In this report, we introduce the Winner method for HACS Temporal Action Localization Challenge 2019. Temporal action localization is challenging since a target proposal may be related to several other candidate proposals in an untrimmed video. Existing methods cannot tackle this challenge well since temporal proposals are considered individually and their temporal dependencies are neglected. To address this issue, we propose sparse 2D temporal adjacent networks to model the temporal relationship between candidate proposals. This method is built upon the recent proposed 2D-TAN approach. The sampling strategy in 2D-TAN introduces the unbalanced context problem, where short proposals can perceive more context than long proposals. Therefore, we further propose a Sparse 2D Temporal Adjacent Network (S-2D-TAN). It is capable of involving more context information for long proposals and further learning discriminative features from them. By combining our S-2D-TAN with a simple action classifier, our method achieves a mAP of 23.49 on the test set, which win the first place in the HACS challenge.

本文介绍了在 HACS 时间动作定位挑战赛 2019 中获胜的 Winner 方法。该方法提出了稀疏 2D 时间相邻网络以建模候选动作的时间关系，并通过结合简单的动作分类器，最终在测试集上获得了 23.49 的平均精确度，赢得了比赛的第一名。

学习稀疏2D时间相邻网络用于时间动作定位