Learning scene-adaptive pseudo annotations for pedestrian detection in semi-supervised scenarios

Sufficient labeled training data may not be available for pedestrian detection in many real-world scenes. Semi-supervised settings naturally apply for the case where an adequate number of images are collected in a target scene but only a small proportion of them can be manually annotated. A common strategy is to adopt a detector trained on a well-established dataset (source data) or the limited annotated data to pseudo-annotate unannotated images. However, the domain gap and the lack of supervision in the target scene may lead to low-quality pseudo annotations. In this paper, we propose a Scene-adaptive Pseudo Annotation (SaPA) approach, which aims at exploiting two types of training data: source data providing sufficient supervision and unannotated target data offering domain-specific information. To utilize the source data, an Annotation Network (AnnNet) competes with a domain discriminator to learn domain-invariant features. To exploit the unannotated data, we temporally aggregate the parameters of AnnNet to build a more robust network, which is able to provide training goals for AnnNet. This new approach improves the generalization performance of AnnNet, which eventually leads to high-quality pseudo annotations to the unannotated data. Both manual and pseudo annotations are leveraged to train a more precise and scene-specific detector. We perform extensive experiments on multiple benchmarks to verify the effectiveness and superiority of SaPA.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Sufficient labeled training data may not be available for pedestrian detection in many real-world scenes. In this paper, a Scene-adaptive Pseudo Annotation (SaPA) approach is proposed to improve the generalization performance and pseudo annotation quality for training a more precise and scene-specific pedestrian detector, by exploiting both source data with sufficient supervision and unannotated target data with domain-specific information.