视频编码技术进展研究

视频编码技术的不断进步正深刻影响着现代社会的方方面面，作为数字视频的核心技术，视频编码的重要性日益突出，基于内容的交互性是新一代视频编码标准的核心思想，这对于视频编码技术的发展方向及广泛应用都具有特别重要的意义。     

移动视频服务在主流市场普及的十大因素

2006年，宽带及网络多媒体的成功应用令移动网络开始广泛应用于视频服务领域。各地的企业和消费者在日常生活中成功使用移动视频服务的例子多不胜数，使用时间远远超过十亿分钟，同时带来了逾十亿美元的收入。如果运营商、集成商、广播机构及内容提供商实施一系列措施以进一步推广这些服务的应用，仅移动视频一项，就将在2007年增长三倍以上。以下就是服务提供商现已实施的举措。     

视频编码流的转换编码

１引言目前,ＡＴＳＣ和ＤＶＢ标准的视频压缩部分都是ＭＰＥＧ２标准的一个子集。ＭＰＥＧ通过提供多种“类”和“等级”来覆盖尽可能多的应用领域,但目前真正得到广泛重视和支持的主要是主类。ＭＰＥＧ２提供了分层编码工具以支持一些较为复杂的应用,但是受编解码器复杂度的制约,分层编码的层数有限,在很多情况下无法与数字电视格式和传输信道特性的多样性相匹配。在视频点播应用中,分层的特点限制了用户的选择,并且可能与未来的网络不能很好地适应,如移动网采用低码率传送视频。为解决这类问题,近来多种视频转换编码技术得到…     

IPTV标准化中的视频编码相关问题探讨

一、概述 视频编码技术是IPTV的关键技术之一。通过IP网传输音视频节目，为用户提供音视频播放类业务是目前IPTV的主要形式。而原始的数字音视频内容信息量巨大，无法在网络上直接进行传输，必须经过压缩处理。也正是近年来数字视频编码技术的快速发展，才使得在现有网络上传输数字视频内容有了重要的技术基础。     

网络电视的技术基础、发展概况与对策建议

网络电视的发展将使广播电视、通信、计算机技术进一步融合。对于传统的广播电视而言，网络电视既是机遇，也是挑战，如何抓住机遇，面对挑战，是广播业者面临的问题。本文重点介绍网络电视的技术基础及其发展概况。     

流媒体传输中的视频编码技术

概述了流媒体广播的系统结构和主要技术，介绍了流媒体中的视频编码技术，主要分析了精细可分级编码(FGSC)和渐进精细可分级编码(PFGSC)两种编码方法的原理与实现。     

手机电视冲出大门

Mobile TV的原意本来是指移动电视,很多移动视频设备,如车载电视现在在各个城市里都已开始运营。但现在一提到Mobile TV,人们想到的就是手机电视。为什么手机电视更受人们的关注？因为在所有移动电视的应用里手机电视是最有趣的。整个手机电视的产业链中,芯片技术是核心,以此为基础发展出设备和设备供应商,设备供应商为运营商提供产品,运营商又需要内容和服务,所以内容提供商和服务提供商也出现了。产业链最上端则是个人消费者和企业用户。产业链上每个环节之间都需要密切的沟通和配合,才能形成良性循环,创造出最大的价值。     

话音编码技术的进展

本文是数字语音技术与标准的回顾。随着通信的进展已建立了许多高质量数字语音的新业务,例如象ISDN终端、个人通信业务、移动电话、卫星小站和声音信号存储系统等等应用。按传统电话学概念达到网络质量的语音传输速率已降到32kb/s,并且目前已到16kb/s;用于蜂窝无线传输的通信质量语音在欧洲已以13kb/sGSM标准实现于移动电话网,同时8kb/sIS-54标准已在美国应用,目前的焦点是实现高质量半速率4kb/s数字语音技术。     

基于内容的视频编码技术

介绍了基于内容的交互性及视频对象面（ＶＯＰ）的新概念,给出了一种基于内容的视频编码系统框架,并展望了基于内容的视频编码的应用前景。     

Steganalysis of transcoding steganography

Transcoding steganography (TranSteg) is a fairly new IP telephony steganographic method that functions by compressing overt (voice) data to make space for the steganogram by means of transcoding. It offers high steganographic bandwidth, retains good voice quality, and is generally harder to detect than other existing VoIP steganographic methods. In TranSteg, after the steganogram reaches the receiver, the hidden information is extracted, and the speech data is practically restored to what was originally sent. This is a huge advantage compared with other existing VoIP steganographic methods, where the hidden data can be extracted and removed, but the original data cannot be restored because it was previously erased due to a hidden data insertion process. In this paper, we address the issue of steganalysis of TranSteg. Various TranSteg scenarios and possibilities of warden(s) localization are analyzed with regards to the TranSteg detection. A novel steganalysis method based on Gaussian mixture models and mel-frequency cepstral coefficients was developed and tested for various overt/covert codec pairs in a single warden scenario with double transcoding. The proposed method allowed for efficient detection of some codec pairs (e.g., G.711/G.729), while some others remained more resistant to detection (e.g., iLBC/AMR).     

