分布式视频编码中基于多概率混合分布的相关噪声建模方法

相关噪声建模(Correlation Noise Modeling,CNM)的准确度是影响分布式视频编码(Distributed Video Coding,DVC)系统性能的关键因素之一.针对经过8×8离散余弦变换(Discrete Cosine Transform,DCT)后的相关噪声子带,本文提出了全新的基于多概率混合分布的CNM方法.该方法可根据子带的信息熵与子带在柯西、拉普拉斯和高斯三种概率分布下信息熵的相似度,自适应选择合适的概率分布对子带进行建模,提高了CNM的准确度.实验结果表明,采用本文提出的离线和在线CNM方法与现有典型的CNM方法相比,DVC系统的率失真(Rate-Distortion,R-D)性能均获得显著的提高.     

Adaptive Multiview Video Coding Scheme Based on Spatiotemporal Correlation Analyses

In this paper, we propose an adaptive multiview video coding scheme based on spatiotemporal correlation analyses using hierarchical B picture (AMVC‐HBP) for the integrative encoding performances, including high compression efficiency, low complexity, fast random access, and view scalability, by integrating multiple prediction structures. We also propose an in‐coding mode‐switching algorithm that enables AMVC‐HBP to adaptively select a better prediction structure in the encoding process without any additional complexity. Experimental results show that AMVC‐HBP outperforms the previous multiview video coding scheme based on H.264/MPEG‐4 AVC using the hierarchical B picture (MVC‐HBP) on low complexity for 21.5%, on fast random access for about 20%, and on view scalability for 11% to 15% on average. In addition, distinct coding gain can be achieved by AMVC‐HBP for dense and fast‐moving sequences compared with MVC‐HBP.     

无反馈分布式视频编码中码率分配算法研究

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.     

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

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。     

Error Concealment Using Inter‐layer Correlation for Scalable Video Coding

In this paper, we propose a new error concealment (EC) method using inter‐layer correlation for scalable video coding. In the proposed method, the auxiliary motion vector (MV) and the auxiliary mode number (MN) of intra prediction are interleaved into the bitstream to recover the corrupted frame. In order to reduce the bit rate, the proposed method encodes the difference between the original and the predicted values of the MV and MN instead of the original values. Experimental results show that the proposed EC outperforms the conventional EC by 2.8 dB to 6.7 dB.     

Efficient Mode Decision Algorithm Based on Spatial,Temporal, and Inter‐layer Rate‐Distortion Correlation Coefficients for Scalable Video Coding

The layered coding structure of scalable video coding (SVC) with adaptive inter‐layer prediction causes noticeable computational complexity increments when compared to existing video coding standards. To lighten the computational complexity of SVC, we present a fast algorithm to speed up the inter‐mode decision process. The proposed algorithm terminates inter‐mode decision early in the enhancement layers by estimating the rate‐distortion (RD) cost from the macroblocks of the base layer and the enhancement layer in temporal, spatial, and inter‐layer directions. Moreover, a search range decision algorithm is also proposed in this paper to further increase the motion estimation speed by using the motion vector information from temporal, spatial, or inter‐layer domains. Simulation results show that the proposed algorithm can determine the best mode and provide more efficient total coding time saving with very slight RD performance degradation for spatial and quality scalabilities.     

分布式编码中广义伽马分布相关噪声模型研究

针对现有相关噪声模型—Laplacian模型不能精确描述相关噪声,导致分布式视频编码(DVC, distributed video coding)系统的率失真性能不高的问题,提出像素域DVC中广义伽马分布相关噪声模型。首先分析了相关噪声的统计特性,发现Laplacian分布的峰值比实际相关噪声分布的低,然后采用广义伽马分布对相关噪声进行拟合,并给出在线估计广义伽马分布参数的方法。实验结果表明,提出的模型能较精确地描述相关噪声,且有效地改善了系统的率失真性能,并减少了解码端计算复杂度。     

Multiple Region‐of‐Interest Support in Scalable Video Coding

In this letter, we propose a new functionality to scalable video coding (SVC), that is, the support of multiple region of interests (ROIs) for heterogeneous display resolution. The main objective of SVC is to provide temporal, spatial, and quality scalability of an encoded bitstream. The ROI is an area that is semantically important to a particular user, especially users with heterogeneous display resolutions. Less transmission bandwidth is needed compared to when the entire region is transmitted/decoded and then sub‐sampled or cropped. To support multiple ROIs in SVC, we adopt flexible macroblock ordering (FMO), a tool defined in H.264, and based on it, we propose a way to encode and, independently, decode ROIs. The proposed method is implemented on the joint scalable video model (JSVM) and its functionality verified.     

