free linux tools to repair corrupted mp4 video

I need to repair a mp4 video, which was deleted and undeleted, so I expect that sections of it are missing or corrupted. Does anyone know of some free tools to stitch together what is left?

Other posts don't help because they usually deal regenerating metadata that is lost when the end is cut off. E.g. http://stackoverflow.com/questions/23202611/repairing-a-corrupt-mp4-video-file