A bilateral attention based generative adversarial network for DIBR 3D image watermarking

This paper presents a bilateral attention based generative adversarial network (BAGAN) for depth-image-based rendering (DIBR) 3D image watermarking to protect the image copyright. Convolutional block operations are employed to extract main image features for robust watermarking, but embedding watermark into some features will degrade image quality much. To relieve this kind of image distortion, the bilateral attention module (BAM) is utilized by mining correlations of the center view and the depth map to compute attention of the 3D image for guiding watermark to distribute over different image regions. Since a modality gap exists between the center view and the depth map, a cross-modal feature fusion module (CMFFM) is designed for BAM to bridge the cross-view gap. Because the depth map has lots of flat background information including many redundant features, to prune them, the depth redundancy elimination module (DREM) is used for cross-view feature fusion. In the decoder, two extractors with the same structure are built to recover watermark from the center view and the synthesized view, respectively. In addition, the discriminator is supposed to build a competitive relationship with the encoder to increase the image quality. The noise sub-network is used to train different image attacks for robustness. Extensive experimental results have demonstrated that the proposed BAGAN can obtain higher watermarking invisibility and robustness compared with existing DIBR 3D watermarking methods. Ablation experiments have also proven the effectiveness of DREM, CMFFM and BAM on BAGAN.     

基于Kinect的实时深度提取与多视绘制算法

提出了一种基于Kinect的实时深度提取算法和单纹理+深度的多视绘制方法。在采集端,使用Kinect提取场景纹理和深度,并针对Kinect输出深度图的空洞提出一种快速修复算法。在显示端,针对单纹理+深度的基于深度图像的绘制(DIBR,depth image based rendering)绘制产生的大空洞,采用一种基于背景估计和前景分割的绘制方法。实验结果表明,本文方法可实时提取质量良好的深度图,并有效修复了DIBR绘制过程中产生的大空洞,得到质量较好的多路虚拟视点图像。以所提出的深度获取和绘制算法为核心,实现了一种基于深度的立体视频系统,最终的虚拟视点交织立体显示的立体效果良好,进一步验证了本文算法的有效性。本文系统可用于实景的多视点立体视频录制与播放。     

High efficiency depth image-based rendering with simplified inpainting-based hole filling

Hole and crack filling is the most important issue in depth-image-based rendering (DIBR) algorithms for generating virtual view images when only one view image and one depth map are available. This paper proposes a priority patch inpainting algorithm for hole filling in DIBR algorithms by generating multiple virtual views. A texture-based interpolation method is applied for crack filling. Then, an inpainting-based algorithm is applied patch by patch for hole filling. A prioritized method for selecting the critical patch is also proposed to reduce computation time. Finally, the proposed method is realized on the compute unified device architecture parallel computing platform which runs on a graphics processing unit. Simulation results show that the proposed algorithm is 51-fold faster for virtual view synthesis and achieves better virtual view quality compared to the traditional DIBR algorithm which contains depth preprocessing, warping, and hole filling.     

零视差点重组在三维图像数字水印中的应用

在基于深度图像渲染（DIBR）水印方案中,利用深度图像和中央彩色图像通过像素平移渲染出左眼视图和右眼视图,嵌入到中央图像的水印信息会受到严重破坏,无法在左眼视图和右眼视图中正确提取水印信息。本文提出一种DIBR中零视差点的三维图像数字水印方法,利用深度值确定视差值,标定视差为零的点,重新组合成新的载体图像,进行水印嵌入。由于视差为零的像素点在生成左右眼视图时没有发生水平移动,所以此方法克服了DIBR过程中的像素平移带来的攻击。实验证明此方法能得到和二维水印一致的效果并且对于高斯噪声和JPEG压缩都具有良好的鲁棒性。      

Stereoscopic view synthesis based on region-wise rendering and sparse representation

Depth image-based rendering (DIBR), which is used to render virtual views with a color image and the corresponding depth map, is one of the key techniques in the 2D to 3D conversion process. One of the main problems in DIBR is how to reduce holes that occur on the generated virtual view images. In this paper, we make two main contributions to deal with the problem. Firstly, a region-wise rendering framework, which divides the original image regions into three special classes and renders each with optimal adaptive process respectively, is introduced. Then, a novel sparse representation-based inpainting method, which can yield visually satisfactory results with less computational complexity for high quality 2D to 3D conversion, is proposed. Numerical experimental results demonstrate the good performance of the proposed methods.     

