Vehicle Classification Framework: Online Classification with Tracking
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Video surveillance has significant application prospects such as security, law enforcement, and traffic monitoring. Visual traffic surveillance using computer vision techniques can be non-invasive, cost effective and automated. Detecting and recognizing the objects in a video is an important part of many video surveillance systems which can help in tracking of the detected objects and gathering important information. In case of traffic video surveillance, vehicle detection and classification is important as it can help in traffic control and gathering of traffic statistics that can be used in intelligent transportation systems. Vehicle classification poses a difficult problem as vehicles have high intra class variation and relatively low inter class variation. In this work, we investigate five different object recognition techniques: PCA+DFVS, PCA+DIVS, PCA+SVM, LDA, and constellation based modeling applied to the problem of vehicle classification. We also compare them with the state-of-the-art techniques in vehicle classification. In case of the PCA based approaches, we extend face detection using a PCA approach for the problem of vehicle classification to carry out multi-class classification. We also implement constellation model-based approach that uses the dense representation of SIFT features. We consider three classes: sedans, vans, and taxis and record classification accuracy as high as 99.25% in case of cars vs vans and 97.57% in case of sedans vs taxis. We also present a fusion approach that uses both PCA+DFVS and PCA+DIVS and achieves classification accuracy of 96.42% in case of sedans vs vans vs taxis. We incorporated three of the techniques that performed well into a unified traffic surveillance system for online classification of vehicles which uses tracking results to improve the classification accuracy. We processed 31 minutes of traffic video containing multi-lane traffic intersection to evaluate the accuracy of the system. We were able to achieve classification accuracy as high as 90.49% while classifying correctly tracked vehicles into four classes: Cars, SUVs/Vans, Pickup Trucks, and Buses/Semis. While processing a video, our system also records important traffic parameters such as color of a vehicle, speed of a vehicle, etc. This information was later used in a search assistant tool (SAT) to find interesting traffic events. For the evaluation of video surveillance applications that employ an object classification module, it is important to establish the ground truth. However, it is a time consuming process when done manually. We developed a ground truth verification tool (GTVT) that can help in this process by automating some of the work.