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码率分配是无反馈分布式视频编码中的关键技术之一.本文研究编码端快速边信息生成方法,基于边信息和Wyner-Ziv帧各个位平面误码率,提出了一种编码端码率分配算法(Bitplane Error Probability based Encoder Rate Control,BEP_ERC).还提出在编码端精确估计拉普拉斯-柯西混合分布(Laplace-Cauchy Mixture Distribution,LCMD)模型参数α和μ的思想.实验表明本文算法与现有算法相比,率失真性能提升0.1~0.4dB,且降低了编码端计算复杂度. 相似文献
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分布式视频编码中拉普拉斯-柯西混合分布相关噪声模型研究 总被引:2,自引:0,他引:2
该文通过研究变换域分布式视频编码中原始Wyner-Ziv(WZ)帧与相应边信息的残差系数特性,发现大残差和小残差系数统计分布与传统的拉普拉斯分布存在一定偏差。为了减少这种差异,提出一种拉普拉斯-柯西混合分布(LCMD)相关噪声模型及其参数估计算法。该混合模型利用改进的拉普拉斯分布描述小残差系数的分布,采用柯西分布描述大残差系数。实验结果表明该文提出的混合模型能较精确地描述WZ帧和边信息间的残差系数分布,从而有效地改善了变换域分布式视频编码的率失真性能,并减少系统解码端计算复杂度。 相似文献
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分布式视频编码框架中,准确地估计WZ帧与辅助边信息之间的统计特性,也即对它们之间的虚拟"相关信道"准确设计模型,并估计其参数,对于提高编码压缩效率,进而准确进行码率控制十分重要.讨论了模拟信道的模型选取和参数优化,研究了视频序列中常用的Laplace模型和Gauss模型,提出了一种带校正系数的虚拟相关信道参数估计方法,验证了虚拟相关信道更接近残差数据的真实分布. 相似文献
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压缩感知(Compressed Sensing,CS)结合了视频信号的变换和信息压缩过程,为简化编码算法提供了一种新的解决思路.把分布式视频编码(DVC)和CS结合在一起,构建简单的视频编码框架,并利用原始视频帧与边信息之间的相关性进行残差重构,提出了一种基于边信息的分布式视频压缩感知编解码方案.此方法对关键帧采用传统的帧内编、解码;对非关键帧CS进行随机观测提取观测向量,解码端利用优化的边信息和传输的CS观测向量进行联合重构.实验结果表明,该方法在运动较平滑的序列中比参考方案的恢复质量提高了4 ~6 dB. 相似文献
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该文针对H.264帧内编码码率控制(RC)效果不佳的问题,提出了一种新颖的图像复杂度自适应I帧RC算法。首先用Sobel算子检测I帧亮度像素的梯度,建立44块的边缘方向直方图,得到每个44块最可能的帧内预测模式和相应重构块,最终获得与实际编码相近的残差图像。用残差的平均绝对值表达I帧编码复杂度,并提出了一种经验型码率-量化(R-Q)模型,同时考虑缓冲区状态和序列特性为I帧分配合适的目标比特,最后为每一个图像组(GOP)得到了合适的I帧量化参数(QP)。实验结果表明,该文算法能更准确地控制I帧输出码率,有效阻止缓冲区溢出和跳帧,得到更加平稳的视频质量,序列PSNR波动减少了60%以上。 相似文献
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Wyner-Ziv视频编码中无反馈速率控制算法研究 总被引:1,自引:0,他引:1
为了避免在分布式视频编码系统中使用反馈信道,提出了一种基于Wyner-Ziv编码的无反馈速率控制算法。首先,利用目标码率和目标帧率进行GOP层码率分配;然后,根据原始图像的帧间相关性动态选择量化因子和量化矩阵来分配每个GOP内关键帧和Wyner-Ziv帧的比特数;接下来,利用系数带级的相关性计算相关噪声模型参数,并选择对应的LDPC校验矩阵,提出Wyner-Ziv帧的无反馈比特面速率控制算法。实验结果表明,在给定目标码率下,所提算法的编码码率误差小于0.57%,且与现有无反馈速率控制算法相比,解码恢复图像的PSNR(峰值信噪比)可以提高1dB。另外,该算法基本没有增加编码端复杂度,可用于实际分布式视频通信系统。 相似文献
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Rate distortion optimization for H.264 interframe coding: a general framework and algorithms. 总被引:1,自引:0,他引:1
Rate distortion (RD) optimization for H.264 interframe coding with complete baseline decoding compatibility is investigated on a frame basis. Using soft decision quantization (SDQ) rather than the standard hard decision quantization, we first establish a general framework in which motion estimation, quantization, and entropy coding (in H.264) for the current frame can be jointly designed to minimize a true RD cost given previously coded reference frames. We then propose three RD optimization algorithms--a graph-based algorithm for near optimal SDQ in H.264 baseline encoding given motion estimation and quantization step sizes, an algorithm for near optimal residual coding in H.264 baseline encoding given motion estimation, and an iterative overall algorithm to optimize H.264 baseline encoding for each individual frame given previously coded reference frames-with them embedded in the indicated order. The graph-based algorithm