In a motion capture project, all Image windows display videos at frames according to the current reference frame. You cannot display one video at a certain frame and another video at a different frame. This feature is necessary to ensure that marking and 3D computation are done using images taken at the same moment.
However, there is a need to view a video at a certain frame without changing the frame of other videos. There is also a need to display different frames of a video simultaneously. In order do do so, you need to open an Auxiliary Image window, or Aux window for short.
The frame displayed in an Aux Image window is independent of the current frame, i.e., the frame in the auxiliary remains unchanged when you play the videos for the (main) Image window. Aux Image windows are used in video synchronization or merging points that appear in different frames.
Each Aux window contains its own controls at the bottom of the window. Those controls are described below: