Synchronization and Self-Calibration for Helmet-Held Consumer Cameras, Applications to Immersive 3D Modeling and 360 Video

This paper presents the first 3D reconstruction system using unsynchronized and helmet-held consumer cameras, without the use of a calibration pattern. Our assumptions are easy to meet in practice: the cameras have the same setting (frequency, image resolution, field-of-view, roughly equiangular). First, the time offsets between cameras are estimated without accurate calibration as input. Second, both inter-camera rotations and intrinsic parameters are refined using structure-from-motion and bundle adjustment. We experiment both synchronization and self-calibration on four GoPro cameras mounted on a helmet, such that the resulting multi-camera is assumed to be central and provides a 360 degree field-of-view in the horizontal plane. A surface is also estimated from a multi-camera video acquired by walking in a city.