Abstract Multi-Person Tracking (MPT) is often addressed within the detection-to-association paradigm. In such approaches, human detections are first extracted in every frame and person trajectories are then recovered by a procedure of data association (usually offline). However, their performances usually degenerate in presence of detection errors, mutual interactions and occlusions. In this paper, we present a deep learning based MPT approach that learns instance-aware representations of tracked persons and robustly online infers states of the tracked persons. Specifically, we design a multi-branch neural network (MBN), which predicts the classification confidences and locations of all targets by taking a batch of candidate regions as input. In our MBN architecture, each branch (instance-subnet) corresponds to an individual to be tracked and new branches can be dynamically created for handling newly appearing persons. Then based on the output of MBN, we construct a joint association matrix that represents meaningful states of tracked persons (e.g., being tracked or disappearing from the scene) and solve it by using the efficient Hungarian algorithm. Moreover, we allow the instance-subnets to be updated during tracking by online mining hard examples, accounting to person appearance variations over time. We comprehensively evaluate our framework on a popular MPT benchmark, demonstrating its excellent performance in comparison with recent online MPT methods.
Recently, researchers actively learn object appearance features with deep learning based models due to their powerful representation learning ability, e.g., convolutional neural networks (CNNs) @cite_25 @cite_10 and recurrent neural networks (RNNs) @cite_49 @cite_8 . A fully convolutional neural network is adopted in @cite_25 for object tracking, where features from top and lower layers that characterize the target from different perspectives are jointly used with a switch mechanism. In @cite_49 , a recurrently target-attending tracking method is presented, which attempts to identify and exploit reliable parts that are beneficial for the tracking process. But these mentioned deep learning based methods mainly focus on single object tracking with the object being indicated at the first video frame. As for MOT, recently Leal- @cite_6 exploit siamese CNN for pairwise pedestrian similarity mesurement in offline tracking, while Gaidon and Vig @cite_45 take advantage of the convolutional features in online domain adaption between instances and category in a Bayesian tracking framework. Different from these methods, in this paper we employ a MBN network for instance-aware object representations, in which a backbone-subnet is trained with a novel multi-task loss and instance-subnets are dynamically initialized from a det-pruning-subnet and trained discriminatively online.
@cite_8 @cite_6 @cite_45 @cite_49 @cite_10 @cite_25
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Recently using convolutional neural networks (CNNs) has gained popularity in visual tracking, due to its robust feature representation of images. Recent methods perform online tracking by fine-tuning a pre-trained CNN model to the specific target object using stochastic gradient descent (SGD) back-propagation, which is usually time-consuming. In this paper, we propose a recurrent filter generation methods for visual tracking. We directly feed the target's image patch to a recurrent neural network (RNN) to estimate an object-specific filter for tracking. As the video sequence is a spatiotemporal data, we extend the matrix multiplications of the fully-connected layers of the RNN to a convolution operation on feature maps, which preserves the target's spatial structure and also is memory-efficient. The tracked object in the subsequent frames will be fed into the RNN to adapt the generated filters to appearance variations of the target. Note that once the off-line training process of our network is finished, there is no need to fine-tune the network for specific objects, which makes our approach more efficient than methods that use iterative fine-tuning to online learn the target. Extensive experiments conducted on widely used benchmarks, OTB and VOT, demonstrate encouraging results compared to other recent methods. We propose a new approach for general object tracking with fully convolutional neural network. Instead of treating convolutional neural network (CNN) as a black-box feature extractor, we conduct in-depth study on the properties of CNN features offline pre-trained on massive image data and classification task on ImageNet. The discoveries motivate the design of our tracking system. It is found that convolutional layers in different levels characterize the target from different perspectives. A top layer encodes more semantic features and serves as a category detector, while a lower layer carries more discriminative information and can better separate the target from distracters with similar appearance. Both layers are jointly used with a switch mechanism during tracking. It is also found that for a tracking target, only a subset of neurons are relevant. A feature map selection method is developed to remove noisy and irrelevant feature maps, which can reduce computation redundancy and improve tracking accuracy. Extensive evaluation on the widely used tracking benchmark [36] shows that the proposed tacker outperforms the state-of-the-art significantly. Abstract Object appearance model is a crucial module for object tracking and numerous schemes have been developed for object representation with impressive performance. Traditionally, the features used in such object appearance models are predefined in a handcrafted offline way but not tuned for the tracked object. In this paper, we propose a deep learning architecture to learn the most discriminative features dynamically via a convolutional neural network (CNN). In particular, we propose to enhance the discriminative ability of the appearance model in three-fold. First, we design a simple yet effective method to transfer the features learned from CNNs on the source tasks with large scale training data to the new tracking tasks with limited training data. Second, to alleviate the tracker drifting problem caused by model update, we exploit both the ground truth appearance information of the object labeled in the initial frames and the image observations obtained online. Finally, a heuristic schema is used to judge whether updating the object appearance models or not. Extensive experiments on challenging video sequences from the CVPR2013 tracking benchmark validate the robustness and effectiveness of the proposed tracking method. Defining hand-crafted feature representations needs expert knowledge, requires timeconsuming manual adjustments, and besides, it is arguably one of the limiting factors of object tracking. In this paper, we propose a novel solution to automatically relearn the most useful feature representations during the tracking process in order to accurately adapt appearance changes, pose and scale variations while preventing from drift and tracking failures. We employ a candidate pool of multiple Convolutional Neural Networks (CNNs) as a data-driven model of different instances of the target object. Individually, each CNN maintains a specific set of kernels that favourably discriminate object patches from their surrounding background using all available low-level cues. These kernels are updated in an online manner at each frame after being trained with just one instance at the initialization of the corresponding CNN. Given a frame, the most promising CNNs in the pool are selected to evaluate the hypothesises for the target object. The hypothesis with the highest score is assigned as the current detection window and the selected models are retrained using a warm-start back-propagation which optimizes a structural loss function. In addition to the model-free tracker, we introduce a class-specific version of the proposed method that is tailored for tracking of a particular object class such as human faces. Our experiments on a large selection of videos from the recent benchmarks demonstrate that our method outperforms the existing state-of-the-art algorithms and rarely loses the track of the target object.