一种新型的无损视频压缩算法

多次使用有损压缩技术压缩数字视频,会导致视频的质量大幅下降,从而降低了数字视频的可再利用率,为此设计了一种新型的无损视频压缩算法。 该算法的特点在于:(1)提出了一种改进的基于上下文树的算术编码来压缩运动补偿后的误差帧。(2)针对改进的算术编码,优化基于宏块的运动估计与补偿算法,以提高无损视频压缩算法的压缩率。对于压缩运动补偿后误差帧的算法,与静态图像无损压缩算法JPEG-LS和CALIC相比表明,该文设计的无损视频压缩算法的压缩率超过JPEG-LS算法最高为23.3%,超过CALIC算法最高为19.3%。     

3D scanning-based compression technique for digital hologram video

In this paper, we proposed an efficient coding method for digital hologram video using a three-dimensional (3D) scanning method and two-dimensional (2D) video compression technique. It consists of separation of the captured 3D image into R, G, and B color space components, localization by segmenting the fringe pattern in to M×N [pixel²], frequency-transform by 2D discrete cosine transform (2D DCT), 3D-scanning the segments to form a video sequence, classification of coefficients, and hybrid video coding with H.264/AVC, differential pulse code modulation (DPCM), and lossless coding method. The experimental results with this method showed that the proposed method has compression ratios of 8–16 times higher than the previous researches. Thus, we expect it to contribute to reduce the amount of digital hologram data for communication or storage.     

用整数小波结合改进SPIHT编码实现静止图像无损压缩

无损图像压缩是图像处理中的一个重要领域 ,传统的基于熵编码的无损压缩编码方式存在一定的局限。利用提升算法构造整数小波变换 ,然后针对无损压缩特点 ,对 SPIHT算法加以改进 ,实现了一种可行的图像无损压缩编码方案。实验表明 ,优于传统熵编码和直接采用 SPIHT的无损压缩方法     

三维矩阵彩色图像WDCT压缩编码

本文深入研究了三维矩阵,首次提出了一种新的基于三维矩阵的宽离散余弦变换(3-D WDCT),并且定义了它的运算准则,证明了它的正反变换和相关性质,将之应用到彩色图像的压缩编码中.我们知道,彩色图像的三帧是同一物理模型的映射,具有相同的纹理,边缘和灰度变化等.本文充分考虑了彩色图像三帧间的结构相似性,把彩色图像的各个分量表示在一个统一的数学模型里,使彩色图像的R,G,B三帧第一次作为一个整体进行压缩编码,同时去除帧间的与帧内的冗余,而不是象其他方法那样把各个分量独立处理.实验结果表明,这种方法的重建图像无论是压缩比,信噪比,还是视觉效果都有明显提高.本文运用并发展了目前较为成熟的离散余弦变换技术,与JPEG和MPEG都有很好的兼容性.     

Lossless compression of color mosaic images.

Lossless compression of color mosaic images poses a unique and interesting problem of spectral decorrelation of spatially interleaved R, G, B samples. We investigate reversible lossless spectral-spatial transforms that can remove statistical redundancies in both spectral and spatial domains and discover that a particular wavelet decomposition scheme, called Mallat wavelet packet transform, is ideally suited to the task of decorrelating color mosaic data. We also propose a low-complexity adaptive context-based Golomb-Rice coding technique to compress the coefficients of Mallat wavelet packet transform. The lossless compression performance of the proposed method on color mosaic images is apparently the best so far among the existing lossless image codecs.     

Motion compensated lossy-to-lossless compression of 4-D medical images using integer wavelet transforms.

This paper proposes a method for progressive lossy-to-lossless compression of four-dimensional (4-D) medical images (sequences of volumetric images over time) by using a combination of three-dimensional (3-D) integer wavelet transform (IWT) and 3-D motion compensation. A 3-D extension of the set-partitioning in hierarchical trees (SPIHT) algorithm is employed for coding the wavelet coefficients. To effectively exploit the redundancy between consecutive 3-D images, the concepts of key and residual frames from video coding is used. A fast 3-D cube matching algorithm is employed to do motion estimation. The key and the residual volumes are then coded using 3-D IWT and the modified 3-D SPIHT. The experimental results presented in this paper show that our proposed compression scheme achieves better lossy and lossless compression performance on 4-D medical images when compared with JPEG-2000 and volumetric compression based on 3-D SPIHT.     

