ITU standardisation of very low bitrate video coding algorithms

The ITU near term standard for very low bitrate video coding, H.263 (ITU-T SG 15/1 Rapporteurs Group for Very Low Bitrate Visual Telephony, 1995), is described. Both QCIF and a sub-QCIF format (128 × 96) are mandatory picture formats for the decoder; the CIF picture format is optional. The H.263 algorithm consists of a mandatory core algorithm and four negotiable options. With H.263 a significantly better picture quality than with H.261 can be achieved, depending on the content of the video scene and the coding parameters. Also, the cost of the H.263 video codec can be kept low if only the minimum required is implemented. The negotiable options of H.263 increase the complexity of the video codec, but also significantly improve the picture quality. H.263 is part of a set of recommendations for a very low bitrate audio visual terminal that was frozen in January 1995 and is based on existing technology. A long term activity is planned by ITU for the development of a new video coding algorithm (H.263/L) with a considerable better picture quality than H.263. This standard will be developed in joint co-operation with MPEG4.     

低比特率通信的H.263视频编解码

本文介绍了国际电联组织ITU-T 于1995年2月起草并通过的 H.263建议草案中低比特率视频编解码的原理、实现流程和图像的数据结构,并对H.263建议的4个增强编解码模式以及 H.263建议与H.261建议编解码的不同之处进行了探讨。     

Object-oriented H.263 compatible video coding platform forconferencing applications

This paper describes a prototype video coding platform meant for the conception and testing of multimedia products such as next-generation videophones. The platform is largely based on ITU-T Recommendation H.263, with a number of additional object-oriented quality enhancement features which make it especially well suited for very low bit-rate coding of “head-and-shoulders” video material typical of real-time multimedia applications, video teleconferencing, and video telephony. These features consist of: (1) segmentation into objects of interest, (2) segmentation-based prefiltering, (3) model-assisted rate control, (4) adaptive vector quantization, and finally (5) segmentation-based postfiltering. In the spirit of Recommendation H.263, these enhancements are modular and can be selectively turned on or off, thereby enabling a wide variety of coding modes     

一种H.264运动估计器的VLSI设计

MPEG4AVC／ITU—T H．264视频编码标准中所采用的多模式运动估计算法与传统的MPEG4、H．263 高级预测模式相比较而言，编码效率和性能都大大提高。但其诸如模式决策等问题却给运动估计器，特别是硬件运动估计器带来非常大的运算复杂度。本文提出一种H．264运动估计器硬件结构，它采用了新的模式决策算法和快速运动估计算法。仿真结果证明，这两种算法不但能使运动估计器降低其硬件实现成本，而且能减少模式决策和运动估计的时间。     

自适应分区DCT/DWT低码率视频编码算法

为了降低低码率视频编码算法的块效应与环效应，提出了一种基于自适应分区余弦变换／子波变换和重叠运动补偿的视频编码算法，首先给了一种空－是相关自适应运动估计算法，有效降低运算复杂性，然后通过过层游动窗块区域形成算法检测现帧间预测误差场的高能量区域，对大区域进行了子波变换和量化，对零散区域进行余弦变换和量化，根据人类视觉系统（ＨＶＳ）的空－频和时－频特性，给出基于ＨＶＳ的量化模型，以期在信噪比约束下获得     

MPEG-4自然视频编码技术

对MPEG－4自然视频编码的关键技术作了详细的分析和阐述。首先介绍MPEG－4频语法结构，并对视频编码的框架概要分析。接着分析了自然视频编码中涉及到的关键技术，包括：VOP的产生；二值和灰度级α平面的编码技术；运动估计和补偿方法；纹理编码；基于对象的时间分级和空间分级；MPEG－4提供的再同步和各种错误掩盖，刷新方法，精 编码技术和零树小波基的静止图像编码技术。指出MPEG－4和MPEG－1，MPEG－2等标准的异同，突出MPEG－4的三个主要特点。最后给出MPEG－4技术在网络视频传输中的应用，并给出测试和分析。     

视频压缩编解码标准在广电的应用

目前视频传输流中最为重要的编解码标准包括国际电联的H.261、H.263,运动静止图像专家组的M-JPEG,国际标准化组织运动图像专家组的MPEG系列标准,以及在互联网上广泛应用的RealVideo、WMT、Quick Time等,介绍了视频压缩编解码标准及其在广电的应用.     

