Compressed Digital Video:Accelerating the Video Communications Revolution

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AVS2视频编码标准技术特色及应用

围绕视频编码核心技术,简单介绍AVS视频编码标准发展历程,详细介绍了最新一代AVS视频编码标准——AVS2(GB/T 33475.2-2016)的核心创新技术,主要包括:灵活的预测划分方式、多假设帧间预测、优化的层次变换设计和自适应环路滤波处理技术以及面向场景视频应用AVS2提出的基于场景建模的高效预测编码技术.和第一代AVS视频编码标准相比,AVS2编码效率提升一倍以上;和同期HEVC/H.265国际标准相比,AVS2在场景视频编码方面有显著优势.另外简单介绍了AVS标准在数字电视广播等行业中的应用情况.     

Digital video coding standards and their role in videocommunications

The efficient digital representation of image and video signals has been subject of considerable research over the past 20 years. With the growing availability of digital transmission links, progress in signal processing, VLSI technology and image compression research, visual communications has become more feasible than ever. Digital video coding technology has developed into a mature field and a diversity of products has been developed-targeted for a wide range of emerging applications, such as video on demand, digital TV/HDTV broadcasting, and multimedia image/video database services. With the increased commercial interest in video communications the need for international image and video coding standards arose. Standardization of video coding algorithms holds the promise of large markets for video communication equipment. Interoperability of implementations from different vendors enables the consumer to access video from a wider range of services and VLSI implementations of coding algorithms conforming to international standards can be manufactured at considerably reduced costs. The purpose of this paper is to provide an overview of today's image and video coding standards and their role in video communications. The different coding algorithms developed for each standard are reviewed and the commonalities between the standards are discussed     

Adaptive Pixel Interpolation for Spatial Error Concealment

Error concealment techniques are widely used as efficient ways to recover the lost information at the decoder. This paper proposes an adaptive pixel interpolation technique for spatial error concealment in the block based coding system. For a missing pixel in a corrupted block, its value is derived from four neighborhoods of the block through interpolation using multiple prediction strategy. The weighting rules of these four neighborhood blocks are carefully designed with regard to three factors, the distance to the missing pixels within the given corrupted block, the percentage of uncorrupted pixels, and the similarity to the given corrupted block. The proposed method works effectively in consecutive block loss situation, which is common in real applications of video transmission. Experimental results show the proposed technique gains more accurate recovery of the missing pixels than the existing schemes.     

Overview of AVS-video coding standards

Audio-video coding standard (AVS) is a working group of audio and video coding standard in China, which established in 2002. AVS-video coding standards are important parts of productions of AVS working group. Considering the different requirements of various video applications, AVS-video coding standards define different profiles, combining advanced video coding tools with trade-off between coding efficiency and encoder/decoder implementation complexity as well as functional properties. This paper provides an overview of major AVS-video coding tools and their combinations as profiles.     

一种视频编码数据分割方案

数据分割是在无线移动信道等传输视频码流时用于抵御信道误码、提高编码比特流健壮性的一种机制.在对现在流行的视频编码标准中数据分割方案进行研究的基础上,文中提出了一种视频编码中数据分割的新方案.在该方案中,运动矢量信息和头信息分割于不同部分;而且运动矢量的水平和垂直分量也可以分割到不同的部分,从而可以更好地抵御信道误码.在这种分割方案下,又提出了可以改进运动矢量编码效率的新编码方法.实验表明该方法对具有尖峰概率密度函数的情形尤为有效.采用文中数据分割方案具有抗信道误码能力强、运动矢量编码比特位数少、编码效率高等优点.     

Adaptive nonuniform polar quantization application to high quality speech compression

The logarithmic companding technique has shown to be extremely useful in speech quantization with rate of 8 bits/sample. However, for lower bit rates it is not the ideal solution for high quality speech coding. Because of that, in this paper we establish source coding scheme which enables better spectrum efficiency for input that has a large dynamic range. Since our wish is also to improve signal quality in comparison with quality defined with standards G.711 and G.712, we opt for adaptive technique application to the speech coding. Our research shows that proper design of forward gain-adaptive polar quantization can enable compression of about 1 bit/sample as well as significantly better quality than in case of using coder designed according to standard G.711. Furthermore, performances can be sustained over the whole speech dynamic range. Also, if the requisite speech quality is not supposed to be lower than G.712 standard quality, the achieved compression can be almost 1.5 bits/sample. Besides, we propose knew simple encoding rule which can additionally reduce bit rate for 0.1 bit/sample.     

