I have issue using OpenCV 3 tracking module for tracking. It behaves same, either I use interface class (cv::Tracker) or class with implementation (like cv::TrackerMedianFlo
I just ran into the same problem, here's how I got it to work :
tracker->clear(); Ptr trackerNew = Tracker::create( tracker_algorithm ); tracker = trackerNew; tracker->init( image, boundingBox );
Might not be the right way or the prettiest but it does the job :)