H.263视频编码算法原理及DSP实现

介绍ITU-T H.263视频编码器在德州仪器（Texas Instruments)公司新一代数字信号处理芯片IMS320C6000上的实时实现技术。编程实现了H.263标准的主要内容及H.263 中提出的新的编码技术，重点讨论了H.263编码在TMS320C6711 DSP上的优化和实现。     

Performance of the H.263 Video Compression Standard

The draft international standard ITU-T H.263 is closely related to the well known and widely used ITU-T Recommendation H.261. However, H.263 does provide the same subjective image quality at less than half the bit-rate. In this paper we investigate to what extend single enhancements of H.263 contribute to this performance gain, and consider the trade-off quality vs. complexity. Based on typical test sequences, H.263 with its various modes is compared to H.261 on the basis of rate distortion curves at bit-rates up to 128 kbps. At 64 kbps, the performance gain of H.263 in its default mode compared to H.261 is approximately 2 dB. This improvement is achieved with only little increase of complexity, and is mainly due to more accurate motion compensation with half-pel accuracy. Considering the trade-off quality vs. complexity, the combination of the optional coding-modes Advanced prediction mode and PB-frames mode is a good compromise, resulting in an additional performance gain of 1.5 dB PSNR at 64 kbps. The Syntax-based arithmetic coding mode on the other hand, offers only a very small performance gain (0.1 dB at 64 kbps) for its increased computational complexity. Results from profiling an H.263 software codec are presented in order to support complexity considerations of the optional coding-modes.     

H.263建议的原理及其特点

本文讨论了ＩＴＵ－Ｈ．２６３建议的原理和它的一些主要特点，如ＰＢ帧模式，运动补偿、算术编码等，把它们与Ｈ．２６１建议和ＭＰＥＧ标准作了比较，并通过计算机模拟检验其效果。     

A single-chip CIF 30-Hz, H261, H263, and H263+ videoencoder/decoder with embedded display controller

A single-chip video codec with embedded display controller for videotelephony applications is described. It encodes and decodes simultaneously up to 30 CIF pictures per second according to video-conferencing recommendations H261, H263 (all five options), and H263+ (six additional options). The die area is 132 mm² in a 0.35-μm technology, and the power consumption is 1.4 W. The chip uses a distributed dedicated multiprocessor architecture; where computation-intensive functions are done by dedicated hardware, and where picture quality or standard dependent parts are done in software on dedicated programmable processors. Main architectural choices are discussed, and emphasis is put on hardware/software partitioning and codesign     

Low bit-rate video coding with spatio-temporal geometric transforms

A low bit-rate video coding technique that uses spatio-temporal geometric transforms is presented. Motion compensation based on the bilinear transform is employed to reduce the temporal redundancy of the video. The spatial redundancy of the motion compensated error images is reduced by a combination of fractals and the DCT. It is shown that in the objects boundaries of the motion compensated error image fractals outperforms the DCT, while in the smooth areas the DCT is better than fractals. A hybrid combination of fractals and the DCT gives the best result. The performance of this hybrid codec with geometrically transformed motion compensation is compared against the H.261 standard video codec at 64 kbit/s     

一种新的小波可视电话编码算法

针对极低比特率应用提出一种新的结合H.263与SLCCA的混合小波视频编码算法。在提出的算法中,首先,用基于H.263的微调运动估计减小时间冗余,用无遗漏覆盖块运动补偿保证运动补偿误差帧的连续性;第二,对运动补偿误差帧进行小波变换得到全局能量压缩;第三,用SLCCA组织和表示小波变换后的数据,最后,运动向量的水平和垂直分量分别用自适应算法编码,算法在A级测试序列Akiyo和B级测试序列Foreman（QFIF）上测试取得了良好效果。     

Introduction to the High-Efficiency Video Coding Standard

The high-efficiency video coding(HEVC) standard is the newest video coding standard currently under joint development by ITU-T Video Coding Experts Group(VCEG) and ISO/IEC Moving Picture Experts Group(MPEG).HEVC is the next-generation video coding standard after H.264/AVC.The goals of the HEVC standardization effort are to double the video coding efficiency of existing H.264/AVC while supporting all the recognized potential applications,such as,video telephony,storage,broadcast,streaming,especially for large picture size video(4k × 2k).The HEVC standard will be completed as an ISO/IEC and ITU-T standard in January 2013.In February 2012,the HEVC standardization process reached its committee draft(CD) stage.The ever-improving HEVC standard has demonstrated a significant gain in coding efficiency in rate-distortion efficiency relative to the existing H.264/AVC.This paper provides an overview of the technical features of HEVC close to HEVC CD stage,covering high-level structure,coding units,prediction units,transform units,spatial signal transformation and PCM representation,intra-picture prediction,inter-picture prediction,entropy coding and in-loop filtering.The HEVC coding efficiency performances comparing with H.264/AVC are also provided.     