一种用于深度图编码的虚拟视失真估计模型

多视视频加深度(MVD,multi-view video plus depth)的3D视频格式中,深度图提供视频的场景几何信息,其不在终端成像显示而是通过基于深度图像的绘制(DIBR)技术用于绘制虚拟视图像。在深度图的压缩编码过程中,深度图的失真会引起绘制的虚拟视图像的失真。深度图用于绘制而不用于显示的特性使得准确估计深度图绘制的虚拟视失真可以提高深度图编码的率失真性能。本文分析了不同的深度图失真引起的不同的虚拟视失真,进而提出一种估计深度图失真引起虚拟视失真的指数模型,并将模型用于深度图编码的率失真优化(RDO)中。实验结果表明,本文提出的模型可以准确估计深度图失真引起的虚拟视失真,提高深度图编码性能,相比于HTM的VSO可以降低约10%的编码时间,并且虚拟视质量略优于HTM。     

Depth map misalignment correction and dilation for DIBR view synthesis

The quality of the synthesized views by Depth Image Based Rendering (DIBR) highly depends on the accuracy of the depth map, especially the alignment of object boundaries of texture image. In practice, the misalignment of sharp depth map edges is the major cause of the annoying artifacts at the disoccluded regions of the synthesized views. Conventional smooth filter approach blurs the depth map to reduce the disoccluded regions. The drawbacks are the degradation of 3D perception of the reconstructed 3D videos and the destruction of the texture in background regions. Conventional edge preserving filter utilizes the color image information in order to align the depth edges with color edges. Unfortunately, the characteristics of color edges and depth edges are very different which causes annoying boundaries artifacts in the synthesized virtual views. Recent solution of reliability-based approach uses reliable warping information from other views to fill the holes. However, it is not suitable for the view synthesis in video-plus-depth based DIBR applications. In this paper, a new depth map preprocessing approach is proposed. It utilizes Watershed color segmentation method to correct the depth map misalignment and then the depth map object boundaries are extended to cover the transitional edge regions of color image. This approach can handle the sharp depth map edges lying inside or outside the object boundaries in 2D sense. The quality of the disoccluded regions of the synthesized views can be significantly improved and unknown depth values can also be estimated. Experimental results show that the proposed method achieves superior performance for view synthesis by DIBR especially for generating large baseline virtual views.     

基于逆向映射的空洞填补方法

为了有效填补虚拟视点图像中的公共空洞,提出 了一种基于逆向映射的空洞填补方法。 首先利用深度图像绘制(DIBR)技术将左、右参考视点映射到虚拟视点位置,利用图像膨胀方 法将映射的虚拟视图中的空 洞区域进行扩大,以消除虚拟视点图像中的伪影瑕疵;然后,提取出膨胀后空洞区域的边界 ,并将其逆映 射到原始的参考图像中,根据空洞与边界的相对位置,选取原始图像中相对位置上的像素来 填充虚拟视图 中的空洞区域;最后,将空洞填补之后的左、右视点映射的虚拟视图进行融合获得最终的虚 拟视图。实验 证明,本文方法有效解决了传统空洞填补方法容易将前景像素填充到背景区域的问题,能 够获得较好的视觉观看效果和较高的客观峰值信噪比(PSNR)值。     

基于卷积神经网络的虚拟视点空洞填补

为了提高虚拟视点绘制中空洞填补的质量,本文提 出一种基于卷积神经网络的虚拟视点空洞填补算 法,包括图像预处理、特征提取和空洞填补三部分。首先,对双视点虚拟视点图像进行预处 理,即利用深 度图像绘制(Depth Image Based Rendering,DIBR)技术得到空洞填补前的图像和空洞掩膜 ;然后,通过卷积 神经网络对虚拟视点图像提取多维特征,针对空洞区域,使用结构相似性损失函数优化网络 ;最后,利用 提取的特征填补虚拟视点中的空洞。实验结果表明,本文算法能较好地保持虚拟视点图像前 景和背景的锐 利边缘,主观视觉感知效果佳,同时,对不同场景测试序列的客观评价指标PS NR和SSIM都能取得满意结果,该方法能有效地填补虚拟视点中的空洞。     

