ASIC Design of DA-Based 2-D Inverse Discrete Cosine Transform

Aim To present an ASIC design of DA based 2 D IDCT. Methods\ In the design of 1 D IDCT is utilized a Chen based fast IDCT algorithm, and multiplier accumulators based on distributed algorithm contributes in reducing the hardware amount and in enhancing the speed performance. Results and Conclusion\ VHDL simulation, synthesis and layout design of system are implemented. This 2 D IDCT ASIC design owns best timing performance when compared with other better designs internationally. Results of design prove to be excellent.

Audio Zero-Watermark Scheme Based on Discrete Cosine Transform-Discrete Wavelet TransformSingular Value Decomposition

Traditional watermark embedding schemes inevitably modify the data in a host audio signal and lead to the degradation of the host signal.In this paper,a novel audio zero-watermarking algorithm based on discrete wavelet transform(DWT),discrete cosine transform(DCT),and singular value decomposition(SVD) is presented.The watermark is registered by performing SVD on the coefficients generated through DWT and DCT to avoid data modification and host signal degradation.Simulation results show that the proposed zero-watermarking algorithm is strongly robust to common signal processing methods such as requantization,MP3 compression,resampling,addition of white Gaussian noise,and low-pass filtering.

A Dual Tree Complex Discrete Cosine Harmonic Wavelet Transform (ADCHWT) and Its Application to Signal/Image Denoising

A new simple and efficient dual tree analytic wavelet transform based on Discrete Cosine Harmonic Wavelet Transform DCHWT (ADCHWT) has been proposed and is applied for signal and image denoising. The analytic DCHWT has been realized by applying DCHWT to the original signal and its Hilbert transform. The shift invariance and the envelope extraction properties of the ADCHWT have been found to be very effective in denoising speech and image signals, compared to that of DCHWT.

Implementation of Variable Tone Variable Bits Gray-Scale Image Stegnography Using Discrete Cosine Transform

Secure exchange of information is the basic need of modern digital world of e-communication which is achieved either by encrypting information or by hiding information in other information called cover media. Concealing information requires a well designed technique of Stegnography. This work presents a technique, variable tone variable bits (VTVB) Stegnography, to hide information in a cover image. The VTVB Stegnography hides variable data in discrete cosine transform (DCT) coefficients of the cover image. VTVB Stegnography provides variable data hiding capacity and variable distortion. Additional large data hiding this technique provide extra security due to the large key size making VTVB Stegnography technique much more immune to steganalysis. The hiding makes the existence of information imperceptible for steganalysis and the key of keeping a secret makes the recovering of information difficult for an intruder. The key size is depending on cover image and numbers of bits of discrete cosine transform (DCT) coefficients used for information embedding. This is a very flexible technique and can be used for low payload applications, e.g. watermarking to high payload applications, e.g. network Stegnography.

Peak-to-Average Power Ratio Performance Analysis for Orthogonal Chirp Division Multiplexing Multicarrier Systems Based on Discrete Fractional Cosine Transform

In doubly selective fading channels, the orthogonal frequency division multiplexing (OFDM) multicarrier system may fail. Chirp like basis (fractional Fourier transform-fractional cosine transform) may be used instead of complex exponential basis in this case to improve the system performance. However, in multicarrier transmission, the high peak to average power ratio (PAPR) of the transmitted signal is one of the difficult problems that face both the chirp and the exponential basis. In this paper, an evaluation for the PAPR performance of a multicarrier system based on the fractional cosine transform (FrCT) is introduced and then compared with DFrFT and FFT. Moreover, applying the SLAM technique over these systems is provided to understand the behaviour of these systems when applying SLAM. Simulations verify that this system obtains a better PAPR performance. Moreover, further PAPR reduction can be gained using the well-known PAPR reduction methods. Moreover, applying SLAM technique improves the performance of (dB) by 4 dB to 5 dB and all systems become as competitive to each other when SLAM is applied. Finally, BER performance comparison among OFDM, Discrete Cosine Transform MCM (DCT- MCM), Discrete Hartley Transform MCM (DHT-MCM), DFrFT-OCDM and DFrCT- OCDM MCM systems was done by means of simulation over 100,000 multicarrier blocks for each one and showed that our proposed scenario gave the best performance.