Adaptive rate control algorithm for low power video coding systems

With the recent development of third-generation communication technologies, low power video coding system (such as PDA, Handphone or system on chip) has found wide applications such as live video using a PDA and sharing it among friends, etc. However, video coding in a low power system has two major hurdles to overcome: (1) In a low power system, video coding needs to meet the rigorous constraints of the available memory and computational capacity; (2) In a low power system, the computational power allocated to video coding may vary drastically (in bursts). In this paper, a new adaptive rate control algorithm is proposed for low power video coding system. This adaptive rate control scheme takes into account the time constraint of a low power system, and its bit allocation depends not only on the available data bits, but more importantly, on the available coding time. Experimental results show that, compared to the existing rate control scheme, the new algorithm can always achieve the maximum frame rate, maximize the utilization of the available bandwidth and computing power, increase the average PSNR, and improve the subjective perceptual quality of the reconstructed video.     

A survey of hybrid MC/DPCM/DCT video coding distortions

The motion-compensated hybrid DCT/DPCM algorithm has been successfully adopted in various video coding standards, such as H.261, H.263, MPEG-1 and MPEG-2. However, its robustness is challenged in the face of an inadequate bit allocation, either globally for the whole video sequence, or locally as a result of an inappropriate distribution of the available bits. In either of these situations, the trade-off between quality and the availability of bits results in a deterioration in the quality of the decoded video sequence, both in terms of the loss of information and the introduction of coding artifacts. These distortions are an important factor in the fields of filtering, codec design, and the search for objective psychovisual-based quality metrics; therefore, this paper presents a comprehensive analysis and classification of the numerous coding artifacts which are introduced into the reconstructed video sequence through the use of the hybrid MC/DPCM/DCT video coding algorithm. Artifacts which have already been briefly described in the literature, such as the blocking effect, ringing, the mosquito effect, MC mismatch, blurring, and color bleeding, will be comprehensively analyzed. Additionally, we will present artifacts with unique properties which have not been previously identified in the literature.     

一种基于立体视觉显著性的多视点视频比特分配方法

针对多视点立体视频压缩编码,提出了一种基于立 体视觉显著性的比 特分配方法。研究综合利用多视点立体视频数据中场景的运动、深度以及深度边缘信息提取 人眼感兴趣区 域(ROI)的方法;然后根据ROI的划分结果优化区域比特分配。实验结果表 明,本文提出的算法能有效提 高ROI区域的编码性能,同时整体视频的率失真性能有一定程度的提高。     

Enabling stereoscopic high dynamic range video

Stereoscopic and high dynamic range (HDR) imaging are two methods that enhance video content by respectively improving depth perception and light representation. A large body of research has looked into each of these technologies independently, but very little work has attempted to combine them due to limitations in capture and display; HDR video capture (for a wide range of exposure values over 20 f-stops) is not yet commercially available and few prototype HDR video cameras exist. In this work we propose techniques which facilitate stereoscopic high dynamic range (SHDR) video capture by using an HDR and LDR camera pair. Three methods are proposed: one based on generating the missing HDR frame by warping the existing one using a disparity map; increasing the range of LDR video using a novel expansion operator; and a hybrid of the two where expansion is used for pixels within the LDR range and warping for the rest. Generated videos were compared to the ground truth SHDR video captured using two HDR video cameras. Results show little overall error and demonstrate that the hybrid method produces the least error of the presented methods.     

Low complexity distributed video coding

ContextConventional video encoding is a computationally intensive process that requires a lot of computing resources, power and memory. Such codecs cannot be deployed in remote sensors that are constrained in terms of power, memory and computational capabilities. For such applications, distributed video coding might hold the answer.ObjectiveIn this paper, we propose a distributed video coding (DVC) architecture that adheres to the principles of DVC by shifting the computational complexity from the encoder to the decoder and caters to low-motion scenarios like video conferencing and surveillance of hallways and buildings.MethodThe architecture presented is block-based and introduces a simple yet effective classification scheme that aims at maximizing the use of skip blocks to exploit temporal correlation between consecutive frames. In addition to the skip blocks, a dynamic GOP size control algorithm is proposed that instantaneously alters the GOP size in response to the video statistics without causing any latency and without the need to buffer additional frames at the encoder. To facilitate real-time video delivery and consumption, iterative channel codes like low density parity check codes and turbo codes are not used and in their place a Bose–Chaudhuri–Hocquenghem (BCH) code with encoder rate control is used.ResultsIn spite of reducing the complexity and eliminating the feedback channel, the proposed architecture can match and even surpass the performance of current DVC systems making it a viable solution as a codec for low-motion scenarios.ConclusionWe conclude that the proposed architecture is a suitable solution for applications that require real-time, low bit rate video transmission but have constrained resources and cannot support the complex conventional video encoding solutions.Practical implicationsThe practical implications of the proposed DVC architecture include deployment in remote video sensors like hallway and building surveillance, video conferencing, video sensors that are deployed in remote regions (wildlife surveillance applications), and capsule endoscopy.     

