视频图像去雾算法的自适应机制设计及FPGA加速实现

该文提出了一种自适应图像去雾算法,充分考虑不同复杂场景下的图像特征,建立了算法的自适应机制。该机制包含对图像是否有雾、是否为天空区域、滤波器尺寸等的自适应调整,解决了传统图像去雾算法在深度断层处可能产生的光晕效应等问题。该文同时对上述自适应图像去雾算法进行FPGA加速实现,实验结果表明,该文算法在XC7K325T型号FPGA视频处理平台上可以满足对1080P@60Hz视频去雾的实时性要求。对于大多数轻雾或浓雾场景,该文算法去雾后图像色彩自然无过饱和,全局对比度和饱和度提升比率均值为0.309和0.994,相比于本领域其他去雾算法优势明显。     

一种改进的自适应分段线性变换算法

红外成像设备获取到的原始图像经过转化可成为适合人类观看以及计算机处理的灰度图像,但转化后的图像会存在对比度低的问题。针对这一问题,本文提出一种改进的自适应分段线性变换算法,通过比较灰度直方图簇的个数的方式在候选集中自动选取适合于当前原始图像的参数取值,随后经过灰度线性变换即可得到增强后的图像。在实际红外原始数据上的实验表明,该算法增强效果较好,且计算时间相对较低,能够实现完全自适应。因此,该算法有望应用于红外成像设备的实时处理过程。     

一种改进的NLMS自适应滤波器的FPGA实现

针对当前广泛应用的自适应滤波器,提出了一种改进的变步长NLMS自适应算法,在不增加计算复杂度的条件下获得了更好的收敛速度。在硬件实现过程中,利用FPGA并行处理的特点,采用自上而下的设计方法和流水线设计技术,获得了较好的滤波效果和较快的处理速度,完全满足自适应信号处理领域中实时性的要求。     

基于FPGA的图像自适应AWB系统设计与实现

为了解决常见自动白平衡(Auto White Balance, AWB)方法的场景适应能力不足且实时性较差等问题,提出了一种基于颜色通道直方图重构的自适应AWB方法,并使用现场可编程门阵列(FPGA)对所提出的算法进行硬件电路实现,在校正图像白平衡的同时也确保了系统高速实时处理图像。首先对图像进行限制对比度自适应直方图均衡化(CLAHE)处理来提高图像对比度,然后对图像进行灰度级区间的通道分区统计,对不同场景类别的图像采用颜色直方图匹配或平移的重构方式做自适应处理。实验结果表明,该算法在处理图像白平衡时,相比基于光源估计的AWB算法,色温校正准确率提高了14%,对不同色彩场景有更好的适应性,具有实时处理能力。     

Detection and estimation using an adaptive rational function filter

Proposes a new nonlinear adaptive filter structure based on rational functions. There are several advantages to the use of this filter. First, it is a universal approximator and a good extrapolator. Second, it ran be trained by a linear adaptive algorithm, which makes it suitable for real-time adaptive signal processing. Third, it has a best approximation for a specified function. To demonstrate its utility as a tool for solving adaptive signal processing problems, the authors apply the adaptive rational function filter to the problem of estimation and detection. The estimation problem pertains to the direction of arrival (DOA) estimation problem in array signal processing. For the detection problem, the authors consider the detection of a weak radar target (a small piece of ice) in an ocean environment     

实时图像处理系统中EDMA实现数据搬移

实时视频图像处理系统对图像处理的实时性要求很高，而且图像处理系统处理的数据量大。为了解决上述问题，除了要有优化的算法之外，还要充分利用DSP处理器的一切可用的硬件资源。本文阐述了基于TI公司TMS32005713 DSP的实时视频图像处理系统通过EDMA提高数据搬移速度的方法。     

基于NIOSⅡ的红外弱小目标检测算法实现

介绍了基于可编程片上系统SOPC技术的图像处理系统的软硬件设计,系统采用FPGA作为视频信号采集控制模块,利用FPGA内建NIOSⅡ软核微控制器作为图像处理单元。针对天空背景下红外弱小目标,提出了一种基于形态学和仿生学相结合的图像预处理算法,该算法在基于数学形态学滤波的基础上利用人眼固视微动辨别信息的原理对图像进行背景抑制和目标增强;采用自适应阈值分割法确定目标。硬件实验结果表明系统实时性好,图像处理效果良好,目标检测率高,验证了预处理算法的有效性和实时性。     

