基于OpenFlow的SVC流媒体时延自适应分级传输方法

针对当前互联网流媒体传输的时延敏感性问题,提出一种基于OpenFlow的SVC（scalable video coding,可分级视频编码）流媒体时延自适应分级传输方法,该方法有效结合SVC流媒体可分级和OpenFlow灵活可编程的特性,在网络带宽受限和链路拥塞的复杂网络环境下,通过构建基础层和增强层2个独立路由,实现了动态网络下SVC流媒体分级自适应高效传输。仿真结果表明,该方法在提升SVC流媒体传输效率和质量,改善用户体验方面有重要作用。     

面向VVC帧内编码的快速CU划分和角度模式决策

多功能视频编码(versatile video coding,VVC)是 最新的视频编码标准,与高效视频编 码(high efficiency video coding,HEVC)相比进一步提高了压缩效率,但由于引入了包括 二 叉树和三叉树在内的多类树结构,同时帧内角度模式从35种增加到67种,导致编码复杂度剧 增。为了降低计算复杂度,本文提出了一种基于快速编码单元(coding unit,CU)划分和角度 模式决策的VVC帧内编码算法。首先根据自适应标准差阈值对CU纹理复杂度进行分类,初 步缩减划分模式列表;然后采用Sobel梯度算子确定纹理方向,跳过非最优划分模式;最后 根据统计结果筛选淘汰掉概率小于2%的 角度模式。实验结果表明,与VTM-2.1相比,该算 法能节省51.05%的编码时间,BDBR (Bjontegarrd delta bit rate)仅上升1.98 %。     

分布式编码中广义伽马分布相关噪声模型研究

针对现有相关噪声模型—Laplacian模型不能精确描述相关噪声,导致分布式视频编码(DVC, distributed video coding)系统的率失真性能不高的问题,提出像素域DVC中广义伽马分布相关噪声模型。首先分析了相关噪声的统计特性,发现Laplacian分布的峰值比实际相关噪声分布的低,然后采用广义伽马分布对相关噪声进行拟合,并给出在线估计广义伽马分布参数的方法。实验结果表明,提出的模型能较精确地描述相关噪声,且有效地改善了系统的率失真性能,并减少了解码端计算复杂度。     

结合预处理的深度视频帧内快速编码算法

多视点彩色加深度(MVD)视频是三维(3D)视频的 主流格式。在3D高效视频编码中,深度视频帧内编码 具有较高的编码复杂度;深度估计软件获取的深度视频由于不够准确会使深度图平坦 区域纹理增加, 从而进一步增加帧内编码复杂度。针对以上问题,本文提出了一种联合深度处理的深度视频 帧内低复杂度 编码算法。首先,在编码前对深度视频进行预处理,减少由于深度图不准确而出现的纹理信 息;其次,运 用反向传播神经网络(BPNN,backpropagation neural network)预测最大编码单元 (LCU,la rgest coding unit)的最大划分深度;最后联合深度视频的边缘信 息及对应的彩色LCU最大划分深度进行CU提前终止划分和快速模式选取。实验结果表明, 本文算法在保证 虚拟视点质量的前提下,BDBR下降0.33% ,深度视频编码时间平均节省50.63%。     

基于H.264/SVC的视频加密技术研究

随着网络的不断普及和发展,视频数据在网络中有了越来越多的应用,随之也提出了视频安全的问题,通过视频加密可以很好地解决此问题。文中分析了目前主流的H.264SVC标准所采用的可分级视频编码技术,根据视频分级编码特点选取关键信息进行分层加密,实现不同级别的视频加密。同时,所提方案采用了序列密码进行加密,具有较高的安全性。试验结果表明:该方案具有安全性高、复杂度适中、实时性好等特点。     

