Press F 12 to enter the debugging page of the developer's tools (some laptops need to press Fn+F 12). Click the console with the mouse (the position shown by arrow 1), and then move the mouse to the position of arrow 2, and you can see that the cursor is flashing. 1.5 represents the double speed I want to play. This value can be adjusted according to your own needs, and the maximum is not more than 16. Press Enter, and the video will be played at the set double speed. In this way, you can finish a class efficiently.