Variable Bit Rate Fuzzy Control for Low Delay Video Coding

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.

Improved Rate Control Using Statistical Information in Unit-Layer for H.264/AVC

The purpose of this paper is to improve allocation of the number of bits by estimating the target bits in H.264/AVC rate control.In the scheme,an enhancement method of the target unit-layer bit allocation is proposed,which uses a frame and unit complexity estimation to improve the existing mean absolute difference(MAD)complexity measurement.Using the statistical characteristics,we obtain change of occurrence bit about QP to apply the bit amount by QP from the video characteristics in the estimated bit amount of the current frame.Simulation results show that not only the proposed rate control scheme could achieve time saving of more than 99% over existing rate control algorithm,but also PSNR and bit rate were almost the same as the performance in all the sequences.

Efficient Rate Control Algorithm for Multi-view Video Coding

Rate control is one of the key factors influencing the multi-view video transmission.However,there is not a rate control algorithm in the existing Joint Multi-view Video Coding Model.In this paper,an efficient rate control algorithm and a bit allocation strategy for multi-view video coding are proposed.In order to obtain the consistent view quality,a bit allocation model based on the Lagrange optimum algorithm is firstly proposed.Secondly,considering the encoding statistical characteristics of different view types,a view weighting factor is introduced,and it will help improve the precision of bit allocation among views.Compared with the fixed QP control strategy,experiment results show that the proposed algorithm can efficiently control the bit rate and obtain more consistent views,with video visual quality improved.

BUFFER DIMENSIONING FOR RATE-BASED CONTROL IN ATM NETWORK

Available Bit Rate (ABR) service has been developed to support data applications to asynchronous transfer mode (ATM) networks.Since a ratebased feedback flow control mechanism has been selected as a standard by ATM Forum,buffering becomes an issue that needs intensive study.In this paper,the queuing performance in a switch is studied in detail.It is theoretically proven that the goals of no cell loss and full utilization of link capacity can be achieved by choosing an appropriate buffersize and threshold of the switch buffer which is supported by our simulation results of a complex network.

Novel Rate-Control Algorithm Based on TM5 Framework

Rate control is a key technology in the fields of video coding and transmission, and it has attracted a great attention and has been studied extensively. The TM5 framework of MPEG-2 is a classical rate control algo-rithm and has being widely used. However, it has some underlying drawbacks during practical applications such as the poor rate control precision and high computational complexity. Hence, in this paper, a novel rate-control algorithm based on the TM5 framework is proposed. The drawback of the target bit allocation method of the original TM5 algorithm is firstly analyzed and improved. Then, a new rate-distortion model is incorporated into the rate control algorithm to implement rate prediction to enhance the rate-control precision. Meanwhile, the macro-block (MB) level rate control is adapted to be frame level to reduce the computational complexity. Experiments are conducted and some results are given. Compared with the original TM5 algo-rithm, the improved novel algorithm not only can enhance the rate-control precision but also can reduce the complexity and the fluctuation of decoded image quality.

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。

基于时域依赖的编码树单元级零延时码率控制算法

基于高效视频编码标准的x265编码器根据图像复杂度来分配比特,复杂图像往往包含运动变化较大的高频信息,其时域相关性较弱且消耗较多比特,导致分配给运动变化平缓图像的比特减少,进而影响编码质量且码率波动较大。同时,x265编码器采用独立率失真优化技术编码,忽略了编码单元间在时域上的相关性,进而损失编码性能。针对上述问题,提出一种基于时域依赖的编码树单元级码率控制算法。首先,根据迭代策略寻找最合适的量化参数进行帧级比特分配;其次,建立零延时的失真时域反向传播模型并计算失真影响因子;最后,将失真影响因子用于调整编码单元的拉格朗日乘子及量化参数。实验结果显示,相较于x265-3.6的码率控制算法,所提算法的平均BD-rate码率节省达到5.6%。

