随着移动互联网技术的发展，视频流媒体直播已成为现今的热门应用。如何改善直播过程中的用户体验质量是学术界和产业界关注的焦点。码率自适应算法通过动态切换视频码率，使业务适应信道的时变特征，可以有效提升用户的体验质量。因此，研究面向流媒体直播场景的码率自适应算法具有重要意义。本文以视频流媒体直播为背景，以提高用户体验质量为目标，充分考虑业务的时延需求和传输环境特征，提出了一种基于PID控制的码率自适应算法。

With the development of the Internet, real-time video streaming has become one of the most popular applications. An important focus of real-time video is how to improve the quality of experience. A proper rate adaptation scheme can dynamically switch the bitrate of a video to adapt to a time-varying channel, which effectively improves the quality of experience. Therefore, it is important to research on the adaptive bitrate algorithms for live streaming. In this paper, we propose an adaptive bitrate algorithm based on PID controller for live video streaming, with the goal of improving the quality of experience, while taking into full consideration the time delay requirements and transmission environment characteristics.