基于视频内容的MPEG视频VBR业务流量模型

视频业务流量模型是网络性能仿真的一个重要前置环节,但由于视频内容的千差万别,使得很难建立统一的视频业务流量模型。本文根据MPEG视频图像内容的纹理及运动复杂度,通过3×3 Kohonen自组织神经网络对视频序列进行划分,将其分割为一段段近似平稳的“视频片段”。然后,用半马尔可夫随机过程描述“视频片段”间的转移概率及其持续时间分布规律,用AR模型描述“视频片段”内部过程,从而建立了一种通用MPEG视频业务流量模型。     

An adaptive temporal-spatial filter for MPEG decoded video signals

A new adaptive post-processing algorithm for the MPEG decoded video sequences is proposed. We use a motion compensated averaging filter to reduce the noises in the temporal domain and an adaptive spatial filter to remove noise in the spatial domain and preserve the edge of different orientations in the image. A MPEG decoded video sequence called table tennis is processed by our proposed filter. The post-processed video sequence shows that its image quality is improved, especially of the moving objects.     

A multi-stage spatio-temporal adaptive network for video super-resolution

Video super-resolution aims at restoring the spatial resolution of the reference frame based on consecutive input low-resolution (LR) frames. Existing implicit alignment-based video super-resolution methods commonly utilize convolutional LSTM (ConvLSTM) to handle sequential input frames. However, vanilla ConvLSTM processes input features and hidden states independently in operations and has limited ability to handle the inter-frame temporal redundancy in low-resolution fields. In this paper, we propose a multi-stage spatio-temporal adaptive network (MS-STAN). A spatio-temporal adaptive ConvLSTM (STAC) module is proposed to handle input features in low-resolution fields. The proposed STAC module utilizes the correlation between input features and hidden states in the ConvLSTM unit and modulates the hidden states adaptively conditioned on fused spatio-temporal features. A residual stacked bidirectional (RSB) architecture is further proposed to fully exploit the processing ability of the STAC unit. The proposed STAC and RSB architecture promote the vanilla ConvLSTM’s ability to exploit the inter-frame correlations, thus improving the reconstruction quality. Furthermore, different from existing methods that only aggregate features from the temporal branch once at a specified stage of the network, the proposed network is organized in a multi-stage manner. The corresponding temporal correlation in features at different stages can be fully exploited. Experimental results on Vimeo-90K-T and UMD10 datasets show that the proposed method has comparable performance with current video super-resolution methods. The code is available at https://github.com/yhjoker/MS-STAN.     

An adaptive spatio-temporal coding scheme for indoor wireless communication

Systems that employ multiple antennas in both the transmitter and the receiver of a wireless system have been shown to promise extraordinary spectral efficiency. With full channel knowledge at the transmitter and receiver, Raleigh and Cioffi (1998) proposed a spatio-temporal coding scheme, discrete matrix multitone (DMMT), to achieve asymptotically optimum multiple-input-multiple-output (MIMO) channel capacity. The DMMT can be regarded as an extension of the discrete multitone for a digital subscriber lines (DSL) system to the MIMO wireless application. However, the DMMT is basically impracticable in nonstationary wireless environments due to its high-computational complexity. Exploring second-order statistics, we develop an efficient adaptive blind coding scheme for a high-capacity time-division duplexing (TDD) system with slow time-varying frequency-selective MIMO channels. With this method, neither a training sequence nor feedback of channel information is required in the proposed blind approach. Besides, the computational complexity of the proposed scheme is significantly lower than that of the coding scheme described by Raleigh and Cioffi. Simulation results show that the proposed architecture works efficiently in indoor wireless local area network applications.     

Study on adaptive job assignment for multiprocessor implementationof MPEG2 video encoding

The high demand on computation performance by multimedia information processing such as digital video compression and decompression has made multiprocessor computation more and more popular. In this paper, we present our study on adaptive job assignment for multiprocessor implementation of a Motion Picture Expert Group 2 (MPEG2) video encoding algorithm. Data partitioning technique is used for job assignment to the processors in the multiprocessor environment to exploit the data structure adopted by the MPEG standard that divides a frame of a picture into macro blocks (MBs) which are processed independently during encoding. An adaptive data partitioning scheme is developed to cope with the inherent nonuniform spatial distribution of motion activities, such that the computation load distribution over processors is as uniform as possible, which helps improve the speedup of the whole multiprocessor system. Simulations with several video sequences have shown that, in comparison to its nonadaptive counterpart, the adaptive scheme can effectively improve the speedup of the multiprocessor system. In addition, the speedup scales well with the increase of the number of processors used in the computation     

