AVS1.0中熵编码技术的研究

对AVS1.0熵编码器的设计进行了介绍.在AVS1.0熵编码器中,对一个块的残差系数进行编码时,为了适应不同阶段的非零系数概率分布状况,通过前向预测建立了多张码表与之匹配,以达到基于上下文自适应的目的.还提出了一种新的前向预测机制,较传统VLC性能有显著的提高.     

AVS视频编码中熵编码器的硬件设计

简要介绍了AVS标准视频压缩部分的特点,重点研究AVS可变长熵编码的算法、结构,提出并行扫描的游程扫描方式和分段寻址的码表查表方式,提高了系统的速度以满足实时编码的要求.在此基础上,给出了主要的块变化系数熵编码器硬件结构.最后给出仿真波形及硬件综合结果,符合AVS视频编码标准,满足硬件加速的要求.     

CABAC熵编码机制下有效的变换域码率估计技术

 CABAC是H.264/AVC视频压缩标准中采用的一种熵编码机制,结合RDO模式选择技术,可以降低20％的码率.在RDO模式选择过程中,需要对编码块的每一种候选模式进行熵编码以获得编码位数,这在很大程度上增加了视频编码的计算复杂度.为了避免复杂的Lagrange耗费计算,本文第一次提出了一种CABAC熵编码机制下的变换域码率估计方法,基于量化变换系数和运动向量差对熵编码位数进行估计.在此基础上,本文将码率估计技术应用在RDO模式选择中,提出了基于码率估计的快速模式选择算法,减少了模式选择的计算时间.模拟结果显示,本文提出的CABAC熵编码机制下的变换域码率估计技术在对编码性能影响不大的情况下,减少了模式选择中51％的率失真耗费计算时间,采用全搜索运动估计算法时,节省33％的总编码时间.     

AVS2标准及未来展望

概要介绍了AVS2国家标准《信息技术高效多媒体编码》系统、视频、音频三个部分,分析了AVS2与AVS1以及AVC/H.264和HEVC/H.265在编码效率上的对比,具体阐释了帧结构、块结构、帧内预测、帧间预测、变换、熵编码、环路滤波等为AVS2带来的编码增益。介绍了AVS2的特色功能——场景视频编码的概念、思路及优势。最后展望了AVS3云媒体编码标准。     

AVS2标准及未来展望黄铁军

概要介绍了AVS2国家标准《信息技术 高效多媒体编码》系统、视频、音频三个部分,分析了AVS2 与AVS1以及AVC/H.264和HEVC/H.265在编码效率上的对比,具体阐释了帧结构、块结构、帧内预测、帧间预测、变换、熵编码、环路滤波等为AVS2带来的编码增益。介绍了AVS2的特色功能——场景视频编码的概念、思路及优势。最后展望了AVS3云媒体编码标准。     

数码视讯超级编码器填补了国内移动（地面）数字电视编码器技术空白

针对目前国内移动(地面)数字电视系统中对低码率编码的需求，数码视讯自主研发并推出SMSX 10K121型超级编码器，为SMSX系列编码器中又新增了一款独具特色的产品。该编码器最大的优势体现在低码率压缩技术方面，它采用数码视讯自主产权的低码率技术，具有强大的图像预处理能力和硬件匀速码率处理技术，能够最大限度地去掉冗余信息，并根据图像源的信息量大小自适应调节编码器的输出码率，在编码输出码率低于2M甚至1．2M的情况下，依然能保证良好的视频质量。     

AVS2视频编码标准中熵编码模块的优化设计

在对高清和超高清视频进行压缩时,编码效率不再是衡量视频压缩技术的唯一指标,为了提高视频编码器的处理速度和降低其功耗,数据吞吐率已经成为衡量视频压缩技术优劣的重要指标.作为AVS2的核心模块之一,熵编码模块在去除信源符号的统计冗余方面有着不可替代的作用.然而,在AVS2熵编码模块的设计过程中,由于没有充分考虑到数据吞吐率这一性能指标,使得其熵编码模块包含非常紧密的编码依赖关系,严重地限制着其数据吞吐率.为了解决这个问题,本文从3个方面对AVS2的熵编码模块进行了优化设计.首先,本文提出了一种快速的,与标准兼容的算术编码引擎归一化方法.该方法仅仅需要一次查表操作即可完成归一化过程.其次,本文提出了一个快速的bypass bin(概率等于0.5的二进制符号)的编解码过程,使得编解码bypass bin仅仅需要移位和加法操作即可完成.最后,本文改进了AVS2中变换系数的编码过程,来最大限度地降低变换系数之间的编码依赖关系.实验结果表明,上述3个技术可以极大地提高AVS2中的熵编码模块的数据吞吐率,同时性能损失也比较小.     

