A FINE GRANULAR JOINT SOURCE CHANNEL CODING METHOD

An improved FGS (Fine Granular Scalability) coding method is proposed in this letter,which is based on human visual characteristics.This method adjusts FGS coding frame rate according to the evaluation of video sequences so as to improve the coding efficiency and subject perceived quality of reconstructed images.Finally,a fine granular joint source channel coding is proposed based on the source coding method,which not only utilizes the network resources efficiently,but guarantees the reliable transmission of video information.     

面向头肩序列图像的质量可精细扩展视频编码方法

FGS编码方法具有细粒度的可扩展能力,能很好地适应网络带宽的动态变化,被认为是一种适合于网络视频传输的编码方案.但现有的MPEG-4 FGS编码标准效率低,限制了其进一步的推广应用.因此,本文面向视频应用中常见的头肩序列图像,实现了一种质量可精细扩展的视频编码方法.该方法采用H.26L对基本层进行编码,采用基于DCT变换的SPIHT方法对原始图像与基本层重建图像之间的残差进行编码得到增强层的码流.然后将复杂背景下的人脸检测与跟踪技术与选择性增强技术结合起来,对人脸区域优先编码.实验结果表明,该方法不仅编码效率高于现有的MPEG-4 FGS标准,码流具有可精细扩展的特性,还可以选择性地提高人脸区域重建图像的主观感受水平.     

Architecture Design of Fine Grain Quality Scalable Encoder with CABAC for H.264/AVC Scalable Extension

In addition to coding efficiency, the scalable extension of H.264/AVC provides good functionality for video adaptation in heterogeneous environments. Fine grain scalability (FGS) is a technique to extract video bitstream at the finest quality level under the given bandwidth. In this paper, an architecture of FGS encoder with low external memory bandwidth and low hardware cost is proposed. Up to 99% of bandwidth reduction can be attained by the proposed scan bucket algorithm, early context modeling with context reduction, and first scan pre-encoding. The area-efficient hardware architecture is implemented by layer-wise hardware reuse. Besides, three design strategies for enhancement layer coder are explored so that the trade-off between external memory bandwidth and silicon area is allowed. The proposed hardware architecture can real-time encode HDTV 1920×1080 video with two FGS enhancement layers at 200 MHz working frequency, or HDTV 1280×720 video with three FGS enhancement layers at 130 MHz working frequency.     

基于H.264的FGS视频编码水环扫描算法

提出一种FGS增强层扫描算法,基本层仍采用H.264编码方式,增强层则采用水环扫描算法来代替栅格扫描算法.由于优先传输感兴趣区域的编码信息,水环扫描算法能明显改善视频图像的主观质量.实验表明,对于特定序列,此算法效果较好.     

基于H.26L的精细度可伸缩视频编码

提出了一种基于H．26L精细度可伸缩(fine granularity scalability)视频编码方案，称为EFGS-H．26L。在该方案中，以MPEG-4的FGS为基础构造了一种新的可伸缩结构(EFGS，enhanced fine granularity scalability)，在EFGS结构中，基本层采用H．26L编码，增强层采用类似于JPEG2000的基于上下文的位平面编码。由于H．26L优良的编码性能，使得基本层的编码效率大大提高，为了提高增强层的编码效率，首先把残余图像按子带的顺序重新排列，这样就可以利用子带系数的相关性来实现冗余信息消除。JPEG2000标准中的EBCOT算法已经被证明是非常高效的位平面编码方法，所以对重排后的DCT系数采用一种类似于JPEG2000的基于上下文的位平面编码方法。实验结果证明，在高比特率时，本文提出的精细度可伸缩编码方案编码效率比MPEG-4中的FGS提高3．0dB左右。     

Fine granularity scalable video: implications for streaming and a trace-based evaluation methodology

Fine granularity scalability (FGS) is a new development in the area of video coding, which is designed to facilitate video streaming over communication networks. With FGS coding, the video stream can be flexibly truncated at very fine granularity to adapt to the available network resources. In this article, we introduce the communications generalist to the basic properties of FGS video coding to provide background for the design of video streaming mechanisms for FGS video. We then outline a methodology for evaluating streaming mechanisms for FGS encoded video. The methodology relies on traces of the rate-distortion characteristics of FGS encoded video and enables networking researchers and practitioners without access to video codecs and video sequences to develop and evaluate rate distortion optimized streaming mechanisms for FGS encoded video.     

