H.263: video coding for low-bit-rate communication

This article provides an overview of H.263, the new ITU-T Recommendation for low-bit-rate video communication. H.263 specifies a coded representation for compressing the moving picture component of audio-visual signals at low bit rates. The basic structure of the video source coding algorithm is taken from ITU-T Recommendation H.261 and is a hybrid of interpicture prediction to reduce temporal redundancy and transform coding of the prediction residual to reduce spatial redundancy. The source coder can operate on five standardized picture formats: sub-QCIF, QCIF, CIF, 4CIF, and 16CIF. The decoder has motion compensation capability with half-pixel precision, in contrast to H.261 which uses full-pixel precision and employs a loop filter. H.263 includes four negotiable coding options which provide improved coding efficiency: unrestricted motion vectors, syntax-based arithmetic coding, advanced prediction, and PB-frames     

一种基于H.263+的双正交小波视频编码技术

在分析了双正交小波特点的基础上，提出了基于Ｈ．２６３＋的双正交小波视频编码方案，并用实验证明了此项技术的可行性与有效性。     

兼容H.263/H.263+的低码率视频编解码算法优化

针对视频编码各部分功能模块进行了算法研究和性能分析,在保证最后解码图像的质量下降不大的前提下,提高编解码的处理速度。对于DCT／IDCT、运动估计以及P帧编码中的条件性略过宏块等作了分析,同时给出了判据和实验结果。最后对程序的体系结构和程序设计给出了一般性的规则。     

AN ERROR-RESILIENT H.263＋ CODING SCHEME FOR VIDEO TRANSMISSION OVER WIRELESS NETWORKS

Video transmission over wireless networks has received much attention recently for its restricted bandwidth and high bit-error rate, Based on H.263＋, by reversing part stream sequences of each Group Of Block （GOB）, an error resilient scheme is presented to improve video robustness without additional bandwidth burden. Error patterns are employed to simulate Widcband Code Division Multiple Acccss,（WCDMA） channels to check out error resilience performances. Simulation results show that both subjective and objective qualities of the reconstructed images are improved remarkably. The mean Peak Signal to Noise Ratio （PSNR） is increased by 0.5dB, and the highest increment is 2dB.     

H.263的差错恢复视频编码及其在IP网络传输中的应用

以H.263 为主要依据，详细介绍了H.263标准中的差错恢复技术，着重探讨了差错恢复视频编码技术在基于分组的网络（IP网）视频传输中的应用。     

An FPGA implementation of HW/SW codesign architecture for H.263 video coding

In this paper, we present an efficient HW/SW codesign architecture for H.263 video encoder and its FPGA implementation. Each module of the encoder is investigated to find which approach between HW and SW is better to achieve real-time processing speed as well as flexibility. The hardware portions include the Discrete Cosine Transform (DCT), inverse DCT (IDCT), quantization (Q) and inverse quantization (IQ). Remaining parts were realized in software executed by the NIOS II softcore processor. This paper also introduces efficient design methods for HW and SW modules. In hardware, an efficient architecture for the 2-D DCT/IDCT is suggested to reduce the chip size. A NIOS II Custom instruction logic is used to implement Q/IQ. Software optimization technique is also explored by using the fast block-matching algorithm for motion estimation (ME). The whole design is described in VHDL language, verified in simulations and implemented in Stratix II EP2S60 FPGA. Finally, the encoder has been tested on the Altera NIOS II development board and can work up to 120 MHz. Implementation results show that when HW/SW codesign is used, a 15.8-16.5 times improvement in coding speed is obtained compared to the software based solution.     

H.263编码视频流的混合错误掩盖

当H．263编码视频流在因特网上传输时，易受错误的影响，错误不但会影响当前帧还会继续扩散到以后的解码帧，从而导致图像质量的严重恶化，目前消除错误影响的常用算法是空域掩盖和时域掩盖算法，但是单纯地使用空域算法会造成图像的钝化，而时域算法则无法处理大运动的图像区域，因此，建议了一种时域和空域混合掩盖算法，同时使用两类算法对发生错误的图像帧进行掩盖。模拟结果显示该算法能够达到可以接受的图像质量，适应于视频会议、远程教育等应用的要求。     

Perceptual adaptive quantisation scheme for H.263 video coder

The authors propose an efficient perceptual adaptive quantisation scheme that uses Q-N (quantisation step-number of output bits) mapping tables and fuzzy perceptual classifiers. Using this adaptive quantisation scheme, stable perceptual quality and good visual effects can be obtained at a constant output bit rate     

H．263 VIDEO CODEC IMPLEMENTATION BASED ON MULTIMEDIA DSP

This letter introduces the implementation of H.263 video codec based on multimedia DSP TM1300,and discuses several key problems related to video coding.     