for near optimal SDQ is the core; given motion estimation and quantization step sizes, it is guaranteed to perform optimal SDQ if the weak adjacent block dependency utilized in the context adaptive variable length coding of H.264 is ignored for optimization. The proposed algorithms have been implemented based on the reference encoder JM82 of H.264 with complete compatibility to the baseline profile. Experiments show that for a set of typical video testing sequences, the graph-based algorithm for near optimal SDQ, the algorithm for near optimal residual coding, and the overall algorithm achieve on average, 6%, 8%, and 12%, respectively, rate reduction at the same PSNR (ranging from 30 to 38 dB) when compared with the RD optimization method implemented in the H.264 reference software. 相似文献
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针对当前基于传感器模式噪声(sensor pattern noise,SPN)提取模型处理压缩 视频来源检测的识别效果较差问题,提出一种基 于多尺度变换域自适应维纳滤波和一种加权最大似然估计的改进SPN提取模型。 首先干预视 频的编解码过程,在编解码器的环路滤波模块前提取视频帧,然后将视频帧输入双密度双树 复小波变换 自适应维纳滤波模型中提取噪声残差,最后使用加权最大似然估计从噪声残差中估计得到SPN。在公共视频源取证数据库VISION上进行测试比较,实验结果表明所提出的改进SPN提取 模型在ROC曲线和Kappa统计系数两种评价指标上的识别效果优于 传统SPN提取算法。 相似文献
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A nonlinear quantisation algorithm for pixel domain distributed video codec (DVC) is proposed. A residual signal is generated at the encoder considering the Wyner-Ziv frame to be encoded and adjacent reference frames and this residual signal is quantised using a nonlinear quantiser. The proposed algorithm is simulated for a number of test video sequences and the results depict a significant improvement of rate distortion performance, by reducing the bit rate while keeping the same PSNR when compared with available pixel domain DVC codec that uses a linear quantiser. 相似文献
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针对传统Polar码译码算法在相关噪声信道下性能严重下降的问题,提出了一种基于前置预判-卷积神经网络(Prior Decision-Convolutional Neural Networks,PD-CNN)的译码算法。通过前置预判深度优化CNN,使其准确地估计信道噪声并使残余噪声尽可能遵循高斯分布,再根据残余噪声分布统计更新出可靠的似然比信息。分析了不同译码算法对不同码率Polar码在不同噪声相关强度下的译码性能,并与本文所提出的译码算法进行对比。仿真结果表明:在相关噪声信道下,当误码率为10-5时,本文所提出的译码算法与标准置信度传播算法相比可获得约2.5 Bd的增益。此外,在高信噪比时,与置信度传播-卷积神经网络算法相比,本文提出的译码算法具有相同的性能,但复杂度更低,译码延迟最大可减少42%。 相似文献
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针对自同步扰码系统的联合信源信道译码问题,本文将自同步扰码看作一种特殊的卷积编码,提出了类似卷积译码的软输入软输出(SISO)自同步去扰算法。该算法利用信源冗余更新扰码序列的外信息,在信道译码时作为先验信息进行译码,实现了自同步去扰与信道译码之间的软信息交互,充分利用了信源冗余信息,使得接收系统的性能得到了有效提升。仿真结果表明,在TPC编码条件下,当信源冗余度为70%时,联合信源信道译码的性能增益约为4.1dB。相比于单一纠错编码系统,当通信系统中存在自同步扰码时,联合信源信道译码具有更大的性能增益。 相似文献
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针对时分多址(Time Division Multiple Access,TDMA)信号提出了宽范围的载波同步译码联合迭代处理的方案。该方案主要分为三个部分,首先利用TDMA信号的同步码进行数据辅助同步,对信号中的大频偏和相偏进行粗估计和纠正;然后利用线性调频Z变换(Chirp-Z Transform,CZT)算法针对整突发帧进行非数据辅助同步,精确估计和纠正信号的剩余频偏;最后通过利用译码器输出的软信息进行编码辅助同步,多次迭代得到剩余相偏的精确估计,最终实现载波的精确同步并输出译码结果。实验结果表明,所提方案具有同步捕获范围宽、参数估计精度高、译码输出误比特率低等优点,在低信噪比环境下也能表现出优良性能。 相似文献
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Rate-Distortion Optimized Motion-Compensated Prediction for Packet Loss Resilient Video Coding 总被引:1,自引:0,他引:1