结合深度信息的多视点视频编码快速模式选择算法

多视点视频加深度(MVD,multi-view video plus depth)的编码格式包含多个纹理视频序列及其对应的深度图,深度图与对应的纹理视频具有相似的边缘信息。传统的编码模式不考虑两者的联系,单独编码导致复杂度高、编码时间过长。因此,合理利用深度图与纹理图的相似性进行编码,可以有效降低编码复杂度,同时应该确保编码质量不受影响。本文利用深度图的这一特点辅助纹理视频的编码,提出一种帧间快速模式选择算法,充分利用深度图与纹理图之间的相似性,建立一种联合复杂度模型,根据模型得到每个宏块的复杂度。对于复杂度低的宏块,在计算率失真代价之前跳过编码中一些不必要的模式,从而降低编码复杂度。实验表明,本文提出的快速模式选择算法,在保证率失真性能基本不变的情况下,能减少60.57%的编码复杂度,并最高能减少80.64%的编码时间。     

基于H.264/AVC的空域可伸缩编码及其在流媒体中应用的研究

可伸缩视频编码是目前国际上视频技术研究的热点。联合视频组在近年来围绕可伸缩视频编码(SVC)展开了大量的研究工作,提出了作为H.264/AVC扩展集的SVC方案,实现了时域、空域和质量等三个维度上的可伸缩性,而其中基于视频尺寸(空域)的分层是这一方案的基本结构。因此,本文研究了基于H.264/AVC的空域可伸缩编码技术的基本结构和技术要点,并分析了这一技术在流媒体系统中应用所带来的好处。     

基于朴素贝叶斯分类的DVC-HEVC快速转码

分布式视频编码(DVC)与传统视频编码之间的转码为移动终端设备之间的低功耗视频通信提供了一种有效的实现思路。以DVC与HEVC转码为研究对象,利用DVC解码端信息,针对高效视频编码(HEVC)中复杂度极高的编码单元(CU)划分过程进行复杂度优化研究。在DVC解码端提取与CU划分相关的纹理复杂度、运动矢量及预测残差3种特征信息;在HEVC编码端基于朴素贝叶斯原理建立CU快速划分模型,模型生成后便可以通过输入特征信息对当前CU划分进行快速决策,避免大量率失真(RD)代价计算过程。实验结果表明,本方案在编码比特率略有上升的情况下大幅缩短了HEVC编码时间,平均下降幅度达到58.26%,且几乎不影响视频质量。     

分布式视频编码中频域帧的非均衡编码

对基于低密度累积校验码(LDPCA)的分布式视频编码(DVC)方案,提出一种非均衡的WZ(频域)帧编码方法.根据视频序列的低频和高频成分所包含信息的不同重要性,对不同频率成分采用不同的编码方法.提取出WZ帧的低频和高频成分;然后分别对低频和高频成分进行基于块的非均衡编码.与传统的低频和高频成分统一编码方法相比,非均衡编码方法具有更好的解码性能.     

基于网络编码的分级视频权限控制方法

提出一种基于随机线性网络编码的可分级视频流的权限控制算法,该算法充分考虑了网络编码技术和可分级技术的有机结合,从数据包加密和分配2个方面详细阐述了其实现机制,给出了基于全局编码向量的加密和分层的视频证书认证算法。提出的方法具有运算复杂度低和易于实现的优点。仿真结果证明提出的方法可以有效且简便地控制视频的使用权限。     

Deep chroma prediction of Wyner–Ziv frames in distributed video coding of wireless capsule endoscopy video

Compression of captured video frames is crucial for saving the power in wireless capsule endoscopy (WCE). A low complexity encoder is desired to limit the power consumption required for compressing the WCE video. Distributed video coding (DVC) technique is best suitable for designing a low complexity encoder. In this technique, frames captured in RGB colour space are converted into YCbCr colour space. Both Y and CbCr representing luma and chroma components of the Wyner–Ziv (WZ) frames are processed and encoded in existing DVC techniques proposed for WCE video compression. In the WCE video, consecutive frames exhibit more similarity in texture and colour properties. The proposed work uses these properties to present a method for processing and encoding only the luma component of a WZ frame. The chroma components of the WZ frame are predicted by an encoder–decoder based deep chroma prediction model at the decoder by matching luma and texture information of the keyframe and WZ frame. The proposed method reduces the computations required for encoding and transmitting of WZ chroma component. The results show that the proposed DVC with a deep chroma prediction model performs better when compared to motion JPEG and existing DVC systems for WCE at the reduced encoder complexity.     

