H.264/AVC图标插入转码算法及软件实现

随着H.264/AVC视频编码标准逐步进入实际应用,在H.264/AVC转换编码过程中加入图标、字幕等应用具有广泛的需求。针对此需求,提供了一种快速的图标插入转换编码方案,采用无再损编码技术,高效地重用了输入码流中编码参数,提高转码效率。实验结果表明,该方案可高效、优质地实现了在标清H.264码流中的图标插入应用。     

基于视频转换编码的数字电视台标机设计

介绍了一种基于视频转换编码技术的数字电视台标机的软件设计,对其采用的图标插入视频转换编码算法进行了深入讨论。该台标机经码流分析仪检测功能正确,且与同类产品相比性价比较高。     

MPEG-2与MPEG-4间转码的关键技术研究与实现

视频转码技术的出现，解决了视频通信领域数据在不同系统和设备间互通互连的问题。本文主要研究了MPEG-2到MPEG-4的转换编码，提出了运动矢量映射的转码结构，并对其中的关键算法进行了研究和实现。仿真试验表明，本文结构和算法在保证了转换编码灵活性的同时，具有较好的转码效率和鲁棒性。     

一种基于网络编码的NC-BT文件共享系统设计与实现

为了克服目前流行BitTorrent系统工作中存在的文件分块调度算法复杂、文件下载稳定性等问题,提出在BitTorrent系统中采用网络编码技术解决这些问题的思路,设计并实现了基于网络编码的NC-BT系统.在实际网络环境中对该系统进行测试和分析,实验结果证明使用网络编码技术方案能够有效解决现有BitTorrent中存在的问题,从而增强系统的鲁棒性,降低系统调度算法复杂性等优点.     

ATM网络的视频编码技术

异步转换模式（ＡＴＭ）的提出对编码技术产生了重大的影响。本文概述了ＡＴＭ下可变比特率（ＶＢＲ）视频编码的优点及存在的问题，扼要介绍了各种信元丢失的预防及补偿方法，着重分析了分层编码技术，并对目前提出的各种可变比特率分层编码算法进行了概括性的评述，指出了有待研究的一些问题。     

AMR与G.729A的参数直接转换算法

提出了一套完整的参数直接转换算法方案，剖析了AMR（Adaptive Multi Rate）与G729A编码方案在几个关键技术上的差异，并以此为基础详细分析和描述了常见的LSP（LineSpectrum Pair）、基音、随机码本和增益等参数的转换算法，在均方误差意义上对LSP参数转换算法做出了性能评估，对转换以后的语音质量采用PESQ MOS（Perceptual Evaluation of Speech Quality Mean Opinion Score）技术给出了客观评价。本文建议的算法与传统的Tandem编码转换方案相比，不仅提高了转换后的语音质量，而且计算复杂度也降低了约25％～64％。参数直接转换算法在该方案中的优异性体现了其相比Tandem编码转换算法的强大优势。     

G.726语音压缩编码的实现

通过对ITU-T G.726语音压缩编码的算法原理进行分析,给出了线性PCM和对数PCM之间的转换对应关系。对使用C程序实现各个单元模块时应注意的问题进行了详细说明,指出在对预测系数进行计算时,由于数值的大小范围差异较大,为了使不同数值都满足一定的量化精度要求,要使用浮点数,及在同步编码调整中避免溢出的问题。最后给出了使用C程序实现ADPCM算法编解码后的结果。     

基于网络编码的衰落信道频谱感知算法

针对传统认知无线电网络中频谱状态转换频繁和频谱检测时延长的问题,提出基于随机线性网络编码的累积和能量检测频谱感知算法。该算法在主用户信道中引入随机线性网络编码,利用网络编码对频谱的整形作用,使频谱状态转换稀疏,频谱结构更规律化,减小频谱检测时延,提高系统吞吐率。此外,针对传统累积和能量检测算法抗衰落性能差的问题,通过比较该算法在五种衰落信道下的检测时延和吞吐率,研究该算法的抗衰落性能。实验结果表明,在一定的虚警概率下,该算法有效降低了检测时延,提高了吞吐率及抗衰落能力,能够更好地适应复杂的衰落信道环境。     