真彩色图像的有损RLE压缩

程编码是一种简单有效的数据压缩编码方法，在信源编码中属于统计编码无损压缩的范畴。一般的图像数据存在内在的相关性，对原始图像数据进行一定变换可将内在相关性提取出来，这就为行程编码在图像压缩领域的应用提供了可能。基于对传统行程编码方法的分析可知，必须对其进行一定改进才能保证对数据的有效压缩，改进后的编码方法可称为简单有损行程编码。图像的内在相关性可通过变换编码加以分析，离散余弦变换就是一种较常用的变换编码方法。对原始图像数据进行离散条弦变换和重排，可使相关性较好的数据集中起来，为利用简单有损行程编码方法创造了条件，该编码方法可称为复合有损行程编码方法。通过实例比较分析，证明了该方法能对真彩色图像进行有效压缩。在可接受的有损范围内，获得较好的压缩比。     

一种结合人眼对比度感知特性的彩色图像压缩算法

为了使图像压缩后的效果更加符合人眼感知特性,提出了一种结合人眼对比度敏感视觉特性的图像压缩算法。算法首先结合视觉特性和图像变换域频谱系数特征,提出一种图像的角频率的计算方法,并依据计算的角频率提出一种人眼觉察图像最小误差阈值的计算方法;然后以此阈值作为量化步长,提出一种图像变换域频谱系数的量化方法;最后采用霍夫曼编码算法进行编解码,实现图像的压缩。并对三幅彩色图像进行了仿真实验,结果表明:与JPEG技术相比,三幅彩色图和各分量图的平均压缩比、PSNR和SSIM依次提高了10.4807%、6.9879%和2.6494%。表明提出的结合人眼视觉特性的图像压缩算法是一种较好的、有实用价值的压缩算法。     

A lossless compression algorithm of remote sensing image for space applications

A simple and adaptive lossless compression algorithm is proposed for remote sensing image compression, which includes integer wavelet transform and the Rice entropy coder. By analyzing the probability distribution of integer wavelet transform coefficients and the characteristics of Rice entropy coder, the divide and rule method is used for high-frequency sub-bands and low-frequency one. High-frequency sub-bands are coded by the Rice entropy coder, and low-frequency coefficients are predicted before coding. The role of predictor is to map the low-frequency coefficients into symbols suitable for the entropy coding. Experimental results show that the average Comprcssion Ratio （CR） of our approach is about two, which is close to that of JPEG 2000. The algorithm is simple and easy to be implemented in hardware. Moreover, it has the merits of adaptability, and independent data packet. So the algorithm can adapt to space lossless compression applications.     

A novel method for lossless image compression and encryption based on LWT,SPIHT and cellular automata

In this paper, a novel method for lossless image encryption based on set partitioning in hierarchical trees and cellular automata. The proposed encryption method embeds the encryption into the compression process, in which a small part of the data is encrypted quickly, while maintaining the good coding characteristics of set partitioning in hierarchical trees (SPIHT). The proposed encryption system adopts three stages of scrambling and diffusion. In each stage of encryption, different chaotic systems are used to generate the plaintext-related key stream to maintain high security and to resist some attacks. Moreover, the channel length of the coded-and-compressed color image is more uncertain, resulting into higher difficulty for attackers to decipher the algorithm. The experimental results indicate that the length of bitstream is compressed to 50% of the original image, showing that our proposed algorithm has higher lossless compression ratio compared with the existing algorithms. Meanwhile, the encryption scheme passes the entropy analysis, sensitivity analysis, lossless recovery test, and SP800-22 test.     

Efficient Differential Pixel Value Coding in CABAC for H.264/AVC Lossless Video Compression

Since context-based adaptive binary arithmetic coding (CABAC) as the entropy coding method in H.264/AVC was originally designed for lossy video compression, it is inappropriate for lossless video compression. Based on the fact that there are statistical differences of residual data between lossy and lossless video compression, we propose an efficient differential pixel value coding method in CABAC for H.264/AVC lossless video compression. Considering the observed statistical properties of the differential pixel value in lossless coding, we modified the CABAC encoding mechanism with the newly designed binarization table and the context-modeling method. Experimental results show that the proposed method achieves an approximately 12% bit saving, compared to the original CABAC method in the H.264/AVC standard.     

基于联想记忆的彩色图像自适应预测编码方法

本文利用牛顿前向插值多项式构建一种联想记忆型神经网络,并基于联想记忆提出一种彩色图像的自适应预测无损编码方法。针对彩色图像帧间相关性较大的特点,首先用R,G,B-G替代R,G,B以减小帧间相关性,然后对R 单独进行预测编码,对C,B—G进行二维矢量预测编码进一步减小空间相关和帧间相关,最后对预测残差进行算术编码。实验证明该算法是可行性的和有效性的,对测试图像的压缩效果优于JPEG-LS标准。     

基于IPCT/3-D Tarp的高光谱图像无损压缩

研究了一种将变换矩阵分解为三角元素可逆矩阵(TERM)实现的主成分变换整数近似算法(IPCT).为限制误差和提高计算效率,改进了TERM分解中选择主元的方法.结合可逆整数PCT和三维Tarp编码技术,提出了一种新的高光谱图像无损压缩算法.该算法在进行空间维小波变换以后,利用改进的IPCT去除谱间相关;在编码阶段,新颖的三维Tarp编码器能利用五个简单的递归滤波器进行概率估计,以驱动一个非自适应算术编码器,对变换系数的显著性映射和细化信息进行熵编码.该算法复杂度较低,能够产生嵌入式码流,并且较已有的算法能获得更高的压缩比.     

