Università degli studi di Modena e Reggio Emilia

The field of multi-object tracking has recently seen a renewed interest in the good old schema of tracking-by-detection, as its simplicity and strong priors spare it from the complex design and painful babysitting of tracking-by-attention approaches. In view of this, we aim at extending tracking-by-detection to multi-modal settings, where a comprehensive cost has to be computed from heterogeneous information e.g., 2D motion cues, visual appearance, and pose estimates. More precisely, we follow a case study where a rough estimate of 3D information is also available and must be merged with other traditional metrics (e.g., the IoU). To achieve that, recent approaches resort to either simple rules or complex heuristics to balance the contribution of each cost. However, i) they require careful tuning of tailored hyperparameters on a hold-out set, and ii) they imply these costs to be independent, which does not hold in reality. We address these issues by building upon an elegant probabilistic formulation, which considers the cost of a candidate association as the negative log-likelihood yielded by a deep density estimator, trained to model the conditional joint probability distribution of correct associations. Our experiments, conducted on both simulated and real benchmarks, show that our approach consistently enhances the performance of several tracking-by-detection algorithms.

Since decades, the problem of multiple people tracking has been tackled leveraging 2D data only. However, people moves and interact in a three-dimensional space. For this reason, using only 2D data might be limiting and overly challenging, especially due to occlusions and multiple overlapping people. In this paper, we take advantage of 3D synthetic data from the novel MOTSynth dataset, to train our proposed 3D people detector, whose observations are fed to a tracker that works in the corresponding 3D space. Compared to conventional 2D trackers, we show an overall improvement in performance with a reduction of identity switches on both real and synthetic data. Additionally, we propose a tracker that jointly exploits 3D and 2D data, showing an improvement over the proposed baselines. Our experiments demonstrate that 3D data can be beneficial, and we believe this paper will pave the road for future efforts in leveraging 3D data for tackling multiple people tracking. The code is available at (https://github.com/GianlucaMancusi/LoCO-Det ).