Discrete Cosine Transform for Driving Liquid Crystal Displays

Despite rapid advances in science and technology of liquid crystal display (LCD); elimination of motion-related artifacts and preservation of color purity in moving images have remained elusive because gray-scale to gray-scale response time, i.e., time taken to switch pixels from one gray-scale to another depends on the initial and final gray shades. A technique wherein gray scale to gray scale response times are less dependent on the initial and final gray shades as compared to other addressing techniques for driving matrix LCD is reported. We also found that the response times are about the same as that of a pixel driven with simple square waveforms and, therefore, the effect of duty cycle due to matrix addressing is minimal with distributed waveforms of this technique.      

A Hybrid Compression Method for Integral Images Using Discrete Wavelet Transform and Discrete Cosine Transform

Integral imaging (II) is a promising three-dimensional (3-D) imaging technique that uses an array of diffractive or refractive optical elements to record the 3-D information on a conventional digital sensor. With II, the object information is recorded in the form of an array of subimages, each representing a slightly different perspective of the object In order to obtain high-quality 3-D images, digital sensors with a large number of pixels are required. Consequently, high-quality II involves recording and processing large amounts of data. In this paper, we present a compression method developed for the particular characteristics of the digitally recorded integral image. The compression algorithm is based on a hybrid technique implementing a four-dimensional transform combining the discrete wavelet transform and the discrete cosine transform. The proposed algorithm outperforms the baseline JPEG compression scheme applied to II and a previous compression method developed for II based on MPEG II.     

改进的层式DCT编码

在对几种具有多分辨率特性的DCT分析基础上提出了一种层式DCT的改进算法.与原始的层式DCT相比,该算法在同样的压缩比,尤其是较低压缩比下可以获得更高的峰值信噪比.     

A Fast Computational Algorithm for the Discrete Cosine Transform

A Fast Discrete Cosine Transform algorithm has been developed which provides a factor of six improvement in computational complexity when compared to conventional Discrete Cosine Transform algorithms using the Fast Fourier Transform. The algorithm is derived in the form of matrices and illustrated by a signal-flow graph, which may be readily translated to hardware or software implementations.     

All-Optical Discrete Sine Transform and Discrete Cosine Transform Based on Multimode Interference Couplers

In this letter, a novel method to realize all-optical discrete sine transform (DST) and discrete cosine transform (DCT) is proposed. The approach requires only one multimode interference (MMI) coupler and several phase shifters at the input and output ports. By properly arranging the length of the MMI coupler and adjusting the phase shifters, the DST can be directly realized all-optically. Meanwhile, the DCT is related to the DST with a simple formula. By changing the input phase and relabeling the output ports, it can also be realized on the MMI structure. The proposed methodology has no limit on the number of the inputs.      

OFDM系统中基于局部离散余弦变换的信道估计

论述了一种新的基于局部离散余弦变换(LDCT, local discrete cosine transform)的正交频分复用(OFDM, orthogonal frequency division multiplexing)系统信道估计方法.与传统的离散傅里叶变换(DFT)和离散余弦变换(DCT)不同,LDCT基函数具有良好的时域能量集中特性,可迅速捕获信号中的时变成分,有效跟踪信号时频结构的变化,有效地抑制符号间干扰(ISI)和信道加性高斯白噪声.仿真结果表明,该方法优于基于DFT和基于DCT的信道估计,是一种可行而且有效的信道估计方法.     

Error-resistance and Low-complexity Integer Inverse Discrete Cosine Transform

In this paper, a low-complexity multiplication-free integer inverse discrete cosine transform (IDCT) based on data flow structure of improved AAN’s fast IDCT is proposed for error drifting resistance of decoder. Two algorithms are used in this integer IDCT improvement. One is common factor extraction which extracts the complicated common factors from transform kernel to scale; the other is two-stage scale which splits a more than 16-bit scale into two less than 16-bit scales. With the two algorithms, high-accuracy integer IDCT is implemented in lower complexity. The experimental results show that the proposed transform exceeds the requirements of IEEE1180-1990 significantly (about 10 times). The results of the proposed IDCT implemented into MPEG-2 and MPEG-4 decoders instead of original 64-bit floating-point IDCT also show that it reduces the error drifting of decoders efficiently.     

基于离散余弦变换的水平集算法研究

针对传统水平集算法只对含有加性噪声的图像有较好处理结果的缺点,提出了一种基于离散余弦变换（DCT）的水平集研究算法。首先以图像中的每一点为中心构造隶属于图像的一系列子图像,对这些子图像进行二维DCT变换得到其变换系数,并受Lee滤波器可以去除乘性噪声的启发对这些系数进行运算,得到去除噪声后的平滑图像,再将平滑图像梯度的递减函数作为水平集演化方程的速度停止项,最后根据水平集演化方程对图像进行演化运算。实验结果表明,该方法能够在抑制乘性噪声的同时较好的对图像进行分割。     

On the Computation of the Discrete Cosine Transform

AnN-point discrete Fourier transform (DFT) algorithm can be used to evaluate a discrete cosine transform by a simple rearrangement of the input data. This method is about two times faster compared to the conventional method which uses a2N-point DFT.     

Fast Discrete Cosine Transform via Computation of Moments

Discrete cosine transform (DCT) is widely used in signal processing. This paper presents a novel approach to perform DCT. DCT is expressed in terms of discrete moments via triangle function transforms and later Taylor series expansion. From this, a fast systolic array for computing moments is converted to compute DCT with only a few multiplications and without any cosine evaluations. The systolic array has advantages of pipelinability, regularity, modularity, local connectivity and scalability, thus making it to be very suitable for VLSI implementation. We provide an estimate of the realizability of our array in a 0.5 m CMOS technology and comparisons with other methods. The execution time of the systolic array is only O(N log₂ N/log₂ log₂ N) in computing 1D N-point DCT if N is sufficiently large. The approach is also applicable to multiple dimensional DCT and DCT inverses.     

