Efficient disparity vector prediction schemes with modified P frame for 2D camera arrays

An efficient disparity estimation algorithm for multi-view video sequences, recorded by a two-dimensional camera array in which the cameras are spaced equidistantly, is presented. Because of the strong geometrical relationship among views, the disparity vectors of a certain view can for most blocks be derived from the disparity vectors of other views. A frame constructed using that idea is called a D frame in this work. Three new prediction schemes which contain D frames are proposed for encoding 5 × 3 multi-view video sequences. The schemes are applied to several multi-view image sequences taken from a camera-array and they are compared in terms of quality, bit-rate and complexity. The experimental results show that the proposed prediction schemes significantly decrease the complexity of the encoder at a very low cost of quality and/or bit-rate.     

面向编码和绘制的多视点图像深度估计

针对自由视点三维电视系统中深度估计不准确将给后续多视点深度编码和虚拟视点绘制带来困难的问题,提出一种面向编码和绘制的多视点图像深度估计算法。首先对初始深度进行一致性检查,并采用自适应匹配误差策略删除不可靠的匹配以减小初始深度的误匹配。然后根据融合准则将多幅参考深度图合成为一幅深度图以提高深度图的精度。最后,采用多边滤波...     

Directional residue prediction with motion alignment for video coding

A directional residue prediction method is proposed, in which motionaligned neighbouring residues are used in the directional prediction for residues in an inter-block. Corresponding motion estimation strategies are also designed. Experiments show that the bit rate saving can be up to 20% with a negligible decoding complexity increase.     

HEVC-based 3D holoscopic video coding using self-similarity compensated prediction

Holoscopic imaging, also known as integral, light field, and plenoptic imaging, is an appealing technology for glassless 3D video systems, which has recently emerged as a prospective candidate for future image and video applications, such as 3D television. However, to successfully introduce 3D holoscopic video applications into the market, adequate coding tools that can efficiently handle 3D holoscopic video are necessary. In this context, this paper discusses the requirements and challenges for 3D holoscopic video coding, and presents an efficient 3D holoscopic coding scheme based on High Efficiency Video Coding (HEVC). The proposed 3D holoscopic codec makes use of the self-similarity (SS) compensated prediction concept to efficiently explore the inherent correlation of the 3D holoscopic content in Intra- and Inter-coded frames, as well as a novel vector prediction scheme to take advantage of the peculiar characteristics of the SS prediction data. Extensive experiments were conducted, and have shown that the proposed solution is able to outperform HEVC as well as other coding solutions proposed in the literature. Moreover, a consistently better performance is also observed for a set of different quality metrics proposed in the literature for 3D holoscopic content, as well as for the visual quality of views synthesized from decompressed 3D holoscopic content.     

Joint video/depth rate allocation for 3D video coding based on view synthesis distortion model

Joint video/depth rate allocation is an important optimization problem in 3D video coding. To address this problem, this paper proposes a distortion model to evaluate the synthesized view without access to the captured original view. The proposed distortion model is an additive model that accounts for the video-coding-induced distortion and the depth-quantization-induced distortion, as well as the inherent geometry distortion. Depth-quantization-induced distortion not only considers the warping error distortion, which is described by a piecewise linear model with the video power spectral property, but also takes into account the warping error correlation distortion between two sources reference views. Geometry distortion is approximated from that of the adjacent view synthesis. Based on the proposed distortion model, a joint rate allocation method is proposed to seek the optimal trade-off between video bit-rate and depth bit-rate for maximizing the view synthesis quality. Experimental results show that the proposed distortion model is capable of approximately estimating the actual distortion for the synthesized view, and that the proposed rate allocation method can almost achieve the identical rate allocation performance as the full-search method at less computational cost. Moreover, the proposed rate allocation method consumes less computational cost than the hierarchical-search method at high bit-rates while providing almost the equivalent rate allocation performance.     

Alternate motion-compensated prediction for error resilient video coding

Since the quality of compressed video is vulnerable to errors, video transmission over unreliable Internet is very challenging today. Two-Hypothesis Motion-Compensated Prediction (THMCP) has been shown to have Error Resilience (ER) capability for video transmission, where each macroblock is predicted from its previous two frames. In this paper, we propose a novel ER approach named Alternate Motion-Compensated Prediction (AMCP). In addition to two-hypothesis prediction, one-hypothesis prediction is alternately used. We use some schemes to determine which kind of prediction should be used, so that in some cases of loss, the propagated error can be first decreased to some extent before it spreads to the subsequent frames. As a result, the expected converged error is less than that obtained from THMCP with fixed weights (THMCPF). Both analysis and simulation results are given to show that AMCP performs better than THMCPF, in terms of both compression efficiency and ER capability.     