An adaptive spatio-temporal perception aware quantization algorithm for AVS2

Adaptive quantization proves to be an effective tool to improve coding performance. In this paper, we propose an adaptive spatiotemporal perception aware quantization algorithm to increase subjective coding performance. To measure the spatiotemporally perceptual redundancy, the perceptual complexity models are firstly established with spatial and temporal characteristics respectively. With the help of the models, the adaptive spatial and temporal quantization parameter (QP) offsets are then calculated for each coding tree unit (CTU), respectively. Finally, the perceptually optimal Lagrange multiplier of each CTU is determined with the spatial–temporal QP offset. Experimental results show that the proposed algorithm reduces 8.6% and 8.4% Bjontegaard-Delta Rate (BD-Rate) with Structural Similarity Index Metric (SSIM) in average over the second generation of Audio Video Coding Standard (AVS2) reference software RD17.0 in Low-Delay-P (LDP) and Random-Access (RA) configurations, respectively. The subjective assessment proves that the proposed algorithm can reduce the bitrates with the same subjective quality significantly.     

A hierarchical adaptive spatio-temporal data compression scheme for wireless sensor networks

Wireless Networks - How to reduce the number of transmissions or prolong the lifetime of wireless sensor networks significantly has become a great challenge. Based on the spatio-temporal...     

一种抑制总线串扰的自适应时空编码方法

片上总线互连线间逐步增强的线间耦合效应加剧了总线信号串扰.本文根据互连线串扰模型,提出先传送奇数位信息,再传送偶数位信息,双时钟周期发送恶性串扰总线数据的自适应时间编码方法.在消除恶性串扰的同时,减小了总线自翻转能耗.并结合码本编码,获得一种自适应时空编码方法.仿真结果显示该方法的时间节省率达到30%以上,能耗节省率为4%～38%.对于32位数据总线,该方法仅需6根冗余线.     

Voxel-based adaptive spatio-temporal modelling of perfusion cardiovascular MRI

Contrast enhanced myocardial perfusion magnetic resonance imaging (MRI) is a promising technique, providing insight into how reduced coronary flow affects the myocardial tissue. Stenosis in a coronary vessel leads to reduced myocardial blood flow, but collaterals may secure the blood supply of the myocardium, with altered tracer kinetics. Due to a low signal-to-noise ratio, quantitative analysis of the signal is typically difficult to achieve at the voxel level. Hence, analysis is often performed on measurements that are aggregated in predefined myocardial segments, that ignore the variability in blood flow in each segment. The approach presented in this paper uses local spatial information that enables one to perform a robust analysis at the voxel level. The spatial dependencies between local response curves are modelled via a hierarchical Bayesian model. In the proposed framework, all local systems are analyzed simultaneously along with their dependencies, producing a more robust context-driven estimation of local kinetics. Detailed validation on both simulated and patient data is provided.     

MPEG2音频编码中的辅助数据

在进行MPEG2音频编码时,对辅助数据进行规范建议和填充,通过解码端的解析,可以使用户对音频信号的控制和操作有更大的自由度和选择权.辅助数据包含了动态范围控制和语音归一化等信息.     

Data adaptive rank-shaping methods for solving least squaresproblems

There are two types of problems in the theory of least squares signal processing: parameter estimation and signal extraction. Parameter estimation is called “inversion” and signal extraction is called “filtering”. In this paper, we present a unified theory of rank shaping for solving overdetermined and underdetermined versions of these problems. We develop several data-dependent rank-shaping methods and evaluate their performance. Our key result is a data-adaptive Wiener filter that automatically adjusts its gains to accommodate realizations that are a priori unlikely. The adaptive filter dramatically outperforms the Wiener filter on a typical realizations and just slightly under-performs it on typical realizations. This is the most one can hope for in a data-adaptive filter     

新的GPS自适应阵的选星方法

提出了2种新的自适应阵选星方法：加权GDOP准则下的自适应阵选星方法给出了自适应阵选星的性能极限；为减少计算代价，提出近似加权GDOP准则下的自适应阵选星方法。这2种自适应阵选星方法的性能均全面优于常规GPS选星方法，不但定位精度有明显提高，而且干扰环境下的卫星信号可用率从40％分别提高到60％以上和90％以上。     

自适应光学系统运行失稳检测方法

自适应光学（AO）系统校正像差是提高光学系统性能的有效技术手段。为了保证AO系统长时间安全、稳定地工作,需要对AO系统运行的数据进行监测,识别系统失稳状态以提供决策建议。基于以上目的,建立了一套127单元AO系统失稳数据仿真平台,通过该平台仿真得到了4种闭环失稳异常。基于变形镜控制电压RMS指标使用Kmeans聚类、K-NN分类和ARIMA预测3种机器学习方法进行识别检测。3种方法在不同类型异常数据中的检测结果有所不同,说明3种异常检测方法对系统失稳检测均有一定的效果和适用范围,在实际使用时,可以根据需要选择一种或综合多种方法进行检测。     

