Calibration of the Frame Rate of High Speed Digital Video Recorders by Stationary Counting Method: Application of the Stroboscopic Effect

Abstract

By applying the characteristic of stroboscopic effect, a new method named Stationary Counting Method for the calibration of the frame rate of digital video recorder has been developed at the Hong Kong Standards and Calibration Laboratory(SCL). The proposed method can determine the frame rate of digital video recorders with the use of a special synchronous counter designed by the SCL. The frequency signal input to the counter is traceable to the Cesium Beam Frequency Standard kept in SCL, as well as traceable to the SI unit. The target devices include high speed digital cameras, smartphones, closed circuit televisions (CCTV) and car cameras. It is common for vehicles to install car cameras to capture the moment when unexpected incidents occur. The recorded videos can be used as court evidences for accident investigation. Therefore, the accuracy of the frame rate is extremely important. The proposed method can be used to find the time duration of the video recorded by a digital camera, as well as the occurrence of skipped or extra frames of the captured video.