一种分块自适应压缩感知图像重构算法

CS理论中,在离散余弦变换下使用OMP算法重构图像时需要较高的测量值可以获得较好的重构效果,但是存在重构图像模糊的问题.为此,提出了基于离散余弦变换的图像分块自适应正交匹配追踪(BAD-OMP)算法.基于分块压缩感知技术,对图像进行均匀分块处理,根据图像块稀疏性进行自适应采样,再用均值滤波算法平滑处理,从而减少重构所需的测量值,降低块效应.仿真结果表明,采样率取0.1 ～0.35 时,BAD-OMP算法重构图像的PSNR值较OMP算法的PSNR值高9～1 1 dB,实现了在低采样率下获得较高的重构质量.     

一种适用于高清视频解码的反离散余弦变换的VLSI实现

提出了一种面向视频处理应用的二维8X8IDCT(反离散余弦变换)处理器结构.该处理器设计利用了IDCT算法中的对称性,采用基于并行的乘累加器的结构加快处理速度.设计过程中对于有限位宽对运算结果误差及精度的影响进行了仿真与分析,并根据要求确定了运算位宽的优化值,在满足精度的条件下使芯片的面积开销最小.该处理器核的面积为48K逻辑门,能够在0.64μs内完成对一个数据块的运算,可以满足对高清晰度视频实时解码的性能需求.     

任意长离散余弦变换的快速递归算法

该文基于Clenshaw递归公式以及离散余弦自身的对称性提出任意长离散余弦变换(DCT)的一种并行递归快速算法,给出了该算法的滤波器实现结构;与现有的其它递归算法以及基于算术傅里叶变换的余弦变换算法进行了计算复杂度的比较分析,结果表明该文算法运算量大大减少。该递归计算的滤波器结构使算法非常适合大规模集成电路(VLSI)实现。     

基于离散余弦变换的图像压缩研究

图像压缩是数据压缩技术在数字图像上的应用,其目的是减少图像数据中的冗余信息,从而用更加高效的格式存储和传输数据。图像压缩可以是有损数据压缩也可以是无损数据压缩。这里所研究的是有损压缩技术,对于此类技术,变换编码是最常用的方法,如离散余弦变换（DCT）或者小波变换这样的傅里叶相关变换,然后进行量化和用熵编码法压缩。     

一种基于Arnold置乱和离散余弦变换的信息隐藏算法

介绍了基于Arnold置乱变换和离散余弦变换(DCT)的图像信息隐藏算法.首先对秘密图像进行Arnold置乱变换,形成秘密信息,然后对载体图像进行DCT变换,秘密信息通过量化处理嵌入到DCT域中.从试验结果来看,该算法在一定程度上满足了信息隐藏的鲁棒性要求.     

一种针对DCT域高压缩图像的去块效应算法

在基于块DCT编码的图像压缩技术中,高压缩图像的块边界会出现块效应,严重损害图像的主观质量.提出一种新的基于图像恢复的去块效应算法,该算法根据图像特征从已分类的图像库中进行匹配,进而对图像噪声进行估计,达到去块效应的效果.经过实验证明,该算法有效.     

基于DCT的分块自适应量化算法及其用于SAR原始数据压缩

该文提出了一种基于离散余弦变换(DCT)和分块自适应量化相结合的SAR原始数据压缩算法。利用SAR原始数据满足局部平稳高斯随机过程的特点,通过将DCT系数进行重排,并对重排后的系数矩阵进行有效的量化比特分配和分块自适应量化,从而大幅度提高了量化增益。通过对真实SAR原始数据的压缩实验结果表明：该文算法与BAQ算法相比,以相对较低的运算复杂度增加,使图像域的压缩性能指标有了明显提高。     

An Approach to the Implementation of a Discrete Cosine Transform

An approach to the implementation of a discrete cosine transform (DCT) for application to coding speech is described. The approach is oriented toward single speech channel encoding. In addition, a detailed computer simulation of an adaptive transform coder is described. The purpose of the computer simulation is to determine the internal precision at various points in the implementation required to avoid subjective degradation. Specific recommmendations are made on the required internal precision in the implementation of the discrete cosine transform. A breadboard implementation of the DCT using SSI and MSI TTL logic based on the results of the computer simulation is reported.     

Reconsideration of "A Fast Computational Algorithm for the Discrete Cosine Transform"

Some corrections are made for the original paper "A fast computational algorithm for the discrete cosine transform," 1 which contains some errors of indexes and of multiplication factors.     

基于离散余弦变换的复值加密图像隐藏技术

提出了一种基于宿主图像离散余弦变换(DCT)的复值加密图像隐藏技术,待隐藏图像经双随机相位编码后的复值加密图像按一定规律隐藏在放大的宿主图像的离散余弦变换系数中.在提取隐藏图像过程中,利用相邻像素相减(NPVS)算法对藏有信息的宿主图像离散余弦变换系数进行运算,提取出隐藏的复值加密图像.经过正确的双随机相位解码,可获得原隐藏图像.研究了不同嵌入权重因子ω下藏有信息的宿主图像和解码后隐藏图像的各自相关度,分析了在ω=0.2情况下藏有信息的宿主图像的剪切对提取的隐藏图像质量的影响和基于数字全息的三维物体信息隐藏,结果表明该图像隐藏技术隐藏信息量大,抗剪切能力强,保密性好.