Click Double Speed in the lower right corner of the video, and then click Normal inside. China University massive open online course, you can click Double Speed in the lower right corner of the video, and then click Normal to cancel double speed playing. Learning duration is the statistics of video viewing duration of all courses on the platform. For example, a 20-minute course video is played at double speed, and the statistical learning time is 10 minute. Therefore, the duration of statistics is the actual time to watch. When you look at offline video in online state, it counts the time, but it doesn't count in offline state.