A New Architecture for Adaptive Intrafield Transform Compression of NTSC Composite Video Signal

In orthogonal transform coding of NTSC video signal, the data are processed in blocks. Processing a block of data that is maximally correlated leads to larger compression. This correspondence describes a new architecture for arranging the pixels in a block that yields higher correlation than the adjacent pixel blocks. The data are processed using adaptive, intrafield, discrete cosine transform, variable bit allocation coding. In subjective tests good quality pictures were obtained for an average of about 2 bits/pel for intrafield processing.     

H.264/AVC在视频监控系统中的应用

H.264/AVC是由国际电信联盟(ITU)和国际标准化组织(ISO)共同制定的新一代视频编码标准,首先指出目前采用其他标准设计视频监控系统的不足,介绍和分析H.264/AVC采用的新编码技术,最后根据视频监控系统的特点,主要讨论H.264/AVC在视频监控应用中涉及的关键技术,包括SP/SI帧技术和分层编码技术。     

基于粗粒度可重构阵列结构的多标准离散余弦变换设计

在视频信号的编解码流程中,离散余弦变换(DCT)是一个至关重要的环节,其决定了视频压缩的质量和效率。针对88尺寸的2维离散余弦变换,该文提出一种基于粗粒度可重构阵列结构(Coarse-Grained Reconfigurable Array, CGRA)的硬件电路结构。利用粗粒度可重构阵列的可重配置的特性,实现在单一平台支持多个视频压缩编码标准的88 2维离散余弦变换。实验结果显示,这种结构每个时钟周期可以并行处理8个像素,吞吐率最高可达1.157109像素/s。与已有结构相比,设计效率和功耗效率最高可分别提升4.33倍和12.3倍,并能够以最高30帧/s的帧率解码尺寸为40962048,格式为4:2:0的视频序列。     

基于比特概率优化算法的分布式视频编码

分布式视频编码器中Turbo码纠错所需要的校验位数量直接决定整个编码器的率失真(RD,Rate-Distortion)性能.分析了传统算法的次优化问题,提出一种新的基于比特概率优化的信道似然值计算算法,该算法首先将原始像素进行比特面分解,然后分别对每个比特面进行独立Turbo码编码及联合解码.解码端在已知已解码比特面的条件下,计算当前解码比特面更准确的信道似然值作为Turbo码的解码输入,减少解码所需要传输的校验位数量,提高编码器RD性能.实验结果表明所提算法能明显提升编码系统的RD性能.     

Application of H.263+ Video Coding Modes in Lossy Packet Network Environments

The quality of real-time audio and video information transmitted via today's Internet suffers severely from often significant packet losses. While this problem is well understood and solved for existing audio coding schemes, support from the video coding standards themselves is required for video streams. This paper presents the newly introduced error resilience mechanisms built into the second version of H.263 (1998), known under its working name H.263+, and addresses the corresponding packetization format issues that together significantly improve the image quality at packet loss rates up to 20%. In particular, it is support from the video coding algorithm itself, paired with appropriate transport layer mechanisms, that leads to significant improvements of perceived image quality for communicative as well as retrieval applications at moderate bit rates up to some 100 kbit/s.     

Adaptive encoding of zoomable video streams based on user access pattern

Zoomable video allows users to selectively zoom and pan into regions of interest within the video for viewing at higher resolutions. Such interaction requires dynamic cropping of RoIs on the source video. We have previously explored two different ways of encoding and transmitting video to support dynamic RoI cropping: (i) Monolithic streaming uses a standard video encoder to encode the video. When an RoI is requested, the bits belonging to the RoI along with other bits required to decode the RoIs (due to encoding dependencies) are transmitted. (ii) Tile streaming divides regions in the standard video into rectangular tiles that are encoded independently. The tiles that intersect with a requested RoI are transmitted. In this paper, we consider how the bandwidth needed to transmit the RoIs can be reduced by carefully encoding the source video for each of the two encoding schemes. The goal is to support bandwidth efficient compressed domain RoI cropping in the context of virtual zoom and pan by tuning encoder parameters. Our key idea is to exploit user access patterns to the RoIs, and encode different regions of the video with different encoding parameters based on the popularity of the region. We show that our encoding method can reduce the expected bandwidth by up to 43% in the test video sequence which we have used.