基于帧内帧间联合预测的深度视频编码方法

在基于多视点加深度(MVD)格式的视频编码方案中,深度视频的编码性能直接影响最终绘制的虚拟视点的质量。对于具有边界的深度块而言,传统的帧内预测和帧间预测模式仍存在一定的提升空间。因此,文中提出一种基于帧内帧间联合预测的深度视频编码方法。该方法首先获取当前深度块的最优帧内预测模式和最优帧间预测模式。然后,将这两种模式应用于边界深度块的不同区域。最后,自适应地调整预测结果的加权系数,实现联合预测。实验结果表明,相对于3D-HEVC平台的传统预测模式,本方法实现了更好的编码性能。     

Novel prediction schemes for error resilient video coding

A conventional video codec uses encoder reconstruction of previous frames for motion compensated prediction. This is designed to minimize the encoder prediction error and assumes error free transmission. In this paper we use a modified prediction mechanism both at the encoder and decoder and propose techniques to improve the error resilience of H.264/AVC when transmitted over error prone networks. In our schemes we provide greater emphasis on Intra pixels during the formation of the reference frame used for prediction, thereby achieving better resilience. We also incorporate leaky prediction to further improve the robustness. We apply leaky prediction selectively at a macroblock level based on a simple mean square error metric in order to reduce the bit-rate penalty. Substantial performance gains have been observed in simulations. The effectiveness of using leaky prediction can be observed in medium and fast moving video sequences.     

Efficient view-temporal prediction structures for multi-view video coding

To compress multi-view video, spatial redundancy between adjacent view sequences as well as temporal redundancy need to be eliminated. View-temporal prediction structures are proposed, which can be adjusted to various characteristics of multi-view videos. The proposed prediction structure achieves better coding performance than the reference prediction structure for the standardisation of multi-view video coding.     

Circular intra prediction for 360 degree video coding

Different from traditional 2D video, the contents of 360 degree video are deformed due to the projection from 3D sphere to 2D plane. As a result, the traditional Angular Intra Prediction (AIP) with a linear pattern may not be always efficient. To further improve the coding performance of 360 degree video, a novel intra prediction method is presented in this paper, i.e., Circular Intra Prediction (CIP), which takes consideration of the spherical characteristics of 360 degree video. In specific, the proposed CIP is performed in a circular pattern, where the center of circle is located around the to-be-predicted block, and different centers of circle are able to produce different CIP modes. The distance between center of this circle and center of the to-be-predicted block is adaptively determined according to the degree of projection deformation, where stronger projection deformation needs shorter distance, and vice versa. As the increase of the distance, the CIP is more and more close to the traditional AIP. In addition, one additional binary flag is utilized to achieve better coding performance from the competition between AIP and CIP with the rate-distortion optimization. The proposed algorithm is implemented on the platform of Versatile video coding Test Model (VTM) 5.0 + 360Lib 9.1. Extensive experiments show that the proposed method can achieve bit rate reduction on this platform for 360 degree video coding.     

Mode dependent down-sampling and interpolation scheme for high efficiency video coding

In this paper, a mode dependent down-sampling and interpolation scheme is proposed to improve the coding efficiency of the intra prediction module. In the proposed method, we elaborately design the down-sampling structures and interpolation schemes for each directional intra prediction mode by minimizing the spatial prediction distance. The sampled pixels are predicted with a traditional directional intra prediction scheme, and the non-sampled pixels are predicted from the interpolation of their neighboring reconstructed sampling pixels. Both the residuals of the sampled and non-sampled pixels are encoded at last. Experimental results show that the proposed method achieves an average 7.52% bitrate reduction relative to KTA reference software. Since the down-sampling structure and interpolation method is only related to the intra mode, there is no additional overhead at the encoder.     