Error resilience in video and multiplexing layers for very lowbit-rate video coding systems

The transmission of audio-visual services on low-bit-rate, wireless telecommunications systems requires the use of coding techniques that are both efficient in their use of bits and robust against errors introduced in transmission. In this paper, we present efficient techniques for improving the error resilience of audio-visual services. These techniques are based on coding simultaneously for synchronization and error protection or detection. We apply the techniques to improve the performance of the multiplexing protocol (which combines the video and audio streams so that they can be transmitted on a single circuit), and also to improve the robustness of the coded video. We show through simulations that the techniques are efficient in their use of bits and effective against bursty errors common in wireless channels. For a simulation of the DECT channel at a bit-error rate of 10^-3, the techniques give an order of magnitude improvement in the probability of lost packets in the multiplexer layer over more conventional techniques. In the video layer, the techniques give an improvement of between 1-2 dB over ITU-T Recommendation H.263. The techniques proposed for the video layer also have the advantage of permitting simple transcoding with bit streams complying with H.263     

Predictive RD optimized motion estimation for very low bit-ratevideo coding

Predictive rate-distortion (RD) optimized motion estimation techniques are studied and developed for very low bit-rate video coding. Four types of predictors are studied: mean, weighted mean, median, and statistical mean. The weighted mean is obtained using conventional linear prediction techniques. The statistical mean is obtained using a finite-state machine modeling method based on dynamic vector quantization. By employing prediction, the motion vector search can then be constrained to a small area. The effective search area is reduced further by varying its size based on the local statistics of the motion field, through using a Lagrangian as the search matching measure and imposing probabilistic models during the search process. The proposed motion estimation techniques are analyzed within a simple DCT-based video coding framework, where an RD criterion is used for alternating among three coding modes for each 8×8 block: motion only, motion-compensated prediction and DCT, and intra-DCT. Experimental results indicate that our techniques yield very good computation-performance tradeoffs. When such techniques are applied to an RD optimized H.263 framework at very low bit rates, the resulting H.263 compliant video coder is shown to outperform the H.263 TMN5 coder in terms of compression performance and computations simultaneously     

A parametric model for perceptual video quality estimation

In this paper, a parametric model is proposed which provides estimation for the perceived quality of video, coded with different codecs, at any bit rate and display format. The video quality metric used is one of the standardized Full Reference models in Recommendations ITU-T J.144 and ITU-R BT.1683. The proposed model is based on the video quality estimation described in Recommendation ITU-T G.1070, but incorporates different enhancements, allowing a much better estimation of the perceptual MOS values, especially in low bit rate ranges. The error obtained with the proposed model, regarding to the ITU models, is between the ITU algorithms error margins, according to the subjective tests developed by the VQEG. Studies were made for more than 1500 processed video clips, coded in MPEG-2 and H.264/AVC, in bit rate ranges from 50 kb/s to 12 Mb/s, in SD, VGA, CIF and QCIF display formats.     

低码率活动图像帧间预测编码的研究

主要研究适于窄带低码率活动图像的帧间预测编码算法。依据Ｈ．２６３建议中的算法和编码方案，着重论述了三种先进的帧间预测模式：无约束运动矢量模式、高级预测模式和ＰＢ帧模式，并分别对其编、解码的效果作出计算机仿真及分析。     

视频编码标准H．263码流结构的分析

视频编码标准H.263视频复用规定为四层分级结构,从顶向下依次为:图像层、块组层、宏块层和块层。视频编码标准H.263关键技术包含有:图像的帧结构、运动补偿加DCT的混合编码方法以及宏块统一使用同样的量化步长进行量化等。视频编码标准H.263标准的比特流功能、大小和语法在其协议中做了详细的规定,但是产生这些必选码流分支和可选码流分支的条件却很复杂。重点对H.263码流结构中比特流语法里面必选码流分支和可选码流分支的条件进行全面详细的分析。