Adaptive Pre‐/Post‐Filters for NRT‐Based Stereoscopic Video Coding

Non‐real‐time delivery of stereoscopic video has been considered as a service scenario for 3DTV to overcome the limited bandwidth in the terrestrial digital television system. A hybrid codec combining MPEG‐2 and H.264/AVC has been suggested for the compression of stereoscopic video for 3DTV. In this paper, we propose a stereoscopic video coding scheme using adaptive pre‐/post‐filters (APPF) to improve the quality of 3D video while retaining compatibility with legacy video coding standards. The APPF are applied adaptively to blocks of various sizes determined by the macroblock coding mode and reference frame index. Experiment results show that the proposed method achieves up to 24.86% bit rate savings relative to a hybrid codec of MPEG‐2 and H.264/AVC including the inter‐view prediction.     

Disparity‐Compensated Stereoscopic Video Coding Using the MAC in MPEG‐4

The MPEG‐4 multiple auxiliary component (MAC) is a good mechanism to achieve one‐stream stereoscopic video coding. However, there is no syntax or semantics for the residual texture data of the disparity‐compensated image in the current MAC. Therefore, we propose a novel disparity‐compensated coding method using the MAC for stereoscopic video. We also define a novel MAC semantics in MPEG‐4 so as to support the proposed coding algorithm. The major difference between the existing and proposed coding methods using the MAC is the addition of the residual texture coding.     

移动环境视频编码功率-码率-失真模型研究

在前期建立视频编码动态功耗模型的基础上,将功率因子引入到经典率失真理论,并对经典码率模型及失真模型进行修正,进而建立视频编码功率-码率-失真模型.实验结果表明,该模型具有较高的精确性,为实现功耗约束条件下视频质量、带宽、功耗达到动态平衡的最优提供理论指导.     

Improved Update Step for Scalable Video Coding in Video Surveillance

Many evolving video services and applications for intelligent security systems require reliable transmission of high quality video to diverse clients over heterogeneous networks using available system resources. Scalable video coding (SVC) is one of the emerging video compression technologies with such potential capabilities. Advances in lifting-based motion-compensated temporal filtering (MCTF) have enabled highly efficient and flexible spatial, temporal, signal-to-noise ratio (SNR), and complexity scalability to be realized over a wide range of bit rates. In this paper, we present an algorithm to improve the update step of MCTF, which serves as an important informative step for the coding performance of SVC. A novel update-step algorithm, which takes advantage of the chrominance information of the video sequence and the correlation of the motion vectors (MVs) of the neighboring blocks as well as the correlation of the derived update MVs in the low-pass frames, is proposed to improve update step of MCTF by (1) computing correct update motion information, (2) generating correct amount of energy contained in the high-pass frames. Experimental results show that the proposed algorithm can significantly improve the quality of the reconstructed video sequence in visual quality.

Color Noise Reduction Method in Non‐constant Luminance Signal for High Dynamic Range Video Service

A high dynamic range (HDR) video service is an upcoming issue in the broadcasting industry. For compatibility with legacy devices receiving a non‐constant luminance (NCL) signal, new tools supporting an HDR video service are required. The current pre‐processing chain of HDR video can produce color noise owing to the chroma component down‐sampling process for video encoding. Although a luma adjustment method has been proposed to solve this problem, some disadvantages still remain. In this paper, we present an adaptive color noise reduction method for an NCL signal of an HDR video service. The proposed method adjusts the luma component of an NCL signal adaptively according to the information of the luma component from a constant luminance signal and the level of color saturation. Experiment results show that the color noise problem is resolved by applying our proposed method. In addition, the speed of the pre‐processing is increased more than two‐fold compared to a previous method.     

Simple Detection Based on Soft‐Limiting for Binary Transmission in a Mixture of Generalized Normal‐Laplace Distributed Noise and Gaussian Noise

In this letter, a simplified suboptimum receiver based on soft‐limiting for the detection of binary antipodal signals in non‐Gaussian noise modeled as a generalized normal‐Laplace (GNL) distribution combined with Gaussian noise is presented. The suboptimum receiver has low computational complexity. Furthermore, when the number of diversity branches is small, its performance is very close to that of the Neyman‐Pearson optimum receiver based on the probability density function obtained by the Fourier inversion of the characteristic function of the GNL‐plus‐Gaussian distribution.     

Symbol error probability evaluation for PSK modulation schemes in generalized non‐Gaussian noise channels

The average symbol error probability (ASEP) performance over the faded radio frequency (RF) link when the noise is additive in nature and has generalized Laplacian distribution is evaluated in this paper. The additive white generalized Laplacian noise (AWGLN) distribution can model different impulsive and non‐Gaussian noise environments often encountered in practice and provides a robust alternative to Gaussian distribution. A new expression for evaluating the exact symbol error probability over a multilevel M‐ary PSK‐modulated AWGLN channel is derived. Based on the obtained expression, the ASEP for the single‐hop RF link that models the shadowing and fading conditions over the RF channel by a generalized –K (GK) distribution is derived. Further, the error performance of a decode‐and‐forward relayed and GK‐distributed two‐hop RF link is discussed, and the results are validated through numerical plots.     

