Rate-distortion理论在H.264编码器中的应用

编码模式的选择是视频编码器控制的一个重要功能,它直接决定了编码器的性能和效率。新的视频压缩协议H.264协议比其它视频压缩协议提出了更多的编码模式,这就决定了H.264编码器不能像H.263编码器一样,通过比较某个门限值来简单地决定采用哪种编码模式。另一方面,根据Rate-distortion理论,在失真度与比特率之间存在一个最佳折衷点。如果确定了合适的拉各朗日(Lagrangian)参数,就能利用拉各朗日公式找到这个最佳折衷点。把这一理论作为H.264编码器的模式选择算法,将会使H.264编码器根据图像内容自适应地选择最佳的编码模式,达到最佳的压缩效果。

Distortion Evaluation of EMP Sensors Using Associated-Hermite Functions

Electromagnetic pulse(EMP)is a kind of transient electromagnetic phenomenon with short rise time of the leading edge and wide spectrum,which usually disrupts communications and damages electronic equipment and system.It is challenging for an EMP sensor to measure a wideband electromagnetic pulse without distortion for the whole spectrum.Therefore,analyzing the distortion of EMP measurement is crucial to evaluating the sensor distortion characteristics and correcting the measurement results.Waveform fidelity is usually employed to evaluate the distortion of an antenna.However,this metric depends on specific signal waveforms,thus is unsuitable for evaluating and analyzing the distortion of EMP sensors.In this paper,an associated-hermite-function based distortion analysis method including system transfer matrices and distortion rates is proposed,which is general and independent from individual waveforms.The system transfer matrix and distortion rate can be straightforwardly calculated by the signal orthogonal transformation coefficients using associated-hermite functions.Distortion of a sensor vs.frequency is then visualized via the system transfer matrix,which is convenient in quantitative analysis of the distortion.Measurement of a current probe,a coaxial pulse voltage probe and a B-field sensor were performed,based on which the feasibility and effectiveness of the proposed distortion analysis method is successfully verified.

Rate-distortion optimized frame dropping and scheduling for multi-user conversational and streaming video

We propose a Rate-Distortion (RD) optimized strategy for frame-dropping and scheduling of multi-user conversa- tional and streaming videos. We consider a scenario where conversational and streaming videos share the forwarding resources at a network node. Two buffers are setup on the node to temporarily store the packets for these two types of video applications. For streaming video, a big buffer is used as the associated delay constraint of the application is moderate and a very small buffer is used for conversational video to ensure that the forwarding delay of every packet is limited. A scheduler is located behind these two buffers that dynamically assigns transmission slots on the outgoing link to the two buffers. Rate-distortion side information is used to perform RD-optimized frame dropping in case of node overload. Sharing the data rate on the outgoing link between the con- versational and the streaming videos is done either based on the fullness of the two associated buffers or on the mean incoming rates of the respective videos. Simulation results showed that our proposed RD-optimized frame dropping and scheduling ap- proach provides significant improvements in performance over the popular priority-based random dropping (PRD) technique.

Enhanced stability and rate performance of zinc-doped cobalt hexacyanoferrate (CoZnHCF) by the limited crystal growth and reduced distortion