数字视频转换编码技术

针对目前最流行的MPEG－2和MPEG－4两个压缩编码标准，就MPEG－2视频码流之间的转换编码、MPEG－2视频码流转换成MPEG－4码流以及MPEG－4视频码流之间的转换编码中的一些核心问题进行研讨。     

转换编码模拟实验平台

给出了转换编码模拟实验平台的简要构成，它包括视频编码、音频编码、复用／解复用、码流转换、分析、输出／播放及工具模块；着重剖析了作为搭建实验环境纽带的MPEG4IP软件包，包括MPEG-4视频、音频编码，码流复用、播放。实验表明，基于该平台可有效地进行转换编码研究。     

分布式视频转码服务调度算法研究

针对分布式环境下视频转码服务的任务请求自适应接收问题以及处理后视频序列分段向客户端的端传输控制问题,通过分析视频转码处理对资源占用的特点以及流式媒体服务实现的过程,提出了基于处理节点资源与客户信道质量反馈的视频转码任务自适应接收策略和用于实现客户端流畅视频服务的视频任务分段传输控制算法。实验表明,相比现有算法,该自适应客户请求接入策略能够依据客户端的信道质量选择最适合的任务版本;在用户播放缓冲区有限的条件下,提出的传输控制算法可以达到更小的任务失败几率。     

Accurate rate control method in transcoding

An accurate rate control method for transcoding is presented. A linear relationship between the number of bits generated from the quantised discrete cosine transform (DCT) coefficients and the number of nonzero DCT coefficients is used in this method. By estimating variation of average values of run-level codes at different bit rates, errors of model parameters are corrected. Good results compared to TM5 are reported.     

自适应多码率语音编码流的可靠传输

自适应多码率语音编码已入选为第三代移动通信系统的语音压缩编码方案。本文提出了一种适合压缩语音传输的联合信源信道编码方法并对其性能进行了统计比较。利用压缩语音比特流中的固用冗余的信道译码算法是本文的研究重点。仿真结果表明利用信源冗余信息的信道译码器可以获得较大的编码增益。本文所用的信道编码方案为适合语音传输的卷积码。     

Requantization for transcoding of MPEG-2 intraframes

An investigation on requantization for transcoding of video signals is carried out. Specifically, MPEG-2 compatible discrete cosine transform (DCT) intraframe coding is addressed. The aim of this work is twofold: first, to provide a theoretical analysis of the transcoding problem, and second, to derive quantization methods for efficient transcoding based on the results of the analysis. The mean squared error (MSE) cost function is proposed for designing a quantizer with minimum distortion resulting in up to 1.3 dB gain compared with the quantizer used in the MPEG-2 reference coder TM5. However, the MSE quantizer leads in general to a larger bit rate and may therefore only be applied locally to blocks of sensitive image content. A better rate-distortion performance can be provided by the maximum a posteriori (MAP) cost function. In critical cases, the MAP quantizer gives a 0.4 dB larger signal-to-noise-ratio (SNR) at the same bit rate compared with the TM5 quantizer. The results are not limited to MPEG-2 and can be adapted to other coding schemes such as H.263 or JPEG.     

Foveation embedded DCT domain video transcoding

Video transcoding is a key technology to support video communications over heterogeneous networks. Although quite a bit of research effort has been made in video transcoding due to its wide applications, most video transcoding techniques proposed in the literature are optimized based on the simple mean squared error (MSE) metric which does not correlate well with the human visual perception. In this paper, foveation, a property of the HVS, is exploited in video transcoding. The proposed foveation embedded DCT domain video transcoding can reduce the bit rate without compromising visual quality or achieve better subjective quality for a given bit rate by shaping the compression distortion according to the foveated contrast sensitivity function of the HVS. In addition, fast algorithms for video foveation filtering and DCT domain inverse motion compensation are developed, which significantly improve the efficiency of video transcoding.     

Video transcoding for mobile digital television

Mobile digital television is one of the new services introduced recently by telecommunications operators. Due to the possibilities of personalization and interaction provided, together with the increasing demand for this type of portable services, it will undoubtedly be a successful technology in the near future. Multimedia content is generally encoded by reducing the storage capacity necessary and bandwidth consumption in order to be transmitted. In order to adapt to the different characteristics of the networks and the varying capabilities of the devices, scalable video coding schemes have been proposed that provide temporal, spatial, and quality scalability, or a combination of these. Most of the existing video content is compressed using H.264/AVC, which is a single-layer codec, so these contents cannot benefit from the scalability tools due to the lack of intrinsic scalability provided in the bitstream at encoding time. This paper proposes a technique to convert from the single-layer H.264/AVC bitstream to a scalable bitstream with temporal scalability. Applying this approach, a reduction of 60% in coding complexity is achieved while maintaining the coding efficiency.     

视频转码技术回顾

随着各种视频压缩标准的制定及计算机硬件、网络技术的发展，视频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，视频转码成为视频编码领域一个新的研究热点。本文从视频转码的应用、体系结构和关键技术三个方面，回顾近几年来在视频转码方面的研究进展。