Annihilation-reordering look-ahead pipelined CORDIC-based RLSadaptive filters and their application to adaptive beamforming

The novel annihilation-reordering look-ahead technique is proposed as an attractive technique for pipelining of Givens rotation (or CORDIC)-based adaptive filters. Unlike the existing relaxed look-ahead, the annihilation-reordering look-ahead does not depend on the statistical properties of the input samples. It is an exact look-ahead based on CORDIC arithmetic, which is known to be numerically stable. The conventional look-ahead is based on multiply-add arithmetic. The annihilation-reordering look-ahead technique transforms an orthogonal sequential adaptive filtering algorithm into an equivalent orthogonal concurrent one by creating additional concurrency in the algorithm. Parallelism in the transformed algorithm is explored and different implementation styles including pipelining, block processing, and incremental block processing are presented. Their complexities are also studied and compared. The annihilation-reordering look-ahead is employed to develop fine-grain pipelined QR decomposition-based RLS adaptive filters. Both QRD-RLS and inverse QRD-RLS algorithms are considered. The proposed pipelined architectures can be operated at arbitrarily high sample rate without degrading the filter convergence behavior. Stability under finite-precision arithmetic are studied and proved for the proposed architectures. The pipelined CORDIC-based RLS adaptive filters are then employed to develop high-speed linear constraint minimum variance (LCMV) adaptive beamforming algorithms. Both QR decomposition-based minimum variance distortionless response (MVDR) realization and generalized sidelobe canceller (GSC) realization are presented. The complexity of the pipelined architectures are analyzed and compared. The proposed architectures can be operated at arbitrarily high sample rate and consist of only Givens rotations, which can be scheduled onto CORDIC arithmetic-based processors     

Narrow-band interference excision in spread-spectrum systems usingself-orthogonalizing transform-domain adaptive filters

Among many transform-domain interference excision techniques, transform-domain adaptive filtering has many advantages. It is based on a true optimization of some particular performance parameters such as the bit-error rate (BER). Moreover, it is insensitive to jammer frequency. However, transform-domain adaptive filtering also has the drawback of being incapable of tracking a rapidly changing interference because most adaptive algorithms require time to converge to the optimal solution. In this paper, a self-orthogonalizing transform-domain least mean square (SO-TRLMS) algorithm is used to speed up the convergence. Compared to a traditional transform-domain least mean square (TRLMS) algorithm, the SO-TRLMS algorithm can significantly improve the convergence rate of the LMS algorithm, thus making the transform-domain adaptive filtering technique more suitable for real-time processing. In order to show how the system performance is affected by various factors such as interference power and the transform used, this paper presents an analytical result for the BER performance that is applicable for arbitrary orthogonal linear transforms. Simulation results are also presented to demonstrate the validity of the analysis     

Recursive Estimation of Local Characteristics of Edges in TV Pictures as Applied to ADPCM Coding

In this paper, an algorithm is presented for extracting edges and estimating their local characteristics in TV pictures; the algorithm is designed for application to adaptive DPCM coding of TV pictures and it has the following properties: 1) it takes into account the causality constraint encountered in DPCM coding; 2) it is fitted to the line-by-line scanning of TV pictures; 3) it is fast, involving only a small amount of computation, and thus allowing real-time implementation. The whole processing is split into a local preprocessing and a global processing where the characteristics of the edges are renewed recursively line by line. This algorithm was used for implementing an adaptive choice of the prediction in DPCM coding of TV pictures.     

