Another problem may arise when performing your own calibrations. If the lens distortions are really too severe (for fisheye lenses for example), the simple guiding tool based on a single distortion coefficient kc may not be sufficient to provide good enough initial guesses for the corner locations. The video was filmed in Czech Republic and the instrumentation prominently included the classic guitar. The optimization is done by iterative gradient descent with an explicit (closed-form) computation of the Jacobian matrix (program name: go_calib_optim.m). The Calibration parameters are stored in a number of variables.