Some embodiments provide a method of specifying speed effects for playing a video clip. The method defines a set of speed effects for the video clip. It then displays in real-time a presentation of the video clip that accounts for the set of speed effects defined for the video clip. In some embodiments, this method represents the playback speed of a video clip in terms of a graph that is part of a graphical user interface (“GUI”). This graph is defined along two axes, with one axis representing the playback time, and the other axis representing the content-time (i.e., the time within the video clip). In these embodiments, a user can change the playback speed of the video clip by using a set of GUI operations to select and modify the graph. For instance, a user can select and adjust the graph at different instances in time in order to change the playback speed of the video clip at these instances. Different embodiments use different types of graphs to represent playback speed. For instance, some embodiments use a deformable line bar that is superimposed on a rectangle that represents the video clip.