  Temporal sentence grounding (TSG) aims to locate a specific moment from an
untrimmed video with a given natural language query. Recently, weakly
supervised methods still have a large performance gap compared to fully
supervised ones, while the latter requires laborious timestamp annotations. In
this study, we aim to reduce the annotation cost yet keep competitive
performance for TSG task compared to fully supervised ones. To achieve this
goal, we investigate a recently proposed glance-supervised temporal sentence
grounding task, which requires only single frame annotation (referred to as
glance annotation) for each query. Under this setup, we propose a Dynamic
Gaussian prior based Grounding framework with Glance annotation (D3G), which
consists of a Semantic Alignment Group Contrastive Learning module (SA-GCL) and
a Dynamic Gaussian prior Adjustment module (DGA). Specifically, SA-GCL samples
reliable positive moments from a 2D temporal map via jointly leveraging
Gaussian prior and semantic consistency, which contributes to aligning the
positive sentence-moment pairs in the joint embedding space. Moreover, to
alleviate the annotation bias resulting from glance annotation and model
complex queries consisting of multiple events, we propose the DGA module, which
adjusts the distribution dynamically to approximate the ground truth of target
moments. Extensive experiments on three challenging benchmarks verify the
effectiveness of the proposed D3G. It outperforms the state-of-the-art weakly
supervised methods by a large margin and narrows the performance gap compared
to fully supervised methods. Code is available at
https://github.com/solicucu/D3G.