Adaptive depth truncation filter for MVC based compressed depth image

In multiview video plus depth (MVD) format, virtual views are generated from decoded texture videos with corresponding decoded depth images through depth image based rendering (DIBR). 3DV-ATM is a reference model for the H.264/AVC based multiview video coding (MVC) and aims at achieving high coding efficiency for 3D video in MVD format. Depth images are first downsampled then coded by 3DV-ATM. However, sharp object boundary characteristic of depth images does not well match with the transform coding based nature of H.264/AVC in 3DV-ATM. Depth boundaries are often blurred with ringing artifacts in the decoded depth images that result in noticeable artifacts in synthesized virtual views. This paper presents a low complexity adaptive depth truncation filter to recover the sharp object boundaries of the depth images using adaptive block repositioning and expansion for increasing the depth values refinement accuracy. This new approach is very efficient and can avoid false depth boundary refinement when block boundaries lie around the depth edge regions and ensure sufficient information within the processing block for depth layers classification. Experimental results demonstrate that the sharp depth edges can be recovered using the proposed filter and boundary artifacts in the synthesized views can be removed. The proposed method can provide improvement up to 3.25 dB in the depth map enhancement and bitrate reduction of 3.06% in the synthesized views.     

Texture aided depth frame interpolation

Recent development of depth acquiring technique has accelerated the progress of 3D video in the market. Utilizing the acquired depth, arbitrary view frames can be generated based on depth image based rendering (DIBR) technique in free viewpoint video system. Different from texture video, depth sequence is mainly utilized for virtual view generation rather than viewing. Inspired by this, a depth frame interpolation scheme using texture information is proposed in this paper. The proposed scheme consists of a texture aided motion estimation (TAME) and texture aided motion compensation (TAMC) to fully explore the correlation between depth and the accompanying textures. The optimal motion vectors in TAME and the best interpolation weights in TAMC are respectively selected taking the geometric mapping relationship between depth and the accompanying texture frames into consideration. The proposed scheme is able to not only maintain the temporal consistency among interpolated depth sequence but also improve the quality of virtual frames generated by interpolated depth. Besides, it can be easily applied to arbitrary motion compensation based frame interpolation scheme. Experimental results demonstrate that the proposed depth frame interpolation scheme is able to improve the quality of virtual view texture frames in both subjective and objective criterions compared with existing schemes.     

一种基于脊波域的盲检数字水印算法

本文提出了一种脊波域的水印嵌入和盲检测算法.脊波变换(ridgelet transform,RT)具有方向敏感性和各向异性的特点,它可获得具有直线特征的图像的稀疏表示.对这类图像进行多尺度脊波变换后,其中最重要的脊波系数代表了图像能量最集中方向的特征,即沿着图像的边缘方向的特征.对一般含有曲线边缘或纹理的图像,可将图像分成小块,将曲线近似作直线处理.然后,对每个小块进行多尺度脊波变换,选择出脊波系数能量大于某个阈值的方向,并在该方向的中频脊波带嵌入水印.实验证明,水印使用该嵌入方法具有很强的鲁棒性和透明性.     

基于JNDD模型面向虚拟视绘制的快速深度图编码

为降低深度数据的编码复杂度并保证重建虚拟视点的质量,提出了一种基于JNDD模型面向虚拟视点绘制的快速深度图编码算法,引入最小可觉深度差模型,将深度图划分为对绘制失真敏感的竖直边缘区域与失真难以被人眼察觉的平坦区域,并相应地为编码过程中的宏块模式选择设计了两种搜索策略。实验结果表明,与JM编码方案相比,本文所提出的方法在保证虚拟视质量与编码码率基本不变的前提下,显著降低了编码复杂度,有助于在三维视频系统中提高深度编码模块的编码速度。     

View synthesis for FTV systems based on a minimum spatial distance and correspondence field

Multidimensional Systems and Signal Processing - The main problems with virtual view synthesis based on the common Depth-Image-Based Rendering (DIBR) algorithms are image rectification, depth map...     