Cobalt hexacyanoferrate (CoHCF) is a potential cathode for aqueous Na-ion batteries due to its high theoretical specific capacity (170 m Ah g^(-1));however,its lower rate capability and cyclability limit its applications.Structural distortion at a weak N-coordinated crystal field during cycling disintegrates Co,yielding an irreversible reaction.Different Zn amounts ranging 0–1 were added to the Co site to suppress the structural irreversibility of CoHCF,yielding Co_(1-x)Zn_(x)HCF powder;this Zn (x≤0.09) addition reduced the powder’s dimension because the lower four coordination of Zn–N,not the six coordination of Co–N,limits the powder growth.Simultaneously,a small lattice parameter and interaxial angle (~90°) are obtained,implying that a narrower Co_(1-x)Zn_(x)HCF inner structure is formed to accommodate Na ions.Moreover,the electronic conductivity of Co_(1-x)Zn_(x)HCF gradually increased within 0–0.09 range.A smaller particle size with a high surface area leads to a near-surface-limited redox process,similar to a capacitive reaction.Both the surface-limited reaction and electronic conductivity enhances the reversibility due to the smaller charge transfer resistance at the electrode/electrolyte interface caused by Zn addition.Replacing redox-active Co with non-active Zn amount of 0.07 (Co_(1-x)Zn_(x)HCF) slightly reduces the specific capacity from 127 to 119 mAh g^(-1)at 0.1 A g^(-1)due to the shrunken Co charging sites.Rate performance is enhanced by compromising the capacity and reduced distortion,resulting in 81%retention at a 20-times-faster charging rate.Notably,the Co_(1-x)Zn_(x)HCF sample exhibited the good stability while preserving 74%of the initial capacity at 0.5 A g^(-1)after 200 cycles.

Dynamic Reconfigurable Structure with Rate Distortion Optimization

The Rate Distortion Optimization(RDO)algorithm in High Efficiency Video Coding(HEVC)has many iterations and a large number of calculations.In order to decrease the calculation time and meet the requirements of fast switching of RDO algorithms of different scales,an RDO dynamic reconfigurable structure is proposed.First,the Quantization Parameter(QP)and bit rate values were loaded through an H⁃tree Configurable Network(HCN),and the execution status of the array was detected in real time.When the switching request of the RDO algorithm was detected,the corresponding configuration information was delivered.This self⁃reconfiguration implementation method improved the flexibility and utilization of hardware.Experimental results show that when the control bit width was only increased by 31.25%,the designed configuration network could increase the number of controllable processing units by 32 times,and the execution cycle was 50%lower than the same type of design.Compared with previous RDO algorithm,the RDO algorithm implemented on the reconfigurable array based on the configuration network had an average operating frequency increase of 12.5%and an area reduction of 56.4%.

Joint Source-Channel Bit Allocation Based on Expected End-to-End Distortion Model

An adaptive joint source channel bit allocation method for video communications over error-prone channel is proposed.To protect the bit-streams from the channel bit errors,the rate compatible punctured convolution(RCPC)code is used to produce coding rates varying from 4/5 to 1/2 using the same encoder and the Viterbi decoder.An expected end-to-end distortion model was presented to estimate the distortion introduced in compressed source coding due to quantization and channel bit errors jointly.Based on the proposed end-to-end distortion model,an adaptive joint source-channel bit allocation method was proposed under time-varying error-prone channel conditions.Simulated results show that the proposed methods could utilize the available channel capacity more efficiently and achieve better video quality than the other fixed coding-based bit allocation methods when transmitting over error-prone channels.

Distortion-Free Data Embedding Scheme for High Dynamic Range Images

Distortion-free data embedding is a technique which can assure that not only the secret data is correctly extracted but also the cover media is recovered without any distortion after secret data is extracted completely. Because of these advantages, this technique attracts the attention of many researchers. In this paper, a new distortion-free data embedding scheme for high dynamic range （HDR） images is proposed. By depending on Cartesian product, this scheme can obtain higher embedding capacity while maintaining the exactly identical cover image and stego image when using the tone mapping algorithms. In experimental results, the proposed scheme is superior to Yu et aL＇s scheme in regard to the embedding rate——an average embedding rate of 0.1355 bpp compared with Yn et aL＇s scheme （0.1270 bpp）.

R(D) Definition Domain Deriving of Limited Distortion Source Coding With Different Sources

For limited distortion source coding, it is generally considered that the minimum value of the coding average distortion is 0, and the maximum value is the minimum distortion value of making R(D) = 0. This is the definition domain of the information rate distortion function. In this paper, the upper and lower bounds of the information rate distortion function R(D) are derived and computed for the typical sources. The results show that the lower bound of the coding average distortion D is related to the symbol distortion function, which can further improve the theory of limited distortion source coding.

