战场电视侦察系统中视频压缩技术及其DSP实现

数字视频压缩是多媒体应用中的关键技术。该文针对战场电视侦察系统的需求提出了一种可行的MPEG-4视频编解码方案,阐述了基于数字信号处理器ADSP21160、数字视频采集芯片Bt829、数字视频合成芯片ADV7175的硬件设计电路以及MPEG-4视频压缩标准的软件程序的算法及其实现。实验表明该文提出的MPEG-4视频编解码器设计方案是可行的。     

基于MPEG-4的数字监视系统解码器的设计

MPEG-4是基于第二代视音频编码技术制定的压缩标准,主要用于视频存贮、视频广播和视频流媒体;而数字监视系统则是将所有的视频信息输入计算机,由MPEG-4编码器将模拟视频信号转化成数字视频信号,完成视频信息的采集、浏览、传输等功能,其涉及到的技术主要有视频采集、数据存储、采样量化编码、解码、显示等技术。故又引入了H.264标准,该标准是由ITU-T与ISO/IEC联合进行开发的,主要用于实时视频通信。本文从MPEG-4编解码原理开始讲起,对MPEG-4多种编解码技术进行分析,同时又引入了数字监视系统解码器的模型,在此基础上,实现了数字监视系统解码器的方法。     

基于红外视频的变电站监控系统的实现

变电站的红外视频监控系统能有效监控变电设备的发热情况．但目前还没有针对红外视频特点的专用编解码方案。一般的视频监控（或图像监控）系统主要基于H．26L、MPEC-1、MPEG-2、JPEG2000等标准设计，由于没有针对红外视频进行优化，都有一定的不足。MPGE-4是一种压缩效率较高、系统开销合理的视频压缩标准，经适当优化后，适于变电站视频监控。本文讨论了MPEC-4标；住中的几个关键技术，并给出了一种MPEG-4标准下基于红外视频的变电站监控系统实现方案。     

Simple intra prediction algorithms for heterogeneous MPEG-2/H.264 video transcoders

Recent developments have given birth to H.264/AVC: a video coding standard offering better bandwidth to video quality ratios than MPEG-2. It is expected that the H.264/AVC will take over the digital video market, replacing the use of MPEG-2 in most digital video applications. The complete migration to the new video-coding algorithm will take several years given the wide scale use of MPEG-2 in the market place today. This creates an important need for MPEG-2/H264 transcoding technologies. However, given the significant differences between both encoding algorithms, the transcoding process of such systems is much more complex to other heterogeneous video transcoding processes. In this work, we start by analyzing the methods defined in the H.264 video coding standard for the intra prediction: a central element of every H.264 encoder. We then introduce and evaluate six fast intra mode decision algorithms which should enable the development of MPEG-2 to H.264 transcoders. Having evaluated all the proposed methods, we have come out with a high-efficient method, namely DC-ABS pixel. Our results show that our algorithm considerable reduces the complexity involved in the intra prediction with respect the mode decision algorithms used in H.264 JM reference software, while exhibiting a slight degradation on the RD function.. Finally, we analyze a comparative study with two of the most prominent fast intra prediction methods presented in the literature. The results show that the proposed DC-ABS pixel method achieves the best results for video transcoding applications.

MPEG-2视频解码器在DirectShow中的实现

MPEG-2是目前应用最为广泛的数字音视频编码国际标准,大部分数字音视频节目是以MPEG-2的形式存在.DirectShow是目前windows操作系统上的优秀的多媒体开发编程接口.提出一个MPEG-2视频解码器在DirectShow中的实现方案.这一实现在多媒体应用中具有广泛的参考价值.     

Software defined QCIF simple profile MPEG-4 for portable devices using dynamically reconfigurable DSP

The ISO MPEG-4 standard is emerging as the dominant digital video standard, and efficient, programmable MPEG-4 video codecs are paramount for emerging mobile devices that aggregate telecommunications with features including digital video. Efficient QCIF simple profile MPEG-4 video codec algorithms are developed for typical 16-bit, dual execution unit DSPs and the additional impact of tightly coupled, co-processors used to dynamically reconfigure the DSP data path is quantified. Efficient, programmable solutions consuming approximately 63 Mcycles, significantly lower than estimates as high as 400 Mcycles, are generated, while dynamic reconfiguration reduces this cost an additional 20%.     