基于H.264的FGS视频编码及其在视频会议系统中的应用

主要介绍视频会议系统的基本概念及其对视频编解码技术提出的要求,在MPEG-4精细可伸缩性编码(FGS)的基础上,提出了一种基于H.264的精细可伸缩性视频编码方案,仿真和实验结果表明,基于H.264的FGS具有更高的信噪比和视觉质量,能较好地满足基于IP的H.323视频会议系统不同终端的视频质量要求。     

精细可伸缩性视频编码的研究

针对MPEG-4可伸缩编解码方案FGS存在编码效率低的缺陷,出现了不少改进方案,如渐进的精细可伸缩视频编码方案和运动补偿精细可伸缩视频编码方案.对各种编码方案进行了研究和比较.     

Layered Wyner-Ziv video coding.

Following recent theoretical works on successive Wyner-Ziv coding (WZC), we propose a practical layered Wyner-Ziv video coder using the DCT, nested scalar quantization, and irregular LDPC code based Slepian-Wolf coding (or lossless source coding with side information at the decoder). Our main novelty is to use the base layer of a standard scalable video coder (e.g., MPEG-4/H.26L FGS or H.263+) as the decoder side information and perform layered WZC for quality enhancement. Similar to FGS coding, there is no performance difference between layered and monolithic WZC when the enhancement bitstream is generated in our proposed coder. Using an H.26L coded version as the base layer, experiments indicate that WZC gives slightly worse performance than FGS coding when the channel (for both the base and enhancement layers) is noiseless. However, when the channel is noisy, extensive simulations of video transmission over wireless networks conforming to the CDMA2000 1X standard show that H.26L base layer coding plus Wyner-Ziv enhancement layer coding are more robust against channel errors than H.26L FGS coding. These results demonstrate that layered Wyner-Ziv video coding is a promising new technique for video streaming over wireless networks.     

Layered Wyner–Ziv Video Coding

Following recent theoretical works on successive Wyner-Ziv coding (WZC), we propose a practical layered Wyner-Ziv video coder using the DCT, nested scalar quantization, and irregular LDPC code based Slepian-Wolf coding (or lossless source coding with side information at the decoder). Our main novelty is to use the base layer of a standard scalable video coder (e.g., MPEG-4/H.26L FGS or H.263+) as the decoder side information and perform layered WZC for quality enhancement. Similar to FGS coding, there is no performance difference between layered and monolithic WZC when the enhancement bitstream is generated in our proposed coder. Using an H.26L coded version as the base layer, experiments indicate that WZC gives slightly worse performance than FGS coding when the channel (for both the base and enhancement layers) is noiseless. However, when the channel is noisy, extensive simulations of video transmission over wireless networks conforming to the CDMA2000 1X standard show that H.26L base layer coding plus Wyner-Ziv enhancement layer coding are more robust against channel errors than H.26L FGS coding. These results demonstrate that layered Wyner-Ziv video coding is a promising new technique for video streaming over wireless networks     

Content-based FGS coding mode determination for video streaming over wireless networks

Video streaming is the major subject of Amendment for MPEG-4 and it is developed in response to the growing needs on a video-coding standard for the video communication. The fine-granular scalability (FGS) combined with the temporal scalability addresses a variety of challenging problems in delivering video. The FGS video encoder makes the coding mode decision based on the video content and the current available bandwidth in order to achieve higher perceptual video quality. In this paper, we develop a mode selection method to find the most suitable scalable coding mode from six coding schemes: FGS, FGST, FGS-SE, and FGST with background composition based on the contents of the video sequences.     

WAVELET－BASED FINE GRANULARITY SCALABLE VIDEO CODING

This letter proposes an efficient wavelet-based fine Granularity Scalable(FGS)coding scheme,where the base layer is encoded with a newly designed wavelet-based coder,and the entancement layer is encoded with Progressive Fins Granularity Scalable(PFGS)coding.This algorithm involves multi-frame motion compensationk,rate-distortion optimizing strategy with Lagrangian cost function and context-based adaptive arithmetic coding.In order to improve efficiency of the enhancenent layer coding,an improved motion estimation scheme that uses both information from the base layer and the enhancement layer is also proposed in this letter.The wavelet-based coder significantly improves the coding efficiency of the base layer compared with MPEG-4 ASP(Advanced Simple Profile)and H.26L TML9.The PFGS coding is a significant improvement over MPEG-4 FGS coding at the enhancement layer.Experiments show that single layer coding efficiency gain of the proposed scheme is about 2.0-3.0dB and 0.3-1.0dB higher than that of MPEG-4 ASP and H.26L TML9,respectively.The overall coding efficiency gain of the proposed scheme is about 4.0-5.0dB higher than that of MPEG04 FGS.     