Novel Rate Control Scheme for Low Delay Video Coding of HEVC

In this paper, a novel rate control scheme for low delay video coding of High Efficiency Video Coding (HEVC) is proposed. The proposed scheme is developed by considering a new temporal prediction structure of HEVC. In the proposed scheme, the relationship between bit rate and quantization step is exploited firstly to formulate an accurate quadratic rate‐quantization (R‐Q) model. Secondly, a method of determining the quantization parameters (QPs) for the first frames within a group of pictures is proposed. Thirdly, an accurate frame‐level bit allocation method is proposed for HEVC. Finally, based on the proposed R‐Q model and the target bit allocated for the frame, the QPs are predicted for coding tree units by using rate‐distortion (R‐D) optimization. We compare our scheme against that of three other state‐of‐the‐art rate control schemes. Experimental results show that the proposed rate control scheme can increase the Bjøntegaard delta peak signal‐to‐noise ratio by 0.65 dB and 0.09 dB on average compared with the JCTVC‐I0094 and JCTVC‐M0036 schemes, respectively, both of which have been implemented in an HEVC test model encoder; furthermore, the proposed scheme achieves a similar R‐D performance to Wang's scheme, as well as obtaining the smallest bit rate mismatch error of all the schemes.     

面向HBP编码格式的立体视频B帧整帧丢失分层错误隐藏算法

针对分层B帧(HBP)编码格式的立体视频B帧整帧丢失的问题,该文分析了双视点视频中存在的视点间运动矢量相关性,提出一种分层错误隐藏算法。该算法与当前主流的方法有两大不同：一是该算法采用分级隐藏,根据B帧的重要性等级不同采用不同的错误隐藏方法;二是该算法考虑了相邻视点序列之间的宏块运动矢量相关性。实验表明,该算法的性能优于当前常用的H.264多视点视频整帧丢失错误隐藏方法。     

自适应位置切换相关滤波目标跟踪

为解决卷积特征目标跟踪算法精确度和速度相互制约的问题,文中提出了一种基于峰值旁瓣比的自适应位置切换的相关滤波目标跟踪算法。将Pool4和Conv5-3层作为特征提取层,通过特征能量均值比获取有效的卷积特征,提高算法的速度;然后利用不同样本分布训练多个相关滤波器,并根据峰值旁瓣比筛选出最适分类器进行位置预测,提高了跟踪器的泛化能力;最后利用稀疏模型更新策略更新滤波器模板,减小过拟合现象的同时进一步提高算法的速度。在OTB100标准数据集上测试该算法,实验结果表明,文中所提算法的精确度为88.8%,较原分层卷积跟踪算法提高了6.1%;跟踪速度为47.5帧/s,是原算法的5倍,显示了良好的实时性能。     

Joint Source/Channel Coding Based on Two‐Dimensional Optimization for Scalable H.264/AVC Video

The scalable extension of the H.264/AVC video coding standard (SVC) demonstrates superb adaptability in video communications. Joint source and channel coding (JSCC) has been shown to be very effective for such scalable video consisting of parts of different significance. In this paper, a new JSCC scheme for SVC transmission over packet loss channels is proposed which performs two‐dimensional optimization on the quality layers of each frame in a rate‐distortion (R‐D) sense as well as on the temporal hierarchical structure of frames under dependency constraints. To compute the end‐to‐end R‐D points of a frame, a novel reduced trellis algorithm is developed with a significant reduction of complexity from the existing Viterbi‐based algorithm. The R‐D points of frames are sorted under the hierarchical dependency constraints and optimal JSCC solution is obtained in terms of the best R‐D performance. Experimental results show that our scheme outperforms the existing scheme of [13] with average quality gains of 0.26 dB and 0.22 dB for progressive and non‐progressive modes respectively.     

Optimal Amplify‐and‐Forward Scheme for Parallel Relay Networks with Correlated Relay Noise

This paper studies a parallel relay network where the relays employ an amplify‐and‐forward (AF) relaying scheme and are subjected to individual power constraints. We consider correlated effective relay noise arising from practical scenarios when the relays are exposed to common interferers. Assuming that the noise covariance and the full channel state information are available, we investigate the problem of finding the optimal AF scheme in terms of maximum end‐to‐end transmission rate. It is shown that the maximization problem can be equivalently transformed to a convex semi‐definite program, which can be efficiently solved. Then an upper bound on the maximum achievable AF rate of this network is provided to further evaluate the performance of the optimal AF scheme. It is proved that the upper bound can be asymptotically achieved in two special regimes when the transmit power of the source node or the relays is sufficiently large. Finally, both theoretical and numerical results are given to show that, on average, noise correlation is beneficial to the transmission rate — whether the relays know the noise covariance matrix or not.