支持ROI优先编码策略的码率控制方案

低码率视频通信应用日益广泛,感兴趣区（ROI）优先编码策略的应用越来越重要。应用ROI优先编码策略时,感兴趣区编码并不是低码率编码,而属于高码率编码范畴。现有码率控制没有考虑到这一事实,导致 了不应有的控制误差。本文正是针对这一问题,提出了一种码率控制框架,并设计了一种简单有效的感兴趣区码率控制方案。本文方法经过简单推广,还可用于MPEG－4等基于视频对象编码器的码率控制。     

区域追踪匹配甚低码率视频编码算法的研究

本文提出一种基于Gabor变换区域追踪匹配RMP（region matching pursuit)的甚低码率视频编码算法,用于克服块编码带来的块效应及其明显失真;根据图像区域特征重要性优先级选择编码保证编码质量（PSNR）;通过算法自学习实现Gabor追踪匹配集优化提高编码效率。实验测试结果表明,在甚低码率（24kbit/s和10kbit/s）下区域追踪匹配算法与H．263编码算法相比,能够有效保证视频编码质量（PSNR）,降低块效应,有较高的编码效率。同时算法具有码率及PSNR扩展功能。     

基于AVS视频标准的熵编码器的FPGA设计

AVS视频标准中的熵编码部分是将语法元素与量化系数进行Exb-Golomb编码与存储的重要环节。为了进一步提高熵编码器的效率,本文采用了一种检测＂哥伦布首位1＂的FPGA实现算法,用（run,level）联合坐标寻址查找2D-VLC码表,并用FIFO进行暂存和输出码流的方法,降低了运算量以及硬件资源,提高了运行速度。该Exb-Golomb熵编码器已通过RTL（Register Transfer Level）级仿真和综合,占用硬件资源LUT6359门,相比其他同类设计的AVS熵编码器,大大减少了硬件资源的占用。     

Utilisation of downsampling for arbitrary views in multi-view video coding

The effect of using downsampling for arbitrary views inside a multi- view sequence on the multi-view coding (MVC) efficiency is explored. A bit rate adaptive approach is proposed to consider downsampling certain views prior to encoding with relevant downscaling ratios. The inter-view references, if any, are downsampled to the same resolution and the decoded view is upsampled back to the original resolution. The results over several multi-view test sequences imply that up to 0.9 dB gain or 20% reduction in bit rate can be achieved, reducing the computational complexity in the encoder significantly at the same time.     

Fast turbo codes with space‐time block codes in fast fading channels

In this paper, space‐time block coding has been used in conjunction with Turbo codes to provide good diversity and coding gains. A new method of dividing turbo encoder and decoder into several parallel encoding and decoding blocks is considered. These blocks work simultaneously and yield a faster coding scheme in comparison to classical Turbo codes. The system concatenates fast Turbo coding as an outer code with Alamouti's G2 space‐time block coding scheme as an inner code, achieving benefits associated with both techniques including acceptable diversity and coding gain as well as short coding delay. In this paper, fast fading Rayleigh and Rician channels are considered for discussion. For Rayleigh fading channels, a fixed frame size and channel memory length of 5000 and 10, respectively, the coding gain is 7.5 dB and bit error rate (BER) of 10^?4 is achieved at 7 dB. For the same frame size and channel memory length, Rician fading channel yields the same BER at about 4.5 dB. Copyright © 2013 John Wiley & Sons, Ltd.     

基于码率预分配的JPEG2000自适应率控制算法

该文提出一种基于码率预分配和反馈控制的自适应率控制算法.算法引入了预测模板,对图像小波变换和量化后EBCOT编码码块的有效比特平面进行独立的熵估计,并以码块估计熵总和指导码率预分配,同时T2编码器由预分配编码比特率自适应地反馈控制编码深度、完成优化截取.实验结果表明,该算法码率分配精确,并有效地减少了编码器计算量和存储量,提高了编码效率,算法复杂度低,易于硬件实现.     

A coded 8-PSK system for 140 Mb/s information rate transmission over 80 MHz non-linear transponders

A combined 8-PSK modulation and rate 7/9 convolutional coding technique is proposed for 140 Mb/s information rate transmission over the 80 MHz INTELSAT transponders, thus achieving a bandwidth efficiency of 1.75 b/s/Hz of allocated bandwidth. The desired power efficiency is to achieve a bit error rate of 10^?6 at an E_b/N₀ of 11 dB, including modem and codec implementation losses. The proposed system employs an 8-PSK modem operating at a 60 MHz symbol rate (or 180 Mb/s bit rate), as well as a rate 7/9 convolutional encoder and a 16-state Viterbi algorithm decoder operating at 60 MHz. The rate 7/9 code is periodically time varying and is designed to maximize the Euclidean distance between the modulated codeword sequences, thereby achieving a 3 dB asymptotic coding gain relative to the conventional QPSK system over an AWGN channel. This code is also designed to reduce decoder complexity for high-speed operations. The performance of the proposed system over INTELSAT V and VI non-linear transponders was evaluated by Monte Carlo computer simulation. The 180 Mb/s 8 PSK modem, including the automatic frequency control, automatic gain control, carrier recovery and clock recovery circuits, has been implemented and tested. The complete Viterbi decoder is being implemented on five boards, and the critical add-compare-select (ACS) circuit of the high-speed Viterbi algorithm decoder is being implemented with hybrid technology employing 100-K series emitter-coupled logic dies on specially designed ceramic substrates. The ACS circuit operates at a speed exceeding 120 MHz, well over the design goal of 60 MHz. Construction of this codec is almost complete.     