一种HEVC帧内预测编码CU结构快速选择算法

为了提升高效视频编码(HEVC) 帧内预测编码部分的编码效率,提出了一种HEVC帧内预测编码编码单元(CU)结构快速选择算 法。算法通过 对CTU(coding tree unit)四叉树结构的遍历过程进行优化,设计了两种不同的最优CU结 构快速决策算 法,分别从最大划分深度和最小划分深度开始遍历,并在每一步遍历之前,判断是否提前终 止遍历操作。 同时,在对每个CTU进行求解时,依据其纹理复杂度和当前编码状态,从两种算法中选择出 最优快速决策 算法对其进行求解。在HM 15.0的基础上实现了提出的快速选择算法 。实验结果表明,本文算法能够在 保证编码性能的同时,降低31.14%的编码时间,提高了HEVC的编码效 率。     

Distributed video coding based on vector quantization: Application to capsule endoscopy

We present in this paper a new distributed video coding (DVC) architecture for wireless capsule endoscopy. It is based on the state of the art DVC systems, but without using key frames. Instead, it uses an adapted vector quantization (VQ) with a searching complexity that is shifted to the decoder. VQ allows creating a good side information (SI) by exploiting the similarities in human anatomy. Thus, SI is created from a codebook (CB) rather than by motion compensated prediction. This approach decreases largely the complexity of the encoder, which codes only Wyner-Ziv frames, and allows a progressive decoding. The encoder of the proposed DVC generates only a simple hash that is used by the decoder to select the corresponding VQ codeword. The obtained experimental results show that rate-distortion results are better than those of JPEG, and show the possibility of using scalable coding to control the used rate and energy.     

Cross-band noise model refinement for transform domain Wyner-Ziv video coding

Distributed Video Coding (DVC) is a new video coding paradigm, which mainly exploits the source statistics at the decoder based on the availability of decoder side information. One approach to DVC is feedback channel based Transform Domain Wyner-Ziv (TDWZ) video coding. The efficiency of current TDWZ video coding trails that of conventional video coding solutions, mainly due to the quality of side information, inaccurate noise modeling and loss in the final coding step. The major goal of this paper is to enhance the accuracy of the noise modeling, which is one of the most important aspects influencing the coding performance of DVC. A TDWZ video decoder with a novel cross-band based adaptive noise model is proposed, and a noise residue refinement scheme is introduced to successively update the estimated noise residue for noise modeling after each bit-plane. Experimental results show that the proposed noise model and noise residue refinement scheme can improve the rate-distortion (RD) performance of TDWZ video coding significantly. The quality of the side information modeling is also evaluated by a measure of the ideal code length.     

DVC转码技术研究

本文介绍了DVC(分布式视频编码)到传统视频转码的方案,该转码方案适用于移动终端设备之间的视频通信。着重讲述了DVC到H.264的转码,针对转码过程中复杂度高和时延长等问题,利用DVC解码端生成的运动矢量来减少H.264编码的工作量,在几乎不影响视频质量的前提下,极大地降低了转码的计算复杂度和时间,提高了转码效率。同时介绍了DVC转到其它传统视频的方法和方案,最后分析了DVC转码在当前移动视频通信市场中存在的巨大潜能,以及对转码技术的未来发展和方向进行了展望。     

