Group Detection and Tracking

Groups and Crowds Behaviour Analysis

Recently, researchers in video-surveillance shifted the attention from the monitoring of a single person in a camera-monitored environment to that of groups and their behavior. This novel level of abstraction provides event descriptions which are semantically more meaningful, highlighting barely visible relational connections among people.

Automatic Crowd Analysis is a research area which can be used for anomaly detection: panic scenarios, dangerous situations, illegal behaviors, etc. We are currently working on anomaly detection in crowded scenarios using a particle-based paradigm, in which a large set of virtual particles simulates the crowd behavior using visual cues such as the optical flow.

Following the paradigm of people detection and tracking, small group analysis is split in group detection and tracking.

The objective of group detection is to find collection of people who share certain aspects, interact with one another, accept rights and obligations as members of the group and share a common identity. To this end, we aim to investigate novel models and technologies that embeds notions of social psychology into computer vision techniques, offering a novel research perspective for the video surveillance community.

On the other hand, group tracking consists in following tight formations of individuals while they are walking or interacting. One of the major difficulties of group tracking lies in the high variability of the group entity: splitting, merging, initialization and deletion are frequent events that characterize the life of a group, and that are usually modeled by heuristic rules, yielding to a scarce generalization.
Our idea is to perform, at the same time, tracking of individuals and groups. The problem, dubbed as joint individual-group tracking, introduces novel issues that need to be investigated (e.g.: high-dimentional spaces, and highly non-linear dynamics).




  • L. Bazzani, M. Zanotto, M. Cristani, V. Murino
    "Joint Individual-Group Modeling for Tracking"
    IEEE Transactions on Pattern Analysis and Machine Intelligence, Volume 37(4), Pages 746-59, April 2015

  • S. Vascon, E. Z. Mequanint, M. Cristani, H. Hungd, M. Pelillo, V. Murino
    "Detecting conversational groups in images and sequences: A robust game-theoretic approach"
    Computer Vision and Image Understanding, Volume 143, Pages 11-24, February 2015

  • S. Vascon, E. Zemene, M. Cristani, H. Hung, M. Pelillo, V. Murino
    "A Game-Theoretic Probabilistic Approach for Detecting Conversational Groups"
    12th Asian Conference on Computer Vision (ACCV), 2014

  • L. Bazzani, M. Cristani, V. Murino
    "Decentralized Particle Filter for Joint Individual-Group Tracking"
    25th IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2012

  • R. Raghavendra, A. Del Bue, M. Cristani, V. Murino
    "Optimizing interaction force for global anomaly detection in crowded scenes"
    13th IEEE International Conference on Computer Vision Workshops (ICCV Workshops), 2011

  • M. Cristani, L. Bazzani, G. Pagetti, A. Fossati, D. Tosato, A. Del Bue, G. Menegaz, V. Murino
    "Social interaction discovery by statistical analysis of F-formations"
    22nd British Machine Vision Conference (BMVC), 2011