Real-time human action search using random forest based hough voting

Many existing techniques in content based video retrieval treat a video sequence as a whole to match it against a query video or to assign a text label. Such an approach has serious limitations when applied to human action retrieval because an action may occur only in a sub-region and last for a small portion of the video length. In situations like this, we essentially need to match the subvolumes of the video sequences against the query video. A naive exhaustive search is impractical due to large number of possible subvolumes for each video sequence. In this paper, we propose a novel framework for action retrieval which performs pattern matching at subvolume level and is very efficient in handling large corpus of videos. We construct an unsupervised random forest to index the video database, generate a score volume with Hough voting and then employ a max sub-path strategy to quickly search for the temporal and spatial positions of all the video sequences in the database. We present action search experiments on challenging datasets to validate the efficiency and effectiveness of our system.