A 105 Mbit/s Error Correcting Codec

A 105 Mbit/s experimental error correcting encoder/ decoder is described. The device exhibits a coding gain of 1.9 dB at a 10^-5bit error rate and has a 25 percent parity bit overhead. The decoder was constructed without syndrome reset. This allowed the operating speed to be more than doubled, while only sustaining a negligible loss in performance.     

7/8自正交卷积码在宽带无线接入系统中的应用

针对TDMA宽带无线接入系统零星误码的问题,设计了7/8自正交卷积码高效结构的编码器和反馈结构的译码器,7/8自正交卷积码的应用使得宽带无线接入系统的误码性能得到较大改善。针对解调器相位模糊和译码器失步的问题,提出了统一的解决方案,应用该方案可获得3dB的功率增益,而且可快速地获得译码器和编码器之间的同步。     

Entropy Coded Differential Pulse-Code Modulation Systems for Television

This concise paper describes experiments with a television source encoder which consists of a differential PCM encoder followed by entropy coding. This encoder converts analog television signals into a digital bit stream for digital transmission or storage. When optimized, this type of system is known to perform very close to the rate distortion bound. The differential PCM encoder has a 16-level quantizer during low entropy areas of the picture (quiet areas) but switches to a 6-level quantizer in high entropy (busy) areas of the picture which tend to fill up the buffer. This strategy avoids buffer overflow and has the desirable property that it produces low noise in quiet areas of the picture and higher noise in busy areas of the picture.     

Analyse des performances du codage multiniveau pour modulations à grand nombre d’états

In this paper, we analyze the performance of multilevel coding for high level QAM constellations. After the presentation of the encoder principle, we focus our study on a sub-optimal decoder which can be implemented very simply. We analyze the performance of the presented technique in terms of asymptotic gain and bit error rate characteristics. Finally, a pratical application in digital microwave radio links is considered, and one- and two-level coded 128-QAM are studied. At a bit error rate of 10^-8, it is shown that a 4 dB coding gain can be reached with moderate decoder complexity. These coding schemes are therefore very attractive for high-capacity microwave links applications.     

Image coding using dual-tree discrete wavelet transform

In this paper, we explore the application of 2-D dual-tree discrete wavelet transform (DDWT), which is a directional and redundant transform, for image coding. Three methods for sparsifying DDWT coefficients, i.e., matching pursuit, basis pursuit, and noise shaping, are compared. We found that noise shaping achieves the best nonlinear approximation efficiency with the lowest computational complexity. The interscale, intersubband, and intrasubband dependency among the DDWT coefficients are analyzed. Three subband coding methods, i.e., SPIHT, EBCOT, and TCE, are evaluated for coding DDWT coefficients. Experimental results show that TCE has the best performance. In spite of the redundancy of the transform, our DDWT _ TCE scheme outperforms JPEG2000 up to 0.70 dB at low bit rates and is comparable to JPEG2000 at high bit rates. The DDWT _TCE scheme also outperforms two other image coders that are based on directional filter banks. To further improve coding efficiency, we extend the DDWT to an anisotropic dual-tree discrete wavelet packets (ADDWP), which incorporates adaptive and anisotropic decomposition into DDWT. The ADDWP subbands are coded with TCE coder. Experimental results show that ADDWP _ TCE provides up to 1.47 dB improvement over the DDWT _TCE scheme, outperforming JPEG2000 up to 2.00 dB. Reconstructed images of our coding schemes are visually more appealing compared with DWT-based coding schemes thanks to the directionality of wavelets.     

Independent key frame coding using correlated pixels in distributed video coding

A novel intra-coding technique is proposed that eliminates the requirement of a secondary coding scheme for coding the key frames in distributed video coding (DVC). The proposed technique uses the Slepian-Wolf theorem and Wyner-Ziv (WZ) coding with spatially predicted information to transmit the key-frames to the DVC decoder. Simulation results show that the proposed WZ-intra coding technique (WZ-I) can achieve up to 5 dB PSNR gain compared to MPEG-2 intra coding (MPEG-I) at the same bit rate with negligible computational cost to the encoder