Multiple Image Watermarking with Discrete Cosine Transform

Multiple image watermarking is an advanced concept of singular watermarking techniques. The existing singular digital image watermarking techniques cannot obtain all the design goals, such as imperceptibility, robustness, security, and capacity simultaneously with perfection. Hence, the multiple image watermarking technique is designed that embeds several watermarks into the same host image for conveying multiple information. This paper proposed a multiple image watermarking technique with Discrete Cosine Transform (DCT) for ensuring the low computational time for embedding, encryption, decryption as well as extraction of the watermark images. Here, DCT is used to ensure the visual quality of the host image, and a random binary matrix is used to improve the security of the digital image. We have given a basic framework for multiple image watermarking. Our experimental results show satisfactory performance.

NEW FAST ALGORITHM OF 2-D DISCRETE COSINE TRANSFORM

In this paper, a new algorithm for the fast computation of a 2-D discrete cosine transform (DCT) is presented. It is shown that the N×N DCT, where N = 2m, can be computed using only N 1-D DCT’s and additions, instead of using 2N 1-D DCT’s as in the conventional row-column approach. Hence the total number of multiplications for the proposed algorithm is only half of that required for the row-column approach, and is also less than that of most of other fast algorithms, while the number of additions is almost comparable to that of others.

Adaptive Biorthogonal Local Discrete Cosine Transform for Interference Excision in Direct Sequence Spread Spectrum Communications

A novel time-frequency domain interference excision technique is proposed. The technique is based on adaptive biorthogonal local discrete cosine trans form (BLDCT). It uses a redundant library of biorthogonal local discrete cosine bases and an efficient concave cost function to match the transform basis to the interfering signal. The main advantage of the algorithm over conventional trans form domain excision algorithms is that the basis functions are not fixed but ca n be adapted to the time-frequency structure of the interfering signal. It is w e ll suited to transform domain compression and suppression of various types of in terference. Compared to the discrete wavelet transform (DWT) that provides logar ithmic division of the frequency bands, the adaptive BLDCT can provide more flex ible frequency resolution. Thus it is more insensitive to variations of jamming frequency. Simulation results demonstrate the improved bit error rate (BER) perf ormance and the increased robustness of the receiver.

Experiments in Parallelizing the Type IV Discrete Cosine Transform

The Fourier transform is very important to numerous applications in science and engineering. However, its usefulness is hampered by its computational expense. In this paper, in an attempt to develop a faster method for computing Fourier transforms, the authors present parallel implementations of two new algorithms developed for the type IV Discrete Cosine Transform （DCT-IV） which support the new interleaved fast Fourier transform method. The authors discuss the realizations of their implementations using two paradigms. The first involved commodity equipment and the Message-Passing Interface （MPI） library. The second utilized the RapidMind development platform and the Cell Broadband Engine （BE） processor. These experiments indicate that the authors＇ rotation-based algorithm is preferable to their lifting-based algorithm on the platforms tested, with increased efficiency demonstrated by their MPI implementation for large data sets. Finally, the authors outline future work by discussing an architecture-oriented method for computing DCT-IVs which promises further optimization. The results indicate a promising fresh direction in the search for efficient ways to compute Fourier transforms.

FPGA Implementation of Approximate 2D Discrete Cosine Transforms

Discrete cosine transform (DCT) is frequently used in image and video signal processing due to its high energy compaction property. Humans are able to perceive and identify the information from slightly erroneous images. It is enough to produce approximate outputs rather than absolute outputs which in turn reduce the circuit complexity. Numbers of applications like image and video processing need higher dimensional DCT algorithms. So the existing architectures of one dimensional (1D) approximate DCTs are reviewed and extended to two dimensional (2D) approximate DCTs. Approximate 2D multiplier-free DCT architectures are coded in Verilog, simulated in Modelsim to evaluate the correctness, synthesized to evaluate the performance and implemented in virtexE Field Programmable Gate Array (FPGA) kit. A comparative analysis of approximate 2D DCT architectures is carried out in terms of speed and area.

