Video Moment Localization (VML) is a task that seeks to pinpoint the most pertinent segment within an untrimmed video using a linguistic query. Previous works expose the severe data bias issues in VML and note that models avoid understanding visual-textual content by adapting the timestamp distribution. The work investigates data biases from both intrinsic and extrinsic perspectives: The former arises primarily from moment boundary ambiguity and the inputoutput information imbalance. The latter is attributed to the longtail distribution and the semantic bias resulting from the limited tail samples. To reduce the issues, we develop a hybrid multimodal debiasing network with a temporal consistency constraint for VML. Firstly, we propose a multi-temporal Transformer to alleviate boundary ambiguity by merging frame-wise features into segment-wise representations and dynamically aligning with moment boundaries. Subsequently, we implement a temporal consistency constraint to accentuate action information from complex moment context and mitigate the intrinsic bias caused by information imbalance. Moreover, we develop a hybrid linguistic activation module to mitigate the long-tail bias, which offers prior guidance to emphasize distinguishing clues from tail samples. Additionally, we introduce the prior-guided Transformer to alleviate the semantic bias by learning the global semantics of sentences, thereby circumventing the tail-sample overfitting issue. Comprehensive experiments demonstrate the efficacy of our proposed method across three datasets.

Moment Localization with Natural Language (MLNL) aims to locate the target moment from an untrimmed video by a linguistic query. Recent works reveal the severe data bias problem in MLNL and point out that the multi-modal content may not be understood by fitting the timestamp distribution. In this paper, we study the data biases on the intrinsic and extrinsic aspects: the former is mainly caused by the ambiguity of the moment boundary and the information imbalance between input and output; The latter results from the long-tail distribution of moments in MLNL datasets. To alleviate this, we propose a hybrid multi-modal debiasing network with temporal consistency constraint for MLNL. Specifically, we first design the multi-temporal Transformer to mitigate the ambiguity of boundary by integrating frame-wise features into segment-wise and dynamically matching with moment boundaries. Then, we introduce the temporal consistency constraint that highlights the action information in complex moment content to overcome the intrinsic bias from information imbalance.Furthermore, we design the hybrid linguistic activating module with external knowledge to relieve the extrinsic bias, which introduces a prior guidance to focus the discriminative information from the tail samples. Extensive experiments on three public datasets demonstrate that our model outperforms the existing methods.