AdaBoost & Genetic algorithms: application to pedestrian detection Yotam Abramson Ecole des Mines de Paris 9/12/05 Korea-France SafeMove Workshop

Machine learning for visual object detection

Korea-France SafeMove WorkshopApplication Pedestrian impact predictor Calculates the probability of an impact between our car and a pedestrian. If the probability is higher then a given threshold, an alert to the driver is issued or an action is taken (pedestrian airbag, braking…)

Korea-France SafeMove Workshop Machine learning for visual object detection Learning algorithms for object-detection were shown to be better than any hand- crafted ones. Main works in the field: Papageorgiou & Poggio – SVM,wavelets. Papageorgiou & Poggio – SVM,wavelets. Viola & Jones – AdaBoost and simple features. Viola & Jones – AdaBoost and simple features.

Korea-France SafeMove Workshop Machine learning - background Support Vector Machine (SVM) – Vapnik 1990 Neural network

Korea-France SafeMove Workshop Machine learning (Cont.) AdaBoost (Freund & Schapire 1995): A popular learning algorithm. A popular learning algorithm. Easy to understand. Easy to understand. Received a lot of attention in the machine learning and statistics communities. Received a lot of attention in the machine learning and statistics communities. The notion of boosting (AdaBoost = adaptive boosting).

Korea-France SafeMove Workshop AdaBoost at a Glance Assume that we have a simple object classifier, that receives a rectangle in the image and decides if it’s the object. For example: For example:

Korea-France SafeMove Workshop AdaBoost at a Glance (Cont.) A classifier like the one shown is called a weak classifier. And indeed it is weak.. AdaBoost selects (=learns) a set of classifiers and builds a “voting system”. Weak1Weak2Weak3Weak4 Yes NoYes

Korea-France SafeMove Workshop AdaBoost at a Glance (Cont.) Voting is not “democratic”… there is a weight for each weak-classifier. Weak1Weak2Weak3Weak4 Yes NOYesNo

Korea-France SafeMove Workshop AdaBoost at a Glance (Cont.) The output of AdaBoost is a called a strong classifier. AdaBoost was used for face, cars and pedestrian detection by viola and Jones (2000).

Korea-France SafeMove Workshop Weak Classifiers Viola & Jones

Korea-France SafeMove Workshop We have developed new kinds of weak classifiers. Our features are different because they test individual pixels. They deal better with the variation in illumination. Weak classifiers

Korea-France SafeMove Workshop Illumination independent features (cont.) Our features are highly efficient (3-4 image access operations) 2 times faster than Viola&Jones 20% of the memory Better detection rates for pedestrians

Korea-France SafeMove Workshop Learning process using genetic algorithm

Korea-France SafeMove WorkshopSeville SEmi- automatic VIsuaL Learning (With Dr. Yoav Freund, Columbia University)

Korea-France SafeMove WorkshopSeville We start by collecting 10 negative and positive examples. We run the learning, and classify.

Korea-France SafeMove WorkshopSeville We now have 100 examples. We run learning, and the results improve.

Korea-France SafeMove WorkshopSeville We test another sequence. We collect in the same way more examples. We re-run the learning and continue.

Korea-France SafeMove WorkshopSeville We test another sequence. We collect in the same way more examples. We re-run the learning and continue.

Korea-France SafeMove WorkshopSeville Throughout the phases, we use 2/3 of the set as training set, and 1/3 as validation set. We make AdaBoost rounds until the point of overfitting.

Korea-France SafeMove Workshop European project CAMELLIA European union Renault, Philips, Philips semiconductor, Uni. Hannover, Uni. Las-palmas “Smart camera” European union Renault, Philips, Philips semiconductor, Uni. Hannover, Uni. Las-palmas “Smart camera” CAMELLIA

Korea-France SafeMove WorkshopResults

Results

Impact prediction

Korea-France SafeMove Workshop Prediction results

Korea-France SafeMove Workshop Prediction results

Korea-France SafeMove Workshop CAMELLIA was used also for other applications

Korea-France SafeMove WorkshopConclusions We have presented a system for detection of pedestrians. The system is based on AdaBoost and Genetic algorithms. The system was tested and gives good results on real data.

Korea-France SafeMove Workshop Thank you for your attention