无人机航拍视频码率控制算法优化

高效率视频编码(HEVC)在实际应用中很难满足无人机航拍领域的需求。针对此问题,提出一种基于缓冲区状态及视频显著性的码率控制算法。对预处理后的帧进行颜色、纹理特征提取,并采用log-Gabor滤波器对其进行特征滤波,得到当前帧的显著图;计算每帧和每个最小单元(CTU)的显著性权重;以帧的显著性权重和缓冲区状态指导帧层比特分配,以CTU的显著性权重指导CTU层比特分配。实验结果表明,提出的算法可以在缓冲区维持在一个平稳状态的前提下,提高0.61 dB视频显著区域的峰值信噪比,更适用于无人机航拍的场景。

Frame-layer bit allocation for multi-view video coding based on frame complexity estimation

Current multi-view video coding （MVC） reference model in joint video team （JVT） does not provide efficient rate control schemes. This paper presents a rate control algorithm for MVC by improving the quadratic rate-distortion （R-D） model. We reasonably allocate bit-rate among views based on the correlation analysisl The proposed algorithm consists of three levels to control the rate bits more accurately, of which the frame layer allocates bits according to the frame complexity and the temporal activity. Extensive experiments show that the proposed algorithm can control the bit rate efficiently.

Intelligent Flow Control Technique of ABR Service in ATM Networks Based on Fuzzy Neural Networks

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一种基于感兴趣区域的监控类视频编码码率控制算法

为了提高有限码率下基于高效率视频编码(high efficiency video coding,HEVC)监控类视频的编码性能,提出了一种基于感兴趣区域的码率控制改进算法。对于帧层,以编码帧的信息熵和参数调整因子构造一种新的帧层位权重,用于指导帧层目标比特分配;对于最大编码单元(largest coding unit,LCU)层,以LCU的空间复杂度纹理因子和时间复杂度运动因子为感兴趣因子,与特征量化加权系数一起用于指导LCU层目标比特分配,并对模型参数进行自适应更新。性能测试结果表明,提出的算法在低延迟P帧和低延时B帧配置下,与HEVC码率控制算法相比,率失真性能平均分别提高了14.2%和12.2%,结构相似性平均分别提高了0.00483和0.00371,且具有稳定的码率控制精度和较低的编码复杂度。

优化编码树单元级比特分配算法

新一代视频编码标准H.266/VVC(Versatile Video Coding)的码率控制算法采用编码参数相互独立的率失真优化技术。然而,同一帧内的编码树单元(CTU)间在空域上相互影响,且存在全局编码参数;同时,CTU级比特分配公式采用近似的编码参数分配比特,进而降低了码率控制精度和编码性能。针对上述问题,提出空域全局优化CTU级比特分配算法RTE_RC(Rate Control with Recursive Taylor Expansion),并通过递归算法逼近全局编码参数。首先,建立空域全局优化比特分配模型;其次,应用递归算法求解CTU级比特分配模型中的全局拉格朗日乘子;最后,优化编码单元的比特分配并对编码单位进行编码。实验结果表明,在低延时P(Prediction)帧(LDP)配置下,与码率控制算法VTM_RC相比,所提算法的码率控制误差由0.46%下降至0.02%,码率节省了2.48个百分点,编码时间下降了3.52%,显著提升了码率控制精度和率失真性能。

静态推靠式旋转导向控制模型与造斜率预测方法

推靠式旋转导向工具的防斜、稳斜能力强,能基本满足复杂地层安全高效钻进的需要,但目前的造斜率预测方法没有考虑推靠块控制方式及钻进过程的影响,存在造斜率预测精度低的问题。为此,考虑导向工具的结构特性,建立了静态推靠式旋转导向控制模型,给出了可靠的导向力控制方案,利用下部钻具组合力学模型及钻头–地层相互作用模型,得到了基于零侧向钻速条件下的造斜率预测模型,并引入折算系数对造斜率预测结果进行了修正。实例计算及敏感性分析结果表明,该方法预测精度高,能够满足井眼轨迹精确控制的需要;导向合力、钻压、钻头与稳定器的距离对推靠式旋转导向工具的造斜能力影响显著,现场施工时为了充分发挥导向合力的作用,要适当减小钻头与稳定器的距离、降低钻压,以提高旋转导向工具的造斜能力。研究结果为旋转导向钻具组合优选、钻井参数优化等提供了理论依据。