A Discrete Cosine Adaptive Harmonic Wavelet Packet and Its Application to Signal Compression

A new adaptive Packet algorithm based on Discrete Cosine harmonic wavelet transform (DCHWT), (DCAHWP) has been proposed. This is realized by the Discrete Cosine Harmonic Wavelet transform (DCHTWT) which exploits the good properties of DCT viz., energy compaction (low leakage), frequency resolution and computational simplicity due its real nature, compared to those of DFT and its harmonic wavelet version. Hence the proposed wavelet packet is advantageous both in terms of performance and computational efficiency compared to those of existing DFT harmonic wavelet packet. Further, the new DCAHWP also enjoys the desirable properties of a Harmonic wavelet transform over the time domain WT, viz., built in decimation without any explicit antialiasing filtering and easy interpolation by mere concatenation of different scales in frequency (DCT) domain with out any image rejection filter and with out laborious delay compensation required. Further, the compression by the proposed DCAHWP is much better compared to that by adaptive WP based on Daubechies-2 wavelet (DBAWP). For a compression factor (CF) of 1/8, the ratio of the percentage error energy by proposed DCAHWP to that by DBAWP is about 1/8 and 1/5 for considered 1-D signal and speech signal, respectively. Its compression performance is better than that of DCHWT, both for 1-D and 2-D signals. The improvement is more significant for signals with abrupt changes or images with rapid variations (textures). For compression factor of 1/8, the ratio of the percentage error energy by DCAHWP to that by DCHWT, is about 1/3 and 1/2, for the considered 1-D signal and speech signal, respectively. This factor for an image considered is 2/3 and in particular for a textural image it is 1/5.

基于DCT自适应量化的频谱数据有损压缩算法

针对由于我国频谱监测设备数量激增产生了海量频谱监测数据的存储和传输难题,提出一种基于DCT自适应量化的频谱数据有损压缩算法。首先将多帧频谱监测数据组合并经过灰度空间映射形成一幅时频图,后将时频图数据矩阵按列三等分,将等分后的数据作为RGB三通道合成一幅彩色图像并对其进行二维DCT变换,利用BP神经网络估计量化阈值后进行量化,最后经过游程编码与二次熵编码完成频谱监测数据的压缩。通过对真实接收机采集的频谱数据的压缩处理,压缩率约为10%,数据恢复后的百分比均方根误差约为11%。实验结果表明,所提算法具有稳定的压缩率和较小的恢复误差,能够有效地对实际采集的频谱数据进行压缩。

AN IMPROVED ALL ZERO BLOCK FINDING METHOD BASED ON THE STATISTIC CHARACTERISTICS OF DCT TRANSFORM COEFFICIENTS

In the H.263 video codec related systems, motion estimation and Discrete Cosine Transform (DCT) have the most computational requirements. In order to reduce complexity of the encoder to dedicate more resources to other functions, according to the study of existing methods, an Improved All Zero Block Finding (IAZBF) method based on the statistic characteristics of DCT coefficients is proposed. Compared with existing methods, IAZBF improves the detecting efficiency by about 50% without importing too much extra computation requirement. Being computed with additions and shifts instead of complicated multiplications, IAZBF is of low computation complexity, especially for low-end processors. In addition, IAZBF upholds picture fidelity and remains compatible with the H.263 bitstream standard.

基于DCT和维纳滤波的图像PRNU匿名算法

随着智能手机和社交媒体的普及,图像隐私引起的公共安全问题受到了广泛关注。犯罪分子可利用图像信息来侵犯他人隐私,从而进行恶意跟踪和诈骗勒索等活动。针对该问题,本研究从抑制图像源相机识别能力的角度提出了一种新的光响应非均匀性(photo response non uniformity,PRNU)匿名算法,以降低图像被恶意使用的风险。算法首先对图像进行分块,并将离散余弦变换(discrete cosine transform,DCT)和维纳滤波相结合,对图像高频分量进行滤波处理。通过实验发现,迭代维纳滤波可以显著提高匿名算法的效率。将算法在MICHE-I数据集和UBIPR虹膜数据集中进行测试,结果表明,算法能够保证图像质量不受显著影响,并且视觉质量因子平均提高3 dB,有效地抑制了图像溯源能力,保留图像生物特征,并达到了较好的匿名效果,保证了大众隐私安全。