IPTV中的媒体压缩编码转换若干问题探讨

就媒体压缩编码转换中的若干问题进行探讨，包括媒体压缩编码转换的一般技术原理、技术分类和当前主流技术发展状况、媒体压缩编码转换对于IPTV发展的影响，以及结合国际标准发展动态对于下一代网络环境下媒体压缩编码转换发展未来前景的分析。     

在WPS2000中调用Windows95/98的图标

金山公司新近推出的WPS2000集文字处理、电子表格、多媒体演示制作等功能于一身。笔者在使用中发现灵活地使用其“插入新对象”功能,可以非常方便地调用Windows95/98的图标。在编辑电脑应用等方面的文章时,用户有时需要在文档中引用Windows95/98的图标,使自己的文档图文并茂,这时WPS2000的“插入新对象”就可以帮您轻     

DCT域视频转码技术综述

随着数字视频技术的广泛应用,实现各种视频编码格式之间转码的要求越来越迫.视频转码是数字媒体网络网关的关键技术.本文从DCT域视频转码的体系结构、关键技术及最优转码策略三个方面,介绍了现有的各种算法,分析和总结了各自的特点,提出了DCT域视频下采样帧内刷新体系结构和最优视频转码策略解的概念,并指出了下一步的研究方向.     

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.     

On the methods and performances of rational downsizing video transcoding

Video transcoding is a popular technique for adapting the bit-rate or spatial/temporal resolution of a precoded video to suit better the constraints and requirements of different transmission networks and receiving devices. To minimize computational complexity, many fast methods have been proposed to obtain the motion vectors required for transcoding a precoded video through reducing its frame size by an integral factor. In this paper, we extend the existing work by developing and comparing several fast methods of downsizing precoded videos by a rational factor. Methods that outperform others under different conditions or with different computational requirements are identified, and an application scenario that can benefit from the proposed rational downsizing video transcoding is presented. An efficient scheme is also proposed to select the proper reduced frame size for sustaining the best possible video quality at a specified lower bit-rate. The superiority of the proposed transcoding approach in comparison with the existing integral downsizing video transcoding or cascaded video re-encoding methods is evident from the experimental results shown in this paper.     

Video transcoding from H.264/AVC to MPEG-2 with reduced computational complexity

This paper addresses video transcoding from H.264/AVC into MPEG-2 with reduced complexity and high rate-distortion efficiency. While the overall concept is based on a cascaded decoder–encoder, the novel adaptation methods developed in this work have the advantage of providing very good performance in H.264/AVC to MPEG-2 transcoding. The proposed approach exploits the similarities between the coding tools used in both standards, with the objective of obtaining a computationally efficient transcoder without penalising the signal quality. Fast and efficient methods are devised for conversion of macroblock coding modes and translation of motion information in order to compute the MPEG-2 coding format with a reduced number of operations, by reusing the corresponding data embedded in the incoming H.264/AVC coded stream. In comparison with a cascaded decoder–encoder, the fast transcoder achieves computational complexity savings up to 60% with slightly better peak signal-to-noise ratio (PSNR) at the same bitrate.     