可调激光通信传输系统的信号调制方法研究

考虑到可调激光通信传输系统的信号振幅控制效果较差的问题,导致信号误比特率较高、安全性能差。为此,设计新的应用于可调激光通信传输系统的信号调制方法。根据信号种类,构建可调激光通信传输系统信号模型。设计新型振幅调制方法,控制系统中信号噪声量。对通信信号多比特差分进行检测,剔除信号中高斯白噪声,降低噪声影响。仿真实验结果表明,本方法在最大信号增益下误比特率最低达到0.02;信号脉冲为L=8时误比特率最低达到0.01;增加干扰信号分量情况下误比特率最低达到0.01,在多种实验环境中均可降低信号调制误比特率,同时对信号进行调制的精度始终保持在90%以上,具有较好的性能。

H.263活动图像编码器码率控制研究

本文分别在图像层和宏块层进行 Ｈ２６３ 的码率控制。在图像层采用后向自适应控制的方法，通过引入量化步长因子—编码输出比特数映射表，确定每帧图像量化步长因子的基准值。在宏块层采用前向控制的方法，根据视觉掩蔽特性设计模糊分类器，确定人眼对每个宏块的敏感程度和相应的量化步长因子。能在视频输出码率恒定的条件下，保持图像质量的稳定，取得较好的视觉效果。

一种基于视频的彩色图像隐藏方法

描述了一种基于MPEG-2视频流的彩色图像信息隐藏方法,该方法利用人眼的视觉特性,可将彩色图像数据隐藏在人眼不敏感的高空间频域及视频运动区域,有较好的隐蔽性,同时采用了视频码率调节的方法,使藏图视频码流长度保持基本不变。该方法在PC机上实验,得到较好的实验结果。

一种率失真最优的JPEG2000码率自适应控制算法

为解决高分辨率航测图像数据量庞大问题,在研究JPEG2000码率控制算法的基础上,提出一种新的码率预分配自适应控制算法。对图像进行小波分解后,将去除最低频的子带小波系数建模为高斯分布。基于率失真理论推导出每个码块在总码率一定的情况下编码中实际应当贡献的码率,在熵编码时实时截止,而对最低频子带进行完整无失真编码。该算法实现码流的实时截断,减少编码器的计算量和存储空间,提高编码效率。试验结果表明,在图像压缩码率不是很高的情况下(>0.5bpp),采用码率预分配自适应控制算法模型,图像压缩效果要明显好于对整个频带都默认为高斯分布时的效果。

基于码率预分配的JPEG2000自适应率控制算法

该文提出一种基于码率预分配和反馈控制的自适应率控制算法。算法引入了预测模板,对图像小波变换和量化后EBCOT编码码块的有效比特平面进行独立的熵估计,并以码块估计熵总和指导码率预分配,同时T2编码器由预分配编码比特率自适应地反馈控制编码深度、完成优化截取。实验结果表明,该算法码率分配精确,并有效地减少了编码器计算量和存储量,提高了编码效率,算法复杂度低,易于硬件实现。

支持ROI优先编码策略的码率控制方案

低码率视频通信应用日益广泛 ,感兴趣区 (ROI)优先编码策略的应用越来越重要。应用ROI优先编码策略时 ,感兴趣区编码并不是低码率编码 ,而属于高码率编码范畴。现有码率控制方案没有考虑到这一事实 ,导致了不应有的控制误差。本文正是针对这一问题 ,提出了一种码率控制框架 ,并设计了一种简单有效的感兴趣区码率控制方案。本文方法经过简单推广 ,还可用于MPEG 4等基于视频对象编码器的码率控制。

基于输入图像内容的比特率控制

在静止图像的压缩中 ,为得到固定大小的码流文件 ,有必要根据输入图像的特点 ,自适应地控制量化器的参数 ,从而控制输出压缩图像的比特率 .JPEG标准未给出比特率控制方法 ,而一些传统的比特率控制方法为专用的压缩解压缩系统设计 ,并不适用在于开放的基于交换格式的 JPEG压缩系统 .本文提出一种和 JPEG标准完全兼容的比特率控制算法 ,按照输入图像的活动性 ,计算相应的压缩质量因子 ,自适应地为每个 8× 8的块分配比特数 ,并且在熵编码时调整各块的比特数 ,适时启动块截除 ,保证压缩文件的大小不超过预先给定值 .本算法适用于存储容量有限的静止图像压缩的场合 。