一种空间域Wyner-Ziv视频编码系统的性能改进算法

分布式视频编码是建立在Slepian-Wolf和Wyner-Ziv信息编码理论基础上的全新视频编码框架,具有编码复杂度低,编码效率较高,抗误码性能好的特点.本文首先简单介绍了一种典型的分布式视频编码实现方案——空间域Wyner-Ziv视频编码,随后提出一种空间域Wyner-Ziv视频编码系统的性能改进算法,该算法在不增加编码复杂度的基础上,在解码端利用双向运动估计预测获取更高质量的边信息,同时采用基于Huber-Markov随机场约束的联合迭代解码算法重建图像.实验结果表明,在相同的输出码流情况下,本文改进算法在解码端重建图像的峰值信噪比与空间域Wyner-Ziv视频编码算法相比平均提高2dB,并且主观效果有所改善.     

一种HEVC帧内快速编码算法

高效视频编码(HEVC)采用编码单元(CU)四叉树的 分割结构,相比H.264/AVC显著地提升了编码效 率,但却使编码复杂度急剧增加。为此,本文提出一种帧内快速编码算法。首先,根据视 频图像纹理复 杂度,提前判断是否进行最大编码单元(LCU)分割。然后,根据空域相邻CU的深度预测当前C U的深度范围, 跳过不必要的计算;最后,根据预测模式被选为最优预测模式的统计特性,去掉可能性小的 帧内预测模式。本文算法在HM14.0的基础上实现。 仿真结果表明,本文算法在全I帧模式下与HM14.0相比,帧内编码时 间平均减少38%,码率(BR)只增加1.41%,峰值信噪比(PSNR)只降低0.29dB,在保证编码性能和视频质量几乎不变的 情况下,本文算法降低了编码的计算复杂度。     

Scalable Interframe Wavelet Coding with Low Complex Spatial Wavelet Transform

In the decoding process associated with interframe wavelet coding, the inverse wavelet transform requires high computational complexity. However, as video technology starts to pervade all aspects of our lives, decoders are becoming required in various devices such as PDAs, notebooks, PCs, and set‐top boxes. Therefore, a decoder's complexity needs to be adapted to the processor's computational power, and consequently a low‐complexity codec is also required for scalable video coding. In this paper, we propose a method of controlling and lowering the complexity of the spatial wavelet transform while sustaining the same coding efficiency as that currently afforded. In addition, the proposed method may alleviate the ringing effect for slowly changing image sequences.     

面向3G环境下的移动视频编码技术

 随着移动通信迈入3G时代,在众多的3G增值业务中,移动视频业务无疑将会成为3G业务的核心应用,以视频编码技术为代表的多媒体技术是支撑移动业务运营的基础技术。本文首先介绍了面向3G环境下的移动视频业务的发展现状及其面临的技术问题;然后从可分级编码、视频转码、多描述编码、基于视觉特性的编码几个方面论述了针对移动视频的编码技术;最后对面向3G环境下的移动视频编码技术进行了总结和展望。     

Joint Source/Channel Coding Based on Two‐Dimensional Optimization for Scalable H.264/AVC Video

The scalable extension of the H.264/AVC video coding standard (SVC) demonstrates superb adaptability in video communications. Joint source and channel coding (JSCC) has been shown to be very effective for such scalable video consisting of parts of different significance. In this paper, a new JSCC scheme for SVC transmission over packet loss channels is proposed which performs two‐dimensional optimization on the quality layers of each frame in a rate‐distortion (R‐D) sense as well as on the temporal hierarchical structure of frames under dependency constraints. To compute the end‐to‐end R‐D points of a frame, a novel reduced trellis algorithm is developed with a significant reduction of complexity from the existing Viterbi‐based algorithm. The R‐D points of frames are sorted under the hierarchical dependency constraints and optimal JSCC solution is obtained in terms of the best R‐D performance. Experimental results show that our scheme outperforms the existing scheme of [13] with average quality gains of 0.26 dB and 0.22 dB for progressive and non‐progressive modes respectively.