Bit-rate control for MPEG encoders

Bit-rate control is a central problem in designing image sequence compression systems. In this paper we describe a new approach to bit-rate control for inter-frame encoders such as MPEG encoders. This approach uses concepts from control theory. Its central feature is a surprisingly simple but effective model for the encoder, which consists of a gain element, a delay element and additive noise. In our system we control the bit-rate with a PI-controller which is set to achieve two objectives: (1) we want the picture quality to be as uniform as possible, and (2) we want to use as closely as possible the available amount of bits. It is demonstrated in the paper that these two objectives, when considered separately, lead to contradictory settings of the controller. This dilemma can be solved by using Bit Usage Profiles that indicate how the bits have to be spread over the pictures. The effectiveness of the approach is demonstrated by designing a bit-rate control for an MPEG encoder that has a nearly constant bit-rate per group of pictures (GOP). Such a bit-rate control is of high value for applications like magnetic recording, where a constant bit-rate per GOP is required in order to realize playback trick modes, e.g. the fast forward mode.     

基于内容的多媒体信息检索

较系统地介绍了基于内容的多媒体检索技术。对于基于内容的视频检索技术，介绍了基于内容的视频处理、视频检索的方式和ML算法在视频检索中的应用。此外，还介绍了基于内容的压缩方法MPEG-4、MPEG-7、MPEG-21等。     

Transmission of adaptive MPEG video over time-varying wireless channels: modeling and performance evaluation

Wireless channels are characterized by high time-varying bit-error rates (BERs). To cope with this problem, several adaptive forward-error-correction (AFEC) schemes have been proposed in the literature. They work locally at the wireless link, adding a variable amount of redundancy to the transmitted data in order to maintain the packet error rate below an acceptable level. However, when such schemes are utilized, the bandwidth offered to the applications changes when channel conditions change. In this paper, the effects of these bandwidth variations are investigated in the case of real-time Motion Picture Experts Group (MPEG) video transmission. The MPEG encoder is controlled in order to adapt its emission rate to the current bandwidth offered by the wireless link. To this end, the encoding quality is diminished by the source rate controller when the transmission rate has to be decreased due to an increase in the channel BER, whereas it is improved when the transmission rate can be increased due to a decrease in the channel BER. A Markov-based model, denoted as SBBP/SBBP/1/K, has been introduced to model the scenario being considered. The analytical framework allows evaluation of the performance of the system and can be used to optimize the design of a video transmission system for wireless channels, providing the instruments to derive the tradeoff between information corruption in the wireless channel and MPEG video encoding quality.     

面向内容的语音信号压缩感知研究

压缩感知理论依据信号的稀疏性质进行压缩测量,将信号的获取方式从对信号的采样上升为对信息的感知,是信号处理领域的一场革命。本文提出一种基于非确定基字典（Uncertainty Basis Dictionary, UBD）对语音信号进行稀疏表示的方法,将压缩感知理论应用于对语音信号稀疏表示的压缩,并提出了基于求解线性规划问题的方法重构语音信号的算法。通过语音识别、话者识别和情感识别实验,从面向内容分析的角度,研究这种基于压缩感知理论的信息感知方法是否保留了语音信号的主要内容。实验结果表明,语音识别、话者识别和情感识别的准确率,与目前这些领域研究方法得到的结果基本一致,说明基于压缩感知理论的信息感知方法能够很好地获取语音信号的语义、话者和情感方面的信息。      

基于内容的视频语义分析关键技术

分析了视频数据与文本数据的差异,以及视频数据在视频分析检索方面存在的问题。从视频内容分析领域的研究热点出发,分别对视频语义库、与视频分析相关的视频低层特征、视频对象划分与识别、视频信息描述与编码等方面的技术进行了分析和对比。并提出了一个视频语义分析的框架和分析流程。     

Clipping Prevention Scheme for MPEG Surround

MPEG Surround has a potential clipping problem since its encoding is based on downmixing a multichannel signal. We propose a clipping prevention scheme for MPEG Surround, which is composed of modification and recovery processes of a downmix signal with recovery information conveyed in arbitrary downmix gains of an MPEG Surround bitstream. Experiments show that the proposed scheme effectively prevents sound quality degradation caused by clipping problems with negligible additional bit rates.     

Lexicographic Bit Allocation for MPEG Video

We consider the problem of allocating bits among pictures in an MPEG video coder to equalize the visual quality of the coded pictures, while meeting buffer and channel constraints imposed by the MPEG video buffering verifier. We address this problem within a framework that consists of three components: (1) a bit production model for the input pictures, (2) a set of bit-rate constraints imposed by the video buffering verifier, and (3) a novel lexicographic criterion for optimality. Under this framework, we derive simple necessary and sufficient conditions for optimality that lead to efficient algorithms.