text: Multi-object tracking (MOT) is an important and practical task related to both surveillance systems and moving camera applications, such as autonomous driving and robotic vision. However, due to unreliable detection, occlusion and fast camera motion, tracked targets can be easily lost, which makes MOT very challenging. Most recent works treat tracking as a re-identification (Re-ID) task, but how to combine appearance and temporal features is still not well addressed. In this paper, we propose an innovative and effective tracking method called TrackletNet Tracker (TNT) that combines temporal and appearance information together as a unified framework. First, we define a graph model which treats each tracklet as a vertex. The tracklets are generated by appearance similarity with CNN features and intersection-over-union (IOU) with epipolar constraints to compensate camera movement between adjacent frames. Then, for every pair of two tracklets, the similarity is measured by our designed multi-scale TrackletNet. Afterwards, the tracklets are clustered into groups which represent individual object IDs. Our proposed TNT has the ability to handle most of the challenges in MOT, and achieve promising results on MOT16 and MOT17 benchmark datasets compared with other state-of-the-art methods.
  @cite_14: Multi-Target Multi-Camera Tracking (MTMCT) tracks many people through video taken from several cameras. Person Re-Identification (Re-ID) retrieves from a gallery images of people similar to a person query image. We learn good features for both MTMCT and Re-ID with a convolutional neural network. Our contributions include an adaptive weighted triplet loss for training and a new technique for hard-identity mining. Our method outperforms the state of the art both on the DukeMTMC benchmarks for tracking, and on the Market-1501 and DukeMTMC-ReID benchmarks for Re-ID. We examine the correlation between good Re-ID and good MTMCT scores, and perform ablation studies to elucidate the contributions of the main components of our system. Code is available.
  @cite_33: Tracking of vehicles across multiple cameras with nonoverlapping views has been a challenging task for the intelligent transportation system (ITS). It is mainly because of high similarity among vehicle models, frequent occlusion, large variation in different viewing perspectives and low video resolution. In this work, we propose a fusion of visual and semantic features for both single-camera tracking (SCT) and inter-camera tracking (ICT). Specifically, a histogram-based adaptive appearance model is introduced to learn long-term history of visual features for each vehicle target. Besides, semantic features including trajectory smoothness, velocity change and temporal information are incorporated into a bottom-up clustering strategy for data association in each single camera view. Across different camera views, we also exploit other information, such as deep learning features, detected license plate features and detected car types, for vehicle re-identification. Additionally, evolutionary optimization is applied to camera calibration for reliable 3D speed estimation. Our algorithm achieves the top performance in both 3D speed estimation and vehicle re-identification at the NVIDIA AI City Challenge 2018.
  @cite_36: 
  @cite_27: Multi-Object Tracking (MOT) is a challenging task in the complex scene such as surveillance and autonomous driving. In this paper, we propose a novel tracklet processing method to cleave and re-connect tracklets on crowd or long-term occlusion by Siamese Bi-Gated Recurrent Unit (GRU). The tracklet generation utilizes object features extracted by CNN and RNN to create the high-confidence tracklet candidates in sparse scenario. Due to mis-tracking in the generation process, the tracklets from different objects are split into several sub-tracklets by a bidirectional GRU. After that, a Siamese GRU based tracklet re-connection method is applied to link the sub-tracklets which belong to the same object to form a whole trajectory. In addition, we extract the tracklet images from existing MOT datasets and propose a novel dataset to train our networks. The proposed dataset contains more than 95160 pedestrian images. It has 793 different persons in it. On average, there are 120 images for each person with positions and sizes. Experimental results demonstrate the advantages of our model over the state-of-the-art methods on MOT16.
  @cite_31: 
  @cite_34: We present a multi-cue metric learning framework to tackle the popular yet unsolved Multi-Object Tracking (MOT) problem. One of the key challenges of tracking methods is to effectively compute a similarity score that models multiple cues from the past such as object appearance, motion, or even interactions. This is particularly challenging when objects get occluded or share similar appearance properties with surrounding objects. To address this challenge, we cast the problem as a metric learning task that jointly reasons on multiple cues across time. Our framework learns to encode long-term temporal dependencies across multiple cues with a hierarchical Recurrent Neural Network. We demonstrate the strength of our approach by tracking multiple objects using their appearance, motion, and interactions. Our method outperforms previous works by a large margin on multiple publicly available datasets including the challenging MOT benchmark.
  @cite_20: Although many methods perform well in single camera tracking, multi-camera tracking remains a challenging problem with less attention. DukeMTMC is a large-scale, well-annotated multi-camera tracking benchmark which makes great progress in this field. This report is dedicated to briefly introduce our method on DukeMTMC and show that simple hierarchical clustering with well-trained person re-identification features can get good results on this dataset.
summary: Features are very important in the tracking-by-detection framework. There are two types of features that are used in common, i.e., appearance features and temporal features. For appearance features, many works adopt CNN-based features from Re-ID tasks @cite_14 @cite_20 @cite_36 . However, histogram-based features, like color histograms, HOG, and LBP, are still powerful if no training data is provided @cite_33 . As for temporal features, the location, size, and motion of bounding boxes are commonly used. Given the appearance features and temporal features, the tracker can fuse them together using human defined weights @cite_20 @cite_31 @cite_33 . Although @cite_34 @cite_27 propose RNN-based networks to combine features together, it is still empirical and difficult to determine the weight of each feature.