Real-time processing of video waveforms has been implemented for the purpose of analyzing image dynamics. A digital preprocessor yields data sets that describe the difference between selected fields of an input video signal in both the spatial and temporal domains. Further reduction and analysis of the acquired data can provide several measures of image activity such as the frame-to-frame correlation, the frame-difference signal (FDS), and statistics of scene lengths. The results of a series of measurements of the dynamics of typical broadcast television programs are presented. It is demonstrated that image activity is separable into two distinct classes, one caused by image and camera movement, and the other by scene switches.