MPEG的新发展——多媒体框架标准MPEG-21

标准化是产业化活动成功的前提，视、音频编码的各种国际标准的制定集中地反映了视、音频编码技术发展的水平．目前，图象压缩方面的标准主要有MPEG系列(MPEG-1，MPEG-2，MPEG-4，MPEG-7和MPEG-21标准)，以及H．26X系列(H．261，H．263标准)和静止图象压缩标准JPEG．为了使人们对图象压缩标准有所了解，以进一步推动图象压缩方面的研究，首先对MPEG系列的各种已有标准及其应用进行了概述，然后着重讨论了MPEG中的新面孔——正在开发的MPEG-21标准，并就其目标、用户需求、技术要素、关键任务、应用领域以及工作计划做了较详细的描述．     

Supporting constant-bit-rate-encoded MPEG-2 transport over local ATM networks

As one of the fast-developing switch-based high-speed networks, asynchronous transfer mode (ATM) is a promising network standard which may satisfy various requirements of multimedia computing. The Moving Picture Experts Group (MPEG) standard was designed to support full motion video stored on digital storage media at compression ratios up to 200:1. MPEG-2 is the second development phase of the MPEG standard and is designed for higher resolutions (including but not restricted to interlaced video) and higher bit rates (up to 20 Mbits/s). In this paper, the ATM adaptation layer type 5 (AAL-5) protocol was used to encapsulate constant-bit-rate-encoded MPEG-2 transport packets because of AAL-5's general availability. However, there is a mismatch of size between MPEG-2's transport packets (188 bytes) and ATM AAL-5's protocol data units (up to 65 535 bytes). In this paper, we examine and analyze four different packing schemes, 1TP, 2TP, nTP-Tight, and nTP-Loose (the scheme we propose), which encapsulated a certain number of MPEG-2 transport packets into one AAL-5 PDU. nTP-Loose scheme is proposed to have (1) better end-to-end performance than schemes 1TP and 2TP, (2) better error-recovery capability than scheme nTP-Tight, and (3) the same buffer requirement as scheme 2TP. A Power Macintosh ATM platform was used to identify the range of possible ways of packing MPEG-2 transport packets into one ATM AAL-5 PDU, when schemes with more than two MPEG-2 transport packets are chosen. Based on the test results, 10 or 12 MPEG-2 transport packets, which can yield throughputs of 70.36 and 78.98 Mbits/s, respectively, are recommended. Fast forward and backward playing of MPEG-2 movies (several times the video display speed) can be easily achieved via ATM networks.     

多媒体数据压缩标准—MPEG系列

随着各种多媒体数据压缩标准的制定及计算机硬件、网络技术的发展，多媒体信息的应用呈现出爆炸式的增长。为了适应用户终端的多样性及网络自身的传输特性，20世纪90年代后期，一些国际标准化组织制定了几个多媒体数据压缩标准，并且获得了成功的应用，其中最主要的是MPEG系列。在此主要从视频的编码原理，视频数据组织结构和应用领域等方面对MPEG－1、MPEG－2、MPEG－4和MPEG－7做了一些介绍。     

视频传输中的码率控制技术研究进展毕迎春王相海

码率控制技术对提高和平滑解码视频质量起着至关重要的作用。近年来各种视频编码标准和应用都对码率控制技术进行了大量的研究,如基于H.261和H.263的视频会议,基于MPEG-1和MPEG-2的媒体存储,以及最新的基于MPEG-4视频对象编码。首先对码率控制问题进行了基本描述,然后介绍了标准中的经典码率控制技术,接着将目前的码率控制技术归纳为3类:基于DCT视频编码器的码率控制技术、基于小波视频编码器的码率控制技术和精细粒度可分级视频编码的码率分配算法,并对这三类码率控制方法的发展进行了概括性阐述与比较性研究,讨论了各种算法的基本思想及其优缺点,最后对视频传输中的码率控制技术的未来发展趋势进行了展望。     

Watermarking of MPEG-4 video objects

The recent finalization of MPEG-4 will make this standard very attractive for a large range of applications such as video editing, Internet video distribution, wireless video communications. Some of these applications are likely to get great benefit from watermarking technology, since it can enable a number of innovative services, such as conditional access policies, data annotation, data labeling, content authentication, to be implemented at a low price. One of the key points of the MPEG-4 standard is the possibility to access and manipulate objects within a video sequence. Thus object watermarking has to be achieved in such a way that, while a video object is transferred from a sequence to another, it is still possible to correctly access the data embedded within the object itself. The algorithm proposed in this paper embeds a watermark in each video object by imposing a particular relationship between some predefined pairs of quantized discrete cosine transform (DCT) coefficients in the luminance blocks of pseudo-randomly selected macroblocks (MBs). Watermarks are equally embedded into intra and inter MBs. Experimental results are presented validating the effectiveness of the proposed approach.     

