目的为了解决当前混沌图像加密技术忽略了随机序列产生的时间延迟现象,且难以克服其自身迭代的周期性,使其序列的自相关性不理想,导致密文安全性不佳等问题。方法引入级联耦合混沌半导体环形激光器,设计基于物理随机位生成器与混沌像素...目的为了解决当前混沌图像加密技术忽略了随机序列产生的时间延迟现象,且难以克服其自身迭代的周期性,使其序列的自相关性不理想,导致密文安全性不佳等问题。方法引入级联耦合混沌半导体环形激光器,设计基于物理随机位生成器与混沌像素交叉互换的图像加密算法。首先引入SHA-256散列函数,利用明文像素值,生成一个256位的密钥,并将其分割为一系列的8位子密钥;利用这些子密钥来计算Logistic-Sine复合映射的初始条件,以输出一组随机序列;根据混沌序列,定义像素交叉互换机制,对输入明文进行预处理,消除相邻像素之间的相关性;基于级联耦合混沌半导体环形激光器,充分利用其自身的时间延迟与交叉反馈的特性,设计物理随机位生成器,以同步输出考虑时间延迟的控制矩阵与随机位流;将Logistic-Sine复合映射输出的混沌序列转换为一个过渡矩阵,联合控制矩阵,定义像素混淆机制,彻底改变明文的像素位置;最后,利用随机位流,设计像素联系扩散函数,改变图像的像素值。结果实验结果显示,与当前混沌加密技术相比,所提算法具有更高的安全性与鲁棒性,能够有效抗击明文攻击,相应的密文熵值约为7.9958,且NPCR(7)Number of Pixel Change Rate(8)、UACI(Unified Average Changing Intensity)分别为99.50%、33.46%。结论所提加密算法具有较高的安全性和抗攻击能力,能够安全保护图像在网络中传输,在信息防伪等领域具有较好的应用价值。展开更多
针对HEVC(High Efficiency Video Coding)码率控制方案中LCU层利用平均绝对误差(MAD)对图像复杂度估计的不准确性和比特分配的不合理性,提出一种基于像素的线性加权的直方图差值(PHOD)的LCU层码率控制算法。该算法引入PHOD作为LCU层的...针对HEVC(High Efficiency Video Coding)码率控制方案中LCU层利用平均绝对误差(MAD)对图像复杂度估计的不准确性和比特分配的不合理性,提出一种基于像素的线性加权的直方图差值(PHOD)的LCU层码率控制算法。该算法引入PHOD作为LCU层的图像相对复杂度度量手段,使得LCU层目标比特根据图像复杂度进行合理调整和准确分配。同时利用已编码帧码流控制的反馈信息进一步对量化参数和拉格朗日乘数调整,获得更精确的量化值和拉格朗日乘数。仿真结果表明,与参考算法比较,改进的算法对于不同运动情况的视频序列有良好的效果,能更加接近目标码率,图像帧间质量波动减小,最终获得较好的图像主观质量和PSNR。展开更多
Rate control plays a critical role in achieving perceivable video quality under a variable bit rate,limited buffer sizes and low delay applications.Since a rate control system exhibits non-linear and unpredictable cha...Rate control plays a critical role in achieving perceivable video quality under a variable bit rate,limited buffer sizes and low delay applications.Since a rate control system exhibits non-linear and unpredictable characteristics,it is difficult to establish a very accurate rate-distortion(R-D)model and acquire effective rate control performance.Considering the excellent control ability and low computing complexity of the fuzzy logic in non-linear systems,this paper proposes a bitrate control algorithm based on a fuzzy controller,named the Fuzzy Rate Control Algorithm(FRCA),for All-Intra(AI)and low-delay(LD)video source coding.Contributions of the proposed FRCA mainly consist of four aspects.First,fuzzy logic is adopted to minimize the deviation between the actual and the target buffer size in the hypothetical reference decoder(HRD).Second,a fast lookup table is employed in fuzzy rate control,which reduces computing cost of the control process.Third,an input domain determination scheme is proposed to improve the precision of the fuzzy controller.Fourth,a novel scene change detection is introduced and integrated in the FRCA to adaptively adjust the Group-of-Pictures(GOP)length when the source content fluctuates.The FRCA can be transplanted and implemented in various industry coders.Extensive experiments show that the FRCA has accurate variable bit-rate control ability and maintains a steady buffer size during the encoding processes.Compared with the default configuration encoding under AI and LD,the proposed FRCA can achieve the target bit rates more accurately in various classical encoders.展开更多
