video shape recognition in real time
One standard approach is to use object detection / objection recognition / object localization on each individual frame of the video.  This means we can apply algorithms for doing that on a single image.  For speed, once you have detected an object in one frame, we can use object tracking to keep track of where it moves to in the next frames, and we don't need to use an expensive object detection algorithm on the next frame.  For instance, we might apply object detection on every 10th frame, and then use object tracking to track its motion for the next 9 frames.

That should give you enough keywords that you can search and find lots of information on each of those techniques.