  Temporal action proposal generation (TAPG) is a challenging task that aims to
locate action instances in untrimmed videos with temporal boundaries. To
evaluate the confidence of proposals, the existing works typically predict
action score of proposals that are supervised by the temporal
Intersection-over-Union (tIoU) between proposal and the ground-truth. In this
paper, we innovatively propose a general auxiliary Background Constraint idea
to further suppress low-quality proposals, by utilizing the background
prediction score to restrict the confidence of proposals. In this way, the
Background Constraint concept can be easily plug-and-played into existing TAPG
methods (e.g., BMN, GTAD). From this perspective, we propose the Background
Constraint Network (BCNet) to further take advantage of the rich information of
action and background. Specifically, we introduce an Action-Background
Interaction module for reliable confidence evaluation, which models the
inconsistency between action and background by attention mechanisms at the
frame and clip levels. Extensive experiments are conducted on two popular
benchmarks, i.e., ActivityNet-1.3 and THUMOS14. The results demonstrate that
our method outperforms state-of-the-art methods. Equipped with the existing
action classifier, our method also achieves remarkable performance on the
temporal action localization task.