基于H．263视频解码的错误检测和掩盖

本文提出了一种应用于H．263视频编码传输的纠错方法,即基于H．263视频解码的错误检测和掩盖算法。这种算法可应用于公共交换电话网（PSTN）,Internet或移动信道的视频通信。模拟结果表明,这种纠错方法在不降低编码效率的前提下,使在有噪声干扰的信道上传输图像的质量有显著的改善。     

Best packetisation scheme for H.263 Internet video communication

The H.263 codec is an efficient way to stream variable bit-rate video sequences. It is proposed that, for equivalent bandwidth and frame rate, a two-slice packetisation scheme results in superior peak signal-to-noise ratio, rather than the conventional one-slice scheme, and that constant inter-packet gap rather than 'bursty' delivery is preferable.     

The H.264/MPEG4 advanced video coding standard and its applications

H.264/MPEG4-AVC is the latest video coding standard of the ITU-T video coding experts group (VCEG) and the ISO/IEC moving picture experts group (MPEG). H.264/MPEG4-AVC has recently become the most widely accepted video coding standard since the deployment of MPEG2 at the dawn of digital television, and it may soon overtake MPEG2 in common use. It covers all common video applications ranging from mobile services and videoconferencing to IPTV, HDTV, and HD video storage. This article discusses the technology behind the new H.264/MPEG4-AVC standard, focusing on the main distinct features of its core coding technology and its first set of extensions, known as the fidelity range extensions (FRExt). In addition, this article also discusses the current status of adoption and deployment of the new standard in various application areas.     

H.323视频会议系统中的多线程技术解析

结合Win32平台下的多线程编程思想和方法，深入剖析H．323视频会议系统中各线程的协调机制，讨论了用C 语言实现多线程编程的技术。     

实时H.263+视频编码器的DSP实现

在多媒体处理芯片TM-1300的开发平台上,快速实现了H.263 视频编码器。首先,根据H.263 编码算法要求,介绍TM-1300适合视频通信开发的特点及其开发环境;然后,将编码算法移植到TM-1300平台并进行大量的优化,其中,重点讨论了位移估值的优化算法。由实验结果可知,使用本文给出的优化算法,可以在TM-1300上快速实现H.263 编码器,满足视频实时编解码的要求,且已应用于实际视频通信产品中。     

A new rate control scheme for H.263 video transmission

In some image/video applications, the variable bit rate image/video bitstream will be transmitted over a constant bit rate transmission channel, in which a channel buffer is employed. In this study, a new rate control scheme for H.263 video transmission is proposed. Three proposed techniques include: preprocessing the INTRA coded macroblock (MB) incorporated the just-noticeable-distortion (JND) concept, constructing a bit estimation model in the frequency domain (instead of the bit estimation model in the spatial domain employed in Test Model Near-term version 11 (TMN11)), and adjusting quantization parameter (QP) for each MB by a Lagrangian optimization strategy.In the proposed approach, the target number of bits for a video frame is first obtained by using a simple rate control procedure for the frame layer. The proposed JND preprocessing is applied on all the INTRA coded MBs so that the number of coded bits for a scene changed frame will decrease, without any perceptual loss. Within the MB layer, instead of the bit estimation model in the spatial domain employed in TMN11, a bit estimation model in the frequency domain, directly depending on discrete cosine transform coefficients, is proposed. Then the Lagrange multiplier is used to determine the optimal QP for each MB. The resulting QP and number of coded bits of the current MB are fed backward to update the parameters of the bit estimation model.Based on the simulation results obtained in this study, the proposed approach can meet the target bit rate more accurately, keep a lower channel buffer fullness (delay), and have a larger average frame rate than TMN11, whereas the peak signal-to-noise ratio value and the processing time of the proposed approach are “approximately” as good as that of TMN11.     

Comparison of H.263 and H.26L video compression performance with web-cams

The results of a comparison of the compression efficiency of the H.263 and H.26L algorithms are presented when used to compress video from a variety of cameras. It is shown that H.26L achieves better compression performance in most cases, with larger compression gains being achieved when higher quality cameras are used.     

视频编码标准H.263+的新特征研究

介绍了视频编码标准H.263 可协商的编码选项，尤其对于其中的改进PB帆帧模式、片结构模式和前向纠错模式进行了较深入研究。     

H.263与MPEG-4视频码流相互转换的实现

分析了H．263与MPEG-4视频编码标准的不同之处，分别阐述H．263视频码流转换为MPEG-4视频码流以及MPEG-4视频码流转换为H．263视频码流的实现方法，给出了码流转换的结果，并分析说明其有效性和实用性。