分布式视频编码技术研究进展

介绍了分布式视频编码与传统视频编码方法思路的不同及各自适用的应用场景,阐述了分布式视频编码的理论基础和目前普遍采用的编解码框架,分析了分布式视频编码中的Wyner-Ziv编解码器设计、辅助边信息生成、虚拟相关信道建模等几项关键技术存在的问题及各自解决方案的最新研究进展,最后总结了分布式视频编码的发展与研究方向,并介绍了分布式编码在视频领域的其它应用.     

Arbitrary ROI-based wavelet video coding

This paper presents a novel arbitrary shape region of interest (ROI) coding for scalable wavelet video codec. The motion information of the ROIs is estimated by macroblock padding and polygon matching. The derived motion vectors are set as the motion trajectory of the samples to generate a one-dimensional temporal signal. This signal is then filtered to reduce the temporal redundancy using motion compensated temporal filtering for arbitrary shape ROI. Compared to traditional non-ROI coding, the reconstructed quality of the ROI coding can be significantly improved at low bit-rates. The efficiency of motion compensated temporal filtering (MCTF) based on arbitrary ROI is also compared with that of the video object coding in MPEG-4. Based on large number of experiments, the ability of the MCTF to reduce the temporal redundancy is demonstrated as better than (or at least comparable to) that of MPEG-4.     

Efficient video encryption scheme based on advanced video coding

A video encryption scheme combining with advanced video coding (AVC) is presented and analyzed in this paper, which is different from the ones used in MPEG1/2 video encryption. In the proposed scheme, the intra-prediction mode and motion vector difference are encrypted with the length-kept encryption algorithm (LKE) in order to keep the format compliance, and the residue data of the macroblocks are encrypted with the residue data encryption algorithm (RDE) in order to keep low cost. Additionally, a key distribution scheme is proposed to keep the robustness to transmission errors, which assigns sub-keys to different frames or slices independently. The encryption scheme’s security, time efficiency and error robustness are analyzed in detail. Experimental results show that the encryption scheme keeps file format unchanged, is secure against replacement attacks, is efficient in computing, and is robust to some transmission errors. These properties make it a suitable choice for real-time applications, such as secure IPTV, secure videoconference or mobile/wireless multimedia, etc.

Probabilistic motion-compensated prediction in distributed video coding

Distributed video coding (DVC) constitutes an original coding framework to meet the stringent requirements imposed by uplink-oriented and low-power mobile video applications. The quality of the side information available to the decoder and the efficiency of the employed channel codes are primary factors determining the success of a DVC system. This contribution introduces two novel techniques for probabilistic motion compensation in order to generate side information at the Wyner-Ziv decoder. The employed DVC scheme uses a base layer, serving as a hash to facilitate overlapped block motion estimation at the decoder side. On top of the base layer, a supplementary Wyner-Ziv layer is coded in the DCT domain. Both proposed probabilistic motion compensation techniques are driven by the actual correlation channel statistics and reuse information contained in the hash. Experimental results report significant rate savings caused by the novel side information generation methods compared to previous techniques. Moreover, the compression performance of the presented DVC architecture, featuring the proposed side-information generation techniques, delivers state-of-the-art compression performance.     

Wavelet-based video coding with early-predicted zerotrees

The coding efficiency of DCT-based standard video codecs is significantly improved by the use of skipped macroblocks. A similar concept is proposed for zerotree-based wavelet video coders. In a pyramidal wavelet transform, the wavelet coefficients are linked through spatial orientation trees. For each transformed frame, a method is proposed to identify those trees that are likely to be zerotrees throughout the coding process at a given bit budget. These trees are called the early-predicted zerotrees. These trees are then excluded from the subsequent quantisation and encoding processes. The tree classification is based on average energy of coefficients in the tree. The proposed technique is general and can be applied to any zerotree-based coding algorithm, but it is more advantageous to improve the performance of those zerotree-based video coding algorithms that use longer trees, such as virtual set partitioning in hierarchical trees (V-SPIHT). Simulation results demonstrate that the proposed technique can improve the performance of V-SPIHT-based video coder by up to 0.5 dB (on average) and can reduce the computational complexity by up to 80% (i.e. five times faster), for various test video sequences     

一种视频编码的码率控制改进算法

测试模型5(TMS)的位分配策略对基于图像序列编码的图像质量会造成一定影响。文中在分析测试模型的位分配策略的基础上,给出了一种改进的基于MPEG-2的位分配策略。该策略能够提高序列图像编码质量的平滑性,从而避免图像质量之间的失衡。模拟结果表明,改进的码率控制策略在一定程度上提高了图像的质量,同时还保持序列图像之间的平滑性而保持压缩比不变。     

Phase-based side information generation in distributed video coding

Multimedia Tools and Applications - In distributed video coding, the quality of side information (SI) directly affects the final compression efficiency and rate-distortion performance. In the...     