基于MPEG-2标准的视频和音频信号的无线传输

讨论了把数字视/音频信号进行基于MPEG-2标准的处理并转换为I/Q两路信号,接着由满足IEEE 802.11g/b标准的CCK技术来实现信号的无线收发。最后在恢复出原来的信号之前,还要经过解复用,MPEG-2 AVGD Oecoder和视频编码及音频DAC转换的过程。     

Control Mechanisms for Error-Resilient MPEG-2 Video Communications over ATM Networks

The design of digital video communications systems is a very active research area. Due to the stringent requirement of video and characteristics of networking technologies, the provisioning of control mechanisms guaranteeing a certain level of service is essential for the success of distributed video applications. In this paper, we study the use of different schemes for the robust transmission of MPEG-2 video over ATM networks. We compare error-resilience performance of two data-partitioning schemes for MPEG-2 bit stream transmitted over ATM networks where two layers of priority traffic are supported with different cell discarding schemes. The effectiveness of the different control mechanisms is quantitatively evaluated in terms of cells loss rates, end-to-end delay and cell loss distributions. Our results show that the use of control mechanisms at various levels of the protocol stack is essential for the deployment of error resilient video applications.     

一种基于AVS卫星数字视频系统的实现

2002年中国开始制定了新一代数字音视频编解码标准———AVS。由于它采纳了近几年来国内研究的先进音视频编码技术,其不仅与H.264/AVS相比,具有较低的复杂度,并可通过一站式授权方式支付少量费用来获得AVS使用权,因此可作为中国卫星电视直接入户方案的一种较好,且具有竞争力的候选标准。在对AVS和MPEG-2的差异进行比较的基础上,分析了两种在传输系统中替代MPEG-2的方法:直接AVS编码和AVS转码,并给出了一种转码方案,最终实现了新一代基于AVS卫星视频广播系统。     

MPEG-2流中RS纠错编译码的探讨

DVB是数字视频广播标准,它采用MPEG-2传输流作为其传输层标准。将对应用于其系统中的RS（204,188）纠错编译码进行理论上的探讨,给硬件电路的设计与实现提供思路。     

一种H.264/AVC over MPEG-2流的解决方案

对如何将H．264／AVC视频流经MPEG-2的系统传输层传输提出了一种解决方案。要点是：先把H．264／AVC视频作为MPEG-2系统层传输的基本流，然后扩展MPEG-2标准中的传输流系统目标解码器（T-STD），使之可以将H．264／AVC编码视频作为MPEG．2传输流（TS）在Internet上传输和解码。被解码的基本流通常来自于一个“容器”文件（如AVI或者TS），在客户端从服务器端的这个容器中取出H．264／AVC基本流后便可实时解码、显示。仿真实验表明，该方案能够获得较好的流视频效果，在带宽受限的情况下信噪比低于40dB的帧数少于5％，可用于网络流视频或移动视频中。     

Web-based delivery of medical multimedia contents using an MPEG-4 system

Moving picture expert group compression standard version 4 (MPEG-4) is a standard for video coding aimed at multimedia applications. MPEG-4 was developed to enable high compression rate in a low bitrate transmission via the Internet or mobile telecommunications. Although these characteristics of MPEG-4 are suitable for telemedicine, little is known about the possibility of using this technology in the field of telemedicine. We evaluated the quality of MPEG-4-encoded medical video streams and compared them with original analogue videos and audio-video-interleave (AVI) files. Although MPEG-4 video streams have the advantage of small file size, they were found to be inferior to original videos and AVI files in terms of smoothness of motion pictures, sharpness of images and clearness of sound. Illegibility of characters was a major problem in MPEG-4 files. The score for total impression of MPEG-4 files was significantly lower than those for AVI files. The results of this study suggest that the quality of MPEG-4-encoded video streams is not adequate for telemedicine.