Boosting Semi-supervised Crowd Counting with Scale-based Active Learning
Abstract: The core of active semi-supervised crowd counting is the sample selection criteria. However, the scale factor has been neglected in active learning approaches despite the fact that the scale of heads varies drastically in the crowd images. In this paper, we propose a simple yet effective active labeling strategy to explicitly select informative unlabeled images, guided by the intra-scale uncertainty and inter-scale inconsistency metrics. The intra-scale uncertainty is quantified through the sum of the query-level entropy of images at different scales. Images are initially ranked based on this uncertainty for preselection. Inter-scale inconsistency is measured by the divergence between the query-level predictions of upscaled and downscaled images, allowing for the identification of the most informative images exhibiting the highest inconsistency. Additionally, we implement a progressive updating scheme for the semi-supervised crowd counting framework, in which the pseudo-labels for unlabeled images are refined iteratively. It further improves the counting accuracy. Through extensive experiments on widely used benchmarks, the proposed approach has demonstrated superior performance compared to previous state-of-the-art semi-supervised and active semi-supervised crowd counting methods.
Primary Subject Area: [Content] Vision and Language
Secondary Subject Area: [Engagement] Summarization, Analytics, and Storytelling
Relevance To Conference: Crowd counting is a typical task of multimedia processing. We propose a simple yet effective active semi-supervised method, which gives new SOTA and insight for the crowd counting community.
Submission Number: 2043
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