基于光纤传感器的视频图像几何失真校正方法

视频图像在传播过程中会出现信息畸变,致使图像几何失真,为此提出基于光纤传感器的视频图像几何失真校正方法。分析视频图像像素节点在光敏区域分布情况,提取亚像素视差信息,通过面阵CCD图像传感器获取畸变视频图像;利用畸变曲线近似模型计算出视频图像畸变率,确定畸变图像坐标,并结合双线性灰度插值算法推导校正参数,实现视频图像的几何失真校正。实验结果表明,所提方法能够有效校正不同种类的视频图像几何畸变,校正后的图像与原图像相似度高超过0.97,图像边缘模糊程度降低,提高了图像的视觉观测效果。

基于改进变步长LMS算法的谐波电流检测法

针对传统基于瞬时无功功率理论谐波电流检测中的二阶低通滤波器无法同时满足检测精度和响应时间的问题,提出了基于改进的双曲正切函数变步长LMS算法(IVSSLMS)的低通滤波器提取p轴和q轴中直流分量的方法;将两个谐波电流的间隔时间通过适当的调节采样间隔次数来延长,目的是为了达到高次谐波的自相关性能迅速降为零。从理论上分析了算法性能的优越,给出了参数的取值,并在simulink中搭建了仿真模型,仿真实验结果表明,改进后的低通滤波器直流分量的跟踪速度提升了一倍,得到基波正弦波形的THD值下降了0.37%。并得出以下结论:在同样输电条件下,采用改进变步长LMS算法构成低通滤波器加快了直流量的跟踪,提取的基波分量更加接近于理想波形,提升了谐波检测的瞬时性和准确性。

语义通信的数学理论

自从1948年经典信息论诞生以来,在其指导下,现代通信技术已经逼近了理论性能极限,例如信息熵H(U)、信道容量C=max_(p(x))I(X;Y)以及率失真函数R(D)=min_(p(x|x):Ed(x,x)≤D)I(X;X)。长期以来,由于经典信息论只研究语法信息,限制了通信科学的进一步发展。近年来,研究语义信息处理与传输的通信技术获得了学术界的普遍关注,语义通信开辟了未来通信技术发展的新方向,但还缺乏一般性的数学指导理论。为了解决这一难题,构建了语义信息论的理论框架,对语义信息的度量体系与语义通信的理论极限进行了系统性阐述。首先,通过深入分析各类信源的数据特征,以及各种下游任务的需求,总结归纳出语义信息的普遍属性——同义性。由此指出语义信息是语法信息的上级概念,是许多等效或相似语法信息的抽象特征,表征隐藏在数据或消息背后的含义或内容。将语义信息与语法信息之间的关系命名为同义映射,这是一种“一对多”映射,即一个语义符号可以由许多不同的语法符号表示。基于同义映射f这一核心概念,引入语义熵H_(s)(U)作为语义信息的基本度量指标,表示为信源概率分布与同义映射的泛函。在此基础上,引入上/下语义互信息I^(s)(X;Y)(I_(s)(X;Y)),语义信道容量C_(s)=max_(f_(xy))max_(p_((x)))I^(s)(X;Y)以及语义率失真函数R_(s)(D)=min_({f_(x),f_(x)})min_(p(x|x):Ed_(s)(x,x)≤D)I_(s)(X;X),从而构建了完整的语义信息度量体系。这些语义信息度量是经典信息度量的自然延伸,都由同义映射约束,如果采用“一对一”映射,则可以退化为传统的信息度量。由此可见,语义信息度量体系包含语法信息度量,前者与后者具有兼容性。其次,证明了3个重要的语义编码定理,以揭示语义通信的性能优势。基于同义映射,引入新的数学工具——语义渐近均分(AEP),详细探讨了同义典型序列的数学性质,并应用随机编码和同义典型序列译码/编码,证明了语义无失真信源编码定理、语义信道编码定理和语义限失真信源编码定理。类似于经典信息论,这些基本编码定理也都是存在性定理,但它们指出了语义通信系统的性能极限,在语义信息论中起着关键作用。由同义映射和这些基本编码定理可以推断,语义通信系统的性能优于经典通信系统,即语义熵小于信息熵H_(s)(U)≤H(U),语义信道容量大于经典信道容量C_(s)≥C,以及语义率失真函数小于经典率失真函数R_(s)(D)≤R(D)。最后,讨论了连续条件下的语义信息度量。此时,同义映射转换为连续随机变量分布区间的划分方式。相应地,划分后的子区间被命名为同义区间,其平均长度定义为同义长度S。特别是对于限带高斯信道,得到了一个新的信道容量公式C_(s)=B log[S^(4)(1+P/N_(0)B)],其中,平均同义长度S表征了信息的辨识能力。这一容量公式是经典信道容量的重要扩展,当S=1时,该公式退化为著名的香农信道容量公式。综上所述,语义信息论依据同义映射这一语义信息的本质特征,构建了语义信息的度量体系,引入新的数学工具,证明了语义编码的基本定理,论证了语义通信系统的性能极限,揭示了未来语义通信的巨大性能潜力。

