Hash-based frame selection for video phylogeny

Multimedia phylogeny is a research field that aims at tracing back past history of multimedia documents to discover their ancestral relationships. As an example, it might leverage, with the aid of other side information, forensic analysts to detect who was the first user that published online an illegal content (e.g., child pornography). Although relatively well developed for images, this field is still not fully fledged when it comes to analyzing ancestral and evolutionary relationships among digital videos. Dealing with videos is much more challenging, especially as temporal dimension comes into play. In this vein, one of the pivotal tasks for video phylogeny reconstruction is video synchronization in order to compare temporally coherent near-duplicate frames among pairs of sequences. In this work, we propose an algorithm to efficiently select synchronized frame pairs among videos before calculating their phylogenetic relationships. This approach underpins the video phylogeny reconstruction and leverages the analysis on a reduced subset of frames rather than on the full set, thus decreasing the overall computational time. Experimental results show the effectiveness of the proposed method when temporal transformations are considered (i.e., change of frame rate and temporal clipping at any point in the stream).