基于分布式视频编码的井下传感器节点设计

煤矿井下的环境复杂,通信方式和通信范围受应用场景的约束性较大,在煤矿安全生产中引入无线多媒体传感器网络技术(WMSN)可以提高安全生产监管效率,在突发事件中为应急救援工作提供有力的信息指导。为此基于DISCOVER分布式视频编码(DVC)方案,设计了以S3C6410为主处理器芯片的视频传感器节点。给出了节点的硬件框图以及软件流程图。测试表明,该节点运行良好,可以对煤矿安全生产过程进行有效监控,在一定程度上预防煤矿事故的发生。     

Efficient compression and network adaptive video coding for distributed video surveillance

The availability of cheap network based video cameras and the prevalence of wireless networks has lead to a major thrust towards deployment of large scale Distributed Video Surveillance (DVS) systems. This has opened up an important area of research to deal with the issues involved in DVS system for efficient collection and transmission of large scale video streams from the cameras at the guarded sites, to the end users in possibly constrained network conditions. In this paper, we propose a framework based on content-based video classification and scalable compression scheme to provide a robust bandwidth efficient video transmission for DVS. The scheme builds on a Discrete Wavelet Transform (DWT) based Color-Set Partitioning for Hierarchical Trees (CSPIHT) coding to obtain a scalable bitstream. Wavelet domain segmentation and compression assists in development of a DVS architecture. The architecture includes a novel module for dynamic allocation of Network bandwidth based on the current available resources and constraints. Different frame constituents are optimally coded based on their relative significance, perceptual quality, and available estimate of network bandwidth. Experimental result over different video sequences and simulations for Network conditions demonstrate the efficient performance of the approach.     

Efficient depth coding in 3D video to minimize coding bitrate and complexity

Multimedia Tools and Applications - In three-dimensional video (3DV) coding, color videos and depth maps both need to be coded. Usually, two-channel coding method is used in the system of 3DV...     

BLAST-DVC: BitpLAne SelecTive distributed video coding

This paper presents a BitpLAne SelecTive (BLAST) distributed video coding (DVC) system. In the proposed system, the significance of each bitplane is measured at the decoder based on an estimated distortion-rate ratio that makes use of a correlation model for the original source information and the side information. Only the syndrome bits of the bitplanes that have estimated distortion-rate ratios higher than a target distortion-rate ratio, are transmitted and are used to decode the associated bitplanes. The remaining bitplanes are estimated using a minimum-distance symbol reconstruction scheme which makes use of the side information and the LDPCA-decoded bitplanes. Coding results and comparisons with existing DVC schemes and with H.264 intra- and inter-frame coding are presented to illustrate the performance of the proposed system.     

Experiments on block-matching techniques for video coding

Video compression is becoming increasingly important with the advent of compression standards and broadband networks. Recently, several block-based motion-estimation algorithms to exploit the temporal redundancies in a video sequence have been reported in the literature. Some of these algorithms tend to be either computationally expensive or to converge to a local optimum. In this paper, we present results for various block-matching techniques and propose a low-complexity block-matching motion-estimation algorithm that is useful for hybrid video coding schemes, including MPEG video. This algorithm consists of a layered structure search, and, unlike other fast block-matching methods, it does not converge to a local optimum. The proposed method employs a novel matching criterion, namely, the modified pixeldifference classification (MPDC), that offers simplicity with other potential advantages.     

Perceptual auto-regressive texture synthesis for video coding

Traditional video compression methods consider the statistical redundancy among pixels as the only adversary of compression, with the perceptual redundancy totally neglected. However, it is well-known that none criterion is as eloquent as the visual quality of an image. To reach higher compression ratios without perceptually degrading the reconstructed signal, the properties of the human visual system (HVS) need to be better exploited. Recent research indicates that HVS has different sensitivities towards different image content, based on which a novel perceptual video coding method is explored in this paper to achieve better perceptual coding quality while spending fewer bits. A new texture segmentation method exploiting just noticeable distortion (JND) profile is first devised to detect and classify texture regions in video scenes. To effectively remove temporal redundancies while preserving high visual quality, an auto-regressive (AR) model is then applied to synthesize the texture regions and combine with other regions which are encoded by the traditional hybrid coding scheme. To demonstrate the performance, the proposed scheme is integrated into the H.264/AVC video coding system. Experimental results show that on various sequences with different types of texture regions, we can reduce the bit-rate for 15% to 58% while maintaining good perceptual quality.     

Intrafield transform image coding of composite video

Two different schemes, i.e. adaptive and nonadaptive systems, are developed for intrafield transform (2d-DCT) image processing of a digital NTSC color composite video signal, sampled at three times the color subcarrier frequency. The fast transform algorithm for 2d-DCT (8 × 8 subblock) is used. Based on the statistics of the transform coefficients, variable word length quantizers, optimized for minimizing the mean square error, are developed. These techniques lead to reduced bit rates for transmitting color video at broadcast standards. The performance of adaptive system is much better than that of nonadaptive system. Although the necessary hardware will likely exceed what is needed for a nonadaptive system, the benefits will more than offset the hardware complexity. The effect of channel noise in the adaptive system is investigated in terms of severity and propagation patterns. This is carried out by using a forced error scheme which selectively forces the error to occur in the different types of coding bits. Error propagation patterns are studied by series of computer printouts.     

Object-based video coding with dynamic quality control

This paper presents a novel MPEG-4 priority-based multiple video objects coding system integrating User Visual Attention Model (UVAM) and Dynamic Bit Allocation (DBA) rate control mechanism. In the proposed system, the importance of individual objects is defined automatically and the coding parameters are adaptively adjusted so that the perceptual quality of important objects is maximized. The first contribution of the paper is an object-based UVAM utilizing a two-level structure and a blob extraction algorithm. Following that, two DBA algorithms are designed for object-based coding quality control in which weighted bits are allocated to prioritized single or group of video objects. Experimental results confirm that the defined automatic object-based priority is consistent with the observation of human visual system and the coding quality is maximized for the most important object and group of objects. In addition, the proposed system provides object-based coding flexibility and improved efficiency of utilizing coding resources. It offers key techniques to ensure the quality of services for real-time content-based video coding and streaming systems.