Imagine I have a video of a car moving from right to left, and that I want to add a graphic annotation in a specific frame at a certain time.
I would like that this graphic annotation, after I have inserted it, move itself automatically along the timeline using only pixel analysis, looking for pixels similarity frame after frame.
Is there some tool or software library that do it?
That is usually called "tracking" and there are several tools available to do that. Many that are stand alone and export the data to be used in other software aswell as complete editing suites that enable you to do everything from the tracking of the video footage to the animation of the graphic.
Popular examples are Adobe After Effects, Apple Motion and Nuke. The most popular being Adobe After Effects. It offers a fairly easy to use 2D tracker and is a very powerful animation tool.
Though if you want to analyze the global position of the car on the racing track over the course of several different scene you wont be able to achieve that completely automated. Those tools will only analyze the motion for a particular scene and wont make any sense out of the "global picture". While you can certainly track the position of a car in different scenes you will have to manually do that and tell the tracker in every scene what exactly you want to track.