A hybrid frequency–time domain symmetric adaptive decorrelator

Symmetric adaptive decorrelation (SAD) is a semi-blind method of separating convolutely mixed signals. While it has restrictions on the physical layout of the demixing equipment, it is better suited for some applications (e.g., live sound mixing) as no post-processing is required to ascertain which output corresponds with which source. Since SAD is based on the least mean squares algorithm, it can be modified to perform the bulk of the processing in the frequency domain. This makes it more efficient for larger filter sizes and/or larger number of sources but renders it unsuitable for real-time applications as there is a lag between the output and the input. In this paper, we propose a hybrid approach that does not suffer from the lag of the frequency domain approach. While the proposed algorithm is slightly less computationally efferent than the pure frequency domain algorithm, it is significantly more efficient than the time domain approach. A comparison of the frequency domain and hybrid algorithms shows that both achieve separation equivalent to the time domain algorithm in a real-world environment.     

Adaptive multistage beamforming using cyclic higher orderstatistics (CHOS)

A new blind beamforming algorithm for signals that exhibit higher order cyclostationarity is presented. Exploiting some previous theoretical developments, we show how cyclic cumulants of the received signals can be used to obtain the weights of the beamformer that perform blind extraction. The method is based on a spatial interpretation of a deconvolution procedure known as the super-exponential algorithm. The basic block processing algorithm is made fully adaptive using an adaptive URV scheme and applied to a typical mobile communications scenario where several cochannel interferers corrupt the signals of interest     

A fast Discrete Wavelet Transform algorithm for visual processing applications

For visual processing applications, the two-dimensional (2-D) Discrete Wavelet Transform (DWT) can be used to decompose an image into four-subband images. However, when a single band is required for a specific application, the four-band decomposition demands a huge complexity and transpose time. This work presents a fast algorithm, namely 2-D Symmetric Mask-based Discrete Wavelet Transform (SMDWT), to address some critical issues of the 2-D DWT. Unlike the traditional DWT involving dependent decompositions, the SMDWT itself is subband processing independent, which can significantly reduce complexity. Moreover, DWT cannot directly obtain target subbands as mentioned, which leads to an extra wasting in transpose memory, critical path, and operation time. These problems can be fully improved with the proposed SMDWT. Nowadays, many applications employ DWT as the core transformation approach, the problems indicated above have motivated researchers to develop lower complexity schemes for DWT. The proposed SMDWT has been proved as a highly efficient and independent processing to yield target subbands, which can be applied to real-time visual applications, such as moving object detection and tracking, texture segmentation, image/video compression, and any possible DWT-based applications.     

实时视频信号的Sobel边缘检测的FPGA实现

在实时视频信号处理中,由于边缘检测等图像处理算法的数据量大,系统采用FPGA+DSP的图像处理方案。利用FPGA可对数据并行处理的特点,在FPGA中实现数据量大、处理速度要求高,但算法结构简单的低层处理算法。文中介绍了在FPGA中实现Sobel边缘检测算法的方法,并提出了自适应阈值的处理方案。实验结果证明,FPGA能够对实时视频信号完成Sobel边缘检测,且自适应阈值模块保证了系统在环境亮度变化的情况下,得到良好的边缘检测效果。     

基于混合遗传算法的唯相位直接数据域算法

提出一种基于混合遗传算法的唯相位直接数据域最小二乘算法.通过采用标准遗传算法与Neider-Mead单纯形法相结合的混合遗传算法,提高了优化效率和运算速度.首先根据标准直接数据域算法推导得出目标函数,继而将目标函数作为适应度函数,将所有自适应权值的未知相位作为决策变量,通过混合遗传算法进行非线性优化,从而求得各个自适应权值的优化解.作为一种唯相位自适应算法,它在硬件实现上比传统算法更具简单性.同时,它只对单快拍数据进行处理,避免了样本协方差矩阵的构造以及矩阵求逆运算,更适合于实时处理.仿真结果表明,算法具有良好的信号恢复和干扰置零性能,比基于非线性其轭梯度法的唯相位直接数据域算法性能更优.     

基于实时数字信号处理的宽带单比特瞬时测频接收技术

针对现代电子战接收机的大瞬时带宽、实时处理、高灵敏度、快速测频等高性能指标要求,提出了一种基于实时数字信号处理的宽带单比特瞬时测频接收机方案,结合大带宽高速采样的实时快速处理,将单比特接收算法、滑动快速傅里叶变换(FFT)算法、瞬时频率测量算法应用于该算法结构,给出了超高速单比特采样和高速实时信号处理的硬件实现。仿真结果表明,该接收机不仅具备大带宽、实时处理、高频率分辨率等特性,同时具有优异的信号检测灵敏度。     

基于延时相乘及其改进算法的DS/FH信号率线检测

针对DS/FH（直扩/跳频）混合扩频信号截获和参数估计问题,提出了一种基于延时相 乘结合自适应滤波和分段自相关的新方法。该算法首先将输入信号进行自适应滤波以提高 信噪比,滤波后送入延时相乘器,最后将乘积后数据分段进行自相关,通过分析谱图即可检 测DS/FH混合扩频信号的码速率谱线。计算机仿真显示,改进的算法不但能适应低信噪比( -2 0 dB)条件下DS/FH混合扩频信号的检测,而且同时能够实现对码速率的估计。该方法所用 算法简单,适合采用硬件设计实现,且如果是合作目标信号,搜索时间短,实时性强。     

A simple adaptive algorithm for real-time processing in antenna arrays

A new adaptation algorithm designed for real-time data processing in large antenna arrays is presented. The algorithm is used to determine the set of filter coefficients (weights) which minimizes the mean-square error in a multidimensional linear filter. The algorithm forms an estimate of the target signal, which is assumed to be of interest, in the presence of interfering noises. It is assumed that the direction of arrival and spectral density of the target signal are known a priori. No such information is assumed to be available regarding the structure of the interfering noise field. The a priori target information is incorporated directly into the adaptation procedure using a modified gradient descent technique. The mathematical convergence properties of the algorithm are presented and a computer simulation experiment is used as an illustration. It is shown that as the number of iterations becomes large, the expected value of the adaptive solution converges to the minimum mean-square-error solution. It is further shown that the variance of the adapted filter about the optimum solution can be made arbitrarily small by appropriate choice of a scalar constant in the algorithm. These results are based on the assumption that the array signals are Gaussian and that successive time samples are statistically uncorrelated. Thus, the new algorithm is shown to converge to the optimum processor in the limit as the number of adaptations becomes large. Any disadvantage which may arise in the use of such an asymptotically optimum system is offset by the extreme simplicity of the adaptive procedure. This simplicity should prove to be particularly useful in many of the practical array processing problems recently encountered in seismic and sonar data processing.     

基于遗传算法的部分自适应波束形成方法

将一种改进的遗传算法用于星载平面阵列天线方向图的实时综合。为了使遗传算法适合实时应用,在唯相自适应阵列的基础上进一步采用了部分阵元和部分比特的自适应波束形成,以降低算法计算量,提高其收敛速度。对基于改进遗传算法的唯相阵列部分阵元自适应波束形成和部分比特自适应波束形成进行了研究。模拟实验结果表明,两种方案都能够在波束“凝视”方向满足一定增益的前提下有效抑制来自旁瓣的强干扰,而且具有比传统唯相算法更快的收敛速度。     

Implementation of parallel lattice reduction-aided MIMO detector using graphics processing unit

Since H. Yao proposed the lattice reduction (LR)-aided detection algorithm for the MIMO detector, one can exploit the diversity gain provided by the LR method to achieve performance comparable to the maximum likelihood (ML) algorithm but with complexity close to the simple linear detection algorithms such as zero forcing (ZF), minimum mean squared error, and successive interference cancellation, etc. In this paper, in order to reduce the processing time of the LR-aided detector, a graphics processing unit (GPU) has been proposed as the main modem processor in such a way that the detections can be performed in parallel using multiple threads in the GPU. A 2X2 multiple input multiple output (MIMO) WiMAX system has been implemented using a GPU to verify that various MIMO detection algorithms such as ZF, ML, and LR-aided methods can be processed in real-time. From the experimental results, we show that GPUs can realize a 2X2 WiMAX MIMO system adopting an LR-aided detector in real-time. We achieve a processing time of 2.75?ms which meets the downlink duration specification of 3?ms. BER performance of experimental tests also indicates that the LR-aided MIMO detector can fully exploit diversity gain as well as ML detector.