Shot boundary detection for locating subliminal stimuli in films

Abstract

Introduction: With the objective of detecting film shots with a duration that would qualify them as subliminal, this paper proposes a shot boundary detection system to locate shots in a video that last for only one or two frames.Methods: This design prioritizes the complete retrieval of extremely short shots, minimizing false negatives, even at the expense of additional false positives. This is achieved by a sequential filtering strategy, integrating complementary metrics in a cascade, ensuring robustness against motion, luminance variations and noise while reducing the processing time by progressively ruling out potential cases for comparison. The series of processes adopted were a color histogram analysis with a dynamic threshold, a mean squared error analysis (MSE), a structural similarity index measure (SSIM) and a histogram correlation analysis. The system design was tested on 10 films in which the shots that had to be detected were known beforehand, and subsequently on 15 other films that may potentially contain subliminal shots.Results: The results reveal the effective detection of 100% of the shots, although the erroneous detections produced require a visual review at the end of the process. Finally, the analysis was applied to 1,247 films to verify, in a real-world scenario, whether the designed system is effective in detecting one- or two-frame shots.Discussion: It was thus determined that the design proposed can facilitate the identification of short shots for a large number of films, meeting the initial objective of the design and confirming the usefulness of this system for detecting subliminal stimuli in films.