计算机工程 ›› 2012, Vol. 38 ›› Issue (16): 18-22.doi: 10.3969/j.issn.1000-3428.2012.16.005

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基于H.264的屏幕视频实时编码器优化

金 磊 a,谢伟凯 a,林 艺 b,鲁晨平 a,申瑞民 b   

  1. (上海交通大学 a. 现代远程教育研究中心;b. 计算机科学与工程系,上海 200030)
  • 收稿日期:2011-10-20 修回日期:2011-12-08 出版日期:2012-08-20 发布日期:2012-08-17
  • 作者简介:金 磊(1987-),女,硕士研究生,主研方向:屏幕编码;谢伟凯,高级工程师;林 艺,硕士研究生;鲁晨平,硕士;申瑞民,教授
  • 基金项目:

    上海科委科技攻关计划基金资助项目(11511503002)

Optimization for H.264 Based Real-time Screen Video Encoder

JIN Lei a, XIE Wei-kai a, LIN Yi b, LU Chen-ping a, SHEN Rui-min b   

  1. (a. E-learning Lab; b. Department of Computer Science and Engineering, Shanghai Jiaotong University, Shanghai 200030, China)
  • Received:2011-10-20 Revised:2011-12-08 Online:2012-08-20 Published:2012-08-17

摘要:

H.264编码器是目前压缩效率最高的通用视频编码器,但它直接用于实时屏幕视频的压缩存在CPU占用率高和不能有效限制峰值码率等问题。以经典的H.264编码器X264为基础,利用Mirror Driver检测变化区域,对无变化的区域宏块进行快速模式决策,通过自适应地降低局部帧率的峰值码率控制法限制峰值码率。实验结果表明,该方法将CPU的执行时间降低30%,且能严格限制视频的峰值码率,使视频的平均PSNR提高3 dB~8 dB。

关键词: 远程教育, 屏幕编码, 视频编码, H.264标准, 混合图像压缩, 码率控制

Abstract:

H.264 encoder is a general video encoder with the highest compression efficiency. However, to apply it directly into real-time screen video encoding brings the problems, such as high CPU occupancy rate and ineffectiveness in limiting the peak bitrate. To solve the problems above, in one hand, it integrates a Mirror Driver-based changed region computation step into the classic H.264 encoder, X264. After that, it can find the unchanged macroblocks and then quick-find optimized prediction modes. On the other hand, it proposes an adaptive frame rate constant quantization parameter rate control algorithm, which limits peak bitrate by reducing the local frame rate. Experimental results show that the schema reduces CPU time by 30%, strictly controls the peak bitrate and finally achieves 3 dB~8 dB PSNR improvement.

Key words: distance education, screen encoding, video encoding, H.264 standard, compound image compression, rate control

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