Lossless compression of color sequences using optimal linear prediction theory

In this paper, we present a novel technique that uses the optimal linear prediction theory to exploit all the existing redundancies in a color video sequence for lossless compression purposes. The main idea is to introduce the spatial, the spectral, and the temporal correlations in the autocorrelation matrix estimate. In this way, we calculate the cross correlations between adjacent frames and adjacent color components to improve the prediction, i.e., reduce the prediction error energy. The residual image is then coded using a context-based Golomb-Rice coder, where the error modeling is provided by a quantized version of the local prediction error variance. Experimental results show that the proposed algorithm achieves good compression ratios and it is roboust against the scene change problem.     

Deep chroma prediction of Wyner–Ziv frames in distributed video coding of wireless capsule endoscopy video

Compression of captured video frames is crucial for saving the power in wireless capsule endoscopy (WCE). A low complexity encoder is desired to limit the power consumption required for compressing the WCE video. Distributed video coding (DVC) technique is best suitable for designing a low complexity encoder. In this technique, frames captured in RGB colour space are converted into YCbCr colour space. Both Y and CbCr representing luma and chroma components of the Wyner–Ziv (WZ) frames are processed and encoded in existing DVC techniques proposed for WCE video compression. In the WCE video, consecutive frames exhibit more similarity in texture and colour properties. The proposed work uses these properties to present a method for processing and encoding only the luma component of a WZ frame. The chroma components of the WZ frame are predicted by an encoder–decoder based deep chroma prediction model at the decoder by matching luma and texture information of the keyframe and WZ frame. The proposed method reduces the computations required for encoding and transmitting of WZ chroma component. The results show that the proposed DVC with a deep chroma prediction model performs better when compared to motion JPEG and existing DVC systems for WCE at the reduced encoder complexity.     

一种图像自适应预测分组编码无损压缩方法

结合经典无损预测编码方法和变长编码思想,提出了一种有自适应性的预测分组编码方法.通过自适应预测编码对不同纹理特征的图像均能有效地做去相关性处理,再结合图像数据分布规律通过分组编码实现图像的无损压缩.实验结果表明这套方法具有高压缩比和高压缩效率的特点.     

Cross residual transform for lossless intra-coding for HEVC

A new lossless intra-coding method based on a cross residual transform is applied to the next generation video coding standard HEVC (High Efficiency Video Coding). HEVC includes a multi-directional spatial prediction method to reduce spatial redundancy by using neighboring pixels as a prediction for the pixels in a block of data to be encoded. In the new lossless intra-coding method, the spatial prediction is performed as pixelwise DPCM but is implemented as block-based manner by using cross residual transform on the HEVC standard. The experimental results show that the new lossless intra-coding method reduces the bit rate of approximately 8.43% in comparison with the lossless-intra coding method in the HEVC standard and the proposed method results in slightly better compression ratio than the JPEG200 lossless coding.     

彩色图像三维矩阵变换压缩编码

本文提出了一种基于人类视觉的新的彩色图像压缩编码方法，即三维矩阵变换压缩编码，推导了三维矩阵混合变换理论及其实现方法，使得压缩编码更充分地利用极色图象在空间上及各分量之间的相关性，与其它变换压缩编码不同的是：它不是把彩色图像的各分量独立开来，而是将去除各分量内部及各分量之间的冗余同时进行，仿真结果表明，该方法的重建图象具有有较好的视觉效果并有较好的压缩比。     

A Lossless Compression Method for Medical Image Sequences Using JPEG-LS and Interframe Coding

Hospitals and medical centers produce an enormous amount of digital medical images every day, especially in the form of image sequences, which requires considerable storage space. One solution could be the application of lossless compression. Among available methods, JPEG-LS has excellent coding performance. However, it only compresses a single picture with intracoding and does not utilize the interframe correlation among pictures. Therefore, this paper proposes a method that combines the JPEG-LS and an interframe coding with motion vectors to enhance the compression performance of using JPEG-LS alone. Since the interframe correlation between two adjacent images in a medical image sequence is usually not as high as that in a general video image sequence, the interframe coding is activated only when the interframe correlation is high enough. With six capsule endoscope image sequences under test, the proposed method achieves average compression gains of 13.3% and 26.3 % over the methods of using JPEG-LS and JPEG2000 alone, respectively. Similarly, for an MRI image sequence, coding gains of 77.5% and 86.5% are correspondingly obtained.     

Mode-Dependent Templates and Scan Order for H.264/AVC-Based Intra Lossless Coding

In H.264/advanced video coding (AVC), lossless coding and lossy coding share the same entropy coding module. However, the entropy coders in the H.264/AVC standard were original designed for lossy video coding and do not yield adequate performance for lossless video coding. In this paper, we analyze the problem with the current lossless coding scheme and propose a mode-dependent template (MD-template) based method for intra lossless coding. By exploring the statistical redundancy of the prediction residual in the H.264/AVC intra prediction modes, more zero coefficients are generated. By designing a new scan order for each MD-template, the scanned coefficients sequence fits the H.264/AVC entropy coders better. A fast implementation algorithm is also designed. With little computation increase, experimental results confirm that the proposed fast algorithm achieves about 7.2% bit saving compared with the current H.264/AVC fidelity range extensions high profile.