DCT和无损编码的GNSS中频信号压缩算法

针对全球卫星导航系统(GNSS)中频信号在数据回放与分析、模拟测试场景下存储数据量大,内存占用高的问题,提出一种基于离散余弦变换(DCT)和无损编码的GNSS中频信号压缩算法:结合DCT变换和多种主流无损编码技术,根据信号功率谱特性确定压缩方式和多个压缩阈值,实现信号功率谱的多阶层自适应压缩;针对多种采样率信号和多种量化位宽信号进行实验,利用软件接收机评估算法对信号功率估计精度的影响及算法压缩性能。结果表明,DCT_Zstd算法可以同时满足压缩率较低和压缩时间较短的需求,算法对仿真信号和实测信号的最小功率损失分别约为0.16 dBHz和0.51 dBHz,特别是对实测信号的压缩率可达1%的同时,仅对导航定位解算有微小的影响。

DCT-YOLOv5:从频率角度设计目标检测算法

离散余弦变换(DCT)是JPEG压缩算法的核心步骤之一,将图像空间域的像素数据转换为频率域的系数。DCT与深度学习结合的算法非常常见,但并未从频率角度解析卷积结构。为进一步提升目标检测性能,针对该问题提出改进算法:DCT-YOLOv5。首先,证明卷积神经网络(CNNs)、Transformer和MLP架构都是对频域的隐式建模,验证以往模型设计的默认原则:有效感受野总小于理论感受野、多个小卷积核优于大卷积核。其次,考虑输入通道和卷积核选择合理的输出通道数,做到近似无损变换,其中下采样阶段是唯一改变通道数的地方。最后,通过固定参数比较DCT和卷积,二者差异稳定在±0.8%。并且为了最大程度降低计算量,引入固定组内数量的分组卷积。该模型以YOLOv5为基准,在COCO数据集上设计了丰富实验,验证方法的有效性。取得了28.9%的mAP@.5和277.8的FPS,相对于基准模型获得了1.3%的相对提升。测试结果表明,改进后的模型在精度上有显著提升,并能够在更低的算力平台上运行。

改进的基于DCT的自适应水印算法

基于原始图像的纹理特征和亮度特征以及人类视觉系统的特点,给出一种改进的基于DCT的自适应嵌入水印算法。算法采用Arnold变换对水印图像进行预处理,自适应选择强度因子,将一幅二值水印图像嵌入到原始图像中,实现了水印的不可见性和鲁棒性。仿真实验结果表明,算法对常见的图像处理操作具有较强的鲁棒性和稳健性。

DCT和LBP特征融合的人脸识别

提出一种特征融合的人脸识别新方法.该方法将人脸图像中少量的低频离散余弦变换(DCT)系数用作人脸的频域特征;把人脸图像规则地分成多个子块,计算每个子块的局部二值图(LBP)编码直方图.这些子块的LBP直方图连接成一个空域全局直方图,作为人脸的描述向量.这个描述向量经过PCA降维后作为人脸的LBP特征.DCT特征和LBP特征分别归一化,然后进行特征融合.在ORL人脸库上的实验显示了所提方法比单独采用DCT或LBP特征的人脸识别有较好的性能改善.

基于局部DCT系数的图像压缩感知编码与重构

引入了压缩感知(Compressed sensing,CS)理论,给出了在获取局部二维离散余弦变换(Discrete cosine transform,DCT)系数的基础上高质量地编码与重构图像的新方法.研究了在无量化和有量化情况下,基于局部DCT系数的图像CS最小全变差重构算法.在对DCT系数进行量化的过程中得到含噪的局部DCT系数,在此基础上设计了能完成CS重构的图像编解码一般流程,并构建了实际应用系统.实验结果表明,对于稀疏性较强的图像,在图像编解码系统中结合CS理论与方法能得到高质量的重构图像,与传统的直接反离散余弦变换(Inverse DCT,IDCT)方法相比,峰值信噪比(Peak signal to noiseratio,PSNR)最大能提高5dB以上,对于一般图像,PSNR也有较大提高.

基于分块DCT变换和Arnold置乱的自适应图像水印算法

提出了一种基于分块DCT变换和Arnold置乱变换的自适应图像水印算法,该算法在水印嵌入过程中充分考虑了人类视觉系统(HVS)的特点,在不同的DCT块中嵌入不同的水印能量,从而使算法具有自适应能力。实验结果表明:该算法对于常见的图像处理具有较强的鲁棒性,特别是具有十分有效的抗击剪切的能力。