, and thus, keeping it secret is difficult. Another challenge that security algorithms must face with respect to high definition images in medical and remote sensing applications is pattern appearances, which results from existing regions with high density in the same color, such as background regions. An encryption and hiding based new hybrid image security systems are proposed in this paper for the purpose of keeping high definition images secret. First, one hiding method and two encryption methods are used in two hybrid algorithms. The new hiding algorithm proposed here starts by applying reordering and scrambling operations to the six Most Significant Bit planes of the secret image, and then, it hides them in an unknown scene cover image using adding or subtracting operations. Second, two different ciphering algorithms are used to encrypt the stego-image to obtain two different hybrid image security systems. The first encryption algorithm is based on binary code decomposition, while the second algorithm is a modification of an advanced encryption standard. After evaluating each hybrid algorithm alone, a comparison between the two hybrid systems is introduced to determine the best system. Several parameters were used for the performance, including the visual scene, histogram analysis, entropy, security analysis, and execution time.

     

基于二级定位的编码信道信息隐藏算法

分析了以编码信道为载体的信息隐藏算法及容量,指出现有算法存在的问题,提出了一种结合容量上限判断的基于二级定位的信息隐藏算法。所提算法在秘密信息嵌入前首先计算系统隐藏容量上限,并判断是否超出;接着在嵌入位置选择过程中引入二级定位以及循环移位机制。仿真结果表明,相比已有算法,所提算法能较好地避免因隐藏容量过大而导致秘密通道暴露的风险;同时通过二级定位及循环移位机制提高嵌入位置的随机性,避免秘密信息相互覆盖,提升信息隐藏性能。     

Reversible data hiding of a VQ index table based on referred counts

This paper presents a new reversible VQ-based hiding scheme that can recover the original VQ compressed codes after data extraction. Our scheme sorts a VQ codebook using the referred counts. The VQ codebook is then divided into 2^B clusters and half of these clusters are used to embed secret data, in which B denotes the size of the secret data embedded into each VQ index. Compared to Chang et al.’s scheme, which divides a sorted VQ codebook into 2^B?1 × 3 clusters and uses the front one-third clusters to embed secret data, our method can embed more data. Moreover, indicator, index exchanging, and side-match prediction schemes are proposed to further improve our scheme. Under the same sorted VQ codebook, the experimental results demonstrate that our data hiding algorithm has higher capacities and better compression rates.     

High-capacity reversible data hiding in encrypted image based on specific encryption process

This paper proposes a novel reversible data hiding method in encrypted images based on specific encryption process. In the proposed specific encryption algorithm, the stream cipher and prediction error are combined to vacate room for data embedding. After that, a permutation operation is performed on the encrypted image to improve the security. In the embedding process, we can embed a large amount of secret data in the encrypted image by pixel value expansion because most of the pixel values are less than 128 by the specific encryption process. At the receiver end, the encrypted image can be recovered from the marked encrypted image without knowing the secret data. Therefore, even if the recipient only has the encryption key, the original image will be perfectly recovered. If the recipient only has the data-hiding key, the secret data will be extracted. And if the recipient has both keys, the original image and the secret data are both available. The proposed method achieves a higher embedding capacity than that of methods based on vacating room after encryption. It does not require the image owner to perform reversible data hiding techniques on the original image, which is more convenient than methods based on reserving room before encryption. Experimental results demonstrate that the proposed method outperforms other state-of-the-art methods.     

VQ域信息隐藏检测算法

随着信息隐藏技术的发展，基于矢量量化（VQ）的信息隐藏的方法逐渐增多．本文提出了一种VQ域隐藏信息检测方法，首先通过全局搜索在已经解码的无压缩图像中恢复量化码书，然后应用聚类分析的思想将矢量空间中相近的码字归类以判断是否存在隐藏信息，最后根据各个码字的出现概率估计嵌入信息的长度．实验表明，本文提出的算法对隐藏信息的存在性有很高的识别率，对信息量的估计也比较准确．     

在压缩语音编码中集成信息隐藏方法研究

论文针对低速率语音编码过程的特点,提出了一种基于动态码本生成的信息隐藏方法,设计了相应的嵌入和提取算法.该方法解决了现有的基于静态码本分区的信息隐藏方法无法对抗码字统计分析检测的问题.实验表明该隐藏算法在13.3Kbps的载体速率下能获得450bps隐藏容量,而且载密信息的语音质量PESQ值下降不到6%.