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乐应英1,2, 徐丹1, 贺康建1, 张浩1(1.云南大学信息学院, 昆明 650091;2.玉溪师范学院数学与信息技术学院, 玉溪 653100)

摘 要
目的 针对低视点多目标跟踪场景的遮挡问题,提出一种能够遮挡自适应感知的多目标跟踪算法。方法 首先根据每帧图像的全局遮挡状态,提出了“自适应抗遮挡特征”,增强目标特征对遮挡的感知和调整能力。同时,采用“级联筛查机制”,减少由遮挡带来的目标特征剧烈变化而认定为“虚新入目标”的错误跟踪现象。最后,考虑到历史模板库中存在遮挡的模板对跟踪性能的影响,根据每一帧中目标的局部遮挡状态,提出自适应干扰模板更新机制,进一步提高对遮挡的应变和适应能力。结果 实验结果表明,本文算法在MOTA (multiple object tracking accuracy)、MOTP (multiple object tracking precision)、FN (false negatives)、Rcll (recall)、ML (mostly lost tracklets)等指标上明显优于STAM (spatial-temporal attention mechanism)、ATAF (aggregate tracklet appearance features)、STRN (spatial-temporal relation network)、BLSTM_MTP_O (bilinear long short-term memory with multi-track pooling)、IADMR (instance-aware tracker and dynamic model refreshment)等典型算法。消融实验表明,自适应抗遮挡特征在MOTA指标上,相比混合特征、外观特征和运动特征分别提升了1.9%、1.8%和13.6%。去干扰模板更新策略在MOTA指标上,相比带权更新策略和常规更新策略分别提升了10.7%和17.7%。结论 本文算法在低视点跟踪场景下,能够减弱部分遮挡、短时全遮挡和长时全遮挡对跟踪性能的影响,跟踪鲁棒性得到了提升。
An adaptive occlusion-aware multiple targets tracking algorithm for low viewpoint

Yue Yingying1,2, Xu Dan1, He Kangjian1, Zhang Hao1(1.School of Information Science and Engineering, Yunnan University, Kunming 650091, China;2.School of Mathematics and Information Technology, Yuxi Normal University, Yuxi 653100, China)

Objective Multi-target tracking technique is essential for the computer vision-relevant applications like video surveillance, smart cities, and intelligent public transportation. The task of multi-target tracking is required to better location for multiple targets of each frame through the context information of the video sequence. To generate the motion trajectory of each target, its identity information (ID) is required to keep in consistency. So, we focus on low viewpoint-based multi-target tracking with no high viewpoint involved. For low viewpoint tracking scenes, the occlusion can be as a key factor to optimize tracking performance. The occlusion-completed is restricted by the target-captured issues temporarily, which is challenged for target tracking. The partial-occluded target is still challenged to be captured because the visual information of the occluded target is contaminated and the extracted target features are incomplete, and it will cause tracking drift as well. Method To resolve occlusion problem, we develop a low viewpoint-based adaptive occlusion-relevant multiple targets tracking algorithm. The proposed algorithm is composed of three main aspects as following:1) An adaptive anti-occlusion feature is illustrated in terms of the occlusion degree of each frame. To enhance its adaptability for occlusion, global occlusion information is used to adjust feature-related structure dynamically. 2) When the occlusion occurs, the target will disappear temporarily. When it reappears again after occlusion, it is often transferred to a new target and the tracking ID switch occurs. Therefore, a cascade screening mechanism is melted into for new target problem-identified. Due to the intensive change of occlusion-based target features, high-level and low-level features are employed both to prevent the virtual phenomenon for new target. 3) A large amount of target-occluded noise will be introduced into the template library if they are updated into the template library with no clarification. Therefore, an adaptive anti-interference template update mechanism is proposed for that. Multiple weights are given to the target templates-profiled of different occlusion states based on the local occlusion information of all targets, and the weights-based adaptive template-updated is then performed, which can alleviate the interference of severe-occluded targets to the template library. Result Our algorithm is experimented on the low viewpoint tracking videos-selected of MOT16, which includes special tracking scenes like 1) partial occlusion, 2) short-term full occlusion, and 3) long-term full occlusion. The experimental results show that the tracking performance of our algorithm has been improved, achieve improvement of 3.67%, 1.57%, 2.77%, 5.71%, and 3.07% on MOTA (multiple object tracking accuracy) respectively than STAM (spatial-temporal attention mechanism), ATAF (aggregate tracklet appearance features), STRN (spatial-temporal relation network), BLSTM_MTP_O (bilinear long short-term memory with multi-track pooling) and IADMR (instance-aware tracker and dynamic model refreshment). Furthermore, the ablation experiment shows that our anti-occlusion feature proposed can achieve an increase of 1.9% compared to the hybrid feature, an improvement of 1.8% compared to the appearance feature, and an optimization of 13.6% compared to the motion feature on MOTA. Compared with the weighted update strategy, the adaptive anti-interference update strategy proposed has achieved an improvement of 10.7% on MOTA, and an improvement of 17.7% compared with the conventional update strategy. Moreover, compared with the weighted update strategy, the number of ID switching times is significantly reduced from 244 to 119, which shows that our anti-interference update strategy can optimize the cleanliness of the template library and the accuracy of data association. Additionally, to validate the effectiveness of the update strategy we proposed, more indicators are improved obviously, such as Rcll (recall), FN (false negatives), MT (mostly lost tracklets), ML (mostly lost tracklets), and Frag (fragments). Conclusion The low viewpoint-based adaptive occlusion-relevant multiple targets tracking algorithm can be used to enhance the perception and balancing capabilities of the features-used in data association, reduces the impact of severe-occluded target templates beyond template library-profiled on the multi-tracking performance. Limitation and recommendation our proposed algorithm have no motion and speed-related estimation-specific mechanism for the rigid motion of the camera. Our data association-based algorithm is still cohesive to target detection algorithm severely. Therefore, the trajectory has to be disturbed and crossed when the target is missed or falsely detected. The future work can be focused on improving the tracking adaptability to actual tracking scenarios and the immunity of detection errors further.