A Novel DIBR 3D Image Watermarking Algorithm Resist to Geometrical Attacks

A histogram shape based method is utilized to design watermarking algorithm to protect the Depthimage- based rendering (DIBR) 3D images. To make the watermarking method robust to common attacks, much more suitable pixel groups are selected for watermark embedding which are insensitive to geometric attacks. Taking into account the adjusting of baseline distance in DIBR process might affect the watermarking extraction, a postprocessing is proposed after DIBR process to make the proposed watermarking method much more robust to DIBR process. As the experimental results shown, the proposed method is much more robust to the geometric attacks and combined attacks compared with existing methods. In addition, the proposed watermarking method also has good robustness to the adjusting of baseline distance and depth image blurred.     

基于GPU加速的深度图像绘制

基于深度图像的绘制(DIBR)广泛应用于虚拟视点的合成,但是目前实现DIBR的算法复杂度都比较高,很难较实时地应用到3DTV系统中。采用单路纹理图像和其对应的深度图像进行虚拟视点的合成,在图形处理单元(GPU)上应用CUDA(Compute Unified Device Architecture)技术实现了基于深度图像的绘制。通过在NVIDIA Telsa C2050图形卡上运行,绘制分辨力1 024×768和640×480的图像速率分别达到了15 f/s(帧/秒)和24 f/s,分别能够准实时或实时地应用到3DTV系统中;同时本文的绘制方法有效地节约了传输带宽,绘制图像的主观质量良好。     

面向绘制质量的深度图像快速帧内编码

与彩色视频用来直接显示不同,在三维视频系统中深度视频序列的作用是在绘制虚拟视点时提供所需的几何信息,所以直接将现有编码算法应用于深度图像存在一定的局限性.针对深度视频序列的作用以及深度图像自身特征,提出了一种面向绘制质量的深度图像快速帧内编码方法,该方法包括基于深度图像统计特性和空域相关性的图像区域划分算法、HEVC的快速编码单元(CU)和预测块(PB)决策算法和帧内编码模式预先选择算法.实验结果表明:与直接利用HEVC测试软件编码深度视频相比,该快速算法在保证几乎相同的主客观绘制质量的前提下,每个视点的编码速度平均提升了35％以上.     

Discontinuity-based registration of depth and video data in depth image based rendering

Depth image based rendering (DIBR) has been proposed to create content for 3D-TV. In DIBR, stereoscopic images are created from monoscopic images and associated depth data. Since for most of the available video content sensor depth data are lacking, methods to create artificial depth data for video content have been developed. Yet artificial as well as sensor depth data may contain misalignments with respect to video data. Misaligned depth data are a source of artifacts observable in rendered 3D views. We show that by using an edge-based registration method, the spatial alignment of depth and video data can be improved, leading to an alleviation of the observed artifacts.     

Security analyses of the watermarking scheme based on redundant discrete wavelet transform and singular value decomposition

This study analyzes the recent image watermarking schemes based on redundant discrete wavelet transform (RDWT) and singular value decomposition (SVD), and shows that in fact they are insecure and cannot be used for protecting the rightful ownership. The RDWT-SVD watermarking directly embeds a grayscale watermark image of the same size with the host image into the singular value matrix of the RDWT-transformed host image, then produces the left and right orthogonal matrices as side information which is later used in the watermark extraction stage. The RDWT-SVD approach enjoys the advantage of the RDWT redundancy to achieve a high embedding capacity, and preserves the watermark imperceptibility by exploiting the SVD stability properties. It is claimed that RDWT-SVD watermarking is robust against several common image processing and geometrical attacks, yet a fundamental flaw in the RDWT-SVD scheme is found, which leads to severe the false positive issue. Three vulnerable attacks should be considered in the RDWT-SVD scheme: (1) An attacker can easily claim the owner watermarked image; (2) the owner has the ambiguity because of the wrong side information usage, and (3) the owner can extract the correct watermark from arbitrary image. Thus, it is important to highlight these attacks when implementing the RDWT-SVD watermarking scheme.     

Recent MPEG Standardization Activities on 3D Video Coding

The Moving Picture Experts Group(MPEG) has been developing a 3D video(3DV) coding standard for depth-based 3DV data representations,especially for multiview video plus depth(MVD) format.With MVD,depth-image-based rendering(DIBR) is used to synthesize virtual views that are based on a few transmitted pairs of texture and depth data.In this paper,we discuss ongoing 3DV standardization and summarize coding tools proposed in the responses to MPEG’s call for proposals on 3DV coding.