【作者】 常娜；

【导师】 许芬；

【作者基本信息】 北方工业大学 ， 电力电子与电力传动， 2008， 硕士

【摘要】 H.264/AVC规范是由国际电联(ITU-T)和国际标准化组织(ISO)联合制定的新一代视频编解码标准。它具有如下四个特点:低码流,和MPEG2等压缩技术相比,在同等图像质量下,采用H.264技术压缩后的数据量只有MPEG2的1/8;高图象质量,复杂的算法保证了低码流条件下图像仍能保留丰富的细节;容错能力强,提供了解决在不稳定网络环境下容易发生的丢包等错误的必要工具;网络适应性强,提供了网络适应层,数据能在不同网络上传输。但由此带来的代价是复杂度极高的编码过程,尤其是在嵌入式系统中实现具有很大的挑战性。本文主要介绍了基于H.264标准的开源代码T264向DM642平台的移植和优化。优化综合运用了上层和底层的实现方法实现。上层的方法例如使用CCS提供的条件优化代码优化功能,使用IMGLIB中高度优化的函数等,其特点是简便易行,效果良好;底层的实现方法例如使用DM642特有的内联函数,用线性汇编的方式实现算法等,特点是提高了代码运行的并行性,但需要对DM642和H.264有很深刻的理解。目前本设计已成功完成H.264算法在DM642开发板上的运行,压缩QCIF格式视频的速度随图像复杂度的不同达到了35～50帧每秒。此后本设计还继续使用优化后的编码器实现了监控用视频服务器的原型,使得摄像头采集的视频数据在DM642开发板上压缩后传输至PC机,且能够在PC端用配套的程序成功解码并播放。更多还原

【Abstract】 The H.264/AVC standard is a new generation video compression standard founded by ITU-T and ISO. There are four advantages with H.264. Firstly, it has a low bit-rate in comparison with MPEG2 compression technology. With the same quality, the data size generated by H.264/AVC is 1/8 less than that of MPEG2 code. Secondly, its highly sophisticated algorithms ensure rich details reserved even at the low bit-rates condition. Thirdly, it is highly fault tolerant, providing necessary tools to solve packet-loss and other errors caused by instability network Fourthly, it has network adaptive layer, making it more suitable for data transmission across different networks. The codec and the algorithms adopted in the implementation, however, are highly sophisticated.The main task of this paper is to introduce how to transfer and optimize the T264 encoder to DM642 platform. There are two levels to optimize the codec. The way of higher level use the conditional optimization provided by CCS and efficient function in IMGLIB, it is simple and effective; The way of lower level use intrinsics and linear assembly language, it improve the parallelism inherent in the H.264 encoder, but need deep understanding about DM642 and H.264.Our H.264 encoder can encode 35～50 frames per second for QCIF resolution video. And this encoder is used as a video server, it capture video from camera and send it to PC after code the image in DM642, At last a PC software will decode the data and display the video on screen.更多还原