柔性直流输电系统的高频谐波保护方法与工程实践

柔性直流输电系统受电力电子设备本身特性以及控制系统影响,在多种运行工况下易出现不同频率的振荡问题。作为实现设备安全和电网稳定运行的决定因素,保护系统应实现对系统谐波的准确监测以及可靠动作。根据高频振荡时的电流能量累积作用,给出了基于反时限动作的电流类谐波保护算法。基于高频谐波电压特性,分别给出了过零点监测保护算法、谐波畸变率保护算法以及宽谐波保护算法,各保护算法相互配合,实现对不同电压振荡类型的全面保护。最后,给出了国内柔性直流工程实践中配置的高频谐波保护,结合保护原理对系统发生高频振荡后的动作特性进行分析,验证了高频谐波保护的有效性和准确性。

一种基于视觉显著性的码率控制算法

针对当前高效视频编码的码率控制算法未能充分确保视频显著区域的图像质量问题,提出了一种基于视觉显著性的码率控制算法。首先,采用基于图的流形排序显著检测算法获取视频的显著区域;其次,在图像编码过程中,为每个编码单元(Coding Unit,CU)建立基于视觉显著性的加权失真公式,将显著性值作为权重;最后,通过求解得到拉格朗日乘子λ,并根据原始码率控制算法中的λ与量化参数(Quantization Parameter,QP)的关系为每个CU确定QP。试验结果表明,该算法有效地根据视频内容的显著性权重实现了码率的合理分配,并在保持码率控制准确性的同时,提升了视频显著区域的图像质量。

高速率连续波泥浆脉冲解码试验管线仿真分析

随着国内深井、超深井钻探需求增加,连续波泥浆脉冲技术正向远距离、高速率方向发展。中海油服自主搭建了地面6000 m泥浆循环试验系统,由于测试仪器上游采用50.8 mm软管,管线压耗大且变径反射干扰严重,远距离高速率解码试验研究受限。针对此问题,基于试验系统建立了简化脉冲器-管线数值模型,研究50.8 mm软管对连续波信号的影响规律,并通过解码试验验证。研究结果表明:测试仪器上游50.8 mm软管与循环管线存在扩径,产生的反射波与发生波叠加导致波形畸变,且随着频率升高,发生波畸变越严重。50.8 mm软管内径小,管线沿程摩阻压降大,压力波的传输衰减程度高于等长的地下直管。50.8 mm软管换成101.6 mm软管,消除变径反射和降低沿程摩阻压降后,低频压力波波形改善,传输后幅值提高75%以上,有效降低了解码误码率。地面6000 m管线解码试验传输速率从6 bps提高至8 bps,验证了数值仿真分析结果。