Automatic scalable face model design for 2D model-based video coding

Scalable low bit-rate video coding is vital for the transmission of video signals over wireless channels. A scalable model-based video coding scheme is proposed in this paper to achieve this. This paper mainly addresses automatic scalable face model design. Firstly, a robust and adaptive face segmentation method is proposed, which is based on piecewise skin-colour distributions. 43 million skin pixels from 900 images are used to train the skin-colour model, which can identify skin-colour pixels reliably under different lighting conditions. Next, reliable algorithms are proposed for detecting the eyes, mouth and chin that are used to verify the face candidatures. Then, based on the detected facial features and human face muscular distributions, a heuristic scalable face model is designed to represent the rigid and non-rigid motion of head and facial features. A novel motion estimation algorithm is proposed to estimate the object model motion hierarchically. Experimental results are provided to illustrate the performance of the proposed algorithms for facial feature detection and the accuracy of the designed scalable face model for representing face motion.     

Efficient video coding with fractional resolution sprite prediction technique

An efficient algorithm for dynamic sprite-based video coding with fractional resolution motion compensations is presented. Different from the traditional sprite coding, the global motion and local motion are jointly compensated at two stages. The new techniques, developed in a JVT codec, are also utilised. Experimental results demonstrate that the proposed algorithm can averagely save 8% bit rate compared to JVT codec for the typical test sequences.     

Color correction algorithm based on camera characteristics for multi-view video coding

Various types of multi-view camera systems have been proposed for capturing three dimensional scenes. Yet, color distributions among multi-view images remain inconsistent in most cases, degrading multi-view video coding performance. In this paper, we propose a color correction algorithm based on the camera characteristics to effectively solve such a problem. Initially, we model camera characteristics and estimate their coefficients by means of correspondences between views. To consider occlusion in multi-view images, correspondences are extracted via feature-based matching. During coefficient estimation with nonlinear regression, we remove outliers in the extracted correspondences. Consecutively, we generate lookup tables for each camera using the model and estimated coefficients. Such tables are employed for fast color converting in the final color correction process. The experimental results show that our algorithm enhances coding efficiency with gains of up to 0.9 and 0.8 dB for luminance and chrominance components, respectively. Further, the method also improves subjective viewing quality and reduces color distance between views.     

Stereo video coding based on frame estimation and interpolation

The paper proposes a stereo video coding system. To ensure compatibility with monoscopic transmission, one of the view sequences is coded and transmitted conforming to the MPEG standard, referred to as the reference stream, and the other view stream is referred to as target stream. Only a few frames of the latter are coded and transmitted, while the rest are skipped and reconstructed at the decoder using a novel stereoscopic frame compensation and interpolation technique, termed SFEI BLCF. In disparity estimation, smooth and accurate disparity fields are obtained by using hierarchical Markov random field (MRF) and Gibbs random field (GRF) models. A fast search method is used to improve the precision and computation speed. Coding and decoding results show that, with only 8/spl sim/30% additional bandwidth over a single view bit stream, one can transmit, store, and reconstruct stereoscopic video sequences with reasonably good performance.     

瞬态时频内插极低速率图像压缩编码

结合图像信号瞬变、渐变和缓变的特点,从图像信号瞬态非平稳分析与重构角度出发,提出了具有瞬态分析、参数内插和时频重构特点的瞬态时频内插极低速率图像压缩编码方案。瞬态时频分析理论的应用,为今后图像信号处理研究提供了一种新的思路。     

Generalisation of inter-layer intra prediction for scalable video coding

In the scalable video coding (SVC) standard, a simple inter-layer intra prediction (ILIP) method has been adopted to reduce the bit rate of scalable video sequences. Proposed is an improved ILIP method by generalising the original one adopted in the SVC. Experimental results show that the proposed method can reduce bit rates by 4.1 to 5.9%, compared with the original one, while average PSNR is not decreased.     

A motion vector prediction method for multi-view video coding

This paper proposes a new motion vector (MV) prediction method in multi-view video coding (MVC). In order to exploit the information in adjacent views, inter-view MVs as well as temporal MVs are used in conventional MVC. Since the inter-view MVs are usually uncorrelated with the temporal MVs and most neighboring partitions have temporal MVs only, the conventional DPCM coding gain of inter-view MV is very low and thus the inter-view MVs are seldom selected. In order to increase the probability of inter-view MV selection, we define a virtual inter-view MV which can be generated from temporal MVs. Then, an inter-view MV is predicted using these neighboring virtual inter-view MVs, leading to less prediction error than using the temporal MVs. As a result, bit-rates are decreased by up to 9% for the view-temporal prediction structure.