文摘目的为了解决当前混沌图像加密技术忽略了随机序列产生的时间延迟现象,且难以克服其自身迭代的周期性,使其序列的自相关性不理想,导致密文安全性不佳等问题。方法引入级联耦合混沌半导体环形激光器,设计基于物理随机位生成器与混沌像素交叉互换的图像加密算法。首先引入SHA-256散列函数,利用明文像素值,生成一个256位的密钥,并将其分割为一系列的8位子密钥;利用这些子密钥来计算Logistic-Sine复合映射的初始条件,以输出一组随机序列;根据混沌序列,定义像素交叉互换机制,对输入明文进行预处理,消除相邻像素之间的相关性;基于级联耦合混沌半导体环形激光器,充分利用其自身的时间延迟与交叉反馈的特性,设计物理随机位生成器,以同步输出考虑时间延迟的控制矩阵与随机位流;将Logistic-Sine复合映射输出的混沌序列转换为一个过渡矩阵,联合控制矩阵,定义像素混淆机制,彻底改变明文的像素位置;最后,利用随机位流,设计像素联系扩散函数,改变图像的像素值。结果实验结果显示,与当前混沌加密技术相比,所提算法具有更高的安全性与鲁棒性,能够有效抗击明文攻击,相应的密文熵值约为7.9958,且NPCR(7)Number of Pixel Change Rate(8)、UACI(Unified Average Changing Intensity)分别为99.50%、33.46%。结论所提加密算法具有较高的安全性和抗攻击能力,能够安全保护图像在网络中传输,在信息防伪等领域具有较好的应用价值。
文摘针对HEVC(High Efficiency Video Coding)码率控制方案中LCU层利用平均绝对误差(MAD)对图像复杂度估计的不准确性和比特分配的不合理性,提出一种基于像素的线性加权的直方图差值(PHOD)的LCU层码率控制算法。该算法引入PHOD作为LCU层的图像相对复杂度度量手段,使得LCU层目标比特根据图像复杂度进行合理调整和准确分配。同时利用已编码帧码流控制的反馈信息进一步对量化参数和拉格朗日乘数调整,获得更精确的量化值和拉格朗日乘数。仿真结果表明,与参考算法比较,改进的算法对于不同运动情况的视频序列有良好的效果,能更加接近目标码率,图像帧间质量波动减小,最终获得较好的图像主观质量和PSNR。
基金supported by ZTE Industry-Academia-Research Cooperation Funds under Grant No.CON1503180004the Postdoctoral Science Foundation of China under Gant No.2014M552342the Foundation of Science and Technology Department of Sichuan Province,China under Grant No.2014GZ0005
文摘Rate control plays a critical role in achieving perceivable video quality under a variable bit rate,limited buffer sizes and low delay applications.Since a rate control system exhibits non-linear and unpredictable characteristics,it is difficult to establish a very accurate rate-distortion(R-D)model and acquire effective rate control performance.Considering the excellent control ability and low computing complexity of the fuzzy logic in non-linear systems,this paper proposes a bitrate control algorithm based on a fuzzy controller,named the Fuzzy Rate Control Algorithm(FRCA),for All-Intra(AI)and low-delay(LD)video source coding.Contributions of the proposed FRCA mainly consist of four aspects.First,fuzzy logic is adopted to minimize the deviation between the actual and the target buffer size in the hypothetical reference decoder(HRD).Second,a fast lookup table is employed in fuzzy rate control,which reduces computing cost of the control process.Third,an input domain determination scheme is proposed to improve the precision of the fuzzy controller.Fourth,a novel scene change detection is introduced and integrated in the FRCA to adaptively adjust the Group-of-Pictures(GOP)length when the source content fluctuates.The FRCA can be transplanted and implemented in various industry coders.Extensive experiments show that the FRCA has accurate variable bit-rate control ability and maintains a steady buffer size during the encoding processes.Compared with the default configuration encoding under AI and LD,the proposed FRCA can achieve the target bit rates more accurately in various classical encoders.
