Scale coding bag-of-words for action recognition
2014 (English)In: Pattern Recognition (ICPR), 2014 22nd International Conference on, Institute of Electrical and Electronics Engineers Inc. , 2014, no 6976979, 1514-1519 p.Conference paper (Refereed)
Recognizing human actions in still images is a challenging problem in computer vision due to significant amount of scale, illumination and pose variation. Given the bounding box of a person both at training and test time, the task is to classify the action associated with each bounding box in an image. Most state-of-the-art methods use the bag-of-words paradigm for action recognition. The bag-of-words framework employing a dense multi-scale grid sampling strategy is the de facto standard for feature detection. This results in a scale invariant image representation where all the features at multiple-scales are binned in a single histogram. We argue that such a scale invariant strategy is sub-optimal since it ignores the multi-scale information available with each bounding box of a person. This paper investigates alternative approaches to scale coding for action recognition in still images. We encode multi-scale information explicitly in three different histograms for small, medium and large scale visual-words. Our first approach exploits multi-scale information with respect to the image size. In our second approach, we encode multi-scale information relative to the size of the bounding box of a person instance. In each approach, the multi-scale histograms are then concatenated into a single representation for action classification. We validate our approaches on the Willow dataset which contains seven action categories: interacting with computer, photography, playing music, riding bike, riding horse, running and walking. Our results clearly suggest that the proposed scale coding approaches outperform the conventional scale invariant technique. Moreover, we show that our approach obtains promising results compared to more complex state-of-the-art methods.
Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc. , 2014. no 6976979, 1514-1519 p.
, International Conference on Pattern Recognition, ISSN 1051-4651
Electrical Engineering, Electronic Engineering, Information Engineering
IdentifiersURN: urn:nbn:se:liu:diva-116804DOI: 10.1109/ICPR.2014.269ScopusID: 2-s2.0-84919946713ISBN: 9781479952083OAI: oai:DiVA.org:liu-116804DiVA: diva2:801569
22nd International Conference on Pattern Recognition, ICPR 2014