A rate-distortion optimized motion-compensated prediction method for robust video coding is proposed. Contrasting methods from the conventional literature, the proposed approach uses the expected reconstructed distortion after transmission, instead of the displaced frame difference in motion estimation. Initially, the end-to-end reconstructed distortion is estimated through a recursive per-pixel estimation algorithm. Then the total bit rate for motion-compensated encoding is predicted using a suitable rate distortion model. The results are fed into the Lagrangian optimization at the encoder to perform motion estimation. Here, the encoder automatically finds an optimized motion compensated prediction by estimating the best tradeoff between coding efficiency and end-to-end distortion. Finally, rate-distortion optimization is applied again to estimate the macroblock mode. This process uses previously selected optimized motion vectors and their corresponding reference frames. It also considers intraprediction. Extensive computer simulations in lossy channel environments were conducted to assess the performance of the proposed method. Selected results for both single and multiple reference frames settings are described. A comparative evaluation using other conventional techniques from the literature was also conducted. Furthermore, the effects of mismatches between the actual channel packet loss rate and the one assumed at the encoder side have been evaluated and reported in this paper 相似文献
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Jeongeun Lim Chulhee Lee Kwanghoon Sohn 《Circuits, Systems, and Signal Processing》2004,23(2):123-141
A multiview sequence coding technique is proposed in this paper. A multiview
sequence encoder must be able to reduce redundancies in both the time and view domains
because the amount of data increases as the number of views (or cameras) increases.
We define a new coding structure, a group of a group of pictures (GGOP), which is
compatible with MPEG-2 and is flexible with a baseline distance. The GGOP could have
several possible types, e.g., one-I type, two-I type, etc., according to the number of reference
frame sequences. This permits one of these types to be selected according to the
baseline distance among the cameras. In addition, the GGOP is designed for MPEG-2
compatibility. The proposed multiview sequence encoder consists of preprocessing stages,
disparity estimation/compensation, motion estimation/compensation, residual coding, rate
control, and entropy coding. It generates two types of bit streams, the main bit stream and
the auxiliary bit stream. The main bit stream contains information concerning reference
sequences including I-pictures, in order to maintain MPEG-2 compatibility. The auxiliary
bit stream contains information concerning the remaining multiview sequences except for
the sequences that include I-pictures.
The proposed encoder shows improvements in compression ratio as well as in peak
signal-to-noise ratio (PSNR) compared with conventional methods. The dependency of the
GGOP on the baseline distance between cameras is also confirmed. 相似文献