A machine for weaving or winding a fiber preform on a mandrel having an axis of rotation that is substantially horizontal and that serves to receive the preform, the machine having a plurality of cameras pointing towards the underside of the fiber preform in order to scan the hidden face of the fiber preform and acquire images of the hidden face; an image analysis module for processing these images of the hidden face of the fiber preform in a plurality of adjacent scan windows, and for extracting weaving patterns therefrom and comparing them with reference weaving patterns previously stored in the module; a motor for driving the mandrel in rotation about its axis of rotation; and a control unit for stopping rotation of the mandrel if the result of the comparison reveals a difference of appearance between the two weaving patterns.