General Architecture for MPEG-2/H.263/H.264/AVC to H.264/AVC Intra Frame Transcoding

The latest international video-coding standard H.264/AVC significantly achieves better coding performance compared to prior video coding standards such as MPEG-2 and H.263, which have been widely used in today’s digital video applications. To provide the interoperability between different coding standards, this paper proposes an efficient architecture for MPEG-2/H.263/H.264/AVC to H.264/AVC intra frame transcoding, using the original information such as discrete cosine transform (DCT) coefficients and coded mode type. Low-frequency components of DCT coefficients and a novel rate distortion cost function are used to select a set of candidate modes for rate distortion optimization (RDO) decision. For H.263 and H.264/AVC, a mode refinement scheme is utilized to eliminate unlikely modes before RDO mode decision, based on coded mode information. The experimental results, conducted on JM12.2 with fast C8MB mode decision, reveal that average 58%, 59% and 60% of computation (re-encoding) time can be saved for MPEG-2, H.263, H.264/AVC to H.264/AVC intra frame transcodings respectively, while preserving good coding performance when compared with complex cascaded pixel domain transcoding (CCPDT); or average 88% (a speed up factor of 8) when compared with CCPDT without considering fast C8MB. The proposed algorithm for H.264/AVC homogeneous transcoding is also compared to the simple cascaded pixel domain transcoding (with original mode reuse). The results of this comparison indicate that the proposed algorithm significantly outperforms the mode reuse algorithm in coding performance, with only slightly higher computation.     

Video Transcoding with H.263 Bit-Streams

Video transcoding is one of the key technologies in implementing dynamic adaptation of the bit-rate of a coded video bit-stream to the available bandwidth over various networks. Many fast transcoder architectures have been proposed to achieve fast processing. However, they suffer from quality degradation caused by the drift error. In this paper, we investigate the drift caused by the fast transcoder architectures for transcoding H.263 bit-streams. We discuss the limitations of the fast transcoder architectures and the flexibility that can be offered by a cascaded pixel-domain transcoder. Since the cascaded pixel-domain transcoder can achieve drift-free performance, we also propose methods to reduce the computational complexity of the drift-free cascaded pixel-domain transcoder.     

基于Hadoop视频转码的任务调度算法

现有的分布式转码系统大多没有考虑到根据计算节点的处理能力分配转码任务量,对转码过程造成影响,导致转码效率降低。针对这一问题,在对现有Max-Min算法的研究基础上,提出一种新的任务调度算法。利用佩奇排名算法评估机器转码性能,输入视频被分成大小不同的段,依据其复杂度和机器的转码能力进行映射。处理能力强的节点将分配到更多的视频块,最终所有计算节点的完成时间得到均衡化。实验结果表明,该算法能够显著提升视频转码效率,在很大程度上改善了云转码系统。     

基于TMS320C6416的MPEG-2/MPEG-4 视频流转码器设计与实现

目前的视频流转码大致可以分为空域(像素域)转码和压缩域(DCT域)转码两种方法。针对目前最流行的MPEG-2和MPEG-4两个压缩编码标准,采用级联空域转码方案,并且基于TMS320C6416 DSP芯片,探讨了MPEG-2/MPEG-4视频流转码的硬件实现方法。在设计中,通过PCI消息机制,解决了DSP与PC机的数据传输“瓶颈”问题,同时合理分配存储器,并采取各种优化技术,近实时地实现了MPEG视频流转码。     

Video transcoding for adaptive bitrate streaming over edge-cloud continuum

Video transcoding is to create multiple representations of a video for content adaptation. It is deemed as a core technique in Adaptive BitRate (ABR) streaming. How to manage video transcoding affects the performance of ABR streaming in various aspects, including operational cost, streaming delays, Quality of Experience (QoE), etc. Therefore, the problems of implementing video transcoding in ABR streaming must be systematically studied to improve the overall performance of the streaming services. These problems become more worthy of investigation with the emergence of the edge-cloud continuum, which makes the resource allocation for video transcoding more complicated. To this end, this paper provides an investigation of the main technical problems related to video transcoding in ABR streaming, including designing a rate profile for video transcoding, providing resources for video transcoding in clouds, and caching multi-bitrate video contents in networks, etc. We analyze these problems from the perspective of resource allocation in the edge-cloud continuum and cast them into resource and Quality of Service (QoS) optimization problems. The goal is to minimize resource consumption while guaranteeing the QoS for ABR streaming. We also discuss some promising research directions for the ABR streaming services.