Abstract: The unreliable network environment and the unsatisfactory performances of using traditional encoding technologies to encode screen in hybrid presentation scenario limit the development of M-learning. To attack this problem, an M-learning broadcasting system is proposed in this paper. In the system the HTTP-streaming technology is employed to enhance the adaptability to different network environment, and a new rate control algorithm is used to control the peak bit rate of the generated stream and to make the system support the hybrid presentation scenario in teacher’s screen. Experimental results show that the course streamed by this M-learning broadcasting system can play fluently on mobile phones with the mainstream configuration.

Key words: E-learning, M-learning, HTTP-Streaming, screen encoding, rate control

摘要： 移动学习的网络环境中往往无法保证可靠持久的连接，而且在越来越常见的混合演示场景的编码中传统的屏幕编码技术的输出帧率较低而通用视频编码技术的静态图像质量较差。针对上述两个问题提出的支持混合演示场景的移动课程直播系统，利用HTTP-Streaming技术提升系统对不同网络环境的适应能力，并且使用改进的屏幕编码码率控制算法使得系统在有效控制峰值码率的基础上能够支持教师端屏幕可能出现的混合演示场景的编码。实验证明在当前主流配置的手机上课程内容能够流畅播放。

关键词: 远程教育, 移动学习, HTTP-Streaming, 屏幕编码, 码率控制