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。     

从AVS到MPEG-2的转码算法研究

介绍了视频转码的几种基本技术，分析了MPEG-2与AVS的不同，提出了一种从AVS到MPEG-2的转码系统．针对关键的转码算法设计了一种综合优化方案，实验显示图像质量和压缩率都有明显提高。     

MPEG-2到H.264转码中变换系数转换的优化算法

为采用优势明显的H.264编码,并避免已有的大量MPEG-2非线性视频编缉设备被淘汰,研究了从MPEG-2到H.264转码的转换技术,分析了目前的转换算法,提出了一种DCT系数到H.264整数变换(HT)系数转换的优化算法,并针对不同视频终端的应用需求,分别给出了保持图像空间分辨率不变和减半时的转换方法.实验表明,该算法可大幅度简化运算,并具有良好的实时性和视频质量.     

一种新的MPEG-2到H.264的转码算法

研究了MPEG-2到H.264的转码技术,在MPEG-2和H.264压缩算法基础上提出了一种基于MV重用和H.264多参考帧特性的转码算法.实验表明,本算法与反向查找表算法相比在转码效率和转码视频质量两方面都有所提高.     

压缩域MPEG-2到MPEG-4视频转码中不匹配宏块的复原算法

作为一种最有应用前景的先进的压缩编码标准，MPEG-4将会很快在视频传输、存储和剪辑等许多领域中得到应用。不过，MPEG-2和MPEG-4这两种优秀的视频系统肯定会在很长一段时间内共存。本文提出了一种基于MC-DCT域的转码方法。重点解决了两种标准视频流中宏块编码模式不匹配的一些关键问题。仿真结果表明，本算法不仅能有效地实现MPEG-2到MPEG-4的转码，满足实时性和低处迟的需求，而且能隐藏或复原编码模式不匹配宏块，明显地改变视觉质量。     

一种变码率到定码率视频转码压缩系统的实现

提出一种基于MPEG-2的变码率到定码率的压缩转码系统.采用的方法不改变源码流的GOP结构,综合I,P,B帧的性质调整比例调节因子,以尽量减小图像降质.根据解码量化因子及原始码流的复杂度调节转码量化因子,避免了计算宏块复杂度的大量运算.该系统可广泛用于视频媒体库码流向数字电视信道转播及卫星转播等应用.     

基于VC++的H.263到MPEG-4视频流转码的实现

在对H.263和MPEG-4两种视频编码标准以及几种常见转码器结构进行对比的基础上,基于VC++,在PC平台上实现了H.263到MPEG-4的转码系统.通过Foreman标准测试序列的码流进行转码测试,结果没有察觉图像失真,说明该方法能够达到较满意的效果.     

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。     

MPEG-2到MPEG-4视频转编码中的快速运动矢量重估算法

本文讨论了MPEG-2到MPEG-4视频转编码问题，提出了两种快速运动矢量重估算法，分别基于空域和时域。我们的算法利用已有运动信息和DCT变换的直流系数进行运动估计，可明显减少运算量，提高编码速度，并获得了与全搜索算法接近的图像质量，可满足网络视频传输的实时要求。     

基于MPEG-4的网络视频监控系统设计

结合MPEG-4数字视频压缩技术、流媒体传输技术和计算机网络技术,提出了Windows平台一种高效的基于MPEG-4的网络视频监控系统的设计方案,描述了监控系统的组成。重点介绍了监控系统软件的设计实现方法,并给出了提高系统运行效率的措施。     

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.     

一种快速的DCT域MPEG-2到MPEG-1下采样转码技术

文章提出了一种快速的DCT域MPEG-2到MPEG-1准卷积下呆样算法。在转码过程中。头信忠保持不变，且要求将每四个相邻MPEG-2宏块变为一个下采样MPEG-1宏块：用最大最小距离方法确定下采样宏块的运动向量、用简单多数原则确定下采样宏块类型以及用加全平均方案确定下呆样宏块的量化参数。另外，对下采样视频转码失真来源进行了分析。实验结果表明我们提出的转码方案，在同样条件下与级联像素域转码器（TM5）相比，不仅其计算复杂性减少67．6％、PNSR提高0．1dB，而且具有很小的比特控制错误。     

Fast Interframe mode decision algorithm based on mode mapping and MB activity for MPEG-2 to H.264/AVC transcoding

Recently the latest video coding standard H.264/AVC is widely used for the mobile and low bitrate video codec in the various multimedia terminals. On the other hand, the MPEG-2 MP@HL codec has become the center of digital video contents since it is the standard codec for the Digital TV (DTV). To provide the bridge between the contents in MPEG-2 and mobile terminals, the transcoding of MPEG-2 contents into H.264/AVC format is an inevitable technology in the digital video market. The main bottleneck in the process lies in the computational complexity. In H.264/AVC, the variable block size (VBS) mode decision (MD) is used in the Interframe for the improved performance in the motion compensated prediction. For the macroblock (MB) which cannot be accurately predicted with one motion vector (MV), it is partitioned into smaller blocks and predicted with different MVs. In addition, SKIP and Intra modes are also permitted in the Interframe MD of H.264/AVC to further ameliorate the encoding performance. With the VBS MD technology, the Inter prediction accuracy can be improved significantly. However, the incidental side-effect is the high computational complexity. In this paper, we propose a fast Interframe MD algorithm for MPEG-2 to H.264/AVC transcoding. The relationships between SKIP and Intra modes are detected at first to map these two kinds of modes directly from MPEG-2 to H.264/AVC. And then the MB activity will be scaled by the residual DCT energy obtained from the MPEG-2 decoding process to estimate the block sizes of the MB mode for H.264/AVC Interframe MD. In our proposed method, the original redundant candidate modes can be eliminated effectively, resulting in the reduction of the computational complexity. It can reduce about 85% Rate-to-Distortion Cost (RDCost) computing and 45% entire processing time compared with the well-known cascaded transcoder while maintaining the video quality.