一种基于信道预测的FGS视频信源信道联合编码新方法

提出一种基于信道预测的无线FGS视频信源信道联合编码的新方法。该方法利用马尔可夫链对无线信道进行预测，针对FGS分级编码视频流的优先级差异，提供非均匀FEC信道编码保护，根据信道预测的结果，调整视频传输的时隙位置，优化信道编码效率，使得视频在无线传输过程中所需要的数据量最小，同时满足用户的失真要求。实验结果证明了该方法的有效性。     

一种改进的可分级视频编码方法及其网络传输研究

该文提出了一种改进的可分级视频编码方法。为了适应流媒体的分层传输要求,该方法通过对DCT系数量化残差的位平面编码产生视频流的增强层部分,其基本层码流由更多的子基本层组成,各子基本层通过宏块级DCT系数重排及VLC重组生成。同时,该文设计了一种针对该分层视频流数据的网络传输自适应不等重丢包保护(AUPLP)策略,在估计当前可利用带宽资源的基础上,实时调整不同层数据的保护力度,并控制传输截断的层数。仿真结果表明,与传统方法相比该文方案在低带宽时可获得平均1.2dB的编码增益,AUPLP的应用也大大改善了视频流媒体的传输质量。     

基于帧内区域的细粒度可扩展视频编码最优码率分配算法

MPEG-4 FGS是MPEG-4中精细可扩展性编码方法,由于采用帧8*8交织的位平面编码结构,无法支持帧内区域级的动态码率分配,不适合基于内容的增强和流化传输,针对MPEG-4 FGS这编码限制,本文根据MPEG-7的内容描述标准,提出了一种基于帧内区域的细粒度可扩展A-FGS编码,实现了实时的帧内区域流化编码,并就该编码提出了一种最优码率分配算法.利用帧内区域8*8宏块高位平面非零系数很少的特点,提出了动态码率分配算法,使在中等码率范围内编码效率提高了0.5dB左右.     

A ROBUST ADAPTIVE VIDEO ENCODER BASED ON HUMAN VISUAL MODEL

A Robust Adaptive Video Encoder (RAVE) based on human visual model is proposed.The encoder combines the best features of Fine Granularity Scalabla (FGS) coding,frame-dropping coding,video redundancy coding,and human visual model.According to packet loss and available bandwidth of the network,the encoder adjust the output bit rate by jointly adapting quantization step-size instructed by human visual model,rate shaping,and periodically inserting key frame.The proposed encoder is implemented based on MPEG-4 encoder and is compared with the case of a conventional FGS algorithm.It is shown that RAVE is a very efficient robust videl encoder that provides improved visual quality for the receiver and consumes equal or less network resource.Results are confirmed by subjective tests and simulation tests.     

Perceptual feature guided rate distortion optimization for high efficiency video coding

With the advances in understanding perceptual properties of the human visual system, perceptual video coding, which aims to incorporate human perceptual mechanisms into video coding for maximizing the perceptual coding efficiency, becomes an essential research topic. Since the newest video coding standard—high efficiency video coding (HEVC) does not fully consider the perceptual characteristic of the input video, a perceptual feature guided rate distortion optimization (RDO) method is presented to improve its perceptual coding performance in this paper. In the proposed method, for each coding tree unit, the spatial perceptual feature (i.e., gradient magnitude ratio) and the temporal perceptual feature (i.e., gradient magnitude similarity deviation ratio) are extracted by considering the spatial and temporal perceptual correlations. These perceptual features are then utilized to guide the RDO process by perceptually adjusting the corresponding Lagrangian multiplier. By incorporating the proposed method into the HEVC, extensive simulation results have demonstrated that the proposed approach can significantly improve the perceptual coding performance and obtain better visual quality of the reconstructed video, compared with the original RDO in HEVC.     

Motion estimation in low-delay hierarchical p-frame coding using motion vector composition

Low-delay hierarchical prediction structure is currently adopted in various new video coding standards. The only hurdle of this structure is the need of motion estimation in distant reference frames. To maintain high coding efficiency, a large search range for motion estimation can improve the coding efficiency in distant reference pictures. Computational complexity will thus be increased dramatically. In this paper, a fast motion estimation scheme for a low-delay hierarchical P-frame structure is proposed. The proposed scheme adopts a motion vector composition strategy to expedite the motion estimation process for distant reference frames in the hierarchical P structure. In addition, a motion vector composition algorithm is tailor-made with the proposed hierarchical P coding scheme to further improve the coding efficiency. Simulation results show that the proposed scheme can deliver a remarkable complexity savings and coding efficiency improvement on coding a frame in low temporal layers of the hierarchical P structure.