结合人眼视觉感知特性的光场图像编码方法

光场图像可同时记录场景中光线强度与方向信息,但要求更多的存储、传输资源,因而需要高效的编码方案。提出了一种结合人眼视觉感知特性的光场图像编码方法,实现了端到端的感知光场编码。考虑到在光场编码相同的失真等级情况下,显著性区域的失真更易被察觉,提出光场图像感知编码方法。针对子孔径图像感知冗余,考虑到像素域恰可察觉失真(Just Noticeable Distortion,JND)模型没有关注显著区域特性,构建了结合显著性的JND掩蔽模型;其后,针对每一帧子孔径图像进行考虑人眼感知的自适应码率分配。实验结果表明,在低延时模式下,与高效视频编码(High Efficiency Video Coding,HEVC)方法相比,所提方法在相同的显著性加权峰值信噪比SW-PSNR质量指标下平均节省16.01%的码率,在与人眼主观感受契合度更高的情况下,实现了光场图像编码效率的提升。

谐波干扰抑制下的低压配电网母线电压自动控制系统

母线电压的平稳程度,直接影响低压配电网的运行安全,因此设计谐波干扰抑制下的低压配电网母线电压自动控制系统。该系统以配电网调度系统的控制需求为前提,在系统无功补偿层引入抗谐波干扰无功发生器获取母线电压的无功补偿量,母线无功控制需求整定层依据该计算结果和母线电压控制指令,结合母线实时运行电压结果,对比判断母线实际电压结果和参考电压之间的差距,确定母线电压所需的无功补偿量,完成电压控制。测试结果显示:该系统能够有效控制母线电压谐波,谐波畸变率低于4.4%;能够保证电压的稳定,电压控制的偏差结果均在±1.5 V之间,母线在相位阶跃和稳态两种情况下的相位误差结果均低于0.075。

Information-Theoretic Limits on Compression of Semantic Information

As conventional communication systems based on classic information theory have closely approached Shannon capacity,semantic communication is emerging as a key enabling technology for the further improvement of communication performance.However,it is still unsettled on how to represent semantic information and characterise the theoretical limits of semantic-oriented compression and transmission.In this paper,we consider a semantic source which is characterised by a set of correlated random variables whose joint probabilistic distribution can be described by a Bayesian network.We give the information-theoretic limit on the lossless compression of the semantic source and introduce a low complexity encoding method by exploiting the conditional independence.We further characterise the limits on lossy compression of the semantic source and the upper and lower bounds of the rate-distortion function.We also investigate the lossy compression of the semantic source with two-sided information at the encoder and decoder,and obtain the corresponding rate distortion function.We prove that the optimal code of the semantic source is the combination of the optimal codes of each conditional independent set given the side information.

有限转角力矩电机电磁转矩与霍尔感应磁场研究

永磁式齿槽式集中绕组形式有限转角力矩电机一般具有较小的气隙,进而可以增加电机的气隙磁密幅值,提高力矩输出能力。根据这一优势,通过理论设计和有限元仿真软件设计出一种符合基本性能要求的旋转式直驱阀有限转角力矩电机,并研究了充磁方向、斜槽对齿槽转矩和输出转矩的影响,从而达到抑制转矩波动、改善转矩波形的目的。根据线性霍尔具有体积小、反馈信号线性度好等优点,选用线性霍尔接收信号,并研究霍尔位置和偏心距对霍尔波形畸变率的影响。研究表明,对霍尔波形进行优化后成功将谐波畸变率从最初的4.9%降低到0.1%以下,这在工程研究领域具有重要参考意义。

社会保险缴费调整、企业资源配置效率与宏观经济效应

文章实证检验了社会保险缴费调整对企业资源配置效率的影响及其宏观经济效应。研究发现,社会保险费率上调挤出了企业资本要素投入,企业难以维系过度依赖人口红利的增长模式,企业整体资源配置效率显著下降;社会保险费率上调通过提高劳动成本,降低企业内部现金流和增加外部融资约束,从而对投资产生了挤出效应;社会保险费率上调通过增加实际缴费额,受融资约束的企业以降低参保程度的方式降低劳动投入。此外,养老金费率降到16%时,样本期间所有企业的总量生产率年均提升了4.24%,说明社会保险降费有助于从成本端提升企业的中长期竞争力。该研究对深入理解社会保险降费引致经济增长的微观企业传导路径具有重要意义。

视频编码失真估计综述

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