you can edit a movie clip in Timeline mode.
choose the Movie Clip, Click on the right key and select 'Edit Movie Clip',or
click the edit button to open the edit window.
for Movie file and Gif file£¬you will open Movie Clip Editor£º
For animated file, you can do the
the source file's begin and end point
the source File's strech mode
the source file's audio info
the source file's playback speed
For picture file, you can do the
the picture's display time length.
the picture's strech mode.