Design of adaptive and nonadaptive quantizers using subjective criteria

Several properties of visual masking have been investigated with a view to their application to adaptive quantization in DPCM-coding. Quantization characteristics for adaptive and nonadaptive quantizers have been designed using subjective criteria. Special stress has been laid on fixing the changeover levels of an adaptive quantizer. A comparison test involving various quantizing strategies demonstrated the efficiency of the developed techniques. Especially with regard to adaptive quantization with 11 levels (3.5 bits) per picture element, which is suitable for the transmission of broad-band TV-signals with 34 Mbits/s, an improvement on comparable methods could be demonstrated.     

CCD遥感图像的小波分解特性及编码压缩

研究了遥感图像的小波变换系数统计特性及小波系数的相关性.通过试验得出小波变换系数分布的一般规律和遥感图像基本特征,即数据的局部相关性弱、纹理丰富复杂和低冗余度,不利于高保真压缩,而遥感图像的小波变换系数却具有很强的局部相关性.提出了插分预测编码(DPCM)与集合树多级分裂(SPIHT)算法相结合的遥感图像小波编码算法,用该算法对CCD采集的遥感图像进行了3级小波分解和重构,并与EZW算法、SPIHT算法进行了比较.结果表明,算法所得的遥感图像没有方块效应,图像恢复质量较高,在相同压缩比和比特率低的情况下,明显优于其他两种算法.     

JPEG标准下图像压缩算法探讨

图像是互联网中传输信息的重要媒介,一幅没经过任何压缩处理的原始图像会给传输和存储带来很大困难。JPEG图像格式是目前最流行的图像格式,它的一个显著特点是压缩比相当高[1]。在本文笔者对JPEG标准下图像压缩的DCT基准算法和DPCM基准算法作了讨论和分析,为广大图像工作者提供很好的参考。     

DPCM与整数小波变换结合的医学图像无损压缩算法

提出了一种新的用于医学图像无损压缩的算法DPCM—IWT。该算法可进行实时处理，硬件实现简单。实验结果表明，DPCM—IWT算法的压缩率分别比IWT算法和DPCM方法平均提高12％和13．6％左右。     

基于DPCM与Hilbert扫描的灰度图像无损压缩方法

提出一种基于DPCM与Hilbert曲线的医疗图像无损压缩方法,通过差分脉码调制技术（DPCM）对图像进行预测处理,得到差值图像,再利用Hilbert曲线对医疗图像像素的进行扫描,得到图像的一维数据,然后分别用哈夫曼编码、游程编码和字典编码对一维数据进行压缩。实验结果显示Hilbert扫描可以增加像素的相关性,对提高压缩比有一定的贡献。     

基于差分脉码调制的随钻测量数据压缩编码算法

对随钻测井数据信息熵、概率分布和相关系数的分析表明,随钻测井数据具有分布集中、变化平缓和相关性强的规律。以此为根据提出了基于差分脉码调制(DPCM)算法的实时测井数据压缩编码方法。该方法通过降低随钻测井数据的相关冗余达到有效压缩随钻测井数据的目的,具有可灵活调整解码质量、算法复杂度为常数阶的优点。实际随钻测井数据的编码实验结果表明,在保证编码压缩后的随钻测井数据与原始随钻测井数据误差不超过5%的前提下,该方法能将实时传输的随钻测井数据量压缩为原始随钻测井数据量的一半以下,从而使随钻测量系统的传输效率提高到原来的两倍以上。图7表6参18     

DPCM系统中基于量化预测值的图像无损压缩

在超光谱图像和医学图像压缩的领域中,要求这些压缩是无损的,基于预测的方法一直是图像无损压缩的理论框架。在传统无损压缩的模型上,给出了一种有效的预测和量化算法,并结合算术编码对图像进行压缩,实验证明该算法兼有JPEG-JS预测器和Pirsch预测器的优点,有着较好的压缩性能,且算法简单、易于实现。     

基于SystemView的语音通信系统仿真

PCM,DPCM,DM是三种不同的模数、数模转换语音通信系统,是现代数字通信的基础。通过介绍这三种通信系统的基本原理．用SystemView搭建了系统级仿真模型并进行仿真．加深对现代通信系统的理解。     

New prediction schemes for lossless coding of fullband and subband images

This paper presents a study of lossless image compression of fullband and subband images using predictive coding. The performance of a number of different fixed and adaptive predictors are evaluated to establish the relative performance of different predictors at various resolutions and to give an indication of the achievable image resolution for given bit rates. In particular, the median adaptive predictor is compared with two new classes of predictors proposed in this paper. One is based on the weighted median filter, while the other uses context modelling to select the optimum from a set of predictors. A graphical tool is also proposed to analyse the prediction methods. Simulations of the different predictors for a variety of real world and medical images, evaluated both numerically and graphically, show the superiority of median based prediction over this proposed implementation of context model based prediction, for all resolutions. The effects of different subband decomposition techniques are also explored.     

Lossless video coding based on pixel-wise prediction

The state-of-the-art H.264/AVC was designed for lossy video coding in the beginning. Recently, the H.264/AVC FRExt was developed by removing transformation and quantization for lossless coding. In this paper, we propose an efficient intra lossless coding method based on a pixel-wise prediction. The proposed algorithm introduces an additional intra prediction mode that employs the LOCO-I predictor of JPEG LS. We found that the proposed lossless coding algorithm achieved approximately 22.0, 2.6, and 10.7% bit saving in terms of compression ratio, compared to the H.264/AVC FRExt, lossless intra 4:4:4, and Takamura’s lossless coding methods, respectively.