UCL Discovery

Abstract

Given a set of algorithms, which one(s) should you apply to, i) compute optical flow, or ii) perform feature matching? Would looking at the sequence in question help you decide? It is unclear if even a person with intimate knowledge of all the different algorithms and access to the sequence itself could predict which one to apply. Our hypothesis is that the most suitable algorithm can be chosen for each video automatically, through supervised training of a classifier. The classifier treats the different algorithms as black-box alternative "classes," and predicts when each is best because of their respective performances on training examples where ground truth flow was available.Our experiments show that a simple Random Forest classifier is predictive of algorithm-suitability. The automatic feature selection makes use of both our spatial and temporal video features. We find that algorithm-suitability can be determined per-pixel, capitalizing on the heterogeneity of appearance and motion within a video. We demonstrate our learned region segmentation approach quantitatively using four available flow algorithms, on both known and novel image sequences with ground truth flow. We achieve performance that often even surpasses that of the one best algorithm at our disposal.